[PATCH v3 0/2] drm/tinydrm: drm_of_find_backlight helper

[PATCH v3 0/2] drm/tinydrm: drm_of_find_backlight helper

[Meghana Madhyastha]

This patchset introduces some changes such as move
tinydrm_of_find_backlight to drm_of.c and rename it to
drm_of_find_backlight for better organizational structure.

Changes in v3:
-Changed it back to a single patch for the caller in mi0283qt.c
 and the removal and renaming of the helper function.

Meghana Madhyastha (2):
  drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c
  drm/tinydrm: Add devres versions of drm_of_find_backlight

 drivers/gpu/drm/drm_of.c                       | 92 ++++++++++++++++++++++++++
 drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------
 drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
 include/drm/drm_of.h                           |  3 +
 include/drm/tinydrm/tinydrm-helpers.h          |  1 -
 5 files changed, 97 insertions(+), 42 deletions(-)

-- 
2.7.4

[PATCH v3 0/2] drm/tinydrm: drm_of_find_backlight helper

[Meghana Madhyastha]

This patchset introduces some changes such as move
tinydrm_of_find_backlight to drm_of.c and rename it to
drm_of_find_backlight for better organizational structure.

Changes in v3:
-Changed it back to a single patch for the caller in mi0283qt.c
 and the removal and renaming of the helper function.

Meghana Madhyastha (2):
  drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c
  drm/tinydrm: Add devres versions of drm_of_find_backlight

 drivers/gpu/drm/drm_of.c                       | 92 ++++++++++++++++++++++++++
 drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------
 drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
 include/drm/drm_of.h                           |  3 +
 include/drm/tinydrm/tinydrm-helpers.h          |  1 -
 5 files changed, 97 insertions(+), 42 deletions(-)

-- 
2.7.4

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[PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

Rename tinydrm_of_find_backlight to drm_of_find_backlight
and move it into drm_of.c from tinydrm-helpers.c. This is
because other drivers in the drm subsystem might need to call
this function. In that case and otherwise, it is better from
an organizational point of view to move it into drm_of.c along
with the other _of.c functions.

Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
---
Changes in v3:
-Change it back to a single patch from two patches in v2

 drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
 drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
 drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
 include/drm/drm_of.h                           |  1 +
 include/drm/tinydrm/tinydrm-helpers.h          |  1 -
 5 files changed, 47 insertions(+), 42 deletions(-)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index 8dafbdf..d878d3a 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -1,6 +1,7 @@
 #include <linux/component.h>
 #include <linux/export.h>
 #include <linux/list.h>
+#include <linux/backlight.h>
 #include <linux/of_graph.h>
 #include <drm/drmP.h>
 #include <drm/drm_bridge.h>
@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 	return ret;
 }
 EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
+
+/**
+ * drm_of_find_backlight - Find backlight device in device-tree
+ * @dev: Device
+ *
+ * This function looks for a DT node pointed to by a property named 'backlight'
+ * and uses of_find_backlight_by_node() to get the backlight device.
+ * Additionally if the brightness property is zero, it is set to
+ * max_brightness.
+ *
+ * Note: It is the responsibility of the caller to call put_device() when
+ * releasing the resource.
+ *
+ * Returns:
+ * NULL if there's no backlight property.
+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
+ * is found.
+ * If the backlight device is found, a pointer to the structure is returned.
+ */
+struct backlight_device *drm_of_find_backlight(struct device *dev)
+{
+	struct backlight_device *backlight;
+	struct device_node *np;
+
+	np = of_parse_phandle(dev->of_node, "backlight", 0);
+	if (!np)
+		return NULL;
+
+	backlight = of_find_backlight_by_node(np);
+	of_node_put(np);
+
+	if (!backlight)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	if (!backlight->props.brightness) {
+		backlight->props.brightness = backlight->props.max_brightness;
+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
+			      backlight->props.brightness);
+	}
+
+	return backlight;
+}
+EXPORT_SYMBOL(drm_of_find_backlight);
diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
index bd6cce0..cd4c6a5 100644
--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
 EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
 
 /**
- * tinydrm_of_find_backlight - Find backlight device in device-tree
- * @dev: Device
- *
- * This function looks for a DT node pointed to by a property named 'backlight'
- * and uses of_find_backlight_by_node() to get the backlight device.
- * Additionally if the brightness property is zero, it is set to
- * max_brightness.
- *
- * Returns:
- * NULL if there's no backlight property.
- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
- * is found.
- * If the backlight device is found, a pointer to the structure is returned.
- */
-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
-{
-	struct backlight_device *backlight;
-	struct device_node *np;
-
-	np = of_parse_phandle(dev->of_node, "backlight", 0);
-	if (!np)
-		return NULL;
-
-	backlight = of_find_backlight_by_node(np);
-	of_node_put(np);
-
-	if (!backlight)
-		return ERR_PTR(-EPROBE_DEFER);
-
-	if (!backlight->props.brightness) {
-		backlight->props.brightness = backlight->props.max_brightness;
-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
-			      backlight->props.brightness);
-	}
-
-	return backlight;
-}
-EXPORT_SYMBOL(tinydrm_of_find_backlight);
-
-/**
  * tinydrm_enable_backlight - Enable backlight helper
  * @backlight: Backlight device
  *
diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
index 7e5bb7d..5e3d635 100644
--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
@@ -12,6 +12,7 @@
 #include <drm/tinydrm/ili9341.h>
 #include <drm/tinydrm/mipi-dbi.h>
 #include <drm/tinydrm/tinydrm-helpers.h>
+#include <drm/drm_of.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
 	if (IS_ERR(mipi->regulator))
 		return PTR_ERR(mipi->regulator);
 
-	mipi->backlight = tinydrm_of_find_backlight(dev);
+	mipi->backlight = drm_of_find_backlight(dev);
 	if (IS_ERR(mipi->backlight))
 		return PTR_ERR(mipi->backlight);
 
diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
index 104dd51..e8fba5b 100644
--- a/include/drm/drm_of.h
+++ b/include/drm/drm_of.h
@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 				int port, int endpoint,
 				struct drm_panel **panel,
 				struct drm_bridge **bridge);
+struct backlight_device *drm_of_find_backlight(struct device *dev);
 #else
 static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 						  struct device_node *port)
diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
index d554ded..e40ef2d 100644
--- a/include/drm/tinydrm/tinydrm-helpers.h
+++ b/include/drm/tinydrm/tinydrm-helpers.h
@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
 void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
 			       struct drm_clip_rect *clip);
 
-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
 int tinydrm_enable_backlight(struct backlight_device *backlight);
 int tinydrm_disable_backlight(struct backlight_device *backlight);
 
-- 
2.7.4

[PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

Rename tinydrm_of_find_backlight to drm_of_find_backlight
and move it into drm_of.c from tinydrm-helpers.c. This is
because other drivers in the drm subsystem might need to call
this function. In that case and otherwise, it is better from
an organizational point of view to move it into drm_of.c along
with the other _of.c functions.

Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
---
Changes in v3:
-Change it back to a single patch from two patches in v2

 drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
 drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
 drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
 include/drm/drm_of.h                           |  1 +
 include/drm/tinydrm/tinydrm-helpers.h          |  1 -
 5 files changed, 47 insertions(+), 42 deletions(-)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index 8dafbdf..d878d3a 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -1,6 +1,7 @@
 #include <linux/component.h>
 #include <linux/export.h>
 #include <linux/list.h>
+#include <linux/backlight.h>
 #include <linux/of_graph.h>
 #include <drm/drmP.h>
 #include <drm/drm_bridge.h>
@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 	return ret;
 }
 EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
+
+/**
+ * drm_of_find_backlight - Find backlight device in device-tree
+ * @dev: Device
+ *
+ * This function looks for a DT node pointed to by a property named 'backlight'
+ * and uses of_find_backlight_by_node() to get the backlight device.
+ * Additionally if the brightness property is zero, it is set to
+ * max_brightness.
+ *
+ * Note: It is the responsibility of the caller to call put_device() when
+ * releasing the resource.
+ *
+ * Returns:
+ * NULL if there's no backlight property.
+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
+ * is found.
+ * If the backlight device is found, a pointer to the structure is returned.
+ */
+struct backlight_device *drm_of_find_backlight(struct device *dev)
+{
+	struct backlight_device *backlight;
+	struct device_node *np;
+
+	np = of_parse_phandle(dev->of_node, "backlight", 0);
+	if (!np)
+		return NULL;
+
+	backlight = of_find_backlight_by_node(np);
+	of_node_put(np);
+
+	if (!backlight)
+		return ERR_PTR(-EPROBE_DEFER);
+
+	if (!backlight->props.brightness) {
+		backlight->props.brightness = backlight->props.max_brightness;
+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
+			      backlight->props.brightness);
+	}
+
+	return backlight;
+}
+EXPORT_SYMBOL(drm_of_find_backlight);
diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
index bd6cce0..cd4c6a5 100644
--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
 EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
 
 /**
- * tinydrm_of_find_backlight - Find backlight device in device-tree
- * @dev: Device
- *
- * This function looks for a DT node pointed to by a property named 'backlight'
- * and uses of_find_backlight_by_node() to get the backlight device.
- * Additionally if the brightness property is zero, it is set to
- * max_brightness.
- *
- * Returns:
- * NULL if there's no backlight property.
- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
- * is found.
- * If the backlight device is found, a pointer to the structure is returned.
- */
-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
-{
-	struct backlight_device *backlight;
-	struct device_node *np;
-
-	np = of_parse_phandle(dev->of_node, "backlight", 0);
-	if (!np)
-		return NULL;
-
-	backlight = of_find_backlight_by_node(np);
-	of_node_put(np);
-
-	if (!backlight)
-		return ERR_PTR(-EPROBE_DEFER);
-
-	if (!backlight->props.brightness) {
-		backlight->props.brightness = backlight->props.max_brightness;
-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
-			      backlight->props.brightness);
-	}
-
-	return backlight;
-}
-EXPORT_SYMBOL(tinydrm_of_find_backlight);
-
-/**
  * tinydrm_enable_backlight - Enable backlight helper
  * @backlight: Backlight device
  *
diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
index 7e5bb7d..5e3d635 100644
--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
@@ -12,6 +12,7 @@
 #include <drm/tinydrm/ili9341.h>
 #include <drm/tinydrm/mipi-dbi.h>
 #include <drm/tinydrm/tinydrm-helpers.h>
+#include <drm/drm_of.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
 	if (IS_ERR(mipi->regulator))
 		return PTR_ERR(mipi->regulator);
 
-	mipi->backlight = tinydrm_of_find_backlight(dev);
+	mipi->backlight = drm_of_find_backlight(dev);
 	if (IS_ERR(mipi->backlight))
 		return PTR_ERR(mipi->backlight);
 
diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
index 104dd51..e8fba5b 100644
--- a/include/drm/drm_of.h
+++ b/include/drm/drm_of.h
@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 				int port, int endpoint,
 				struct drm_panel **panel,
 				struct drm_bridge **bridge);
+struct backlight_device *drm_of_find_backlight(struct device *dev);
 #else
 static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 						  struct device_node *port)
diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
index d554ded..e40ef2d 100644
--- a/include/drm/tinydrm/tinydrm-helpers.h
+++ b/include/drm/tinydrm/tinydrm-helpers.h
@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
 void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
 			       struct drm_clip_rect *clip);
 
-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
 int tinydrm_enable_backlight(struct backlight_device *backlight);
 int tinydrm_disable_backlight(struct backlight_device *backlight);
 
-- 
2.7.4

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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Daniel Vetter]

On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> Rename tinydrm_of_find_backlight to drm_of_find_backlight
> and move it into drm_of.c from tinydrm-helpers.c. This is
> because other drivers in the drm subsystem might need to call
> this function. In that case and otherwise, it is better from
> an organizational point of view to move it into drm_of.c along
> with the other _of.c functions.
> 
> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> ---
> Changes in v3:
> -Change it back to a single patch from two patches in v2
> 
>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>  include/drm/drm_of.h                           |  1 +
>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>  5 files changed, 47 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index 8dafbdf..d878d3a 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -1,6 +1,7 @@
>  #include <linux/component.h>
>  #include <linux/export.h>
>  #include <linux/list.h>
> +#include <linux/backlight.h>
>  #include <linux/of_graph.h>
>  #include <drm/drmP.h>
>  #include <drm/drm_bridge.h>
> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> +
> +/**
> + * drm_of_find_backlight - Find backlight device in device-tree
> + * @dev: Device
> + *
> + * This function looks for a DT node pointed to by a property named 'backlight'
> + * and uses of_find_backlight_by_node() to get the backlight device.
> + * Additionally if the brightness property is zero, it is set to
> + * max_brightness.
> + *
> + * Note: It is the responsibility of the caller to call put_device() when
> + * releasing the resource.
> + *
> + * Returns:
> + * NULL if there's no backlight property.
> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> + * is found.
> + * If the backlight device is found, a pointer to the structure is returned.
> + */
> +struct backlight_device *drm_of_find_backlight(struct device *dev)
> +{
> +	struct backlight_device *backlight;
> +	struct device_node *np;
> +
> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
> +	if (!np)
> +		return NULL;
> +
> +	backlight = of_find_backlight_by_node(np);
> +	of_node_put(np);
> +
> +	if (!backlight)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	if (!backlight->props.brightness) {
> +		backlight->props.brightness = backlight->props.max_brightness;
> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> +			      backlight->props.brightness);
> +	}
> +
> +	return backlight;
> +}
> +EXPORT_SYMBOL(drm_of_find_backlight);
> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> index bd6cce0..cd4c6a5 100644
> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>  
>  /**
> - * tinydrm_of_find_backlight - Find backlight device in device-tree
> - * @dev: Device
> - *
> - * This function looks for a DT node pointed to by a property named 'backlight'
> - * and uses of_find_backlight_by_node() to get the backlight device.
> - * Additionally if the brightness property is zero, it is set to
> - * max_brightness.
> - *
> - * Returns:
> - * NULL if there's no backlight property.
> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> - * is found.
> - * If the backlight device is found, a pointer to the structure is returned.
> - */
> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> -{
> -	struct backlight_device *backlight;
> -	struct device_node *np;
> -
> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
> -	if (!np)
> -		return NULL;
> -
> -	backlight = of_find_backlight_by_node(np);
> -	of_node_put(np);
> -
> -	if (!backlight)
> -		return ERR_PTR(-EPROBE_DEFER);
> -
> -	if (!backlight->props.brightness) {
> -		backlight->props.brightness = backlight->props.max_brightness;
> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> -			      backlight->props.brightness);
> -	}
> -
> -	return backlight;
> -}
> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
> -
> -/**
>   * tinydrm_enable_backlight - Enable backlight helper
>   * @backlight: Backlight device
>   *
> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> index 7e5bb7d..5e3d635 100644
> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> @@ -12,6 +12,7 @@
>  #include <drm/tinydrm/ili9341.h>
>  #include <drm/tinydrm/mipi-dbi.h>
>  #include <drm/tinydrm/tinydrm-helpers.h>
> +#include <drm/drm_of.h>
>  #include <linux/delay.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/module.h>
> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>  	if (IS_ERR(mipi->regulator))
>  		return PTR_ERR(mipi->regulator);
>  
> -	mipi->backlight = tinydrm_of_find_backlight(dev);
> +	mipi->backlight = drm_of_find_backlight(dev);
>  	if (IS_ERR(mipi->backlight))
>  		return PTR_ERR(mipi->backlight);
>  
> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> index 104dd51..e8fba5b 100644
> --- a/include/drm/drm_of.h
> +++ b/include/drm/drm_of.h
> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>  				int port, int endpoint,
>  				struct drm_panel **panel,
>  				struct drm_bridge **bridge);
> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>  #else
>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>  						  struct device_node *port)

Minor detail I missed: The dummy version for the #else here is missing.
Not a problem for tinydrm, but might be an issue for a driver where
CONFIG_OF is optional.

Otherwise I think this patch looks good.
-Daniel

> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> index d554ded..e40ef2d 100644
> --- a/include/drm/tinydrm/tinydrm-helpers.h
> +++ b/include/drm/tinydrm/tinydrm-helpers.h
> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>  			       struct drm_clip_rect *clip);
>  
> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>  int tinydrm_enable_backlight(struct backlight_device *backlight);
>  int tinydrm_disable_backlight(struct backlight_device *backlight);
>  
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Daniel Vetter]

On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> Rename tinydrm_of_find_backlight to drm_of_find_backlight
> and move it into drm_of.c from tinydrm-helpers.c. This is
> because other drivers in the drm subsystem might need to call
> this function. In that case and otherwise, it is better from
> an organizational point of view to move it into drm_of.c along
> with the other _of.c functions.
> 
> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> ---
> Changes in v3:
> -Change it back to a single patch from two patches in v2
> 
>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>  include/drm/drm_of.h                           |  1 +
>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>  5 files changed, 47 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index 8dafbdf..d878d3a 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -1,6 +1,7 @@
>  #include <linux/component.h>
>  #include <linux/export.h>
>  #include <linux/list.h>
> +#include <linux/backlight.h>
>  #include <linux/of_graph.h>
>  #include <drm/drmP.h>
>  #include <drm/drm_bridge.h>
> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> +
> +/**
> + * drm_of_find_backlight - Find backlight device in device-tree
> + * @dev: Device
> + *
> + * This function looks for a DT node pointed to by a property named 'backlight'
> + * and uses of_find_backlight_by_node() to get the backlight device.
> + * Additionally if the brightness property is zero, it is set to
> + * max_brightness.
> + *
> + * Note: It is the responsibility of the caller to call put_device() when
> + * releasing the resource.
> + *
> + * Returns:
> + * NULL if there's no backlight property.
> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> + * is found.
> + * If the backlight device is found, a pointer to the structure is returned.
> + */
> +struct backlight_device *drm_of_find_backlight(struct device *dev)
> +{
> +	struct backlight_device *backlight;
> +	struct device_node *np;
> +
> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
> +	if (!np)
> +		return NULL;
> +
> +	backlight = of_find_backlight_by_node(np);
> +	of_node_put(np);
> +
> +	if (!backlight)
> +		return ERR_PTR(-EPROBE_DEFER);
> +
> +	if (!backlight->props.brightness) {
> +		backlight->props.brightness = backlight->props.max_brightness;
> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> +			      backlight->props.brightness);
> +	}
> +
> +	return backlight;
> +}
> +EXPORT_SYMBOL(drm_of_find_backlight);
> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> index bd6cce0..cd4c6a5 100644
> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>  
>  /**
> - * tinydrm_of_find_backlight - Find backlight device in device-tree
> - * @dev: Device
> - *
> - * This function looks for a DT node pointed to by a property named 'backlight'
> - * and uses of_find_backlight_by_node() to get the backlight device.
> - * Additionally if the brightness property is zero, it is set to
> - * max_brightness.
> - *
> - * Returns:
> - * NULL if there's no backlight property.
> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> - * is found.
> - * If the backlight device is found, a pointer to the structure is returned.
> - */
> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> -{
> -	struct backlight_device *backlight;
> -	struct device_node *np;
> -
> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
> -	if (!np)
> -		return NULL;
> -
> -	backlight = of_find_backlight_by_node(np);
> -	of_node_put(np);
> -
> -	if (!backlight)
> -		return ERR_PTR(-EPROBE_DEFER);
> -
> -	if (!backlight->props.brightness) {
> -		backlight->props.brightness = backlight->props.max_brightness;
> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> -			      backlight->props.brightness);
> -	}
> -
> -	return backlight;
> -}
> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
> -
> -/**
>   * tinydrm_enable_backlight - Enable backlight helper
>   * @backlight: Backlight device
>   *
> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> index 7e5bb7d..5e3d635 100644
> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> @@ -12,6 +12,7 @@
>  #include <drm/tinydrm/ili9341.h>
>  #include <drm/tinydrm/mipi-dbi.h>
>  #include <drm/tinydrm/tinydrm-helpers.h>
> +#include <drm/drm_of.h>
>  #include <linux/delay.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/module.h>
> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>  	if (IS_ERR(mipi->regulator))
>  		return PTR_ERR(mipi->regulator);
>  
> -	mipi->backlight = tinydrm_of_find_backlight(dev);
> +	mipi->backlight = drm_of_find_backlight(dev);
>  	if (IS_ERR(mipi->backlight))
>  		return PTR_ERR(mipi->backlight);
>  
> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> index 104dd51..e8fba5b 100644
> --- a/include/drm/drm_of.h
> +++ b/include/drm/drm_of.h
> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>  				int port, int endpoint,
>  				struct drm_panel **panel,
>  				struct drm_bridge **bridge);
> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>  #else
>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>  						  struct device_node *port)

Minor detail I missed: The dummy version for the #else here is missing.
Not a problem for tinydrm, but might be an issue for a driver where
CONFIG_OF is optional.

Otherwise I think this patch looks good.
-Daniel

> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> index d554ded..e40ef2d 100644
> --- a/include/drm/tinydrm/tinydrm-helpers.h
> +++ b/include/drm/tinydrm/tinydrm-helpers.h
> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>  			       struct drm_clip_rect *clip);
>  
> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>  int tinydrm_enable_backlight(struct backlight_device *backlight);
>  int tinydrm_disable_backlight(struct backlight_device *backlight);
>  
> -- 
> 2.7.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 28.09.2017 16.08, skrev Daniel Vetter:
> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>> and move it into drm_of.c from tinydrm-helpers.c. This is
>> because other drivers in the drm subsystem might need to call
>> this function. In that case and otherwise, it is better from
>> an organizational point of view to move it into drm_of.c along
>> with the other _of.c functions.
>>
>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>> ---
>> Changes in v3:
>> -Change it back to a single patch from two patches in v2
>>
>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>   include/drm/drm_of.h                           |  1 +
>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>> index 8dafbdf..d878d3a 100644
>> --- a/drivers/gpu/drm/drm_of.c
>> +++ b/drivers/gpu/drm/drm_of.c
>> @@ -1,6 +1,7 @@
>>   #include <linux/component.h>
>>   #include <linux/export.h>
>>   #include <linux/list.h>
>> +#include <linux/backlight.h>
>>   #include <linux/of_graph.h>
>>   #include <drm/drmP.h>
>>   #include <drm/drm_bridge.h>
>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>   	return ret;
>>   }
>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>> +
>> +/**
>> + * drm_of_find_backlight - Find backlight device in device-tree
>> + * @dev: Device
>> + *
>> + * This function looks for a DT node pointed to by a property named 'backlight'
>> + * and uses of_find_backlight_by_node() to get the backlight device.
>> + * Additionally if the brightness property is zero, it is set to
>> + * max_brightness.
>> + *
>> + * Note: It is the responsibility of the caller to call put_device() when
>> + * releasing the resource.
>> + *
>> + * Returns:
>> + * NULL if there's no backlight property.
>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>> + * is found.
>> + * If the backlight device is found, a pointer to the structure is returned.
>> + */
>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>> +{
>> +	struct backlight_device *backlight;
>> +	struct device_node *np;
>> +
>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>> +	if (!np)
>> +		return NULL;
>> +
>> +	backlight = of_find_backlight_by_node(np);
>> +	of_node_put(np);
>> +
>> +	if (!backlight)
>> +		return ERR_PTR(-EPROBE_DEFER);
>> +
>> +	if (!backlight->props.brightness) {
>> +		backlight->props.brightness = backlight->props.max_brightness;
>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>> +			      backlight->props.brightness);
>> +	}
>> +
>> +	return backlight;
>> +}
>> +EXPORT_SYMBOL(drm_of_find_backlight);
>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>> index bd6cce0..cd4c6a5 100644
>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>>   
>>   /**
>> - * tinydrm_of_find_backlight - Find backlight device in device-tree
>> - * @dev: Device
>> - *
>> - * This function looks for a DT node pointed to by a property named 'backlight'
>> - * and uses of_find_backlight_by_node() to get the backlight device.
>> - * Additionally if the brightness property is zero, it is set to
>> - * max_brightness.
>> - *
>> - * Returns:
>> - * NULL if there's no backlight property.
>> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>> - * is found.
>> - * If the backlight device is found, a pointer to the structure is returned.
>> - */
>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
>> -{
>> -	struct backlight_device *backlight;
>> -	struct device_node *np;
>> -
>> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
>> -	if (!np)
>> -		return NULL;
>> -
>> -	backlight = of_find_backlight_by_node(np);
>> -	of_node_put(np);
>> -
>> -	if (!backlight)
>> -		return ERR_PTR(-EPROBE_DEFER);
>> -
>> -	if (!backlight->props.brightness) {
>> -		backlight->props.brightness = backlight->props.max_brightness;
>> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>> -			      backlight->props.brightness);
>> -	}
>> -
>> -	return backlight;
>> -}
>> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
>> -
>> -/**
>>    * tinydrm_enable_backlight - Enable backlight helper
>>    * @backlight: Backlight device
>>    *
>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>> index 7e5bb7d..5e3d635 100644
>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>> @@ -12,6 +12,7 @@
>>   #include <drm/tinydrm/ili9341.h>
>>   #include <drm/tinydrm/mipi-dbi.h>
>>   #include <drm/tinydrm/tinydrm-helpers.h>
>> +#include <drm/drm_of.h>
>>   #include <linux/delay.h>
>>   #include <linux/gpio/consumer.h>
>>   #include <linux/module.h>
>> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>>   	if (IS_ERR(mipi->regulator))
>>   		return PTR_ERR(mipi->regulator);
>>   
>> -	mipi->backlight = tinydrm_of_find_backlight(dev);
>> +	mipi->backlight = drm_of_find_backlight(dev);
>>   	if (IS_ERR(mipi->backlight))
>>   		return PTR_ERR(mipi->backlight);
>>   
>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>> index 104dd51..e8fba5b 100644
>> --- a/include/drm/drm_of.h
>> +++ b/include/drm/drm_of.h
>> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>   				int port, int endpoint,
>>   				struct drm_panel **panel,
>>   				struct drm_bridge **bridge);
>> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>>   #else
>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>   						  struct device_node *port)
> Minor detail I missed: The dummy version for the #else here is missing.
> Not a problem for tinydrm, but might be an issue for a driver where
> CONFIG_OF is optional.

Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
platforms. The only resource that isn't available there is backlight
since there is no platform or ACPI way of describing that dependency.

Another problem I discovered when trying to compile this, is that if
DRM is builtin and LCD_CLASS_DEVICE is a module:

drivers/gpu/drm/drm_of.c:292: undefined reference to 
`of_find_backlight_by_node'

I see that I solved this in tinydrm by just selecting
BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
force LCD_CLASS_DEVICE to be builtin if DRM is builtin.

Arnd fixed a similar type of dependecy in the repaper driver by forcing
repaper to be a module if necessary. To be honest, I don't know why his
fix works:
https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002

Another way of solving this is to put the function in
drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
that does the selection.

Noralf.

> Otherwise I think this patch looks good.
> -Daniel
>
>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>> index d554ded..e40ef2d 100644
>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>>   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>   			       struct drm_clip_rect *clip);
>>   
>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>>   int tinydrm_enable_backlight(struct backlight_device *backlight);
>>   int tinydrm_disable_backlight(struct backlight_device *backlight);
>>   
>> -- 
>> 2.7.4
>>

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 28.09.2017 16.08, skrev Daniel Vetter:
> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>> and move it into drm_of.c from tinydrm-helpers.c. This is
>> because other drivers in the drm subsystem might need to call
>> this function. In that case and otherwise, it is better from
>> an organizational point of view to move it into drm_of.c along
>> with the other _of.c functions.
>>
>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>> ---
>> Changes in v3:
>> -Change it back to a single patch from two patches in v2
>>
>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>   include/drm/drm_of.h                           |  1 +
>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>> index 8dafbdf..d878d3a 100644
>> --- a/drivers/gpu/drm/drm_of.c
>> +++ b/drivers/gpu/drm/drm_of.c
>> @@ -1,6 +1,7 @@
>>   #include <linux/component.h>
>>   #include <linux/export.h>
>>   #include <linux/list.h>
>> +#include <linux/backlight.h>
>>   #include <linux/of_graph.h>
>>   #include <drm/drmP.h>
>>   #include <drm/drm_bridge.h>
>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>   	return ret;
>>   }
>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>> +
>> +/**
>> + * drm_of_find_backlight - Find backlight device in device-tree
>> + * @dev: Device
>> + *
>> + * This function looks for a DT node pointed to by a property named 'backlight'
>> + * and uses of_find_backlight_by_node() to get the backlight device.
>> + * Additionally if the brightness property is zero, it is set to
>> + * max_brightness.
>> + *
>> + * Note: It is the responsibility of the caller to call put_device() when
>> + * releasing the resource.
>> + *
>> + * Returns:
>> + * NULL if there's no backlight property.
>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>> + * is found.
>> + * If the backlight device is found, a pointer to the structure is returned.
>> + */
>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>> +{
>> +	struct backlight_device *backlight;
>> +	struct device_node *np;
>> +
>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>> +	if (!np)
>> +		return NULL;
>> +
>> +	backlight = of_find_backlight_by_node(np);
>> +	of_node_put(np);
>> +
>> +	if (!backlight)
>> +		return ERR_PTR(-EPROBE_DEFER);
>> +
>> +	if (!backlight->props.brightness) {
>> +		backlight->props.brightness = backlight->props.max_brightness;
>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>> +			      backlight->props.brightness);
>> +	}
>> +
>> +	return backlight;
>> +}
>> +EXPORT_SYMBOL(drm_of_find_backlight);
>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>> index bd6cce0..cd4c6a5 100644
>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>>   
>>   /**
>> - * tinydrm_of_find_backlight - Find backlight device in device-tree
>> - * @dev: Device
>> - *
>> - * This function looks for a DT node pointed to by a property named 'backlight'
>> - * and uses of_find_backlight_by_node() to get the backlight device.
>> - * Additionally if the brightness property is zero, it is set to
>> - * max_brightness.
>> - *
>> - * Returns:
>> - * NULL if there's no backlight property.
>> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>> - * is found.
>> - * If the backlight device is found, a pointer to the structure is returned.
>> - */
>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
>> -{
>> -	struct backlight_device *backlight;
>> -	struct device_node *np;
>> -
>> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
>> -	if (!np)
>> -		return NULL;
>> -
>> -	backlight = of_find_backlight_by_node(np);
>> -	of_node_put(np);
>> -
>> -	if (!backlight)
>> -		return ERR_PTR(-EPROBE_DEFER);
>> -
>> -	if (!backlight->props.brightness) {
>> -		backlight->props.brightness = backlight->props.max_brightness;
>> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>> -			      backlight->props.brightness);
>> -	}
>> -
>> -	return backlight;
>> -}
>> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
>> -
>> -/**
>>    * tinydrm_enable_backlight - Enable backlight helper
>>    * @backlight: Backlight device
>>    *
>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>> index 7e5bb7d..5e3d635 100644
>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>> @@ -12,6 +12,7 @@
>>   #include <drm/tinydrm/ili9341.h>
>>   #include <drm/tinydrm/mipi-dbi.h>
>>   #include <drm/tinydrm/tinydrm-helpers.h>
>> +#include <drm/drm_of.h>
>>   #include <linux/delay.h>
>>   #include <linux/gpio/consumer.h>
>>   #include <linux/module.h>
>> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>>   	if (IS_ERR(mipi->regulator))
>>   		return PTR_ERR(mipi->regulator);
>>   
>> -	mipi->backlight = tinydrm_of_find_backlight(dev);
>> +	mipi->backlight = drm_of_find_backlight(dev);
>>   	if (IS_ERR(mipi->backlight))
>>   		return PTR_ERR(mipi->backlight);
>>   
>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>> index 104dd51..e8fba5b 100644
>> --- a/include/drm/drm_of.h
>> +++ b/include/drm/drm_of.h
>> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>   				int port, int endpoint,
>>   				struct drm_panel **panel,
>>   				struct drm_bridge **bridge);
>> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>>   #else
>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>   						  struct device_node *port)
> Minor detail I missed: The dummy version for the #else here is missing.
> Not a problem for tinydrm, but might be an issue for a driver where
> CONFIG_OF is optional.

Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
platforms. The only resource that isn't available there is backlight
since there is no platform or ACPI way of describing that dependency.

Another problem I discovered when trying to compile this, is that if
DRM is builtin and LCD_CLASS_DEVICE is a module:

drivers/gpu/drm/drm_of.c:292: undefined reference to 
`of_find_backlight_by_node'

I see that I solved this in tinydrm by just selecting
BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
force LCD_CLASS_DEVICE to be builtin if DRM is builtin.

Arnd fixed a similar type of dependecy in the repaper driver by forcing
repaper to be a module if necessary. To be honest, I don't know why his
fix works:
https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002

Another way of solving this is to put the function in
drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
that does the selection.

Noralf.

> Otherwise I think this patch looks good.
> -Daniel
>
>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>> index d554ded..e40ef2d 100644
>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>>   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>   			       struct drm_clip_rect *clip);
>>   
>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>>   int tinydrm_enable_backlight(struct backlight_device *backlight);
>>   int tinydrm_disable_backlight(struct backlight_device *backlight);
>>   
>> -- 
>> 2.7.4
>>

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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Tr�nnes wrote:
> 
> Den 28.09.2017 16.08, skrev Daniel Vetter:
> >On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>because other drivers in the drm subsystem might need to call
> >>this function. In that case and otherwise, it is better from
> >>an organizational point of view to move it into drm_of.c along
> >>with the other _of.c functions.
> >>
> >>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>---
> >>Changes in v3:
> >>-Change it back to a single patch from two patches in v2
> >>
> >>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>  include/drm/drm_of.h                           |  1 +
> >>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>index 8dafbdf..d878d3a 100644
> >>--- a/drivers/gpu/drm/drm_of.c
> >>+++ b/drivers/gpu/drm/drm_of.c
> >>@@ -1,6 +1,7 @@
> >>  #include <linux/component.h>
> >>  #include <linux/export.h>
> >>  #include <linux/list.h>
> >>+#include <linux/backlight.h>
> >>  #include <linux/of_graph.h>
> >>  #include <drm/drmP.h>
> >>  #include <drm/drm_bridge.h>
> >>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>  	return ret;
> >>  }
> >>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>+
> >>+/**
> >>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>+ * @dev: Device
> >>+ *
> >>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>+ * Additionally if the brightness property is zero, it is set to
> >>+ * max_brightness.
> >>+ *
> >>+ * Note: It is the responsibility of the caller to call put_device() when
> >>+ * releasing the resource.
> >>+ *
> >>+ * Returns:
> >>+ * NULL if there's no backlight property.
> >>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>+ * is found.
> >>+ * If the backlight device is found, a pointer to the structure is returned.
> >>+ */
> >>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>+{
> >>+	struct backlight_device *backlight;
> >>+	struct device_node *np;
> >>+
> >>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>+	if (!np)
> >>+		return NULL;
> >>+
> >>+	backlight = of_find_backlight_by_node(np);
> >>+	of_node_put(np);
> >>+
> >>+	if (!backlight)
> >>+		return ERR_PTR(-EPROBE_DEFER);
> >>+
> >>+	if (!backlight->props.brightness) {
> >>+		backlight->props.brightness = backlight->props.max_brightness;
> >>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>+			      backlight->props.brightness);
> >>+	}
> >>+
> >>+	return backlight;
> >>+}
> >>+EXPORT_SYMBOL(drm_of_find_backlight);
> >>diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>index bd6cce0..cd4c6a5 100644
> >>--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> >>  /**
> >>- * tinydrm_of_find_backlight - Find backlight device in device-tree
> >>- * @dev: Device
> >>- *
> >>- * This function looks for a DT node pointed to by a property named 'backlight'
> >>- * and uses of_find_backlight_by_node() to get the backlight device.
> >>- * Additionally if the brightness property is zero, it is set to
> >>- * max_brightness.
> >>- *
> >>- * Returns:
> >>- * NULL if there's no backlight property.
> >>- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>- * is found.
> >>- * If the backlight device is found, a pointer to the structure is returned.
> >>- */
> >>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> >>-{
> >>-	struct backlight_device *backlight;
> >>-	struct device_node *np;
> >>-
> >>-	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>-	if (!np)
> >>-		return NULL;
> >>-
> >>-	backlight = of_find_backlight_by_node(np);
> >>-	of_node_put(np);
> >>-
> >>-	if (!backlight)
> >>-		return ERR_PTR(-EPROBE_DEFER);
> >>-
> >>-	if (!backlight->props.brightness) {
> >>-		backlight->props.brightness = backlight->props.max_brightness;
> >>-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>-			      backlight->props.brightness);
> >>-	}
> >>-
> >>-	return backlight;
> >>-}
> >>-EXPORT_SYMBOL(tinydrm_of_find_backlight);
> >>-
> >>-/**
> >>   * tinydrm_enable_backlight - Enable backlight helper
> >>   * @backlight: Backlight device
> >>   *
> >>diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>index 7e5bb7d..5e3d635 100644
> >>--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>@@ -12,6 +12,7 @@
> >>  #include <drm/tinydrm/ili9341.h>
> >>  #include <drm/tinydrm/mipi-dbi.h>
> >>  #include <drm/tinydrm/tinydrm-helpers.h>
> >>+#include <drm/drm_of.h>
> >>  #include <linux/delay.h>
> >>  #include <linux/gpio/consumer.h>
> >>  #include <linux/module.h>
> >>@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> >>  	if (IS_ERR(mipi->regulator))
> >>  		return PTR_ERR(mipi->regulator);
> >>-	mipi->backlight = tinydrm_of_find_backlight(dev);
> >>+	mipi->backlight = drm_of_find_backlight(dev);
> >>  	if (IS_ERR(mipi->backlight))
> >>  		return PTR_ERR(mipi->backlight);
> >>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>index 104dd51..e8fba5b 100644
> >>--- a/include/drm/drm_of.h
> >>+++ b/include/drm/drm_of.h
> >>@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>  				int port, int endpoint,
> >>  				struct drm_panel **panel,
> >>  				struct drm_bridge **bridge);
> >>+struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>  #else
> >>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>  						  struct device_node *port)
> >Minor detail I missed: The dummy version for the #else here is missing.
> >Not a problem for tinydrm, but might be an issue for a driver where
> >CONFIG_OF is optional.
> 
> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> platforms. The only resource that isn't available there is backlight
> since there is no platform or ACPI way of describing that dependency.
> 
> Another problem I discovered when trying to compile this, is that if
> DRM is builtin and LCD_CLASS_DEVICE is a module:
> 
> drivers/gpu/drm/drm_of.c:292: undefined reference to
> `of_find_backlight_by_node'
> 
> I see that I solved this in tinydrm by just selecting
> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> 
> Arnd fixed a similar type of dependecy in the repaper driver by forcing
> repaper to be a module if necessary. To be honest, I don't know why his
> fix works:
> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002

I didn't quite understand how we could use this fix for the current
case. Isn't this specific to the repaper driver dependency ?

> Another way of solving this is to put the function in
> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> that does the selection.
> 
> Noralf.
> 
> >Otherwise I think this patch looks good.
> >-Daniel
> >
> >>diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> >>index d554ded..e40ef2d 100644
> >>--- a/include/drm/tinydrm/tinydrm-helpers.h
> >>+++ b/include/drm/tinydrm/tinydrm-helpers.h
> >>@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> >>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>  			       struct drm_clip_rect *clip);
> >>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> >>  int tinydrm_enable_backlight(struct backlight_device *backlight);
> >>  int tinydrm_disable_backlight(struct backlight_device *backlight);
> >>-- 
> >>2.7.4
> >>
> 

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
> 
> Den 28.09.2017 16.08, skrev Daniel Vetter:
> >On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>because other drivers in the drm subsystem might need to call
> >>this function. In that case and otherwise, it is better from
> >>an organizational point of view to move it into drm_of.c along
> >>with the other _of.c functions.
> >>
> >>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>---
> >>Changes in v3:
> >>-Change it back to a single patch from two patches in v2
> >>
> >>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>  include/drm/drm_of.h                           |  1 +
> >>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>
> >>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>index 8dafbdf..d878d3a 100644
> >>--- a/drivers/gpu/drm/drm_of.c
> >>+++ b/drivers/gpu/drm/drm_of.c
> >>@@ -1,6 +1,7 @@
> >>  #include <linux/component.h>
> >>  #include <linux/export.h>
> >>  #include <linux/list.h>
> >>+#include <linux/backlight.h>
> >>  #include <linux/of_graph.h>
> >>  #include <drm/drmP.h>
> >>  #include <drm/drm_bridge.h>
> >>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>  	return ret;
> >>  }
> >>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>+
> >>+/**
> >>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>+ * @dev: Device
> >>+ *
> >>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>+ * Additionally if the brightness property is zero, it is set to
> >>+ * max_brightness.
> >>+ *
> >>+ * Note: It is the responsibility of the caller to call put_device() when
> >>+ * releasing the resource.
> >>+ *
> >>+ * Returns:
> >>+ * NULL if there's no backlight property.
> >>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>+ * is found.
> >>+ * If the backlight device is found, a pointer to the structure is returned.
> >>+ */
> >>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>+{
> >>+	struct backlight_device *backlight;
> >>+	struct device_node *np;
> >>+
> >>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>+	if (!np)
> >>+		return NULL;
> >>+
> >>+	backlight = of_find_backlight_by_node(np);
> >>+	of_node_put(np);
> >>+
> >>+	if (!backlight)
> >>+		return ERR_PTR(-EPROBE_DEFER);
> >>+
> >>+	if (!backlight->props.brightness) {
> >>+		backlight->props.brightness = backlight->props.max_brightness;
> >>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>+			      backlight->props.brightness);
> >>+	}
> >>+
> >>+	return backlight;
> >>+}
> >>+EXPORT_SYMBOL(drm_of_find_backlight);
> >>diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>index bd6cce0..cd4c6a5 100644
> >>--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> >>  /**
> >>- * tinydrm_of_find_backlight - Find backlight device in device-tree
> >>- * @dev: Device
> >>- *
> >>- * This function looks for a DT node pointed to by a property named 'backlight'
> >>- * and uses of_find_backlight_by_node() to get the backlight device.
> >>- * Additionally if the brightness property is zero, it is set to
> >>- * max_brightness.
> >>- *
> >>- * Returns:
> >>- * NULL if there's no backlight property.
> >>- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>- * is found.
> >>- * If the backlight device is found, a pointer to the structure is returned.
> >>- */
> >>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> >>-{
> >>-	struct backlight_device *backlight;
> >>-	struct device_node *np;
> >>-
> >>-	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>-	if (!np)
> >>-		return NULL;
> >>-
> >>-	backlight = of_find_backlight_by_node(np);
> >>-	of_node_put(np);
> >>-
> >>-	if (!backlight)
> >>-		return ERR_PTR(-EPROBE_DEFER);
> >>-
> >>-	if (!backlight->props.brightness) {
> >>-		backlight->props.brightness = backlight->props.max_brightness;
> >>-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>-			      backlight->props.brightness);
> >>-	}
> >>-
> >>-	return backlight;
> >>-}
> >>-EXPORT_SYMBOL(tinydrm_of_find_backlight);
> >>-
> >>-/**
> >>   * tinydrm_enable_backlight - Enable backlight helper
> >>   * @backlight: Backlight device
> >>   *
> >>diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>index 7e5bb7d..5e3d635 100644
> >>--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>@@ -12,6 +12,7 @@
> >>  #include <drm/tinydrm/ili9341.h>
> >>  #include <drm/tinydrm/mipi-dbi.h>
> >>  #include <drm/tinydrm/tinydrm-helpers.h>
> >>+#include <drm/drm_of.h>
> >>  #include <linux/delay.h>
> >>  #include <linux/gpio/consumer.h>
> >>  #include <linux/module.h>
> >>@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> >>  	if (IS_ERR(mipi->regulator))
> >>  		return PTR_ERR(mipi->regulator);
> >>-	mipi->backlight = tinydrm_of_find_backlight(dev);
> >>+	mipi->backlight = drm_of_find_backlight(dev);
> >>  	if (IS_ERR(mipi->backlight))
> >>  		return PTR_ERR(mipi->backlight);
> >>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>index 104dd51..e8fba5b 100644
> >>--- a/include/drm/drm_of.h
> >>+++ b/include/drm/drm_of.h
> >>@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>  				int port, int endpoint,
> >>  				struct drm_panel **panel,
> >>  				struct drm_bridge **bridge);
> >>+struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>  #else
> >>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>  						  struct device_node *port)
> >Minor detail I missed: The dummy version for the #else here is missing.
> >Not a problem for tinydrm, but might be an issue for a driver where
> >CONFIG_OF is optional.
> 
> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> platforms. The only resource that isn't available there is backlight
> since there is no platform or ACPI way of describing that dependency.
> 
> Another problem I discovered when trying to compile this, is that if
> DRM is builtin and LCD_CLASS_DEVICE is a module:
> 
> drivers/gpu/drm/drm_of.c:292: undefined reference to
> `of_find_backlight_by_node'
> 
> I see that I solved this in tinydrm by just selecting
> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> 
> Arnd fixed a similar type of dependecy in the repaper driver by forcing
> repaper to be a module if necessary. To be honest, I don't know why his
> fix works:
> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002

I didn't quite understand how we could use this fix for the current
case. Isn't this specific to the repaper driver dependency ?

> Another way of solving this is to put the function in
> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> that does the selection.
> 
> Noralf.
> 
> >Otherwise I think this patch looks good.
> >-Daniel
> >
> >>diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> >>index d554ded..e40ef2d 100644
> >>--- a/include/drm/tinydrm/tinydrm-helpers.h
> >>+++ b/include/drm/tinydrm/tinydrm-helpers.h
> >>@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> >>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>  			       struct drm_clip_rect *clip);
> >>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> >>  int tinydrm_enable_backlight(struct backlight_device *backlight);
> >>  int tinydrm_disable_backlight(struct backlight_device *backlight);
> >>-- 
> >>2.7.4
> >>
> 
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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
>> Den 28.09.2017 16.08, skrev Daniel Vetter:
>>> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>>>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>>>> and move it into drm_of.c from tinydrm-helpers.c. This is
>>>> because other drivers in the drm subsystem might need to call
>>>> this function. In that case and otherwise, it is better from
>>>> an organizational point of view to move it into drm_of.c along
>>>> with the other _of.c functions.
>>>>
>>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>>> ---
>>>> Changes in v3:
>>>> -Change it back to a single patch from two patches in v2
>>>>
>>>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>>>   include/drm/drm_of.h                           |  1 +
>>>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>>> index 8dafbdf..d878d3a 100644
>>>> --- a/drivers/gpu/drm/drm_of.c
>>>> +++ b/drivers/gpu/drm/drm_of.c
>>>> @@ -1,6 +1,7 @@
>>>>   #include <linux/component.h>
>>>>   #include <linux/export.h>
>>>>   #include <linux/list.h>
>>>> +#include <linux/backlight.h>
>>>>   #include <linux/of_graph.h>
>>>>   #include <drm/drmP.h>
>>>>   #include <drm/drm_bridge.h>
>>>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>   	return ret;
>>>>   }
>>>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>>>> +
>>>> +/**
>>>> + * drm_of_find_backlight - Find backlight device in device-tree
>>>> + * @dev: Device
>>>> + *
>>>> + * This function looks for a DT node pointed to by a property named 'backlight'
>>>> + * and uses of_find_backlight_by_node() to get the backlight device.
>>>> + * Additionally if the brightness property is zero, it is set to
>>>> + * max_brightness.
>>>> + *
>>>> + * Note: It is the responsibility of the caller to call put_device() when
>>>> + * releasing the resource.
>>>> + *
>>>> + * Returns:
>>>> + * NULL if there's no backlight property.
>>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>> + * is found.
>>>> + * If the backlight device is found, a pointer to the structure is returned.
>>>> + */
>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>> +{
>>>> +	struct backlight_device *backlight;
>>>> +	struct device_node *np;
>>>> +
>>>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>> +	if (!np)
>>>> +		return NULL;
>>>> +
>>>> +	backlight = of_find_backlight_by_node(np);
>>>> +	of_node_put(np);
>>>> +
>>>> +	if (!backlight)
>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>> +
>>>> +	if (!backlight->props.brightness) {
>>>> +		backlight->props.brightness = backlight->props.max_brightness;
>>>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>> +			      backlight->props.brightness);
>>>> +	}
>>>> +
>>>> +	return backlight;
>>>> +}
>>>> +EXPORT_SYMBOL(drm_of_find_backlight);
>>>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>> index bd6cce0..cd4c6a5 100644
>>>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>>>>   /**
>>>> - * tinydrm_of_find_backlight - Find backlight device in device-tree
>>>> - * @dev: Device
>>>> - *
>>>> - * This function looks for a DT node pointed to by a property named 'backlight'
>>>> - * and uses of_find_backlight_by_node() to get the backlight device.
>>>> - * Additionally if the brightness property is zero, it is set to
>>>> - * max_brightness.
>>>> - *
>>>> - * Returns:
>>>> - * NULL if there's no backlight property.
>>>> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>> - * is found.
>>>> - * If the backlight device is found, a pointer to the structure is returned.
>>>> - */
>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
>>>> -{
>>>> -	struct backlight_device *backlight;
>>>> -	struct device_node *np;
>>>> -
>>>> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>> -	if (!np)
>>>> -		return NULL;
>>>> -
>>>> -	backlight = of_find_backlight_by_node(np);
>>>> -	of_node_put(np);
>>>> -
>>>> -	if (!backlight)
>>>> -		return ERR_PTR(-EPROBE_DEFER);
>>>> -
>>>> -	if (!backlight->props.brightness) {
>>>> -		backlight->props.brightness = backlight->props.max_brightness;
>>>> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>> -			      backlight->props.brightness);
>>>> -	}
>>>> -
>>>> -	return backlight;
>>>> -}
>>>> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
>>>> -
>>>> -/**
>>>>    * tinydrm_enable_backlight - Enable backlight helper
>>>>    * @backlight: Backlight device
>>>>    *
>>>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>> index 7e5bb7d..5e3d635 100644
>>>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>> @@ -12,6 +12,7 @@
>>>>   #include <drm/tinydrm/ili9341.h>
>>>>   #include <drm/tinydrm/mipi-dbi.h>
>>>>   #include <drm/tinydrm/tinydrm-helpers.h>
>>>> +#include <drm/drm_of.h>
>>>>   #include <linux/delay.h>
>>>>   #include <linux/gpio/consumer.h>
>>>>   #include <linux/module.h>
>>>> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>>>>   	if (IS_ERR(mipi->regulator))
>>>>   		return PTR_ERR(mipi->regulator);
>>>> -	mipi->backlight = tinydrm_of_find_backlight(dev);
>>>> +	mipi->backlight = drm_of_find_backlight(dev);
>>>>   	if (IS_ERR(mipi->backlight))
>>>>   		return PTR_ERR(mipi->backlight);
>>>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>>>> index 104dd51..e8fba5b 100644
>>>> --- a/include/drm/drm_of.h
>>>> +++ b/include/drm/drm_of.h
>>>> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>   				int port, int endpoint,
>>>>   				struct drm_panel **panel,
>>>>   				struct drm_bridge **bridge);
>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>>>>   #else
>>>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>>>   						  struct device_node *port)
>>> Minor detail I missed: The dummy version for the #else here is missing.
>>> Not a problem for tinydrm, but might be an issue for a driver where
>>> CONFIG_OF is optional.
>> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
>> platforms. The only resource that isn't available there is backlight
>> since there is no platform or ACPI way of describing that dependency.
>>
>> Another problem I discovered when trying to compile this, is that if
>> DRM is builtin and LCD_CLASS_DEVICE is a module:
>>
>> drivers/gpu/drm/drm_of.c:292: undefined reference to
>> `of_find_backlight_by_node'
>>
>> I see that I solved this in tinydrm by just selecting
>> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
>> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
>>
>> Arnd fixed a similar type of dependecy in the repaper driver by forcing
>> repaper to be a module if necessary. To be honest, I don't know why his
>> fix works:
>> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> I didn't quite understand how we could use this fix for the current
> case. Isn't this specific to the repaper driver dependency ?

This is the solution Daniel mentions:

  menuconfig DRM
      tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI 
support)"
      depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
+   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)


We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
That will result in a missing symbol error.

You can try this change to include/linux/backlight.h:

-#ifdef CONFIG_OF
+#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
  struct backlight_device *of_find_backlight_by_node(struct device_node 
*node);
  #else
  static inline struct backlight_device *
  of_find_backlight_by_node(struct device_node *node)
  {
      return NULL;
  }
  #endif

This will need to be a patch of its own since it's another subsystem.

You have to try the various kconfig variations to be sure, I'm no 
kconfig expert.
CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n

Noralf.

>> Another way of solving this is to put the function in
>> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
>> that does the selection.
>>
>> Noralf.
>>
>>> Otherwise I think this patch looks good.
>>> -Daniel
>>>
>>>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>>>> index d554ded..e40ef2d 100644
>>>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>>>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>>>> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>>>>   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>   			       struct drm_clip_rect *clip);
>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>>>>   int tinydrm_enable_backlight(struct backlight_device *backlight);
>>>>   int tinydrm_disable_backlight(struct backlight_device *backlight);
>>>> -- 
>>>> 2.7.4
>>>>

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
>> Den 28.09.2017 16.08, skrev Daniel Vetter:
>>> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>>>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>>>> and move it into drm_of.c from tinydrm-helpers.c. This is
>>>> because other drivers in the drm subsystem might need to call
>>>> this function. In that case and otherwise, it is better from
>>>> an organizational point of view to move it into drm_of.c along
>>>> with the other _of.c functions.
>>>>
>>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>>> ---
>>>> Changes in v3:
>>>> -Change it back to a single patch from two patches in v2
>>>>
>>>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>>>   include/drm/drm_of.h                           |  1 +
>>>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>>> index 8dafbdf..d878d3a 100644
>>>> --- a/drivers/gpu/drm/drm_of.c
>>>> +++ b/drivers/gpu/drm/drm_of.c
>>>> @@ -1,6 +1,7 @@
>>>>   #include <linux/component.h>
>>>>   #include <linux/export.h>
>>>>   #include <linux/list.h>
>>>> +#include <linux/backlight.h>
>>>>   #include <linux/of_graph.h>
>>>>   #include <drm/drmP.h>
>>>>   #include <drm/drm_bridge.h>
>>>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>   	return ret;
>>>>   }
>>>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>>>> +
>>>> +/**
>>>> + * drm_of_find_backlight - Find backlight device in device-tree
>>>> + * @dev: Device
>>>> + *
>>>> + * This function looks for a DT node pointed to by a property named 'backlight'
>>>> + * and uses of_find_backlight_by_node() to get the backlight device.
>>>> + * Additionally if the brightness property is zero, it is set to
>>>> + * max_brightness.
>>>> + *
>>>> + * Note: It is the responsibility of the caller to call put_device() when
>>>> + * releasing the resource.
>>>> + *
>>>> + * Returns:
>>>> + * NULL if there's no backlight property.
>>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>> + * is found.
>>>> + * If the backlight device is found, a pointer to the structure is returned.
>>>> + */
>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>> +{
>>>> +	struct backlight_device *backlight;
>>>> +	struct device_node *np;
>>>> +
>>>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>> +	if (!np)
>>>> +		return NULL;
>>>> +
>>>> +	backlight = of_find_backlight_by_node(np);
>>>> +	of_node_put(np);
>>>> +
>>>> +	if (!backlight)
>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>> +
>>>> +	if (!backlight->props.brightness) {
>>>> +		backlight->props.brightness = backlight->props.max_brightness;
>>>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>> +			      backlight->props.brightness);
>>>> +	}
>>>> +
>>>> +	return backlight;
>>>> +}
>>>> +EXPORT_SYMBOL(drm_of_find_backlight);
>>>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>> index bd6cce0..cd4c6a5 100644
>>>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>>>>   /**
>>>> - * tinydrm_of_find_backlight - Find backlight device in device-tree
>>>> - * @dev: Device
>>>> - *
>>>> - * This function looks for a DT node pointed to by a property named 'backlight'
>>>> - * and uses of_find_backlight_by_node() to get the backlight device.
>>>> - * Additionally if the brightness property is zero, it is set to
>>>> - * max_brightness.
>>>> - *
>>>> - * Returns:
>>>> - * NULL if there's no backlight property.
>>>> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>> - * is found.
>>>> - * If the backlight device is found, a pointer to the structure is returned.
>>>> - */
>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
>>>> -{
>>>> -	struct backlight_device *backlight;
>>>> -	struct device_node *np;
>>>> -
>>>> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>> -	if (!np)
>>>> -		return NULL;
>>>> -
>>>> -	backlight = of_find_backlight_by_node(np);
>>>> -	of_node_put(np);
>>>> -
>>>> -	if (!backlight)
>>>> -		return ERR_PTR(-EPROBE_DEFER);
>>>> -
>>>> -	if (!backlight->props.brightness) {
>>>> -		backlight->props.brightness = backlight->props.max_brightness;
>>>> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>> -			      backlight->props.brightness);
>>>> -	}
>>>> -
>>>> -	return backlight;
>>>> -}
>>>> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
>>>> -
>>>> -/**
>>>>    * tinydrm_enable_backlight - Enable backlight helper
>>>>    * @backlight: Backlight device
>>>>    *
>>>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>> index 7e5bb7d..5e3d635 100644
>>>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>> @@ -12,6 +12,7 @@
>>>>   #include <drm/tinydrm/ili9341.h>
>>>>   #include <drm/tinydrm/mipi-dbi.h>
>>>>   #include <drm/tinydrm/tinydrm-helpers.h>
>>>> +#include <drm/drm_of.h>
>>>>   #include <linux/delay.h>
>>>>   #include <linux/gpio/consumer.h>
>>>>   #include <linux/module.h>
>>>> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>>>>   	if (IS_ERR(mipi->regulator))
>>>>   		return PTR_ERR(mipi->regulator);
>>>> -	mipi->backlight = tinydrm_of_find_backlight(dev);
>>>> +	mipi->backlight = drm_of_find_backlight(dev);
>>>>   	if (IS_ERR(mipi->backlight))
>>>>   		return PTR_ERR(mipi->backlight);
>>>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>>>> index 104dd51..e8fba5b 100644
>>>> --- a/include/drm/drm_of.h
>>>> +++ b/include/drm/drm_of.h
>>>> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>   				int port, int endpoint,
>>>>   				struct drm_panel **panel,
>>>>   				struct drm_bridge **bridge);
>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>>>>   #else
>>>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>>>   						  struct device_node *port)
>>> Minor detail I missed: The dummy version for the #else here is missing.
>>> Not a problem for tinydrm, but might be an issue for a driver where
>>> CONFIG_OF is optional.
>> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
>> platforms. The only resource that isn't available there is backlight
>> since there is no platform or ACPI way of describing that dependency.
>>
>> Another problem I discovered when trying to compile this, is that if
>> DRM is builtin and LCD_CLASS_DEVICE is a module:
>>
>> drivers/gpu/drm/drm_of.c:292: undefined reference to
>> `of_find_backlight_by_node'
>>
>> I see that I solved this in tinydrm by just selecting
>> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
>> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
>>
>> Arnd fixed a similar type of dependecy in the repaper driver by forcing
>> repaper to be a module if necessary. To be honest, I don't know why his
>> fix works:
>> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> I didn't quite understand how we could use this fix for the current
> case. Isn't this specific to the repaper driver dependency ?

This is the solution Daniel mentions:

  menuconfig DRM
      tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI 
support)"
      depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
+   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)


We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
That will result in a missing symbol error.

You can try this change to include/linux/backlight.h:

-#ifdef CONFIG_OF
+#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
  struct backlight_device *of_find_backlight_by_node(struct device_node 
*node);
  #else
  static inline struct backlight_device *
  of_find_backlight_by_node(struct device_node *node)
  {
      return NULL;
  }
  #endif

This will need to be a patch of its own since it's another subsystem.

You have to try the various kconfig variations to be sure, I'm no 
kconfig expert.
CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n

Noralf.

>> Another way of solving this is to put the function in
>> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
>> that does the selection.
>>
>> Noralf.
>>
>>> Otherwise I think this patch looks good.
>>> -Daniel
>>>
>>>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>>>> index d554ded..e40ef2d 100644
>>>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>>>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>>>> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>>>>   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>   			       struct drm_clip_rect *clip);
>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>>>>   int tinydrm_enable_backlight(struct backlight_device *backlight);
>>>>   int tinydrm_disable_backlight(struct backlight_device *backlight);
>>>> -- 
>>>> 2.7.4
>>>>

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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Tr�nnes wrote:
> 
> Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> >On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Tr�nnes wrote:
> >>Den 28.09.2017 16.08, skrev Daniel Vetter:
> >>>On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>>>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>>>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>>>because other drivers in the drm subsystem might need to call
> >>>>this function. In that case and otherwise, it is better from
> >>>>an organizational point of view to move it into drm_of.c along
> >>>>with the other _of.c functions.
> >>>>
> >>>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>>---
> >>>>Changes in v3:
> >>>>-Change it back to a single patch from two patches in v2
> >>>>
> >>>>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>>>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>>>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>>>  include/drm/drm_of.h                           |  1 +
> >>>>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>>>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>>>
> >>>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>>index 8dafbdf..d878d3a 100644
> >>>>--- a/drivers/gpu/drm/drm_of.c
> >>>>+++ b/drivers/gpu/drm/drm_of.c
> >>>>@@ -1,6 +1,7 @@
> >>>>  #include <linux/component.h>
> >>>>  #include <linux/export.h>
> >>>>  #include <linux/list.h>
> >>>>+#include <linux/backlight.h>
> >>>>  #include <linux/of_graph.h>
> >>>>  #include <drm/drmP.h>
> >>>>  #include <drm/drm_bridge.h>
> >>>>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>  	return ret;
> >>>>  }
> >>>>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>>>+
> >>>>+/**
> >>>>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>>>+ * @dev: Device
> >>>>+ *
> >>>>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>+ * Additionally if the brightness property is zero, it is set to
> >>>>+ * max_brightness.
> >>>>+ *
> >>>>+ * Note: It is the responsibility of the caller to call put_device() when
> >>>>+ * releasing the resource.
> >>>>+ *
> >>>>+ * Returns:
> >>>>+ * NULL if there's no backlight property.
> >>>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>+ * is found.
> >>>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>>+ */
> >>>>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>>+{
> >>>>+	struct backlight_device *backlight;
> >>>>+	struct device_node *np;
> >>>>+
> >>>>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>+	if (!np)
> >>>>+		return NULL;
> >>>>+
> >>>>+	backlight = of_find_backlight_by_node(np);
> >>>>+	of_node_put(np);
> >>>>+
> >>>>+	if (!backlight)
> >>>>+		return ERR_PTR(-EPROBE_DEFER);
> >>>>+
> >>>>+	if (!backlight->props.brightness) {
> >>>>+		backlight->props.brightness = backlight->props.max_brightness;
> >>>>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>+			      backlight->props.brightness);
> >>>>+	}
> >>>>+
> >>>>+	return backlight;
> >>>>+}
> >>>>+EXPORT_SYMBOL(drm_of_find_backlight);
> >>>>diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>index bd6cce0..cd4c6a5 100644
> >>>>--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> >>>>  /**
> >>>>- * tinydrm_of_find_backlight - Find backlight device in device-tree
> >>>>- * @dev: Device
> >>>>- *
> >>>>- * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>- * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>- * Additionally if the brightness property is zero, it is set to
> >>>>- * max_brightness.
> >>>>- *
> >>>>- * Returns:
> >>>>- * NULL if there's no backlight property.
> >>>>- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>- * is found.
> >>>>- * If the backlight device is found, a pointer to the structure is returned.
> >>>>- */
> >>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> >>>>-{
> >>>>-	struct backlight_device *backlight;
> >>>>-	struct device_node *np;
> >>>>-
> >>>>-	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>-	if (!np)
> >>>>-		return NULL;
> >>>>-
> >>>>-	backlight = of_find_backlight_by_node(np);
> >>>>-	of_node_put(np);
> >>>>-
> >>>>-	if (!backlight)
> >>>>-		return ERR_PTR(-EPROBE_DEFER);
> >>>>-
> >>>>-	if (!backlight->props.brightness) {
> >>>>-		backlight->props.brightness = backlight->props.max_brightness;
> >>>>-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>-			      backlight->props.brightness);
> >>>>-	}
> >>>>-
> >>>>-	return backlight;
> >>>>-}
> >>>>-EXPORT_SYMBOL(tinydrm_of_find_backlight);
> >>>>-
> >>>>-/**
> >>>>   * tinydrm_enable_backlight - Enable backlight helper
> >>>>   * @backlight: Backlight device
> >>>>   *
> >>>>diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>index 7e5bb7d..5e3d635 100644
> >>>>--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>@@ -12,6 +12,7 @@
> >>>>  #include <drm/tinydrm/ili9341.h>
> >>>>  #include <drm/tinydrm/mipi-dbi.h>
> >>>>  #include <drm/tinydrm/tinydrm-helpers.h>
> >>>>+#include <drm/drm_of.h>
> >>>>  #include <linux/delay.h>
> >>>>  #include <linux/gpio/consumer.h>
> >>>>  #include <linux/module.h>
> >>>>@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> >>>>  	if (IS_ERR(mipi->regulator))
> >>>>  		return PTR_ERR(mipi->regulator);
> >>>>-	mipi->backlight = tinydrm_of_find_backlight(dev);
> >>>>+	mipi->backlight = drm_of_find_backlight(dev);
> >>>>  	if (IS_ERR(mipi->backlight))
> >>>>  		return PTR_ERR(mipi->backlight);
> >>>>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>>>index 104dd51..e8fba5b 100644
> >>>>--- a/include/drm/drm_of.h
> >>>>+++ b/include/drm/drm_of.h
> >>>>@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>  				int port, int endpoint,
> >>>>  				struct drm_panel **panel,
> >>>>  				struct drm_bridge **bridge);
> >>>>+struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>>>  #else
> >>>>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>>>  						  struct device_node *port)
> >>>Minor detail I missed: The dummy version for the #else here is missing.
> >>>Not a problem for tinydrm, but might be an issue for a driver where
> >>>CONFIG_OF is optional.
> >>Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> >>platforms. The only resource that isn't available there is backlight
> >>since there is no platform or ACPI way of describing that dependency.
> >>
> >>Another problem I discovered when trying to compile this, is that if
> >>DRM is builtin and LCD_CLASS_DEVICE is a module:
> >>
> >>drivers/gpu/drm/drm_of.c:292: undefined reference to
> >>`of_find_backlight_by_node'
> >>
> >>I see that I solved this in tinydrm by just selecting
> >>BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> >>force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> >>
> >>Arnd fixed a similar type of dependecy in the repaper driver by forcing
> >>repaper to be a module if necessary. To be honest, I don't know why his
> >>fix works:
> >>https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> >I didn't quite understand how we could use this fix for the current
> >case. Isn't this specific to the repaper driver dependency ?
> 
> This is the solution Daniel mentions:
> 
> �menuconfig DRM
> ���� tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> support)"
> ���� depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> +�� depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)

I had tried this but it resulted in a recursive dependencies error.

Regards,
Meghana
> 
> We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
> That will result in a missing symbol error.
> 
> You can try this change to include/linux/backlight.h:
> 
> -#ifdef CONFIG_OF
> +#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
> �struct backlight_device *of_find_backlight_by_node(struct device_node
> *node);
> �#else
> �static inline struct backlight_device *
> �of_find_backlight_by_node(struct device_node *node)
> �{
> ���� return NULL;
> �}
> �#endif
> 
> This will need to be a patch of its own since it's another subsystem.
> 
> You have to try the various kconfig variations to be sure, I'm no kconfig
> expert.
> CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n
> 
> Noralf.

Sure will try this.

> >>Another way of solving this is to put the function in
> >>drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> >>that does the selection.
> >>
> >>Noralf.
> >>
> >>>Otherwise I think this patch looks good.
> >>>-Daniel
> >>>
> >>>>diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>index d554ded..e40ef2d 100644
> >>>>--- a/include/drm/tinydrm/tinydrm-helpers.h
> >>>>+++ b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> >>>>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>  			       struct drm_clip_rect *clip);
> >>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> >>>>  int tinydrm_enable_backlight(struct backlight_device *backlight);
> >>>>  int tinydrm_disable_backlight(struct backlight_device *backlight);
> >>>>-- 
> >>>>2.7.4
> >>>>
> 

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
> 
> Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> >On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
> >>Den 28.09.2017 16.08, skrev Daniel Vetter:
> >>>On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>>>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>>>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>>>because other drivers in the drm subsystem might need to call
> >>>>this function. In that case and otherwise, it is better from
> >>>>an organizational point of view to move it into drm_of.c along
> >>>>with the other _of.c functions.
> >>>>
> >>>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>>---
> >>>>Changes in v3:
> >>>>-Change it back to a single patch from two patches in v2
> >>>>
> >>>>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>>>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>>>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>>>  include/drm/drm_of.h                           |  1 +
> >>>>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>>>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>>>
> >>>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>>index 8dafbdf..d878d3a 100644
> >>>>--- a/drivers/gpu/drm/drm_of.c
> >>>>+++ b/drivers/gpu/drm/drm_of.c
> >>>>@@ -1,6 +1,7 @@
> >>>>  #include <linux/component.h>
> >>>>  #include <linux/export.h>
> >>>>  #include <linux/list.h>
> >>>>+#include <linux/backlight.h>
> >>>>  #include <linux/of_graph.h>
> >>>>  #include <drm/drmP.h>
> >>>>  #include <drm/drm_bridge.h>
> >>>>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>  	return ret;
> >>>>  }
> >>>>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>>>+
> >>>>+/**
> >>>>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>>>+ * @dev: Device
> >>>>+ *
> >>>>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>+ * Additionally if the brightness property is zero, it is set to
> >>>>+ * max_brightness.
> >>>>+ *
> >>>>+ * Note: It is the responsibility of the caller to call put_device() when
> >>>>+ * releasing the resource.
> >>>>+ *
> >>>>+ * Returns:
> >>>>+ * NULL if there's no backlight property.
> >>>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>+ * is found.
> >>>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>>+ */
> >>>>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>>+{
> >>>>+	struct backlight_device *backlight;
> >>>>+	struct device_node *np;
> >>>>+
> >>>>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>+	if (!np)
> >>>>+		return NULL;
> >>>>+
> >>>>+	backlight = of_find_backlight_by_node(np);
> >>>>+	of_node_put(np);
> >>>>+
> >>>>+	if (!backlight)
> >>>>+		return ERR_PTR(-EPROBE_DEFER);
> >>>>+
> >>>>+	if (!backlight->props.brightness) {
> >>>>+		backlight->props.brightness = backlight->props.max_brightness;
> >>>>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>+			      backlight->props.brightness);
> >>>>+	}
> >>>>+
> >>>>+	return backlight;
> >>>>+}
> >>>>+EXPORT_SYMBOL(drm_of_find_backlight);
> >>>>diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>index bd6cce0..cd4c6a5 100644
> >>>>--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> >>>>  /**
> >>>>- * tinydrm_of_find_backlight - Find backlight device in device-tree
> >>>>- * @dev: Device
> >>>>- *
> >>>>- * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>- * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>- * Additionally if the brightness property is zero, it is set to
> >>>>- * max_brightness.
> >>>>- *
> >>>>- * Returns:
> >>>>- * NULL if there's no backlight property.
> >>>>- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>- * is found.
> >>>>- * If the backlight device is found, a pointer to the structure is returned.
> >>>>- */
> >>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> >>>>-{
> >>>>-	struct backlight_device *backlight;
> >>>>-	struct device_node *np;
> >>>>-
> >>>>-	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>-	if (!np)
> >>>>-		return NULL;
> >>>>-
> >>>>-	backlight = of_find_backlight_by_node(np);
> >>>>-	of_node_put(np);
> >>>>-
> >>>>-	if (!backlight)
> >>>>-		return ERR_PTR(-EPROBE_DEFER);
> >>>>-
> >>>>-	if (!backlight->props.brightness) {
> >>>>-		backlight->props.brightness = backlight->props.max_brightness;
> >>>>-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>-			      backlight->props.brightness);
> >>>>-	}
> >>>>-
> >>>>-	return backlight;
> >>>>-}
> >>>>-EXPORT_SYMBOL(tinydrm_of_find_backlight);
> >>>>-
> >>>>-/**
> >>>>   * tinydrm_enable_backlight - Enable backlight helper
> >>>>   * @backlight: Backlight device
> >>>>   *
> >>>>diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>index 7e5bb7d..5e3d635 100644
> >>>>--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>@@ -12,6 +12,7 @@
> >>>>  #include <drm/tinydrm/ili9341.h>
> >>>>  #include <drm/tinydrm/mipi-dbi.h>
> >>>>  #include <drm/tinydrm/tinydrm-helpers.h>
> >>>>+#include <drm/drm_of.h>
> >>>>  #include <linux/delay.h>
> >>>>  #include <linux/gpio/consumer.h>
> >>>>  #include <linux/module.h>
> >>>>@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> >>>>  	if (IS_ERR(mipi->regulator))
> >>>>  		return PTR_ERR(mipi->regulator);
> >>>>-	mipi->backlight = tinydrm_of_find_backlight(dev);
> >>>>+	mipi->backlight = drm_of_find_backlight(dev);
> >>>>  	if (IS_ERR(mipi->backlight))
> >>>>  		return PTR_ERR(mipi->backlight);
> >>>>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>>>index 104dd51..e8fba5b 100644
> >>>>--- a/include/drm/drm_of.h
> >>>>+++ b/include/drm/drm_of.h
> >>>>@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>  				int port, int endpoint,
> >>>>  				struct drm_panel **panel,
> >>>>  				struct drm_bridge **bridge);
> >>>>+struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>>>  #else
> >>>>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>>>  						  struct device_node *port)
> >>>Minor detail I missed: The dummy version for the #else here is missing.
> >>>Not a problem for tinydrm, but might be an issue for a driver where
> >>>CONFIG_OF is optional.
> >>Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> >>platforms. The only resource that isn't available there is backlight
> >>since there is no platform or ACPI way of describing that dependency.
> >>
> >>Another problem I discovered when trying to compile this, is that if
> >>DRM is builtin and LCD_CLASS_DEVICE is a module:
> >>
> >>drivers/gpu/drm/drm_of.c:292: undefined reference to
> >>`of_find_backlight_by_node'
> >>
> >>I see that I solved this in tinydrm by just selecting
> >>BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> >>force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> >>
> >>Arnd fixed a similar type of dependecy in the repaper driver by forcing
> >>repaper to be a module if necessary. To be honest, I don't know why his
> >>fix works:
> >>https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> >I didn't quite understand how we could use this fix for the current
> >case. Isn't this specific to the repaper driver dependency ?
> 
> This is the solution Daniel mentions:
> 
>  menuconfig DRM
>      tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> support)"
>      depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> +   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)

I had tried this but it resulted in a recursive dependencies error.

Regards,
Meghana
> 
> We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
> That will result in a missing symbol error.
> 
> You can try this change to include/linux/backlight.h:
> 
> -#ifdef CONFIG_OF
> +#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
>  struct backlight_device *of_find_backlight_by_node(struct device_node
> *node);
>  #else
>  static inline struct backlight_device *
>  of_find_backlight_by_node(struct device_node *node)
>  {
>      return NULL;
>  }
>  #endif
> 
> This will need to be a patch of its own since it's another subsystem.
> 
> You have to try the various kconfig variations to be sure, I'm no kconfig
> expert.
> CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n
> 
> Noralf.

Sure will try this.

> >>Another way of solving this is to put the function in
> >>drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> >>that does the selection.
> >>
> >>Noralf.
> >>
> >>>Otherwise I think this patch looks good.
> >>>-Daniel
> >>>
> >>>>diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>index d554ded..e40ef2d 100644
> >>>>--- a/include/drm/tinydrm/tinydrm-helpers.h
> >>>>+++ b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> >>>>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>  			       struct drm_clip_rect *clip);
> >>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> >>>>  int tinydrm_enable_backlight(struct backlight_device *backlight);
> >>>>  int tinydrm_disable_backlight(struct backlight_device *backlight);
> >>>>-- 
> >>>>2.7.4
> >>>>
> 
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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
>> Den 29.09.2017 05.22, skrev Meghana Madhyastha:
>>> On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
>>>> Den 28.09.2017 16.08, skrev Daniel Vetter:
>>>>> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>>>>>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>>>>>> and move it into drm_of.c from tinydrm-helpers.c. This is
>>>>>> because other drivers in the drm subsystem might need to call
>>>>>> this function. In that case and otherwise, it is better from
>>>>>> an organizational point of view to move it into drm_of.c along
>>>>>> with the other _of.c functions.
>>>>>>
>>>>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>>>>> ---
>>>>>> Changes in v3:
>>>>>> -Change it back to a single patch from two patches in v2
>>>>>>
>>>>>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>>>>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>>>>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>>>>>   include/drm/drm_of.h                           |  1 +
>>>>>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>>>>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>>>>> index 8dafbdf..d878d3a 100644
>>>>>> --- a/drivers/gpu/drm/drm_of.c
>>>>>> +++ b/drivers/gpu/drm/drm_of.c
>>>>>> @@ -1,6 +1,7 @@
>>>>>>   #include <linux/component.h>
>>>>>>   #include <linux/export.h>
>>>>>>   #include <linux/list.h>
>>>>>> +#include <linux/backlight.h>
>>>>>>   #include <linux/of_graph.h>
>>>>>>   #include <drm/drmP.h>
>>>>>>   #include <drm/drm_bridge.h>
>>>>>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>>>   	return ret;
>>>>>>   }
>>>>>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>>>>>> +
>>>>>> +/**
>>>>>> + * drm_of_find_backlight - Find backlight device in device-tree
>>>>>> + * @dev: Device
>>>>>> + *
>>>>>> + * This function looks for a DT node pointed to by a property named 'backlight'
>>>>>> + * and uses of_find_backlight_by_node() to get the backlight device.
>>>>>> + * Additionally if the brightness property is zero, it is set to
>>>>>> + * max_brightness.
>>>>>> + *
>>>>>> + * Note: It is the responsibility of the caller to call put_device() when
>>>>>> + * releasing the resource.
>>>>>> + *
>>>>>> + * Returns:
>>>>>> + * NULL if there's no backlight property.
>>>>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>>>> + * is found.
>>>>>> + * If the backlight device is found, a pointer to the structure is returned.
>>>>>> + */
>>>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>>>> +{
>>>>>> +	struct backlight_device *backlight;
>>>>>> +	struct device_node *np;
>>>>>> +
>>>>>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>>>> +	if (!np)
>>>>>> +		return NULL;
>>>>>> +
>>>>>> +	backlight = of_find_backlight_by_node(np);
>>>>>> +	of_node_put(np);
>>>>>> +
>>>>>> +	if (!backlight)
>>>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>>>> +
>>>>>> +	if (!backlight->props.brightness) {
>>>>>> +		backlight->props.brightness = backlight->props.max_brightness;
>>>>>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>>>> +			      backlight->props.brightness);
>>>>>> +	}
>>>>>> +
>>>>>> +	return backlight;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL(drm_of_find_backlight);
>>>>>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>>> index bd6cce0..cd4c6a5 100644
>>>>>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>>> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>>>   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>>>>>>   /**
>>>>>> - * tinydrm_of_find_backlight - Find backlight device in device-tree
>>>>>> - * @dev: Device
>>>>>> - *
>>>>>> - * This function looks for a DT node pointed to by a property named 'backlight'
>>>>>> - * and uses of_find_backlight_by_node() to get the backlight device.
>>>>>> - * Additionally if the brightness property is zero, it is set to
>>>>>> - * max_brightness.
>>>>>> - *
>>>>>> - * Returns:
>>>>>> - * NULL if there's no backlight property.
>>>>>> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>>>> - * is found.
>>>>>> - * If the backlight device is found, a pointer to the structure is returned.
>>>>>> - */
>>>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
>>>>>> -{
>>>>>> -	struct backlight_device *backlight;
>>>>>> -	struct device_node *np;
>>>>>> -
>>>>>> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>>>> -	if (!np)
>>>>>> -		return NULL;
>>>>>> -
>>>>>> -	backlight = of_find_backlight_by_node(np);
>>>>>> -	of_node_put(np);
>>>>>> -
>>>>>> -	if (!backlight)
>>>>>> -		return ERR_PTR(-EPROBE_DEFER);
>>>>>> -
>>>>>> -	if (!backlight->props.brightness) {
>>>>>> -		backlight->props.brightness = backlight->props.max_brightness;
>>>>>> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>>>> -			      backlight->props.brightness);
>>>>>> -	}
>>>>>> -
>>>>>> -	return backlight;
>>>>>> -}
>>>>>> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
>>>>>> -
>>>>>> -/**
>>>>>>    * tinydrm_enable_backlight - Enable backlight helper
>>>>>>    * @backlight: Backlight device
>>>>>>    *
>>>>>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>>> index 7e5bb7d..5e3d635 100644
>>>>>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>>> @@ -12,6 +12,7 @@
>>>>>>   #include <drm/tinydrm/ili9341.h>
>>>>>>   #include <drm/tinydrm/mipi-dbi.h>
>>>>>>   #include <drm/tinydrm/tinydrm-helpers.h>
>>>>>> +#include <drm/drm_of.h>
>>>>>>   #include <linux/delay.h>
>>>>>>   #include <linux/gpio/consumer.h>
>>>>>>   #include <linux/module.h>
>>>>>> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>>>>>>   	if (IS_ERR(mipi->regulator))
>>>>>>   		return PTR_ERR(mipi->regulator);
>>>>>> -	mipi->backlight = tinydrm_of_find_backlight(dev);
>>>>>> +	mipi->backlight = drm_of_find_backlight(dev);
>>>>>>   	if (IS_ERR(mipi->backlight))
>>>>>>   		return PTR_ERR(mipi->backlight);
>>>>>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>>>>>> index 104dd51..e8fba5b 100644
>>>>>> --- a/include/drm/drm_of.h
>>>>>> +++ b/include/drm/drm_of.h
>>>>>> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>>>   				int port, int endpoint,
>>>>>>   				struct drm_panel **panel,
>>>>>>   				struct drm_bridge **bridge);
>>>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>>>>>>   #else
>>>>>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>>>>>   						  struct device_node *port)
>>>>> Minor detail I missed: The dummy version for the #else here is missing.
>>>>> Not a problem for tinydrm, but might be an issue for a driver where
>>>>> CONFIG_OF is optional.
>>>> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
>>>> platforms. The only resource that isn't available there is backlight
>>>> since there is no platform or ACPI way of describing that dependency.
>>>>
>>>> Another problem I discovered when trying to compile this, is that if
>>>> DRM is builtin and LCD_CLASS_DEVICE is a module:
>>>>
>>>> drivers/gpu/drm/drm_of.c:292: undefined reference to
>>>> `of_find_backlight_by_node'
>>>>
>>>> I see that I solved this in tinydrm by just selecting
>>>> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
>>>> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
>>>>
>>>> Arnd fixed a similar type of dependecy in the repaper driver by forcing
>>>> repaper to be a module if necessary. To be honest, I don't know why his
>>>> fix works:
>>>> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
>>> I didn't quite understand how we could use this fix for the current
>>> case. Isn't this specific to the repaper driver dependency ?
>> This is the solution Daniel mentions:
>>
>>   menuconfig DRM
>>       tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
>> support)"
>>       depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
>> +   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> I had tried this but it resulted in a recursive dependencies error.

What's the error?
Could this have something to do with tinydrm selecting backlight and 
depending on DRM?

Noralf.

> Regards,
> Meghana
>> We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
>> That will result in a missing symbol error.
>>
>> You can try this change to include/linux/backlight.h:
>>
>> -#ifdef CONFIG_OF
>> +#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
>>   struct backlight_device *of_find_backlight_by_node(struct device_node
>> *node);
>>   #else
>>   static inline struct backlight_device *
>>   of_find_backlight_by_node(struct device_node *node)
>>   {
>>       return NULL;
>>   }
>>   #endif
>>
>> This will need to be a patch of its own since it's another subsystem.
>>
>> You have to try the various kconfig variations to be sure, I'm no kconfig
>> expert.
>> CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n
>>
>> Noralf.
> Sure will try this.
>
>>>> Another way of solving this is to put the function in
>>>> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
>>>> that does the selection.
>>>>
>>>> Noralf.
>>>>
>>>>> Otherwise I think this patch looks good.
>>>>> -Daniel
>>>>>
>>>>>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>>>>>> index d554ded..e40ef2d 100644
>>>>>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>>>>>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>>>>>> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>>>>>>   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>>>   			       struct drm_clip_rect *clip);
>>>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>>>>>>   int tinydrm_enable_backlight(struct backlight_device *backlight);
>>>>>>   int tinydrm_disable_backlight(struct backlight_device *backlight);
>>>>>> -- 
>>>>>> 2.7.4
>>>>>>

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
>> Den 29.09.2017 05.22, skrev Meghana Madhyastha:
>>> On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
>>>> Den 28.09.2017 16.08, skrev Daniel Vetter:
>>>>> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>>>>>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>>>>>> and move it into drm_of.c from tinydrm-helpers.c. This is
>>>>>> because other drivers in the drm subsystem might need to call
>>>>>> this function. In that case and otherwise, it is better from
>>>>>> an organizational point of view to move it into drm_of.c along
>>>>>> with the other _of.c functions.
>>>>>>
>>>>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>>>>> ---
>>>>>> Changes in v3:
>>>>>> -Change it back to a single patch from two patches in v2
>>>>>>
>>>>>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>>>>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>>>>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>>>>>   include/drm/drm_of.h                           |  1 +
>>>>>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>>>>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>>>>> index 8dafbdf..d878d3a 100644
>>>>>> --- a/drivers/gpu/drm/drm_of.c
>>>>>> +++ b/drivers/gpu/drm/drm_of.c
>>>>>> @@ -1,6 +1,7 @@
>>>>>>   #include <linux/component.h>
>>>>>>   #include <linux/export.h>
>>>>>>   #include <linux/list.h>
>>>>>> +#include <linux/backlight.h>
>>>>>>   #include <linux/of_graph.h>
>>>>>>   #include <drm/drmP.h>
>>>>>>   #include <drm/drm_bridge.h>
>>>>>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>>>   	return ret;
>>>>>>   }
>>>>>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>>>>>> +
>>>>>> +/**
>>>>>> + * drm_of_find_backlight - Find backlight device in device-tree
>>>>>> + * @dev: Device
>>>>>> + *
>>>>>> + * This function looks for a DT node pointed to by a property named 'backlight'
>>>>>> + * and uses of_find_backlight_by_node() to get the backlight device.
>>>>>> + * Additionally if the brightness property is zero, it is set to
>>>>>> + * max_brightness.
>>>>>> + *
>>>>>> + * Note: It is the responsibility of the caller to call put_device() when
>>>>>> + * releasing the resource.
>>>>>> + *
>>>>>> + * Returns:
>>>>>> + * NULL if there's no backlight property.
>>>>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>>>> + * is found.
>>>>>> + * If the backlight device is found, a pointer to the structure is returned.
>>>>>> + */
>>>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>>>> +{
>>>>>> +	struct backlight_device *backlight;
>>>>>> +	struct device_node *np;
>>>>>> +
>>>>>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>>>> +	if (!np)
>>>>>> +		return NULL;
>>>>>> +
>>>>>> +	backlight = of_find_backlight_by_node(np);
>>>>>> +	of_node_put(np);
>>>>>> +
>>>>>> +	if (!backlight)
>>>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>>>> +
>>>>>> +	if (!backlight->props.brightness) {
>>>>>> +		backlight->props.brightness = backlight->props.max_brightness;
>>>>>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>>>> +			      backlight->props.brightness);
>>>>>> +	}
>>>>>> +
>>>>>> +	return backlight;
>>>>>> +}
>>>>>> +EXPORT_SYMBOL(drm_of_find_backlight);
>>>>>> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>>> index bd6cce0..cd4c6a5 100644
>>>>>> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>>> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
>>>>>> @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>>>   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
>>>>>>   /**
>>>>>> - * tinydrm_of_find_backlight - Find backlight device in device-tree
>>>>>> - * @dev: Device
>>>>>> - *
>>>>>> - * This function looks for a DT node pointed to by a property named 'backlight'
>>>>>> - * and uses of_find_backlight_by_node() to get the backlight device.
>>>>>> - * Additionally if the brightness property is zero, it is set to
>>>>>> - * max_brightness.
>>>>>> - *
>>>>>> - * Returns:
>>>>>> - * NULL if there's no backlight property.
>>>>>> - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>>>> - * is found.
>>>>>> - * If the backlight device is found, a pointer to the structure is returned.
>>>>>> - */
>>>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
>>>>>> -{
>>>>>> -	struct backlight_device *backlight;
>>>>>> -	struct device_node *np;
>>>>>> -
>>>>>> -	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>>>> -	if (!np)
>>>>>> -		return NULL;
>>>>>> -
>>>>>> -	backlight = of_find_backlight_by_node(np);
>>>>>> -	of_node_put(np);
>>>>>> -
>>>>>> -	if (!backlight)
>>>>>> -		return ERR_PTR(-EPROBE_DEFER);
>>>>>> -
>>>>>> -	if (!backlight->props.brightness) {
>>>>>> -		backlight->props.brightness = backlight->props.max_brightness;
>>>>>> -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>>>> -			      backlight->props.brightness);
>>>>>> -	}
>>>>>> -
>>>>>> -	return backlight;
>>>>>> -}
>>>>>> -EXPORT_SYMBOL(tinydrm_of_find_backlight);
>>>>>> -
>>>>>> -/**
>>>>>>    * tinydrm_enable_backlight - Enable backlight helper
>>>>>>    * @backlight: Backlight device
>>>>>>    *
>>>>>> diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>>> index 7e5bb7d..5e3d635 100644
>>>>>> --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>>> +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
>>>>>> @@ -12,6 +12,7 @@
>>>>>>   #include <drm/tinydrm/ili9341.h>
>>>>>>   #include <drm/tinydrm/mipi-dbi.h>
>>>>>>   #include <drm/tinydrm/tinydrm-helpers.h>
>>>>>> +#include <drm/drm_of.h>
>>>>>>   #include <linux/delay.h>
>>>>>>   #include <linux/gpio/consumer.h>
>>>>>>   #include <linux/module.h>
>>>>>> @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
>>>>>>   	if (IS_ERR(mipi->regulator))
>>>>>>   		return PTR_ERR(mipi->regulator);
>>>>>> -	mipi->backlight = tinydrm_of_find_backlight(dev);
>>>>>> +	mipi->backlight = drm_of_find_backlight(dev);
>>>>>>   	if (IS_ERR(mipi->backlight))
>>>>>>   		return PTR_ERR(mipi->backlight);
>>>>>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>>>>>> index 104dd51..e8fba5b 100644
>>>>>> --- a/include/drm/drm_of.h
>>>>>> +++ b/include/drm/drm_of.h
>>>>>> @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>>>   				int port, int endpoint,
>>>>>>   				struct drm_panel **panel,
>>>>>>   				struct drm_bridge **bridge);
>>>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev);
>>>>>>   #else
>>>>>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>>>>>   						  struct device_node *port)
>>>>> Minor detail I missed: The dummy version for the #else here is missing.
>>>>> Not a problem for tinydrm, but might be an issue for a driver where
>>>>> CONFIG_OF is optional.
>>>> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
>>>> platforms. The only resource that isn't available there is backlight
>>>> since there is no platform or ACPI way of describing that dependency.
>>>>
>>>> Another problem I discovered when trying to compile this, is that if
>>>> DRM is builtin and LCD_CLASS_DEVICE is a module:
>>>>
>>>> drivers/gpu/drm/drm_of.c:292: undefined reference to
>>>> `of_find_backlight_by_node'
>>>>
>>>> I see that I solved this in tinydrm by just selecting
>>>> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
>>>> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
>>>>
>>>> Arnd fixed a similar type of dependecy in the repaper driver by forcing
>>>> repaper to be a module if necessary. To be honest, I don't know why his
>>>> fix works:
>>>> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
>>> I didn't quite understand how we could use this fix for the current
>>> case. Isn't this specific to the repaper driver dependency ?
>> This is the solution Daniel mentions:
>>
>>   menuconfig DRM
>>       tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
>> support)"
>>       depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
>> +   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> I had tried this but it resulted in a recursive dependencies error.

What's the error?
Could this have something to do with tinydrm selecting backlight and 
depending on DRM?

Noralf.

> Regards,
> Meghana
>> We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
>> That will result in a missing symbol error.
>>
>> You can try this change to include/linux/backlight.h:
>>
>> -#ifdef CONFIG_OF
>> +#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
>>   struct backlight_device *of_find_backlight_by_node(struct device_node
>> *node);
>>   #else
>>   static inline struct backlight_device *
>>   of_find_backlight_by_node(struct device_node *node)
>>   {
>>       return NULL;
>>   }
>>   #endif
>>
>> This will need to be a patch of its own since it's another subsystem.
>>
>> You have to try the various kconfig variations to be sure, I'm no kconfig
>> expert.
>> CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n
>>
>> Noralf.
> Sure will try this.
>
>>>> Another way of solving this is to put the function in
>>>> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
>>>> that does the selection.
>>>>
>>>> Noralf.
>>>>
>>>>> Otherwise I think this patch looks good.
>>>>> -Daniel
>>>>>
>>>>>> diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
>>>>>> index d554ded..e40ef2d 100644
>>>>>> --- a/include/drm/tinydrm/tinydrm-helpers.h
>>>>>> +++ b/include/drm/tinydrm/tinydrm-helpers.h
>>>>>> @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
>>>>>>   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
>>>>>>   			       struct drm_clip_rect *clip);
>>>>>> -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
>>>>>>   int tinydrm_enable_backlight(struct backlight_device *backlight);
>>>>>>   int tinydrm_disable_backlight(struct backlight_device *backlight);
>>>>>> -- 
>>>>>> 2.7.4
>>>>>>

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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Tr�nnes wrote:
> 
> Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> >On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Tr�nnes wrote:
> >>Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> >>>On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Tr�nnes wrote:
> >>>>Den 28.09.2017 16.08, skrev Daniel Vetter:
> >>>>>On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>>>>>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>>>>>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>>>>>because other drivers in the drm subsystem might need to call
> >>>>>>this function. In that case and otherwise, it is better from
> >>>>>>an organizational point of view to move it into drm_of.c along
> >>>>>>with the other _of.c functions.
> >>>>>>
> >>>>>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>>>>---
> >>>>>>Changes in v3:
> >>>>>>-Change it back to a single patch from two patches in v2
> >>>>>>
> >>>>>>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>>>>>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>>>>>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>>>>>  include/drm/drm_of.h                           |  1 +
> >>>>>>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>>>>>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>>>>>
> >>>>>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>>>>index 8dafbdf..d878d3a 100644
> >>>>>>--- a/drivers/gpu/drm/drm_of.c
> >>>>>>+++ b/drivers/gpu/drm/drm_of.c
> >>>>>>@@ -1,6 +1,7 @@
> >>>>>>  #include <linux/component.h>
> >>>>>>  #include <linux/export.h>
> >>>>>>  #include <linux/list.h>
> >>>>>>+#include <linux/backlight.h>
> >>>>>>  #include <linux/of_graph.h>
> >>>>>>  #include <drm/drmP.h>
> >>>>>>  #include <drm/drm_bridge.h>
> >>>>>>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>>>  	return ret;
> >>>>>>  }
> >>>>>>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>>>>>+
> >>>>>>+/**
> >>>>>>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>>>>>+ * @dev: Device
> >>>>>>+ *
> >>>>>>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>>>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>>>+ * Additionally if the brightness property is zero, it is set to
> >>>>>>+ * max_brightness.
> >>>>>>+ *
> >>>>>>+ * Note: It is the responsibility of the caller to call put_device() when
> >>>>>>+ * releasing the resource.
> >>>>>>+ *
> >>>>>>+ * Returns:
> >>>>>>+ * NULL if there's no backlight property.
> >>>>>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>>>+ * is found.
> >>>>>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>>>>+ */
> >>>>>>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>>>>+{
> >>>>>>+	struct backlight_device *backlight;
> >>>>>>+	struct device_node *np;
> >>>>>>+
> >>>>>>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>>>+	if (!np)
> >>>>>>+		return NULL;
> >>>>>>+
> >>>>>>+	backlight = of_find_backlight_by_node(np);
> >>>>>>+	of_node_put(np);
> >>>>>>+
> >>>>>>+	if (!backlight)
> >>>>>>+		return ERR_PTR(-EPROBE_DEFER);
> >>>>>>+
> >>>>>>+	if (!backlight->props.brightness) {
> >>>>>>+		backlight->props.brightness = backlight->props.max_brightness;
> >>>>>>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>>>+			      backlight->props.brightness);
> >>>>>>+	}
> >>>>>>+
> >>>>>>+	return backlight;
> >>>>>>+}
> >>>>>>+EXPORT_SYMBOL(drm_of_find_backlight);
> >>>>>>diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>>>index bd6cce0..cd4c6a5 100644
> >>>>>>--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>>>+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>>>@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>>>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> >>>>>>  /**
> >>>>>>- * tinydrm_of_find_backlight - Find backlight device in device-tree
> >>>>>>- * @dev: Device
> >>>>>>- *
> >>>>>>- * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>>>- * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>>>- * Additionally if the brightness property is zero, it is set to
> >>>>>>- * max_brightness.
> >>>>>>- *
> >>>>>>- * Returns:
> >>>>>>- * NULL if there's no backlight property.
> >>>>>>- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>>>- * is found.
> >>>>>>- * If the backlight device is found, a pointer to the structure is returned.
> >>>>>>- */
> >>>>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> >>>>>>-{
> >>>>>>-	struct backlight_device *backlight;
> >>>>>>-	struct device_node *np;
> >>>>>>-
> >>>>>>-	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>>>-	if (!np)
> >>>>>>-		return NULL;
> >>>>>>-
> >>>>>>-	backlight = of_find_backlight_by_node(np);
> >>>>>>-	of_node_put(np);
> >>>>>>-
> >>>>>>-	if (!backlight)
> >>>>>>-		return ERR_PTR(-EPROBE_DEFER);
> >>>>>>-
> >>>>>>-	if (!backlight->props.brightness) {
> >>>>>>-		backlight->props.brightness = backlight->props.max_brightness;
> >>>>>>-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>>>-			      backlight->props.brightness);
> >>>>>>-	}
> >>>>>>-
> >>>>>>-	return backlight;
> >>>>>>-}
> >>>>>>-EXPORT_SYMBOL(tinydrm_of_find_backlight);
> >>>>>>-
> >>>>>>-/**
> >>>>>>   * tinydrm_enable_backlight - Enable backlight helper
> >>>>>>   * @backlight: Backlight device
> >>>>>>   *
> >>>>>>diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>>>index 7e5bb7d..5e3d635 100644
> >>>>>>--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>>>+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>>>@@ -12,6 +12,7 @@
> >>>>>>  #include <drm/tinydrm/ili9341.h>
> >>>>>>  #include <drm/tinydrm/mipi-dbi.h>
> >>>>>>  #include <drm/tinydrm/tinydrm-helpers.h>
> >>>>>>+#include <drm/drm_of.h>
> >>>>>>  #include <linux/delay.h>
> >>>>>>  #include <linux/gpio/consumer.h>
> >>>>>>  #include <linux/module.h>
> >>>>>>@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> >>>>>>  	if (IS_ERR(mipi->regulator))
> >>>>>>  		return PTR_ERR(mipi->regulator);
> >>>>>>-	mipi->backlight = tinydrm_of_find_backlight(dev);
> >>>>>>+	mipi->backlight = drm_of_find_backlight(dev);
> >>>>>>  	if (IS_ERR(mipi->backlight))
> >>>>>>  		return PTR_ERR(mipi->backlight);
> >>>>>>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>>>>>index 104dd51..e8fba5b 100644
> >>>>>>--- a/include/drm/drm_of.h
> >>>>>>+++ b/include/drm/drm_of.h
> >>>>>>@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>>>  				int port, int endpoint,
> >>>>>>  				struct drm_panel **panel,
> >>>>>>  				struct drm_bridge **bridge);
> >>>>>>+struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>>>>>  #else
> >>>>>>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>>>>>  						  struct device_node *port)
> >>>>>Minor detail I missed: The dummy version for the #else here is missing.
> >>>>>Not a problem for tinydrm, but might be an issue for a driver where
> >>>>>CONFIG_OF is optional.
> >>>>Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> >>>>platforms. The only resource that isn't available there is backlight
> >>>>since there is no platform or ACPI way of describing that dependency.
> >>>>
> >>>>Another problem I discovered when trying to compile this, is that if
> >>>>DRM is builtin and LCD_CLASS_DEVICE is a module:
> >>>>
> >>>>drivers/gpu/drm/drm_of.c:292: undefined reference to
> >>>>`of_find_backlight_by_node'
> >>>>
> >>>>I see that I solved this in tinydrm by just selecting
> >>>>BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> >>>>force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> >>>>
> >>>>Arnd fixed a similar type of dependecy in the repaper driver by forcing
> >>>>repaper to be a module if necessary. To be honest, I don't know why his
> >>>>fix works:
> >>>>https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> >>>I didn't quite understand how we could use this fix for the current
> >>>case. Isn't this specific to the repaper driver dependency ?
> >>This is the solution Daniel mentions:
> >>
> >> �menuconfig DRM
> >> ���� tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> >>support)"
> >> ���� depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> >>+�� depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> >I had tried this but it resulted in a recursive dependencies error.
> 
> What's the error?
> Could this have something to do with tinydrm selecting backlight and
> depending on DRM?
> 
> Noralf.

Looks like a case of circular dependencies. The exact error is this:

scripts/kconfig/mconf  Kconfig
drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
selected by FB_CLPS711X
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
DRM_KMS_FB_HELPER
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
DRM_FBDEV_EMULATION
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
DRM

Long story short, the dependency loop is as follows:

DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
DRM_FBDEV_EMULATION -> DRM

Regards,
Meghana

> >Regards,
> >Meghana
> >>We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
> >>That will result in a missing symbol error.
> >>
> >>You can try this change to include/linux/backlight.h:
> >>
> >>-#ifdef CONFIG_OF
> >>+#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
> >> �struct backlight_device *of_find_backlight_by_node(struct device_node
> >>*node);
> >> �#else
> >> �static inline struct backlight_device *
> >> �of_find_backlight_by_node(struct device_node *node)
> >> �{
> >> ���� return NULL;
> >> �}
> >> �#endif
> >>
> >>This will need to be a patch of its own since it's another subsystem.
> >>
> >>You have to try the various kconfig variations to be sure, I'm no kconfig
> >>expert.
> >>CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n
> >>
> >>Noralf.
> >Sure will try this.
> >
> >>>>Another way of solving this is to put the function in
> >>>>drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> >>>>that does the selection.
> >>>>
> >>>>Noralf.
> >>>>
> >>>>>Otherwise I think this patch looks good.
> >>>>>-Daniel
> >>>>>
> >>>>>>diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>>>index d554ded..e40ef2d 100644
> >>>>>>--- a/include/drm/tinydrm/tinydrm-helpers.h
> >>>>>>+++ b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>>>@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> >>>>>>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>>>  			       struct drm_clip_rect *clip);
> >>>>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> >>>>>>  int tinydrm_enable_backlight(struct backlight_device *backlight);
> >>>>>>  int tinydrm_disable_backlight(struct backlight_device *backlight);
> >>>>>>-- 
> >>>>>>2.7.4
> >>>>>>
> 

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Trønnes wrote:
> 
> Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> >On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
> >>Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> >>>On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
> >>>>Den 28.09.2017 16.08, skrev Daniel Vetter:
> >>>>>On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>>>>>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>>>>>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>>>>>because other drivers in the drm subsystem might need to call
> >>>>>>this function. In that case and otherwise, it is better from
> >>>>>>an organizational point of view to move it into drm_of.c along
> >>>>>>with the other _of.c functions.
> >>>>>>
> >>>>>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>>>>---
> >>>>>>Changes in v3:
> >>>>>>-Change it back to a single patch from two patches in v2
> >>>>>>
> >>>>>>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>>>>>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>>>>>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>>>>>  include/drm/drm_of.h                           |  1 +
> >>>>>>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>>>>>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>>>>>
> >>>>>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>>>>index 8dafbdf..d878d3a 100644
> >>>>>>--- a/drivers/gpu/drm/drm_of.c
> >>>>>>+++ b/drivers/gpu/drm/drm_of.c
> >>>>>>@@ -1,6 +1,7 @@
> >>>>>>  #include <linux/component.h>
> >>>>>>  #include <linux/export.h>
> >>>>>>  #include <linux/list.h>
> >>>>>>+#include <linux/backlight.h>
> >>>>>>  #include <linux/of_graph.h>
> >>>>>>  #include <drm/drmP.h>
> >>>>>>  #include <drm/drm_bridge.h>
> >>>>>>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>>>  	return ret;
> >>>>>>  }
> >>>>>>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>>>>>+
> >>>>>>+/**
> >>>>>>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>>>>>+ * @dev: Device
> >>>>>>+ *
> >>>>>>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>>>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>>>+ * Additionally if the brightness property is zero, it is set to
> >>>>>>+ * max_brightness.
> >>>>>>+ *
> >>>>>>+ * Note: It is the responsibility of the caller to call put_device() when
> >>>>>>+ * releasing the resource.
> >>>>>>+ *
> >>>>>>+ * Returns:
> >>>>>>+ * NULL if there's no backlight property.
> >>>>>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>>>+ * is found.
> >>>>>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>>>>+ */
> >>>>>>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>>>>+{
> >>>>>>+	struct backlight_device *backlight;
> >>>>>>+	struct device_node *np;
> >>>>>>+
> >>>>>>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>>>+	if (!np)
> >>>>>>+		return NULL;
> >>>>>>+
> >>>>>>+	backlight = of_find_backlight_by_node(np);
> >>>>>>+	of_node_put(np);
> >>>>>>+
> >>>>>>+	if (!backlight)
> >>>>>>+		return ERR_PTR(-EPROBE_DEFER);
> >>>>>>+
> >>>>>>+	if (!backlight->props.brightness) {
> >>>>>>+		backlight->props.brightness = backlight->props.max_brightness;
> >>>>>>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>>>+			      backlight->props.brightness);
> >>>>>>+	}
> >>>>>>+
> >>>>>>+	return backlight;
> >>>>>>+}
> >>>>>>+EXPORT_SYMBOL(drm_of_find_backlight);
> >>>>>>diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>>>index bd6cce0..cd4c6a5 100644
> >>>>>>--- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>>>+++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> >>>>>>@@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>>>  EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> >>>>>>  /**
> >>>>>>- * tinydrm_of_find_backlight - Find backlight device in device-tree
> >>>>>>- * @dev: Device
> >>>>>>- *
> >>>>>>- * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>>>- * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>>>- * Additionally if the brightness property is zero, it is set to
> >>>>>>- * max_brightness.
> >>>>>>- *
> >>>>>>- * Returns:
> >>>>>>- * NULL if there's no backlight property.
> >>>>>>- * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>>>- * is found.
> >>>>>>- * If the backlight device is found, a pointer to the structure is returned.
> >>>>>>- */
> >>>>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> >>>>>>-{
> >>>>>>-	struct backlight_device *backlight;
> >>>>>>-	struct device_node *np;
> >>>>>>-
> >>>>>>-	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>>>-	if (!np)
> >>>>>>-		return NULL;
> >>>>>>-
> >>>>>>-	backlight = of_find_backlight_by_node(np);
> >>>>>>-	of_node_put(np);
> >>>>>>-
> >>>>>>-	if (!backlight)
> >>>>>>-		return ERR_PTR(-EPROBE_DEFER);
> >>>>>>-
> >>>>>>-	if (!backlight->props.brightness) {
> >>>>>>-		backlight->props.brightness = backlight->props.max_brightness;
> >>>>>>-		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>>>-			      backlight->props.brightness);
> >>>>>>-	}
> >>>>>>-
> >>>>>>-	return backlight;
> >>>>>>-}
> >>>>>>-EXPORT_SYMBOL(tinydrm_of_find_backlight);
> >>>>>>-
> >>>>>>-/**
> >>>>>>   * tinydrm_enable_backlight - Enable backlight helper
> >>>>>>   * @backlight: Backlight device
> >>>>>>   *
> >>>>>>diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>>>index 7e5bb7d..5e3d635 100644
> >>>>>>--- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>>>+++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> >>>>>>@@ -12,6 +12,7 @@
> >>>>>>  #include <drm/tinydrm/ili9341.h>
> >>>>>>  #include <drm/tinydrm/mipi-dbi.h>
> >>>>>>  #include <drm/tinydrm/tinydrm-helpers.h>
> >>>>>>+#include <drm/drm_of.h>
> >>>>>>  #include <linux/delay.h>
> >>>>>>  #include <linux/gpio/consumer.h>
> >>>>>>  #include <linux/module.h>
> >>>>>>@@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> >>>>>>  	if (IS_ERR(mipi->regulator))
> >>>>>>  		return PTR_ERR(mipi->regulator);
> >>>>>>-	mipi->backlight = tinydrm_of_find_backlight(dev);
> >>>>>>+	mipi->backlight = drm_of_find_backlight(dev);
> >>>>>>  	if (IS_ERR(mipi->backlight))
> >>>>>>  		return PTR_ERR(mipi->backlight);
> >>>>>>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>>>>>index 104dd51..e8fba5b 100644
> >>>>>>--- a/include/drm/drm_of.h
> >>>>>>+++ b/include/drm/drm_of.h
> >>>>>>@@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>>>  				int port, int endpoint,
> >>>>>>  				struct drm_panel **panel,
> >>>>>>  				struct drm_bridge **bridge);
> >>>>>>+struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>>>>>  #else
> >>>>>>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>>>>>  						  struct device_node *port)
> >>>>>Minor detail I missed: The dummy version for the #else here is missing.
> >>>>>Not a problem for tinydrm, but might be an issue for a driver where
> >>>>>CONFIG_OF is optional.
> >>>>Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> >>>>platforms. The only resource that isn't available there is backlight
> >>>>since there is no platform or ACPI way of describing that dependency.
> >>>>
> >>>>Another problem I discovered when trying to compile this, is that if
> >>>>DRM is builtin and LCD_CLASS_DEVICE is a module:
> >>>>
> >>>>drivers/gpu/drm/drm_of.c:292: undefined reference to
> >>>>`of_find_backlight_by_node'
> >>>>
> >>>>I see that I solved this in tinydrm by just selecting
> >>>>BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> >>>>force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> >>>>
> >>>>Arnd fixed a similar type of dependecy in the repaper driver by forcing
> >>>>repaper to be a module if necessary. To be honest, I don't know why his
> >>>>fix works:
> >>>>https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> >>>I didn't quite understand how we could use this fix for the current
> >>>case. Isn't this specific to the repaper driver dependency ?
> >>This is the solution Daniel mentions:
> >>
> >>  menuconfig DRM
> >>      tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> >>support)"
> >>      depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> >>+   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> >I had tried this but it resulted in a recursive dependencies error.
> 
> What's the error?
> Could this have something to do with tinydrm selecting backlight and
> depending on DRM?
> 
> Noralf.

Looks like a case of circular dependencies. The exact error is this:

scripts/kconfig/mconf  Kconfig
drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
selected by FB_CLPS711X
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
DRM_KMS_FB_HELPER
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
DRM_FBDEV_EMULATION
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
DRM

Long story short, the dependency loop is as follows:

DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
DRM_FBDEV_EMULATION -> DRM

Regards,
Meghana

> >Regards,
> >Meghana
> >>We also have another problem: CONFIG_OF=y && CONFIG_LCD_CLASS_DEVICE=n
> >>That will result in a missing symbol error.
> >>
> >>You can try this change to include/linux/backlight.h:
> >>
> >>-#ifdef CONFIG_OF
> >>+#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_LCD_CLASS_DEVICE)
> >>  struct backlight_device *of_find_backlight_by_node(struct device_node
> >>*node);
> >>  #else
> >>  static inline struct backlight_device *
> >>  of_find_backlight_by_node(struct device_node *node)
> >>  {
> >>      return NULL;
> >>  }
> >>  #endif
> >>
> >>This will need to be a patch of its own since it's another subsystem.
> >>
> >>You have to try the various kconfig variations to be sure, I'm no kconfig
> >>expert.
> >>CONFIG_OF=y/n, CONFIG_DRM=y/m, CONFIG_LCD_CLASS_DEVICE=y/m/n
> >>
> >>Noralf.
> >Sure will try this.
> >
> >>>>Another way of solving this is to put the function in
> >>>>drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> >>>>that does the selection.
> >>>>
> >>>>Noralf.
> >>>>
> >>>>>Otherwise I think this patch looks good.
> >>>>>-Daniel
> >>>>>
> >>>>>>diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>>>index d554ded..e40ef2d 100644
> >>>>>>--- a/include/drm/tinydrm/tinydrm-helpers.h
> >>>>>>+++ b/include/drm/tinydrm/tinydrm-helpers.h
> >>>>>>@@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> >>>>>>  void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> >>>>>>  			       struct drm_clip_rect *clip);
> >>>>>>-struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> >>>>>>  int tinydrm_enable_backlight(struct backlight_device *backlight);
> >>>>>>  int tinydrm_disable_backlight(struct backlight_device *backlight);
> >>>>>>-- 
> >>>>>>2.7.4
> >>>>>>
> 
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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 29.09.2017 16.13, skrev Meghana Madhyastha:
> On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Trønnes wrote:
>> Den 29.09.2017 14.20, skrev Meghana Madhyastha:
>>> On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
>>>> Den 29.09.2017 05.22, skrev Meghana Madhyastha:
>>>>> On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
>>>>>> Den 28.09.2017 16.08, skrev Daniel Vetter:
>>>>>>> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>>>>>>>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>>>>>>>> and move it into drm_of.c from tinydrm-helpers.c. This is
>>>>>>>> because other drivers in the drm subsystem might need to call
>>>>>>>> this function. In that case and otherwise, it is better from
>>>>>>>> an organizational point of view to move it into drm_of.c along
>>>>>>>> with the other _of.c functions.
>>>>>>>>
>>>>>>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>>>>>>> ---
>>>>>>>> Changes in v3:
>>>>>>>> -Change it back to a single patch from two patches in v2
>>>>>>>>
>>>>>>>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>>>>>>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>>>>>>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>>>>>>>   include/drm/drm_of.h                           |  1 +
>>>>>>>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>>>>>>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>>>>>>> index 8dafbdf..d878d3a 100644
>>>>>>>> --- a/drivers/gpu/drm/drm_of.c
>>>>>>>> +++ b/drivers/gpu/drm/drm_of.c
>>>>>>>> @@ -1,6 +1,7 @@
>>>>>>>>   #include <linux/component.h>
>>>>>>>>   #include <linux/export.h>
>>>>>>>>   #include <linux/list.h>
>>>>>>>> +#include <linux/backlight.h>
>>>>>>>>   #include <linux/of_graph.h>
>>>>>>>>   #include <drm/drmP.h>
>>>>>>>>   #include <drm/drm_bridge.h>
>>>>>>>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>>>>>   	return ret;
>>>>>>>>   }
>>>>>>>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_of_find_backlight - Find backlight device in device-tree
>>>>>>>> + * @dev: Device
>>>>>>>> + *
>>>>>>>> + * This function looks for a DT node pointed to by a property named 'backlight'
>>>>>>>> + * and uses of_find_backlight_by_node() to get the backlight device.
>>>>>>>> + * Additionally if the brightness property is zero, it is set to
>>>>>>>> + * max_brightness.
>>>>>>>> + *
>>>>>>>> + * Note: It is the responsibility of the caller to call put_device() when
>>>>>>>> + * releasing the resource.
>>>>>>>> + *
>>>>>>>> + * Returns:
>>>>>>>> + * NULL if there's no backlight property.
>>>>>>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>>>>>> + * is found.
>>>>>>>> + * If the backlight device is found, a pointer to the structure is returned.
>>>>>>>> + */
>>>>>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>>>>>> +{
>>>>>>>> +	struct backlight_device *backlight;
>>>>>>>> +	struct device_node *np;
>>>>>>>> +
>>>>>>>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>>>>>> +	if (!np)
>>>>>>>> +		return NULL;
>>>>>>>> +
>>>>>>>> +	backlight = of_find_backlight_by_node(np);
>>>>>>>> +	of_node_put(np);
>>>>>>>> +
>>>>>>>> +	if (!backlight)
>>>>>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>>>>>> +
>>>>>>>> +	if (!backlight->props.brightness) {
>>>>>>>> +		backlight->props.brightness = backlight->props.max_brightness;
>>>>>>>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>>>>>> +			      backlight->props.brightness);
>>>>>>>> +	}
>>>>>>>> +
>>>>>>>> +	return backlight;
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL(drm_of_find_backlight);

<snip>

>>>>>> Another problem I discovered when trying to compile this, is that if
>>>>>> DRM is builtin and LCD_CLASS_DEVICE is a module:
>>>>>>
>>>>>> drivers/gpu/drm/drm_of.c:292: undefined reference to
>>>>>> `of_find_backlight_by_node'
>>>>>>
>>>>>> I see that I solved this in tinydrm by just selecting
>>>>>> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
>>>>>> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
>>>>>>
>>>>>> Arnd fixed a similar type of dependecy in the repaper driver by forcing
>>>>>> repaper to be a module if necessary. To be honest, I don't know why his
>>>>>> fix works:
>>>>>> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
>>>>> I didn't quite understand how we could use this fix for the current
>>>>> case. Isn't this specific to the repaper driver dependency ?
>>>> This is the solution Daniel mentions:
>>>>
>>>>   menuconfig DRM
>>>>       tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
>>>> support)"
>>>>       depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
>>>> +   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
>>> I had tried this but it resulted in a recursive dependencies error.
>> What's the error?
>> Could this have something to do with tinydrm selecting backlight and
>> depending on DRM?
>>
>> Noralf.
> Looks like a case of circular dependencies. The exact error is this:
>
> scripts/kconfig/mconf  Kconfig
> drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
> selected by FB_CLPS711X
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
> DRM_KMS_FB_HELPER
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
> DRM_FBDEV_EMULATION
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
> DRM
>
> Long story short, the dependency loop is as follows:
>
> DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
> DRM_FBDEV_EMULATION -> DRM

I have messed up the options here, it should be BACKLIGHT_CLASS_DEVICE:

menuconfig DRM
     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)

It doesn't help with the recusrsive problem, but at least it makes sense:

drivers/gpu/drm/Kconfig:7:      symbol DRM depends on BACKLIGHT_CLASS_DEVICE
drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is 
selected by DRM_RADEON
drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM

I don't know how to solve this...

Noralf.

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 29.09.2017 16.13, skrev Meghana Madhyastha:
> On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Trønnes wrote:
>> Den 29.09.2017 14.20, skrev Meghana Madhyastha:
>>> On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
>>>> Den 29.09.2017 05.22, skrev Meghana Madhyastha:
>>>>> On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
>>>>>> Den 28.09.2017 16.08, skrev Daniel Vetter:
>>>>>>> On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
>>>>>>>> Rename tinydrm_of_find_backlight to drm_of_find_backlight
>>>>>>>> and move it into drm_of.c from tinydrm-helpers.c. This is
>>>>>>>> because other drivers in the drm subsystem might need to call
>>>>>>>> this function. In that case and otherwise, it is better from
>>>>>>>> an organizational point of view to move it into drm_of.c along
>>>>>>>> with the other _of.c functions.
>>>>>>>>
>>>>>>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>>>>>>> ---
>>>>>>>> Changes in v3:
>>>>>>>> -Change it back to a single patch from two patches in v2
>>>>>>>>
>>>>>>>>   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
>>>>>>>>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
>>>>>>>>   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
>>>>>>>>   include/drm/drm_of.h                           |  1 +
>>>>>>>>   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
>>>>>>>>   5 files changed, 47 insertions(+), 42 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>>>>>>> index 8dafbdf..d878d3a 100644
>>>>>>>> --- a/drivers/gpu/drm/drm_of.c
>>>>>>>> +++ b/drivers/gpu/drm/drm_of.c
>>>>>>>> @@ -1,6 +1,7 @@
>>>>>>>>   #include <linux/component.h>
>>>>>>>>   #include <linux/export.h>
>>>>>>>>   #include <linux/list.h>
>>>>>>>> +#include <linux/backlight.h>
>>>>>>>>   #include <linux/of_graph.h>
>>>>>>>>   #include <drm/drmP.h>
>>>>>>>>   #include <drm/drm_bridge.h>
>>>>>>>> @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>>>>>>   	return ret;
>>>>>>>>   }
>>>>>>>>   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
>>>>>>>> +
>>>>>>>> +/**
>>>>>>>> + * drm_of_find_backlight - Find backlight device in device-tree
>>>>>>>> + * @dev: Device
>>>>>>>> + *
>>>>>>>> + * This function looks for a DT node pointed to by a property named 'backlight'
>>>>>>>> + * and uses of_find_backlight_by_node() to get the backlight device.
>>>>>>>> + * Additionally if the brightness property is zero, it is set to
>>>>>>>> + * max_brightness.
>>>>>>>> + *
>>>>>>>> + * Note: It is the responsibility of the caller to call put_device() when
>>>>>>>> + * releasing the resource.
>>>>>>>> + *
>>>>>>>> + * Returns:
>>>>>>>> + * NULL if there's no backlight property.
>>>>>>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>>>>>>> + * is found.
>>>>>>>> + * If the backlight device is found, a pointer to the structure is returned.
>>>>>>>> + */
>>>>>>>> +struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>>>>>> +{
>>>>>>>> +	struct backlight_device *backlight;
>>>>>>>> +	struct device_node *np;
>>>>>>>> +
>>>>>>>> +	np = of_parse_phandle(dev->of_node, "backlight", 0);
>>>>>>>> +	if (!np)
>>>>>>>> +		return NULL;
>>>>>>>> +
>>>>>>>> +	backlight = of_find_backlight_by_node(np);
>>>>>>>> +	of_node_put(np);
>>>>>>>> +
>>>>>>>> +	if (!backlight)
>>>>>>>> +		return ERR_PTR(-EPROBE_DEFER);
>>>>>>>> +
>>>>>>>> +	if (!backlight->props.brightness) {
>>>>>>>> +		backlight->props.brightness = backlight->props.max_brightness;
>>>>>>>> +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
>>>>>>>> +			      backlight->props.brightness);
>>>>>>>> +	}
>>>>>>>> +
>>>>>>>> +	return backlight;
>>>>>>>> +}
>>>>>>>> +EXPORT_SYMBOL(drm_of_find_backlight);

<snip>

>>>>>> Another problem I discovered when trying to compile this, is that if
>>>>>> DRM is builtin and LCD_CLASS_DEVICE is a module:
>>>>>>
>>>>>> drivers/gpu/drm/drm_of.c:292: undefined reference to
>>>>>> `of_find_backlight_by_node'
>>>>>>
>>>>>> I see that I solved this in tinydrm by just selecting
>>>>>> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
>>>>>> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
>>>>>>
>>>>>> Arnd fixed a similar type of dependecy in the repaper driver by forcing
>>>>>> repaper to be a module if necessary. To be honest, I don't know why his
>>>>>> fix works:
>>>>>> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
>>>>> I didn't quite understand how we could use this fix for the current
>>>>> case. Isn't this specific to the repaper driver dependency ?
>>>> This is the solution Daniel mentions:
>>>>
>>>>   menuconfig DRM
>>>>       tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
>>>> support)"
>>>>       depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
>>>> +   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
>>> I had tried this but it resulted in a recursive dependencies error.
>> What's the error?
>> Could this have something to do with tinydrm selecting backlight and
>> depending on DRM?
>>
>> Noralf.
> Looks like a case of circular dependencies. The exact error is this:
>
> scripts/kconfig/mconf  Kconfig
> drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
> selected by FB_CLPS711X
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
> DRM_KMS_FB_HELPER
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
> DRM_FBDEV_EMULATION
> For a resolution refer to Documentation/kbuild/kconfig-language.txt
> subsection "Kconfig recursive dependency limitations"
> drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
> DRM
>
> Long story short, the dependency loop is as follows:
>
> DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
> DRM_FBDEV_EMULATION -> DRM

I have messed up the options here, it should be BACKLIGHT_CLASS_DEVICE:

menuconfig DRM
     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)

It doesn't help with the recusrsive problem, but at least it makes sense:

drivers/gpu/drm/Kconfig:7:      symbol DRM depends on BACKLIGHT_CLASS_DEVICE
drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is 
selected by DRM_RADEON
drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM

I don't know how to solve this...

Noralf.

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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 05:41:04PM +0200, Noralf Tr�nnes wrote:
> 
> Den 29.09.2017 16.13, skrev Meghana Madhyastha:
> >On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Tr�nnes wrote:
> >>Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> >>>On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Tr�nnes wrote:
> >>>>Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> >>>>>On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Tr�nnes wrote:
> >>>>>>Den 28.09.2017 16.08, skrev Daniel Vetter:
> >>>>>>>On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>>>>>>>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>>>>>>>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>>>>>>>because other drivers in the drm subsystem might need to call
> >>>>>>>>this function. In that case and otherwise, it is better from
> >>>>>>>>an organizational point of view to move it into drm_of.c along
> >>>>>>>>with the other _of.c functions.
> >>>>>>>>
> >>>>>>>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>>>>>>---
> >>>>>>>>Changes in v3:
> >>>>>>>>-Change it back to a single patch from two patches in v2
> >>>>>>>>
> >>>>>>>>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>>>>>>>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>>>>>>>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>>>>>>>  include/drm/drm_of.h                           |  1 +
> >>>>>>>>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>>>>>>>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>>>>>>>
> >>>>>>>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>>>>>>index 8dafbdf..d878d3a 100644
> >>>>>>>>--- a/drivers/gpu/drm/drm_of.c
> >>>>>>>>+++ b/drivers/gpu/drm/drm_of.c
> >>>>>>>>@@ -1,6 +1,7 @@
> >>>>>>>>  #include <linux/component.h>
> >>>>>>>>  #include <linux/export.h>
> >>>>>>>>  #include <linux/list.h>
> >>>>>>>>+#include <linux/backlight.h>
> >>>>>>>>  #include <linux/of_graph.h>
> >>>>>>>>  #include <drm/drmP.h>
> >>>>>>>>  #include <drm/drm_bridge.h>
> >>>>>>>>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>>>>>  	return ret;
> >>>>>>>>  }
> >>>>>>>>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>>>>>>>+
> >>>>>>>>+/**
> >>>>>>>>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>>>>>>>+ * @dev: Device
> >>>>>>>>+ *
> >>>>>>>>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>>>>>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>>>>>+ * Additionally if the brightness property is zero, it is set to
> >>>>>>>>+ * max_brightness.
> >>>>>>>>+ *
> >>>>>>>>+ * Note: It is the responsibility of the caller to call put_device() when
> >>>>>>>>+ * releasing the resource.
> >>>>>>>>+ *
> >>>>>>>>+ * Returns:
> >>>>>>>>+ * NULL if there's no backlight property.
> >>>>>>>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>>>>>+ * is found.
> >>>>>>>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>>>>>>+ */
> >>>>>>>>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>>>>>>+{
> >>>>>>>>+	struct backlight_device *backlight;
> >>>>>>>>+	struct device_node *np;
> >>>>>>>>+
> >>>>>>>>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>>>>>+	if (!np)
> >>>>>>>>+		return NULL;
> >>>>>>>>+
> >>>>>>>>+	backlight = of_find_backlight_by_node(np);
> >>>>>>>>+	of_node_put(np);
> >>>>>>>>+
> >>>>>>>>+	if (!backlight)
> >>>>>>>>+		return ERR_PTR(-EPROBE_DEFER);
> >>>>>>>>+
> >>>>>>>>+	if (!backlight->props.brightness) {
> >>>>>>>>+		backlight->props.brightness = backlight->props.max_brightness;
> >>>>>>>>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>>>>>+			      backlight->props.brightness);
> >>>>>>>>+	}
> >>>>>>>>+
> >>>>>>>>+	return backlight;
> >>>>>>>>+}
> >>>>>>>>+EXPORT_SYMBOL(drm_of_find_backlight);
> 
> <snip>
> 
> >>>>>>Another problem I discovered when trying to compile this, is that if
> >>>>>>DRM is builtin and LCD_CLASS_DEVICE is a module:
> >>>>>>
> >>>>>>drivers/gpu/drm/drm_of.c:292: undefined reference to
> >>>>>>`of_find_backlight_by_node'
> >>>>>>
> >>>>>>I see that I solved this in tinydrm by just selecting
> >>>>>>BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> >>>>>>force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> >>>>>>
> >>>>>>Arnd fixed a similar type of dependecy in the repaper driver by forcing
> >>>>>>repaper to be a module if necessary. To be honest, I don't know why his
> >>>>>>fix works:
> >>>>>>https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> >>>>>I didn't quite understand how we could use this fix for the current
> >>>>>case. Isn't this specific to the repaper driver dependency ?
> >>>>This is the solution Daniel mentions:
> >>>>
> >>>> �menuconfig DRM
> >>>> ���� tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> >>>>support)"
> >>>> ���� depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> >>>>+�� depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> >>>I had tried this but it resulted in a recursive dependencies error.
> >>What's the error?
> >>Could this have something to do with tinydrm selecting backlight and
> >>depending on DRM?
> >>
> >>Noralf.
> >Looks like a case of circular dependencies. The exact error is this:
> >
> >scripts/kconfig/mconf  Kconfig
> >drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
> >selected by FB_CLPS711X
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
> >DRM_KMS_FB_HELPER
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
> >DRM_FBDEV_EMULATION
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
> >DRM
> >
> >Long story short, the dependency loop is as follows:
> >
> >DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
> >DRM_FBDEV_EMULATION -> DRM
> 
> I have messed up the options here, it should be BACKLIGHT_CLASS_DEVICE:
> 
> menuconfig DRM
> ��� depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> 
> It doesn't help with the recusrsive problem, but at least it makes sense:
> 
> drivers/gpu/drm/Kconfig:7:����� symbol DRM depends on BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:158:��� symbol BACKLIGHT_CLASS_DEVICE is
> selected by DRM_RADEON
> drivers/gpu/drm/Kconfig:164:��� symbol DRM_RADEON depends on DRM
> 
> I don't know how to solve this...
> 
> Noralf.

Looks like select BACKLIGHT_CLASS_DEVICE and BACKLIGHT_LCD_SUPPORT
seemed to work (atleast when I replicated the configurations from the 
kbuild support). Maybe that is because we are not forcing the
dependencies when we do a select ?

Thanks and regards,
Meghana

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 05:41:04PM +0200, Noralf Trønnes wrote:
> 
> Den 29.09.2017 16.13, skrev Meghana Madhyastha:
> >On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Trønnes wrote:
> >>Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> >>>On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
> >>>>Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> >>>>>On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
> >>>>>>Den 28.09.2017 16.08, skrev Daniel Vetter:
> >>>>>>>On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> >>>>>>>>Rename tinydrm_of_find_backlight to drm_of_find_backlight
> >>>>>>>>and move it into drm_of.c from tinydrm-helpers.c. This is
> >>>>>>>>because other drivers in the drm subsystem might need to call
> >>>>>>>>this function. In that case and otherwise, it is better from
> >>>>>>>>an organizational point of view to move it into drm_of.c along
> >>>>>>>>with the other _of.c functions.
> >>>>>>>>
> >>>>>>>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>>>>>>---
> >>>>>>>>Changes in v3:
> >>>>>>>>-Change it back to a single patch from two patches in v2
> >>>>>>>>
> >>>>>>>>  drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> >>>>>>>>  drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> >>>>>>>>  drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> >>>>>>>>  include/drm/drm_of.h                           |  1 +
> >>>>>>>>  include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> >>>>>>>>  5 files changed, 47 insertions(+), 42 deletions(-)
> >>>>>>>>
> >>>>>>>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>>>>>>index 8dafbdf..d878d3a 100644
> >>>>>>>>--- a/drivers/gpu/drm/drm_of.c
> >>>>>>>>+++ b/drivers/gpu/drm/drm_of.c
> >>>>>>>>@@ -1,6 +1,7 @@
> >>>>>>>>  #include <linux/component.h>
> >>>>>>>>  #include <linux/export.h>
> >>>>>>>>  #include <linux/list.h>
> >>>>>>>>+#include <linux/backlight.h>
> >>>>>>>>  #include <linux/of_graph.h>
> >>>>>>>>  #include <drm/drmP.h>
> >>>>>>>>  #include <drm/drm_bridge.h>
> >>>>>>>>@@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>>>>>>  	return ret;
> >>>>>>>>  }
> >>>>>>>>  EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> >>>>>>>>+
> >>>>>>>>+/**
> >>>>>>>>+ * drm_of_find_backlight - Find backlight device in device-tree
> >>>>>>>>+ * @dev: Device
> >>>>>>>>+ *
> >>>>>>>>+ * This function looks for a DT node pointed to by a property named 'backlight'
> >>>>>>>>+ * and uses of_find_backlight_by_node() to get the backlight device.
> >>>>>>>>+ * Additionally if the brightness property is zero, it is set to
> >>>>>>>>+ * max_brightness.
> >>>>>>>>+ *
> >>>>>>>>+ * Note: It is the responsibility of the caller to call put_device() when
> >>>>>>>>+ * releasing the resource.
> >>>>>>>>+ *
> >>>>>>>>+ * Returns:
> >>>>>>>>+ * NULL if there's no backlight property.
> >>>>>>>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>>>>>>+ * is found.
> >>>>>>>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>>>>>>+ */
> >>>>>>>>+struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>>>>>>+{
> >>>>>>>>+	struct backlight_device *backlight;
> >>>>>>>>+	struct device_node *np;
> >>>>>>>>+
> >>>>>>>>+	np = of_parse_phandle(dev->of_node, "backlight", 0);
> >>>>>>>>+	if (!np)
> >>>>>>>>+		return NULL;
> >>>>>>>>+
> >>>>>>>>+	backlight = of_find_backlight_by_node(np);
> >>>>>>>>+	of_node_put(np);
> >>>>>>>>+
> >>>>>>>>+	if (!backlight)
> >>>>>>>>+		return ERR_PTR(-EPROBE_DEFER);
> >>>>>>>>+
> >>>>>>>>+	if (!backlight->props.brightness) {
> >>>>>>>>+		backlight->props.brightness = backlight->props.max_brightness;
> >>>>>>>>+		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> >>>>>>>>+			      backlight->props.brightness);
> >>>>>>>>+	}
> >>>>>>>>+
> >>>>>>>>+	return backlight;
> >>>>>>>>+}
> >>>>>>>>+EXPORT_SYMBOL(drm_of_find_backlight);
> 
> <snip>
> 
> >>>>>>Another problem I discovered when trying to compile this, is that if
> >>>>>>DRM is builtin and LCD_CLASS_DEVICE is a module:
> >>>>>>
> >>>>>>drivers/gpu/drm/drm_of.c:292: undefined reference to
> >>>>>>`of_find_backlight_by_node'
> >>>>>>
> >>>>>>I see that I solved this in tinydrm by just selecting
> >>>>>>BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> >>>>>>force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> >>>>>>
> >>>>>>Arnd fixed a similar type of dependecy in the repaper driver by forcing
> >>>>>>repaper to be a module if necessary. To be honest, I don't know why his
> >>>>>>fix works:
> >>>>>>https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> >>>>>I didn't quite understand how we could use this fix for the current
> >>>>>case. Isn't this specific to the repaper driver dependency ?
> >>>>This is the solution Daniel mentions:
> >>>>
> >>>>  menuconfig DRM
> >>>>      tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> >>>>support)"
> >>>>      depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> >>>>+   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> >>>I had tried this but it resulted in a recursive dependencies error.
> >>What's the error?
> >>Could this have something to do with tinydrm selecting backlight and
> >>depending on DRM?
> >>
> >>Noralf.
> >Looks like a case of circular dependencies. The exact error is this:
> >
> >scripts/kconfig/mconf  Kconfig
> >drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
> >selected by FB_CLPS711X
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
> >DRM_KMS_FB_HELPER
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
> >DRM_FBDEV_EMULATION
> >For a resolution refer to Documentation/kbuild/kconfig-language.txt
> >subsection "Kconfig recursive dependency limitations"
> >drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
> >DRM
> >
> >Long story short, the dependency loop is as follows:
> >
> >DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
> >DRM_FBDEV_EMULATION -> DRM
> 
> I have messed up the options here, it should be BACKLIGHT_CLASS_DEVICE:
> 
> menuconfig DRM
>     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> 
> It doesn't help with the recusrsive problem, but at least it makes sense:
> 
> drivers/gpu/drm/Kconfig:7:      symbol DRM depends on BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is
> selected by DRM_RADEON
> drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM
> 
> I don't know how to solve this...
> 
> Noralf.

Looks like select BACKLIGHT_CLASS_DEVICE and BACKLIGHT_LCD_SUPPORT
seemed to work (atleast when I replicated the configurations from the 
kbuild support). Maybe that is because we are not forcing the
dependencies when we do a select ?

Thanks and regards,
Meghana
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Daniel Vetter]

On Fri, Sep 29, 2017 at 05:41:04PM +0200, Noralf Tr�nnes wrote:
> 
> Den 29.09.2017 16.13, skrev Meghana Madhyastha:
> > On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Tr�nnes wrote:
> > > Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> > > > On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Tr�nnes wrote:
> > > > > Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> > > > > > On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Tr�nnes wrote:
> > > > > > > Den 28.09.2017 16.08, skrev Daniel Vetter:
> > > > > > > > On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> > > > > > > > > Rename tinydrm_of_find_backlight to drm_of_find_backlight
> > > > > > > > > and move it into drm_of.c from tinydrm-helpers.c. This is
> > > > > > > > > because other drivers in the drm subsystem might need to call
> > > > > > > > > this function. In that case and otherwise, it is better from
> > > > > > > > > an organizational point of view to move it into drm_of.c along
> > > > > > > > > with the other _of.c functions.
> > > > > > > > > 
> > > > > > > > > Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> > > > > > > > > ---
> > > > > > > > > Changes in v3:
> > > > > > > > > -Change it back to a single patch from two patches in v2
> > > > > > > > > 
> > > > > > > > >   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> > > > > > > > >   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> > > > > > > > >   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> > > > > > > > >   include/drm/drm_of.h                           |  1 +
> > > > > > > > >   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> > > > > > > > >   5 files changed, 47 insertions(+), 42 deletions(-)
> > > > > > > > > 
> > > > > > > > > diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> > > > > > > > > index 8dafbdf..d878d3a 100644
> > > > > > > > > --- a/drivers/gpu/drm/drm_of.c
> > > > > > > > > +++ b/drivers/gpu/drm/drm_of.c
> > > > > > > > > @@ -1,6 +1,7 @@
> > > > > > > > >   #include <linux/component.h>
> > > > > > > > >   #include <linux/export.h>
> > > > > > > > >   #include <linux/list.h>
> > > > > > > > > +#include <linux/backlight.h>
> > > > > > > > >   #include <linux/of_graph.h>
> > > > > > > > >   #include <drm/drmP.h>
> > > > > > > > >   #include <drm/drm_bridge.h>
> > > > > > > > > @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> > > > > > > > >   	return ret;
> > > > > > > > >   }
> > > > > > > > >   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> > > > > > > > > +
> > > > > > > > > +/**
> > > > > > > > > + * drm_of_find_backlight - Find backlight device in device-tree
> > > > > > > > > + * @dev: Device
> > > > > > > > > + *
> > > > > > > > > + * This function looks for a DT node pointed to by a property named 'backlight'
> > > > > > > > > + * and uses of_find_backlight_by_node() to get the backlight device.
> > > > > > > > > + * Additionally if the brightness property is zero, it is set to
> > > > > > > > > + * max_brightness.
> > > > > > > > > + *
> > > > > > > > > + * Note: It is the responsibility of the caller to call put_device() when
> > > > > > > > > + * releasing the resource.
> > > > > > > > > + *
> > > > > > > > > + * Returns:
> > > > > > > > > + * NULL if there's no backlight property.
> > > > > > > > > + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> > > > > > > > > + * is found.
> > > > > > > > > + * If the backlight device is found, a pointer to the structure is returned.
> > > > > > > > > + */
> > > > > > > > > +struct backlight_device *drm_of_find_backlight(struct device *dev)
> > > > > > > > > +{
> > > > > > > > > +	struct backlight_device *backlight;
> > > > > > > > > +	struct device_node *np;
> > > > > > > > > +
> > > > > > > > > +	np = of_parse_phandle(dev->of_node, "backlight", 0);
> > > > > > > > > +	if (!np)
> > > > > > > > > +		return NULL;
> > > > > > > > > +
> > > > > > > > > +	backlight = of_find_backlight_by_node(np);
> > > > > > > > > +	of_node_put(np);
> > > > > > > > > +
> > > > > > > > > +	if (!backlight)
> > > > > > > > > +		return ERR_PTR(-EPROBE_DEFER);
> > > > > > > > > +
> > > > > > > > > +	if (!backlight->props.brightness) {
> > > > > > > > > +		backlight->props.brightness = backlight->props.max_brightness;
> > > > > > > > > +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> > > > > > > > > +			      backlight->props.brightness);
> > > > > > > > > +	}
> > > > > > > > > +
> > > > > > > > > +	return backlight;
> > > > > > > > > +}
> > > > > > > > > +EXPORT_SYMBOL(drm_of_find_backlight);
> 
> <snip>
> 
> > > > > > > Another problem I discovered when trying to compile this, is that if
> > > > > > > DRM is builtin and LCD_CLASS_DEVICE is a module:
> > > > > > > 
> > > > > > > drivers/gpu/drm/drm_of.c:292: undefined reference to
> > > > > > > `of_find_backlight_by_node'
> > > > > > > 
> > > > > > > I see that I solved this in tinydrm by just selecting
> > > > > > > BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> > > > > > > force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> > > > > > > 
> > > > > > > Arnd fixed a similar type of dependecy in the repaper driver by forcing
> > > > > > > repaper to be a module if necessary. To be honest, I don't know why his
> > > > > > > fix works:
> > > > > > > https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> > > > > > I didn't quite understand how we could use this fix for the current
> > > > > > case. Isn't this specific to the repaper driver dependency ?
> > > > > This is the solution Daniel mentions:
> > > > > 
> > > > >  �menuconfig DRM
> > > > >  ���� tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> > > > > support)"
> > > > >  ���� depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> > > > > +�� depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> > > > I had tried this but it resulted in a recursive dependencies error.
> > > What's the error?
> > > Could this have something to do with tinydrm selecting backlight and
> > > depending on DRM?
> > > 
> > > Noralf.
> > Looks like a case of circular dependencies. The exact error is this:
> > 
> > scripts/kconfig/mconf  Kconfig
> > drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
> > selected by FB_CLPS711X
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
> > DRM_KMS_FB_HELPER
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
> > DRM_FBDEV_EMULATION
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
> > DRM
> > 
> > Long story short, the dependency loop is as follows:
> > 
> > DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
> > DRM_FBDEV_EMULATION -> DRM
> 
> I have messed up the options here, it should be BACKLIGHT_CLASS_DEVICE:
> 
> menuconfig DRM
> ��� depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> 
> It doesn't help with the recusrsive problem, but at least it makes sense:
> 
> drivers/gpu/drm/Kconfig:7:����� symbol DRM depends on BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:158:��� symbol BACKLIGHT_CLASS_DEVICE is
> selected by DRM_RADEON
> drivers/gpu/drm/Kconfig:164:��� symbol DRM_RADEON depends on DRM
> 
> I don't know how to solve this...

You can't mix depends and select on the same symbol. More or less. So
either all depends or all selects, but select only works well if the
option is a top-level one (otherwise you also need to select _all_ its
dependencies).

And yes backlight is known to be an especially bad horror show in Kconfig,
unfortunately no one yet managed to clean up the mess :-/

So correct fix is to check out what all the other drivers do and then do
the same (and hope there's a clear majority).

Also adding Jani, who looked at the backlight Kconfig mess in the past.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Daniel Vetter]

On Fri, Sep 29, 2017 at 05:41:04PM +0200, Noralf Trønnes wrote:
> 
> Den 29.09.2017 16.13, skrev Meghana Madhyastha:
> > On Fri, Sep 29, 2017 at 02:33:12PM +0200, Noralf Trønnes wrote:
> > > Den 29.09.2017 14.20, skrev Meghana Madhyastha:
> > > > On Fri, Sep 29, 2017 at 02:10:31PM +0200, Noralf Trønnes wrote:
> > > > > Den 29.09.2017 05.22, skrev Meghana Madhyastha:
> > > > > > On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
> > > > > > > Den 28.09.2017 16.08, skrev Daniel Vetter:
> > > > > > > > On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> > > > > > > > > Rename tinydrm_of_find_backlight to drm_of_find_backlight
> > > > > > > > > and move it into drm_of.c from tinydrm-helpers.c. This is
> > > > > > > > > because other drivers in the drm subsystem might need to call
> > > > > > > > > this function. In that case and otherwise, it is better from
> > > > > > > > > an organizational point of view to move it into drm_of.c along
> > > > > > > > > with the other _of.c functions.
> > > > > > > > > 
> > > > > > > > > Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> > > > > > > > > ---
> > > > > > > > > Changes in v3:
> > > > > > > > > -Change it back to a single patch from two patches in v2
> > > > > > > > > 
> > > > > > > > >   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> > > > > > > > >   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> > > > > > > > >   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> > > > > > > > >   include/drm/drm_of.h                           |  1 +
> > > > > > > > >   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> > > > > > > > >   5 files changed, 47 insertions(+), 42 deletions(-)
> > > > > > > > > 
> > > > > > > > > diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> > > > > > > > > index 8dafbdf..d878d3a 100644
> > > > > > > > > --- a/drivers/gpu/drm/drm_of.c
> > > > > > > > > +++ b/drivers/gpu/drm/drm_of.c
> > > > > > > > > @@ -1,6 +1,7 @@
> > > > > > > > >   #include <linux/component.h>
> > > > > > > > >   #include <linux/export.h>
> > > > > > > > >   #include <linux/list.h>
> > > > > > > > > +#include <linux/backlight.h>
> > > > > > > > >   #include <linux/of_graph.h>
> > > > > > > > >   #include <drm/drmP.h>
> > > > > > > > >   #include <drm/drm_bridge.h>
> > > > > > > > > @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> > > > > > > > >   	return ret;
> > > > > > > > >   }
> > > > > > > > >   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> > > > > > > > > +
> > > > > > > > > +/**
> > > > > > > > > + * drm_of_find_backlight - Find backlight device in device-tree
> > > > > > > > > + * @dev: Device
> > > > > > > > > + *
> > > > > > > > > + * This function looks for a DT node pointed to by a property named 'backlight'
> > > > > > > > > + * and uses of_find_backlight_by_node() to get the backlight device.
> > > > > > > > > + * Additionally if the brightness property is zero, it is set to
> > > > > > > > > + * max_brightness.
> > > > > > > > > + *
> > > > > > > > > + * Note: It is the responsibility of the caller to call put_device() when
> > > > > > > > > + * releasing the resource.
> > > > > > > > > + *
> > > > > > > > > + * Returns:
> > > > > > > > > + * NULL if there's no backlight property.
> > > > > > > > > + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> > > > > > > > > + * is found.
> > > > > > > > > + * If the backlight device is found, a pointer to the structure is returned.
> > > > > > > > > + */
> > > > > > > > > +struct backlight_device *drm_of_find_backlight(struct device *dev)
> > > > > > > > > +{
> > > > > > > > > +	struct backlight_device *backlight;
> > > > > > > > > +	struct device_node *np;
> > > > > > > > > +
> > > > > > > > > +	np = of_parse_phandle(dev->of_node, "backlight", 0);
> > > > > > > > > +	if (!np)
> > > > > > > > > +		return NULL;
> > > > > > > > > +
> > > > > > > > > +	backlight = of_find_backlight_by_node(np);
> > > > > > > > > +	of_node_put(np);
> > > > > > > > > +
> > > > > > > > > +	if (!backlight)
> > > > > > > > > +		return ERR_PTR(-EPROBE_DEFER);
> > > > > > > > > +
> > > > > > > > > +	if (!backlight->props.brightness) {
> > > > > > > > > +		backlight->props.brightness = backlight->props.max_brightness;
> > > > > > > > > +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> > > > > > > > > +			      backlight->props.brightness);
> > > > > > > > > +	}
> > > > > > > > > +
> > > > > > > > > +	return backlight;
> > > > > > > > > +}
> > > > > > > > > +EXPORT_SYMBOL(drm_of_find_backlight);
> 
> <snip>
> 
> > > > > > > Another problem I discovered when trying to compile this, is that if
> > > > > > > DRM is builtin and LCD_CLASS_DEVICE is a module:
> > > > > > > 
> > > > > > > drivers/gpu/drm/drm_of.c:292: undefined reference to
> > > > > > > `of_find_backlight_by_node'
> > > > > > > 
> > > > > > > I see that I solved this in tinydrm by just selecting
> > > > > > > BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> > > > > > > force LCD_CLASS_DEVICE to be builtin if DRM is builtin.
> > > > > > > 
> > > > > > > Arnd fixed a similar type of dependecy in the repaper driver by forcing
> > > > > > > repaper to be a module if necessary. To be honest, I don't know why his
> > > > > > > fix works:
> > > > > > > https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> > > > > > I didn't quite understand how we could use this fix for the current
> > > > > > case. Isn't this specific to the repaper driver dependency ?
> > > > > This is the solution Daniel mentions:
> > > > > 
> > > > >   menuconfig DRM
> > > > >       tristate "Direct Rendering Manager (XFree86 4.1.0 and higher DRI
> > > > > support)"
> > > > >       depends on (AGP || AGP=n) && !EMULATED_CMPXCHG && HAS_DMA
> > > > > +   depends on (LCD_CLASS_DEVICE || LCD_CLASS_DEVICE=n)
> > > > I had tried this but it resulted in a recursive dependencies error.
> > > What's the error?
> > > Could this have something to do with tinydrm selecting backlight and
> > > depending on DRM?
> > > 
> > > Noralf.
> > Looks like a case of circular dependencies. The exact error is this:
> > 
> > scripts/kconfig/mconf  Kconfig
> > drivers/gpu/drm/Kconfig:7:error: recursive dependency detected!
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/gpu/drm/Kconfig:7:	symbol DRM depends on LCD_CLASS_DEVICE
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/video/backlight/Kconfig:16:	symbol LCD_CLASS_DEVICE is
> > selected by FB_CLPS711X
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/video/fbdev/Kconfig:338:	symbol FB_CLPS711X depends on FB
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/video/fbdev/Kconfig:5:	symbol FB is selected by
> > DRM_KMS_FB_HELPER
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/gpu/drm/Kconfig:73:	symbol DRM_KMS_FB_HELPER is selected by
> > DRM_FBDEV_EMULATION
> > For a resolution refer to Documentation/kbuild/kconfig-language.txt
> > subsection "Kconfig recursive dependency limitations"
> > drivers/gpu/drm/Kconfig:90:	symbol DRM_FBDEV_EMULATION depends on
> > DRM
> > 
> > Long story short, the dependency loop is as follows:
> > 
> > DRM -> LCD_CLASS_DEVICE ->  FB_CLPS711X -> FB -> DRM_KMS_FB_HELPER ->
> > DRM_FBDEV_EMULATION -> DRM
> 
> I have messed up the options here, it should be BACKLIGHT_CLASS_DEVICE:
> 
> menuconfig DRM
>     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> 
> It doesn't help with the recusrsive problem, but at least it makes sense:
> 
> drivers/gpu/drm/Kconfig:7:      symbol DRM depends on BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is
> selected by DRM_RADEON
> drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM
> 
> I don't know how to solve this...

You can't mix depends and select on the same symbol. More or less. So
either all depends or all selects, but select only works well if the
option is a top-level one (otherwise you also need to select _all_ its
dependencies).

And yes backlight is known to be an especially bad horror show in Kconfig,
unfortunately no one yet managed to clean up the mess :-/

So correct fix is to check out what all the other drivers do and then do
the same (and hope there's a clear majority).

Also adding Jani, who looked at the backlight Kconfig mess in the past.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Jani Nikula]

On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
> Also adding Jani, who looked at the backlight Kconfig mess in the past.

I've even sent patches to fix some of the dependency mess, but the
problem is social not technical. The problem is that people think
"select" is more convenient than "depends" because they can just enable
a config that way, while "depends" would require finding and enabling
all the dependencies before the menu option even shows up.

I don't deny, that's annoying. But it's also abuse of select, see
Documentation/kbuild/kconfig-language.txt:

  Note:
	select should be used with care. select will force
	a symbol to a value without visiting the dependencies.
	By abusing select you are able to select a symbol FOO even
	if FOO depends on BAR that is not set.
	In general use select only for non-visible symbols
	(no prompts anywhere) and for symbols with no dependencies.
	That will limit the usefulness but on the other hand avoid
	the illegal configurations all over.

The real fix would be making finding and enabling dependencies
recursively more convenient, but I don't see that happening anytime
soon.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Jani Nikula]

On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
> Also adding Jani, who looked at the backlight Kconfig mess in the past.

I've even sent patches to fix some of the dependency mess, but the
problem is social not technical. The problem is that people think
"select" is more convenient than "depends" because they can just enable
a config that way, while "depends" would require finding and enabling
all the dependencies before the menu option even shows up.

I don't deny, that's annoying. But it's also abuse of select, see
Documentation/kbuild/kconfig-language.txt:

  Note:
	select should be used with care. select will force
	a symbol to a value without visiting the dependencies.
	By abusing select you are able to select a symbol FOO even
	if FOO depends on BAR that is not set.
	In general use select only for non-visible symbols
	(no prompts anywhere) and for symbols with no dependencies.
	That will limit the usefulness but on the other hand avoid
	the illegal configurations all over.

The real fix would be making finding and enabling dependencies
recursively more convenient, but I don't see that happening anytime
soon.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center
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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 02.10.2017 10.13, skrev Jani Nikula:
> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>> Also adding Jani, who looked at the backlight Kconfig mess in the past.
> I've even sent patches to fix some of the dependency mess, but the
> problem is social not technical. The problem is that people think
> "select" is more convenient than "depends" because they can just enable
> a config that way, while "depends" would require finding and enabling
> all the dependencies before the menu option even shows up.
>
> I don't deny, that's annoying. But it's also abuse of select, see
> Documentation/kbuild/kconfig-language.txt:
>
>    Note:
> 	select should be used with care. select will force
> 	a symbol to a value without visiting the dependencies.
> 	By abusing select you are able to select a symbol FOO even
> 	if FOO depends on BAR that is not set.
> 	In general use select only for non-visible symbols
> 	(no prompts anywhere) and for symbols with no dependencies.
> 	That will limit the usefulness but on the other hand avoid
> 	the illegal configurations all over.
>
> The real fix would be making finding and enabling dependencies
> recursively more convenient, but I don't see that happening anytime
> soon.

If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
and CONFIG_BACKLIGHT_CLASS_DEVICE=m.

So we can either do:

menuconfig DRM
     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)

Or we can:

-#ifdef CONFIG_OF
+#if IS_ENABLED(CONFIG_OF) && IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
  struct backlight_device *of_find_backlight_by_node(struct device_node 
*node);
  #else
  static inline struct backlight_device *

Using the second one it won't be obvious to users why backlight doesn't 
work,
they have after all enabled backlight (but as module and DRM builtin).

So I suppose the first one is preferred.
What effect will such a change have on an existing configuration where
DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
be disabled?

Noralf.

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 02.10.2017 10.13, skrev Jani Nikula:
> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>> Also adding Jani, who looked at the backlight Kconfig mess in the past.
> I've even sent patches to fix some of the dependency mess, but the
> problem is social not technical. The problem is that people think
> "select" is more convenient than "depends" because they can just enable
> a config that way, while "depends" would require finding and enabling
> all the dependencies before the menu option even shows up.
>
> I don't deny, that's annoying. But it's also abuse of select, see
> Documentation/kbuild/kconfig-language.txt:
>
>    Note:
> 	select should be used with care. select will force
> 	a symbol to a value without visiting the dependencies.
> 	By abusing select you are able to select a symbol FOO even
> 	if FOO depends on BAR that is not set.
> 	In general use select only for non-visible symbols
> 	(no prompts anywhere) and for symbols with no dependencies.
> 	That will limit the usefulness but on the other hand avoid
> 	the illegal configurations all over.
>
> The real fix would be making finding and enabling dependencies
> recursively more convenient, but I don't see that happening anytime
> soon.

If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
and CONFIG_BACKLIGHT_CLASS_DEVICE=m.

So we can either do:

menuconfig DRM
     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)

Or we can:

-#ifdef CONFIG_OF
+#if IS_ENABLED(CONFIG_OF) && IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
  struct backlight_device *of_find_backlight_by_node(struct device_node 
*node);
  #else
  static inline struct backlight_device *

Using the second one it won't be obvious to users why backlight doesn't 
work,
they have after all enabled backlight (but as module and DRM builtin).

So I suppose the first one is preferred.
What effect will such a change have on an existing configuration where
DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
be disabled?

Noralf.

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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 03.10.2017 16.58, skrev Noralf Trønnes:
>
> Den 02.10.2017 10.13, skrev Jani Nikula:
>> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>>> Also adding Jani, who looked at the backlight Kconfig mess in the past.
>> I've even sent patches to fix some of the dependency mess, but the
>> problem is social not technical. The problem is that people think
>> "select" is more convenient than "depends" because they can just enable
>> a config that way, while "depends" would require finding and enabling
>> all the dependencies before the menu option even shows up.
>>
>> I don't deny, that's annoying. But it's also abuse of select, see
>> Documentation/kbuild/kconfig-language.txt:
>>
>>    Note:
>>     select should be used with care. select will force
>>     a symbol to a value without visiting the dependencies.
>>     By abusing select you are able to select a symbol FOO even
>>     if FOO depends on BAR that is not set.
>>     In general use select only for non-visible symbols
>>     (no prompts anywhere) and for symbols with no dependencies.
>>     That will limit the usefulness but on the other hand avoid
>>     the illegal configurations all over.
>>
>> The real fix would be making finding and enabling dependencies
>> recursively more convenient, but I don't see that happening anytime
>> soon.
>
> If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
> and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
>
> So we can either do:
>
> menuconfig DRM
>     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>

No, this was the thing that didn't work:

drivers/gpu/drm/Kconfig:7:      symbol DRM depends on BACKLIGHT_CLASS_DEVICE
drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is 
selected by DRM_RADEON
drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM

> Or we can:
>
> -#ifdef CONFIG_OF
> +#if IS_ENABLED(CONFIG_OF) && IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>  struct backlight_device *of_find_backlight_by_node(struct device_node 
> *node);
>  #else
>  static inline struct backlight_device *
>
> Using the second one it won't be obvious to users why backlight 
> doesn't work,
> they have after all enabled backlight (but as module and DRM builtin).
>
> So I suppose the first one is preferred.
> What effect will such a change have on an existing configuration where
> DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
> be disabled?
>
> Noralf.
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 03.10.2017 16.58, skrev Noralf Trønnes:
>
> Den 02.10.2017 10.13, skrev Jani Nikula:
>> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>>> Also adding Jani, who looked at the backlight Kconfig mess in the past.
>> I've even sent patches to fix some of the dependency mess, but the
>> problem is social not technical. The problem is that people think
>> "select" is more convenient than "depends" because they can just enable
>> a config that way, while "depends" would require finding and enabling
>> all the dependencies before the menu option even shows up.
>>
>> I don't deny, that's annoying. But it's also abuse of select, see
>> Documentation/kbuild/kconfig-language.txt:
>>
>>    Note:
>>     select should be used with care. select will force
>>     a symbol to a value without visiting the dependencies.
>>     By abusing select you are able to select a symbol FOO even
>>     if FOO depends on BAR that is not set.
>>     In general use select only for non-visible symbols
>>     (no prompts anywhere) and for symbols with no dependencies.
>>     That will limit the usefulness but on the other hand avoid
>>     the illegal configurations all over.
>>
>> The real fix would be making finding and enabling dependencies
>> recursively more convenient, but I don't see that happening anytime
>> soon.
>
> If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
> and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
>
> So we can either do:
>
> menuconfig DRM
>     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>

No, this was the thing that didn't work:

drivers/gpu/drm/Kconfig:7:      symbol DRM depends on BACKLIGHT_CLASS_DEVICE
drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is 
selected by DRM_RADEON
drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM

> Or we can:
>
> -#ifdef CONFIG_OF
> +#if IS_ENABLED(CONFIG_OF) && IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>  struct backlight_device *of_find_backlight_by_node(struct device_node 
> *node);
>  #else
>  static inline struct backlight_device *
>
> Using the second one it won't be obvious to users why backlight 
> doesn't work,
> they have after all enabled backlight (but as module and DRM builtin).
>
> So I suppose the first one is preferred.
> What effect will such a change have on an existing configuration where
> DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
> be disabled?
>
> Noralf.
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

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Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 03.10.2017 18.02, skrev Noralf Trønnes:
>
> Den 03.10.2017 16.58, skrev Noralf Trønnes:
>>
>> Den 02.10.2017 10.13, skrev Jani Nikula:
>>> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>>>> Also adding Jani, who looked at the backlight Kconfig mess in the 
>>>> past.
>>> I've even sent patches to fix some of the dependency mess, but the
>>> problem is social not technical. The problem is that people think
>>> "select" is more convenient than "depends" because they can just enable
>>> a config that way, while "depends" would require finding and enabling
>>> all the dependencies before the menu option even shows up.
>>>
>>> I don't deny, that's annoying. But it's also abuse of select, see
>>> Documentation/kbuild/kconfig-language.txt:
>>>
>>>    Note:
>>>     select should be used with care. select will force
>>>     a symbol to a value without visiting the dependencies.
>>>     By abusing select you are able to select a symbol FOO even
>>>     if FOO depends on BAR that is not set.
>>>     In general use select only for non-visible symbols
>>>     (no prompts anywhere) and for symbols with no dependencies.
>>>     That will limit the usefulness but on the other hand avoid
>>>     the illegal configurations all over.
>>>
>>> The real fix would be making finding and enabling dependencies
>>> recursively more convenient, but I don't see that happening anytime
>>> soon.
>>
>> If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
>> and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
>>
>> So we can either do:
>>
>> menuconfig DRM
>>     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>>
>
> No, this was the thing that didn't work:
>
> drivers/gpu/drm/Kconfig:7:      symbol DRM depends on 
> BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE 
> is selected by DRM_RADEON
> drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM
>

How about putting the dependency in the driver combined with IS_REACHABLE,
but not in backlight.h as I first proposed, that won't work:

  menuconfig DRM_TINYDRM
-    select BACKLIGHT_LCD_SUPPORT
-    select BACKLIGHT_CLASS_DEVICE
+    depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)


struct backlight_device *drm_of_find_backlight(struct device *dev)
{
     struct backlight_device *backlight;
     struct device_node *np;

     if (!IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE))
         return NULL;
[...]
}

But the IS_REACHABLE doesn't feel right.

Maybe the problem is putting a function in DRM that really doesn't
belong there. How about calling it of_find_backlight() instead and
put it in backlight.[hc]?

Noralf.

>> Or we can:
>>
>> -#ifdef CONFIG_OF
>> +#if IS_ENABLED(CONFIG_OF) && 
>> IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>>  struct backlight_device *of_find_backlight_by_node(struct 
>> device_node *node);
>>  #else
>>  static inline struct backlight_device *
>>
>> Using the second one it won't be obvious to users why backlight 
>> doesn't work,
>> they have after all enabled backlight (but as module and DRM builtin).
>>
>> So I suppose the first one is preferred.
>> What effect will such a change have on an existing configuration where
>> DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
>> be disabled?
>>
>> Noralf.
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 03.10.2017 18.02, skrev Noralf Trønnes:
>
> Den 03.10.2017 16.58, skrev Noralf Trønnes:
>>
>> Den 02.10.2017 10.13, skrev Jani Nikula:
>>> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>>>> Also adding Jani, who looked at the backlight Kconfig mess in the 
>>>> past.
>>> I've even sent patches to fix some of the dependency mess, but the
>>> problem is social not technical. The problem is that people think
>>> "select" is more convenient than "depends" because they can just enable
>>> a config that way, while "depends" would require finding and enabling
>>> all the dependencies before the menu option even shows up.
>>>
>>> I don't deny, that's annoying. But it's also abuse of select, see
>>> Documentation/kbuild/kconfig-language.txt:
>>>
>>>    Note:
>>>     select should be used with care. select will force
>>>     a symbol to a value without visiting the dependencies.
>>>     By abusing select you are able to select a symbol FOO even
>>>     if FOO depends on BAR that is not set.
>>>     In general use select only for non-visible symbols
>>>     (no prompts anywhere) and for symbols with no dependencies.
>>>     That will limit the usefulness but on the other hand avoid
>>>     the illegal configurations all over.
>>>
>>> The real fix would be making finding and enabling dependencies
>>> recursively more convenient, but I don't see that happening anytime
>>> soon.
>>
>> If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
>> and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
>>
>> So we can either do:
>>
>> menuconfig DRM
>>     depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>>
>
> No, this was the thing that didn't work:
>
> drivers/gpu/drm/Kconfig:7:      symbol DRM depends on 
> BACKLIGHT_CLASS_DEVICE
> drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE 
> is selected by DRM_RADEON
> drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM
>

How about putting the dependency in the driver combined with IS_REACHABLE,
but not in backlight.h as I first proposed, that won't work:

  menuconfig DRM_TINYDRM
-    select BACKLIGHT_LCD_SUPPORT
-    select BACKLIGHT_CLASS_DEVICE
+    depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)


struct backlight_device *drm_of_find_backlight(struct device *dev)
{
     struct backlight_device *backlight;
     struct device_node *np;

     if (!IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE))
         return NULL;
[...]
}

But the IS_REACHABLE doesn't feel right.

Maybe the problem is putting a function in DRM that really doesn't
belong there. How about calling it of_find_backlight() instead and
put it in backlight.[hc]?

Noralf.

>> Or we can:
>>
>> -#ifdef CONFIG_OF
>> +#if IS_ENABLED(CONFIG_OF) && 
>> IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>>  struct backlight_device *of_find_backlight_by_node(struct 
>> device_node *node);
>>  #else
>>  static inline struct backlight_device *
>>
>> Using the second one it won't be obvious to users why backlight 
>> doesn't work,
>> they have after all enabled backlight (but as module and DRM builtin).
>>
>> So I suppose the first one is preferred.
>> What effect will such a change have on an existing configuration where
>> DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
>> be disabled?
>>
>> Noralf.
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Tue, Oct 03, 2017 at 07:38:29PM +0200, Noralf Tr�nnes wrote:
> 
> Den 03.10.2017 18.02, skrev Noralf Tr�nnes:
> >
> >Den 03.10.2017 16.58, skrev Noralf Tr�nnes:
> >>
> >>Den 02.10.2017 10.13, skrev Jani Nikula:
> >>>On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
> >>>>Also adding Jani, who looked at the backlight Kconfig mess in the
> >>>>past.
> >>>I've even sent patches to fix some of the dependency mess, but the
> >>>problem is social not technical. The problem is that people think
> >>>"select" is more convenient than "depends" because they can just enable
> >>>a config that way, while "depends" would require finding and enabling
> >>>all the dependencies before the menu option even shows up.
> >>>
> >>>I don't deny, that's annoying. But it's also abuse of select, see
> >>>Documentation/kbuild/kconfig-language.txt:
> >>>
> >>>�� Note:
> >>>����select should be used with care. select will force
> >>>����a symbol to a value without visiting the dependencies.
> >>>����By abusing select you are able to select a symbol FOO even
> >>>����if FOO depends on BAR that is not set.
> >>>����In general use select only for non-visible symbols
> >>>����(no prompts anywhere) and for symbols with no dependencies.
> >>>����That will limit the usefulness but on the other hand avoid
> >>>����the illegal configurations all over.
> >>>
> >>>The real fix would be making finding and enabling dependencies
> >>>recursively more convenient, but I don't see that happening anytime
> >>>soon.
> >>
> >>If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
> >>and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
> >>
> >>So we can either do:
> >>
> >>menuconfig DRM
> >>��� depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> >>
> >
> >No, this was the thing that didn't work:
> >
> >drivers/gpu/drm/Kconfig:7:����� symbol DRM depends on
> >BACKLIGHT_CLASS_DEVICE
> >drivers/video/backlight/Kconfig:158:��� symbol BACKLIGHT_CLASS_DEVICE is
> >selected by DRM_RADEON
> >drivers/gpu/drm/Kconfig:164:��� symbol DRM_RADEON depends on DRM
> >
> 
> How about putting the dependency in the driver combined with IS_REACHABLE,
> but not in backlight.h as I first proposed, that won't work:
> 
> �menuconfig DRM_TINYDRM
> -��� select BACKLIGHT_LCD_SUPPORT
> -��� select BACKLIGHT_CLASS_DEVICE
> +��� depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> 
> 
> struct backlight_device *drm_of_find_backlight(struct device *dev)
> {
> ��� struct backlight_device *backlight;
> ��� struct device_node *np;
> 
> ��� if (!IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE))
> ��� ��� return NULL;
> [...]
> }
> 
> But the IS_REACHABLE doesn't feel right.
> 
> Maybe the problem is putting a function in DRM that really doesn't
> belong there. How about calling it of_find_backlight() instead and
> put it in backlight.[hc]?

Wouldn't it make more sense to put the function in DRM ? Because all of
the callers are located in DRM and so I'd think it makes more sense to
put it in DRM along with the other _of functions.

> Noralf.
> 
> >>Or we can:
> >>
> >>-#ifdef CONFIG_OF
> >>+#if IS_ENABLED(CONFIG_OF) &&
> >>IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
> >>�struct backlight_device *of_find_backlight_by_node(struct device_node
> >>*node);
> >>�#else
> >>�static inline struct backlight_device *

I have one question. Why isn't your previous solution a good solution?
i.e IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) which was part of v7

> >>Using the second one it won't be obvious to users why backlight doesn't
> >>work,
> >>they have after all enabled backlight (but as module and DRM builtin).
> >>
> >>So I suppose the first one is preferred.
> >>What effect will such a change have on an existing configuration where
> >>DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
> >>be disabled?

Why would it be disabled in this case ?

Thanks and regards,
Meghana

> >>Noralf.
> >>
> >>_______________________________________________
> >>dri-devel mailing list
> >>dri-devel@lists.freedesktop.org
> >>https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >>
> >
> >_______________________________________________
> >dri-devel mailing list
> >dri-devel@lists.freedesktop.org
> >https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> 

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Meghana Madhyastha]

On Tue, Oct 03, 2017 at 07:38:29PM +0200, Noralf Trønnes wrote:
> 
> Den 03.10.2017 18.02, skrev Noralf Trønnes:
> >
> >Den 03.10.2017 16.58, skrev Noralf Trønnes:
> >>
> >>Den 02.10.2017 10.13, skrev Jani Nikula:
> >>>On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
> >>>>Also adding Jani, who looked at the backlight Kconfig mess in the
> >>>>past.
> >>>I've even sent patches to fix some of the dependency mess, but the
> >>>problem is social not technical. The problem is that people think
> >>>"select" is more convenient than "depends" because they can just enable
> >>>a config that way, while "depends" would require finding and enabling
> >>>all the dependencies before the menu option even shows up.
> >>>
> >>>I don't deny, that's annoying. But it's also abuse of select, see
> >>>Documentation/kbuild/kconfig-language.txt:
> >>>
> >>>   Note:
> >>>    select should be used with care. select will force
> >>>    a symbol to a value without visiting the dependencies.
> >>>    By abusing select you are able to select a symbol FOO even
> >>>    if FOO depends on BAR that is not set.
> >>>    In general use select only for non-visible symbols
> >>>    (no prompts anywhere) and for symbols with no dependencies.
> >>>    That will limit the usefulness but on the other hand avoid
> >>>    the illegal configurations all over.
> >>>
> >>>The real fix would be making finding and enabling dependencies
> >>>recursively more convenient, but I don't see that happening anytime
> >>>soon.
> >>
> >>If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
> >>and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
> >>
> >>So we can either do:
> >>
> >>menuconfig DRM
> >>    depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> >>
> >
> >No, this was the thing that didn't work:
> >
> >drivers/gpu/drm/Kconfig:7:      symbol DRM depends on
> >BACKLIGHT_CLASS_DEVICE
> >drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is
> >selected by DRM_RADEON
> >drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM
> >
> 
> How about putting the dependency in the driver combined with IS_REACHABLE,
> but not in backlight.h as I first proposed, that won't work:
> 
>  menuconfig DRM_TINYDRM
> -    select BACKLIGHT_LCD_SUPPORT
> -    select BACKLIGHT_CLASS_DEVICE
> +    depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
> 
> 
> struct backlight_device *drm_of_find_backlight(struct device *dev)
> {
>     struct backlight_device *backlight;
>     struct device_node *np;
> 
>     if (!IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE))
>         return NULL;
> [...]
> }
> 
> But the IS_REACHABLE doesn't feel right.
> 
> Maybe the problem is putting a function in DRM that really doesn't
> belong there. How about calling it of_find_backlight() instead and
> put it in backlight.[hc]?

Wouldn't it make more sense to put the function in DRM ? Because all of
the callers are located in DRM and so I'd think it makes more sense to
put it in DRM along with the other _of functions.

> Noralf.
> 
> >>Or we can:
> >>
> >>-#ifdef CONFIG_OF
> >>+#if IS_ENABLED(CONFIG_OF) &&
> >>IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
> >> struct backlight_device *of_find_backlight_by_node(struct device_node
> >>*node);
> >> #else
> >> static inline struct backlight_device *

I have one question. Why isn't your previous solution a good solution?
i.e IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) which was part of v7

> >>Using the second one it won't be obvious to users why backlight doesn't
> >>work,
> >>they have after all enabled backlight (but as module and DRM builtin).
> >>
> >>So I suppose the first one is preferred.
> >>What effect will such a change have on an existing configuration where
> >>DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
> >>be disabled?

Why would it be disabled in this case ?

Thanks and regards,
Meghana

> >>Noralf.
> >>
> >>_______________________________________________
> >>dri-devel mailing list
> >>dri-devel@lists.freedesktop.org
> >>https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >>
> >
> >_______________________________________________
> >dri-devel mailing list
> >dri-devel@lists.freedesktop.org
> >https://lists.freedesktop.org/mailman/listinfo/dri-devel
> >
> 
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 05.10.2017 05.53, skrev Meghana Madhyastha:
> On Tue, Oct 03, 2017 at 07:38:29PM +0200, Noralf Trønnes wrote:
>> Den 03.10.2017 18.02, skrev Noralf Trønnes:
>>> Den 03.10.2017 16.58, skrev Noralf Trønnes:
>>>> Den 02.10.2017 10.13, skrev Jani Nikula:
>>>>> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>>>>>> Also adding Jani, who looked at the backlight Kconfig mess in the
>>>>>> past.
>>>>> I've even sent patches to fix some of the dependency mess, but the
>>>>> problem is social not technical. The problem is that people think
>>>>> "select" is more convenient than "depends" because they can just enable
>>>>> a config that way, while "depends" would require finding and enabling
>>>>> all the dependencies before the menu option even shows up.
>>>>>
>>>>> I don't deny, that's annoying. But it's also abuse of select, see
>>>>> Documentation/kbuild/kconfig-language.txt:
>>>>>
>>>>>     Note:
>>>>>      select should be used with care. select will force
>>>>>      a symbol to a value without visiting the dependencies.
>>>>>      By abusing select you are able to select a symbol FOO even
>>>>>      if FOO depends on BAR that is not set.
>>>>>      In general use select only for non-visible symbols
>>>>>      (no prompts anywhere) and for symbols with no dependencies.
>>>>>      That will limit the usefulness but on the other hand avoid
>>>>>      the illegal configurations all over.
>>>>>
>>>>> The real fix would be making finding and enabling dependencies
>>>>> recursively more convenient, but I don't see that happening anytime
>>>>> soon.
>>>> If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
>>>> and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
>>>>
>>>> So we can either do:
>>>>
>>>> menuconfig DRM
>>>>      depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>>>>
>>> No, this was the thing that didn't work:
>>>
>>> drivers/gpu/drm/Kconfig:7:      symbol DRM depends on
>>> BACKLIGHT_CLASS_DEVICE
>>> drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is
>>> selected by DRM_RADEON
>>> drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM
>>>
>> How about putting the dependency in the driver combined with IS_REACHABLE,
>> but not in backlight.h as I first proposed, that won't work:
>>
>>   menuconfig DRM_TINYDRM
>> -    select BACKLIGHT_LCD_SUPPORT
>> -    select BACKLIGHT_CLASS_DEVICE
>> +    depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>>
>>
>> struct backlight_device *drm_of_find_backlight(struct device *dev)
>> {
>>      struct backlight_device *backlight;
>>      struct device_node *np;
>>
>>      if (!IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE))
>>          return NULL;
>> [...]
>> }
>>
>> But the IS_REACHABLE doesn't feel right.
>>
>> Maybe the problem is putting a function in DRM that really doesn't
>> belong there. How about calling it of_find_backlight() instead and
>> put it in backlight.[hc]?
> Wouldn't it make more sense to put the function in DRM ? Because all of
> the callers are located in DRM and so I'd think it makes more sense to
> put it in DRM along with the other _of functions.

I don't think it matters where the callers are, but the fact that the 
functions
are all about backlight and nothing about DRM, except the error messages.

I've made a suggestion in the last version where we have backlight 
maintainer attention.

Noralf.

>> Noralf.
>>
>>>> Or we can:
>>>>
>>>> -#ifdef CONFIG_OF
>>>> +#if IS_ENABLED(CONFIG_OF) &&
>>>> IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>>>>   struct backlight_device *of_find_backlight_by_node(struct device_node
>>>> *node);
>>>>   #else
>>>>   static inline struct backlight_device *
> I have one question. Why isn't your previous solution a good solution?
> i.e IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) which was part of v7
>
>>>> Using the second one it won't be obvious to users why backlight doesn't
>>>> work,
>>>> they have after all enabled backlight (but as module and DRM builtin).
>>>>
>>>> So I suppose the first one is preferred.
>>>> What effect will such a change have on an existing configuration where
>>>> DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
>>>> be disabled?
> Why would it be disabled in this case ?
>
> Thanks and regards,
> Meghana
>
>>>> Noralf.
>>>>
>>>> _______________________________________________
>>>> dri-devel mailing list
>>>> dri-devel@lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Noralf Trønnes]

Den 05.10.2017 05.53, skrev Meghana Madhyastha:
> On Tue, Oct 03, 2017 at 07:38:29PM +0200, Noralf Trønnes wrote:
>> Den 03.10.2017 18.02, skrev Noralf Trønnes:
>>> Den 03.10.2017 16.58, skrev Noralf Trønnes:
>>>> Den 02.10.2017 10.13, skrev Jani Nikula:
>>>>> On Mon, 02 Oct 2017, Daniel Vetter <daniel@ffwll.ch> wrote:
>>>>>> Also adding Jani, who looked at the backlight Kconfig mess in the
>>>>>> past.
>>>>> I've even sent patches to fix some of the dependency mess, but the
>>>>> problem is social not technical. The problem is that people think
>>>>> "select" is more convenient than "depends" because they can just enable
>>>>> a config that way, while "depends" would require finding and enabling
>>>>> all the dependencies before the menu option even shows up.
>>>>>
>>>>> I don't deny, that's annoying. But it's also abuse of select, see
>>>>> Documentation/kbuild/kconfig-language.txt:
>>>>>
>>>>>     Note:
>>>>>      select should be used with care. select will force
>>>>>      a symbol to a value without visiting the dependencies.
>>>>>      By abusing select you are able to select a symbol FOO even
>>>>>      if FOO depends on BAR that is not set.
>>>>>      In general use select only for non-visible symbols
>>>>>      (no prompts anywhere) and for symbols with no dependencies.
>>>>>      That will limit the usefulness but on the other hand avoid
>>>>>      the illegal configurations all over.
>>>>>
>>>>> The real fix would be making finding and enabling dependencies
>>>>> recursively more convenient, but I don't see that happening anytime
>>>>> soon.
>>>> If we don't select BACKLIGHT in drivers, we can end up with CONFIG_DRM=y
>>>> and CONFIG_BACKLIGHT_CLASS_DEVICE=m.
>>>>
>>>> So we can either do:
>>>>
>>>> menuconfig DRM
>>>>      depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>>>>
>>> No, this was the thing that didn't work:
>>>
>>> drivers/gpu/drm/Kconfig:7:      symbol DRM depends on
>>> BACKLIGHT_CLASS_DEVICE
>>> drivers/video/backlight/Kconfig:158:    symbol BACKLIGHT_CLASS_DEVICE is
>>> selected by DRM_RADEON
>>> drivers/gpu/drm/Kconfig:164:    symbol DRM_RADEON depends on DRM
>>>
>> How about putting the dependency in the driver combined with IS_REACHABLE,
>> but not in backlight.h as I first proposed, that won't work:
>>
>>   menuconfig DRM_TINYDRM
>> -    select BACKLIGHT_LCD_SUPPORT
>> -    select BACKLIGHT_CLASS_DEVICE
>> +    depends on (BACKLIGHT_CLASS_DEVICE || BACKLIGHT_CLASS_DEVICE=n)
>>
>>
>> struct backlight_device *drm_of_find_backlight(struct device *dev)
>> {
>>      struct backlight_device *backlight;
>>      struct device_node *np;
>>
>>      if (!IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE))
>>          return NULL;
>> [...]
>> }
>>
>> But the IS_REACHABLE doesn't feel right.
>>
>> Maybe the problem is putting a function in DRM that really doesn't
>> belong there. How about calling it of_find_backlight() instead and
>> put it in backlight.[hc]?
> Wouldn't it make more sense to put the function in DRM ? Because all of
> the callers are located in DRM and so I'd think it makes more sense to
> put it in DRM along with the other _of functions.

I don't think it matters where the callers are, but the fact that the 
functions
are all about backlight and nothing about DRM, except the error messages.

I've made a suggestion in the last version where we have backlight 
maintainer attention.

Noralf.

>> Noralf.
>>
>>>> Or we can:
>>>>
>>>> -#ifdef CONFIG_OF
>>>> +#if IS_ENABLED(CONFIG_OF) &&
>>>> IS_REACHABLE(CONFIG_BACKLIGHT_CLASS_DEVICE)
>>>>   struct backlight_device *of_find_backlight_by_node(struct device_node
>>>> *node);
>>>>   #else
>>>>   static inline struct backlight_device *
> I have one question. Why isn't your previous solution a good solution?
> i.e IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE) which was part of v7
>
>>>> Using the second one it won't be obvious to users why backlight doesn't
>>>> work,
>>>> they have after all enabled backlight (but as module and DRM builtin).
>>>>
>>>> So I suppose the first one is preferred.
>>>> What effect will such a change have on an existing configuration where
>>>> DRM=y and BACKLIGHT_CLASS_DEVICE=m? Will DRM become a module or will it
>>>> be disabled?
> Why would it be disabled in this case ?
>
> Thanks and regards,
> Meghana
>
>>>> Noralf.
>>>>
>>>> _______________________________________________
>>>> dri-devel mailing list
>>>> dri-devel@lists.freedesktop.org
>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Daniel Vetter]

On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Tr�nnes wrote:
> 
> Den 28.09.2017 16.08, skrev Daniel Vetter:
> > On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> > > Rename tinydrm_of_find_backlight to drm_of_find_backlight
> > > and move it into drm_of.c from tinydrm-helpers.c. This is
> > > because other drivers in the drm subsystem might need to call
> > > this function. In that case and otherwise, it is better from
> > > an organizational point of view to move it into drm_of.c along
> > > with the other _of.c functions.
> > > 
> > > Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> > > ---
> > > Changes in v3:
> > > -Change it back to a single patch from two patches in v2
> > > 
> > >   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> > >   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> > >   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> > >   include/drm/drm_of.h                           |  1 +
> > >   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> > >   5 files changed, 47 insertions(+), 42 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> > > index 8dafbdf..d878d3a 100644
> > > --- a/drivers/gpu/drm/drm_of.c
> > > +++ b/drivers/gpu/drm/drm_of.c
> > > @@ -1,6 +1,7 @@
> > >   #include <linux/component.h>
> > >   #include <linux/export.h>
> > >   #include <linux/list.h>
> > > +#include <linux/backlight.h>
> > >   #include <linux/of_graph.h>
> > >   #include <drm/drmP.h>
> > >   #include <drm/drm_bridge.h>
> > > @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> > >   	return ret;
> > >   }
> > >   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> > > +
> > > +/**
> > > + * drm_of_find_backlight - Find backlight device in device-tree
> > > + * @dev: Device
> > > + *
> > > + * This function looks for a DT node pointed to by a property named 'backlight'
> > > + * and uses of_find_backlight_by_node() to get the backlight device.
> > > + * Additionally if the brightness property is zero, it is set to
> > > + * max_brightness.
> > > + *
> > > + * Note: It is the responsibility of the caller to call put_device() when
> > > + * releasing the resource.
> > > + *
> > > + * Returns:
> > > + * NULL if there's no backlight property.
> > > + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> > > + * is found.
> > > + * If the backlight device is found, a pointer to the structure is returned.
> > > + */
> > > +struct backlight_device *drm_of_find_backlight(struct device *dev)
> > > +{
> > > +	struct backlight_device *backlight;
> > > +	struct device_node *np;
> > > +
> > > +	np = of_parse_phandle(dev->of_node, "backlight", 0);
> > > +	if (!np)
> > > +		return NULL;
> > > +
> > > +	backlight = of_find_backlight_by_node(np);
> > > +	of_node_put(np);
> > > +
> > > +	if (!backlight)
> > > +		return ERR_PTR(-EPROBE_DEFER);
> > > +
> > > +	if (!backlight->props.brightness) {
> > > +		backlight->props.brightness = backlight->props.max_brightness;
> > > +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> > > +			      backlight->props.brightness);
> > > +	}
> > > +
> > > +	return backlight;
> > > +}
> > > +EXPORT_SYMBOL(drm_of_find_backlight);
> > > diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> > > index bd6cce0..cd4c6a5 100644
> > > --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> > > +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> > > @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> > >   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> > >   /**
> > > - * tinydrm_of_find_backlight - Find backlight device in device-tree
> > > - * @dev: Device
> > > - *
> > > - * This function looks for a DT node pointed to by a property named 'backlight'
> > > - * and uses of_find_backlight_by_node() to get the backlight device.
> > > - * Additionally if the brightness property is zero, it is set to
> > > - * max_brightness.
> > > - *
> > > - * Returns:
> > > - * NULL if there's no backlight property.
> > > - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> > > - * is found.
> > > - * If the backlight device is found, a pointer to the structure is returned.
> > > - */
> > > -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> > > -{
> > > -	struct backlight_device *backlight;
> > > -	struct device_node *np;
> > > -
> > > -	np = of_parse_phandle(dev->of_node, "backlight", 0);
> > > -	if (!np)
> > > -		return NULL;
> > > -
> > > -	backlight = of_find_backlight_by_node(np);
> > > -	of_node_put(np);
> > > -
> > > -	if (!backlight)
> > > -		return ERR_PTR(-EPROBE_DEFER);
> > > -
> > > -	if (!backlight->props.brightness) {
> > > -		backlight->props.brightness = backlight->props.max_brightness;
> > > -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> > > -			      backlight->props.brightness);
> > > -	}
> > > -
> > > -	return backlight;
> > > -}
> > > -EXPORT_SYMBOL(tinydrm_of_find_backlight);
> > > -
> > > -/**
> > >    * tinydrm_enable_backlight - Enable backlight helper
> > >    * @backlight: Backlight device
> > >    *
> > > diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> > > index 7e5bb7d..5e3d635 100644
> > > --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> > > +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> > > @@ -12,6 +12,7 @@
> > >   #include <drm/tinydrm/ili9341.h>
> > >   #include <drm/tinydrm/mipi-dbi.h>
> > >   #include <drm/tinydrm/tinydrm-helpers.h>
> > > +#include <drm/drm_of.h>
> > >   #include <linux/delay.h>
> > >   #include <linux/gpio/consumer.h>
> > >   #include <linux/module.h>
> > > @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> > >   	if (IS_ERR(mipi->regulator))
> > >   		return PTR_ERR(mipi->regulator);
> > > -	mipi->backlight = tinydrm_of_find_backlight(dev);
> > > +	mipi->backlight = drm_of_find_backlight(dev);
> > >   	if (IS_ERR(mipi->backlight))
> > >   		return PTR_ERR(mipi->backlight);
> > > diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> > > index 104dd51..e8fba5b 100644
> > > --- a/include/drm/drm_of.h
> > > +++ b/include/drm/drm_of.h
> > > @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> > >   				int port, int endpoint,
> > >   				struct drm_panel **panel,
> > >   				struct drm_bridge **bridge);
> > > +struct backlight_device *drm_of_find_backlight(struct device *dev);
> > >   #else
> > >   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> > >   						  struct device_node *port)
> > Minor detail I missed: The dummy version for the #else here is missing.
> > Not a problem for tinydrm, but might be an issue for a driver where
> > CONFIG_OF is optional.
> 
> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> platforms. The only resource that isn't available there is backlight
> since there is no platform or ACPI way of describing that dependency.
> 
> Another problem I discovered when trying to compile this, is that if
> DRM is builtin and LCD_CLASS_DEVICE is a module:
> 
> drivers/gpu/drm/drm_of.c:292: undefined reference to
> `of_find_backlight_by_node'
> 
> I see that I solved this in tinydrm by just selecting
> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.

The usual way to force such an optional depency is

depends on (FOO || FOO=n)

That way it's still optional, but if FOO is enabled as a module, you can't
enable the current symbol as built-in. See e.g. how DRM vs. AGP is
handled.
-Daniel
> 
> Arnd fixed a similar type of dependecy in the repaper driver by forcing
> repaper to be a module if necessary. To be honest, I don't know why his
> fix works:
> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> 
> Another way of solving this is to put the function in
> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> that does the selection.
> 
> Noralf.
> 
> > Otherwise I think this patch looks good.
> > -Daniel
> > 
> > > diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> > > index d554ded..e40ef2d 100644
> > > --- a/include/drm/tinydrm/tinydrm-helpers.h
> > > +++ b/include/drm/tinydrm/tinydrm-helpers.h
> > > @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> > >   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> > >   			       struct drm_clip_rect *clip);
> > > -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> > >   int tinydrm_enable_backlight(struct backlight_device *backlight);
> > >   int tinydrm_disable_backlight(struct backlight_device *backlight);
> > > -- 
> > > 2.7.4
> > > 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[Daniel Vetter]

On Thu, Sep 28, 2017 at 06:02:27PM +0200, Noralf Trønnes wrote:
> 
> Den 28.09.2017 16.08, skrev Daniel Vetter:
> > On Thu, Sep 28, 2017 at 02:44:34PM +0530, Meghana Madhyastha wrote:
> > > Rename tinydrm_of_find_backlight to drm_of_find_backlight
> > > and move it into drm_of.c from tinydrm-helpers.c. This is
> > > because other drivers in the drm subsystem might need to call
> > > this function. In that case and otherwise, it is better from
> > > an organizational point of view to move it into drm_of.c along
> > > with the other _of.c functions.
> > > 
> > > Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> > > ---
> > > Changes in v3:
> > > -Change it back to a single patch from two patches in v2
> > > 
> > >   drivers/gpu/drm/drm_of.c                       | 44 ++++++++++++++++++++++++++
> > >   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 40 -----------------------
> > >   drivers/gpu/drm/tinydrm/mi0283qt.c             |  3 +-
> > >   include/drm/drm_of.h                           |  1 +
> > >   include/drm/tinydrm/tinydrm-helpers.h          |  1 -
> > >   5 files changed, 47 insertions(+), 42 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> > > index 8dafbdf..d878d3a 100644
> > > --- a/drivers/gpu/drm/drm_of.c
> > > +++ b/drivers/gpu/drm/drm_of.c
> > > @@ -1,6 +1,7 @@
> > >   #include <linux/component.h>
> > >   #include <linux/export.h>
> > >   #include <linux/list.h>
> > > +#include <linux/backlight.h>
> > >   #include <linux/of_graph.h>
> > >   #include <drm/drmP.h>
> > >   #include <drm/drm_bridge.h>
> > > @@ -260,3 +261,46 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> > >   	return ret;
> > >   }
> > >   EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> > > +
> > > +/**
> > > + * drm_of_find_backlight - Find backlight device in device-tree
> > > + * @dev: Device
> > > + *
> > > + * This function looks for a DT node pointed to by a property named 'backlight'
> > > + * and uses of_find_backlight_by_node() to get the backlight device.
> > > + * Additionally if the brightness property is zero, it is set to
> > > + * max_brightness.
> > > + *
> > > + * Note: It is the responsibility of the caller to call put_device() when
> > > + * releasing the resource.
> > > + *
> > > + * Returns:
> > > + * NULL if there's no backlight property.
> > > + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> > > + * is found.
> > > + * If the backlight device is found, a pointer to the structure is returned.
> > > + */
> > > +struct backlight_device *drm_of_find_backlight(struct device *dev)
> > > +{
> > > +	struct backlight_device *backlight;
> > > +	struct device_node *np;
> > > +
> > > +	np = of_parse_phandle(dev->of_node, "backlight", 0);
> > > +	if (!np)
> > > +		return NULL;
> > > +
> > > +	backlight = of_find_backlight_by_node(np);
> > > +	of_node_put(np);
> > > +
> > > +	if (!backlight)
> > > +		return ERR_PTR(-EPROBE_DEFER);
> > > +
> > > +	if (!backlight->props.brightness) {
> > > +		backlight->props.brightness = backlight->props.max_brightness;
> > > +		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> > > +			      backlight->props.brightness);
> > > +	}
> > > +
> > > +	return backlight;
> > > +}
> > > +EXPORT_SYMBOL(drm_of_find_backlight);
> > > diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> > > index bd6cce0..cd4c6a5 100644
> > > --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> > > +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> > > @@ -237,46 +237,6 @@ void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> > >   EXPORT_SYMBOL(tinydrm_xrgb8888_to_gray8);
> > >   /**
> > > - * tinydrm_of_find_backlight - Find backlight device in device-tree
> > > - * @dev: Device
> > > - *
> > > - * This function looks for a DT node pointed to by a property named 'backlight'
> > > - * and uses of_find_backlight_by_node() to get the backlight device.
> > > - * Additionally if the brightness property is zero, it is set to
> > > - * max_brightness.
> > > - *
> > > - * Returns:
> > > - * NULL if there's no backlight property.
> > > - * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> > > - * is found.
> > > - * If the backlight device is found, a pointer to the structure is returned.
> > > - */
> > > -struct backlight_device *tinydrm_of_find_backlight(struct device *dev)
> > > -{
> > > -	struct backlight_device *backlight;
> > > -	struct device_node *np;
> > > -
> > > -	np = of_parse_phandle(dev->of_node, "backlight", 0);
> > > -	if (!np)
> > > -		return NULL;
> > > -
> > > -	backlight = of_find_backlight_by_node(np);
> > > -	of_node_put(np);
> > > -
> > > -	if (!backlight)
> > > -		return ERR_PTR(-EPROBE_DEFER);
> > > -
> > > -	if (!backlight->props.brightness) {
> > > -		backlight->props.brightness = backlight->props.max_brightness;
> > > -		DRM_DEBUG_KMS("Backlight brightness set to %d\n",
> > > -			      backlight->props.brightness);
> > > -	}
> > > -
> > > -	return backlight;
> > > -}
> > > -EXPORT_SYMBOL(tinydrm_of_find_backlight);
> > > -
> > > -/**
> > >    * tinydrm_enable_backlight - Enable backlight helper
> > >    * @backlight: Backlight device
> > >    *
> > > diff --git a/drivers/gpu/drm/tinydrm/mi0283qt.c b/drivers/gpu/drm/tinydrm/mi0283qt.c
> > > index 7e5bb7d..5e3d635 100644
> > > --- a/drivers/gpu/drm/tinydrm/mi0283qt.c
> > > +++ b/drivers/gpu/drm/tinydrm/mi0283qt.c
> > > @@ -12,6 +12,7 @@
> > >   #include <drm/tinydrm/ili9341.h>
> > >   #include <drm/tinydrm/mipi-dbi.h>
> > >   #include <drm/tinydrm/tinydrm-helpers.h>
> > > +#include <drm/drm_of.h>
> > >   #include <linux/delay.h>
> > >   #include <linux/gpio/consumer.h>
> > >   #include <linux/module.h>
> > > @@ -189,7 +190,7 @@ static int mi0283qt_probe(struct spi_device *spi)
> > >   	if (IS_ERR(mipi->regulator))
> > >   		return PTR_ERR(mipi->regulator);
> > > -	mipi->backlight = tinydrm_of_find_backlight(dev);
> > > +	mipi->backlight = drm_of_find_backlight(dev);
> > >   	if (IS_ERR(mipi->backlight))
> > >   		return PTR_ERR(mipi->backlight);
> > > diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> > > index 104dd51..e8fba5b 100644
> > > --- a/include/drm/drm_of.h
> > > +++ b/include/drm/drm_of.h
> > > @@ -29,6 +29,7 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> > >   				int port, int endpoint,
> > >   				struct drm_panel **panel,
> > >   				struct drm_bridge **bridge);
> > > +struct backlight_device *drm_of_find_backlight(struct device *dev);
> > >   #else
> > >   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> > >   						  struct device_node *port)
> > Minor detail I missed: The dummy version for the #else here is missing.
> > Not a problem for tinydrm, but might be an issue for a driver where
> > CONFIG_OF is optional.
> 
> Yeah, we need a dummy version. tinydrm can in theory be used on non-DT
> platforms. The only resource that isn't available there is backlight
> since there is no platform or ACPI way of describing that dependency.
> 
> Another problem I discovered when trying to compile this, is that if
> DRM is builtin and LCD_CLASS_DEVICE is a module:
> 
> drivers/gpu/drm/drm_of.c:292: undefined reference to
> `of_find_backlight_by_node'
> 
> I see that I solved this in tinydrm by just selecting
> BACKLIGHT_LCD_SUPPORT and LCD_CLASS_DEVICE. I'm not aware of a way to
> force LCD_CLASS_DEVICE to be builtin if DRM is builtin.

The usual way to force such an optional depency is

depends on (FOO || FOO=n)

That way it's still optional, but if FOO is enabled as a module, you can't
enable the current symbol as built-in. See e.g. how DRM vs. AGP is
handled.
-Daniel
> 
> Arnd fixed a similar type of dependecy in the repaper driver by forcing
> repaper to be a module if necessary. To be honest, I don't know why his
> fix works:
> https://github.com/torvalds/linux/commit/8312a3fe84b96e30a010fa20f933606d976ac002
> 
> Another way of solving this is to put the function in
> drivers/gpu/drm/drm_backlight.c and add a DRM_BACKLIGHT konfig option
> that does the selection.
> 
> Noralf.
> 
> > Otherwise I think this patch looks good.
> > -Daniel
> > 
> > > diff --git a/include/drm/tinydrm/tinydrm-helpers.h b/include/drm/tinydrm/tinydrm-helpers.h
> > > index d554ded..e40ef2d 100644
> > > --- a/include/drm/tinydrm/tinydrm-helpers.h
> > > +++ b/include/drm/tinydrm/tinydrm-helpers.h
> > > @@ -46,7 +46,6 @@ void tinydrm_xrgb8888_to_rgb565(u16 *dst, void *vaddr,
> > >   void tinydrm_xrgb8888_to_gray8(u8 *dst, void *vaddr, struct drm_framebuffer *fb,
> > >   			       struct drm_clip_rect *clip);
> > > -struct backlight_device *tinydrm_of_find_backlight(struct device *dev);
> > >   int tinydrm_enable_backlight(struct backlight_device *backlight);
> > >   int tinydrm_disable_backlight(struct backlight_device *backlight);
> > > -- 
> > > 2.7.4
> > > 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1089 bytes --]

Hi Meghana,

[auto build test ERROR on drm/drm-next]
[also build test ERROR on v4.14-rc2 next-20170929]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Meghana-Madhyastha/drm-tinydrm-drm_of_find_backlight-helper/20170930-063127
base:   git://people.freedesktop.org/~airlied/linux.git drm-next
config: arm-sunxi_defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

All errors (new ones prefixed by >>):

   drivers/gpu/drm/drm_of.o: In function `drm_of_find_backlight':
>> drm_of.c:(.text+0x3bc): undefined reference to `of_find_backlight_by_node'

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 23035 bytes --]

Re: [PATCH v3 1/2] drm/tinydrm: Move tinydrm_of_find_backlight into drm_of.c

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 1089 bytes --]

Hi Meghana,

[auto build test ERROR on drm/drm-next]
[also build test ERROR on v4.14-rc2 next-20170929]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Meghana-Madhyastha/drm-tinydrm-drm_of_find_backlight-helper/20170930-063127
base:   git://people.freedesktop.org/~airlied/linux.git drm-next
config: arm-sunxi_defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

All errors (new ones prefixed by >>):

   drivers/gpu/drm/drm_of.o: In function `drm_of_find_backlight':
>> drm_of.c:(.text+0x3bc): undefined reference to `of_find_backlight_by_node'

---
0-DAY kernel test infrastructure                Open Source Technology Center
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[PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Meghana Madhyastha]

Add devm_drm_of_find_backlight and the corresponding release
function because some drivers such as tinydrm use devres versions
of functions for requiring device resources.

Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
---
Changes in v3:
-None

 drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_of.h     |  2 ++
 2 files changed, 50 insertions(+)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index d878d3a..238e8e5 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
 	return backlight;
 }
 EXPORT_SYMBOL(drm_of_find_backlight);
+
+/**
+ * devm_drm_of_find_backlight_release - Release backlight device
+ * @dev: Device
+ *
+ * This is the release function corresponding to the devm_drm_of_find_backlight.
+ * Each devres entry is associated with a release function.
+ */
+static void devm_drm_of_find_backlight_release(void *data)
+{
+	put_device(data);
+}
+EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
+
+/**
+ * devm_drm_of_find_backlight - Find backlight device in device-tree
+ * devres version of the function
+ * @dev: Device
+ *
+ * This is the devres version of the function drm_of_find_backlight.
+ * Some drivers such as tinydrm use devres versions of functions for
+ * requiring device resources.
+ *
+ * Returns:
+ * NULL if there's no backlight property.
+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
+ * is found.
+ * If the backlight device is found, a pointer to the structure is returned.
+ */
+struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
+{
+	struct backlight_device *backlight;
+	int ret;
+
+	backlight = drm_of_find_backlight(dev);
+	if (IS_ERR_OR_NULL(backlight))
+		return backlight;
+
+	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
+			      &backlight->dev);
+	if (ret) {
+		put_device(&backlight->dev);
+		return ERR_PTR(ret);
+	}
+
+	return backlight;
+}
+EXPORT_SYMBOL(devm_drm_of_find_backlight);
diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
index e8fba5b..071fb3b 100644
--- a/include/drm/drm_of.h
+++ b/include/drm/drm_of.h
@@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 				struct drm_panel **panel,
 				struct drm_bridge **bridge);
 struct backlight_device *drm_of_find_backlight(struct device *dev);
+struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
 #else
+static void devm_drm_of_find_backlight_release(void *data);
 static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 						  struct device_node *port)
 {
-- 
2.7.4

[PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Meghana Madhyastha]

Add devm_drm_of_find_backlight and the corresponding release
function because some drivers such as tinydrm use devres versions
of functions for requiring device resources.

Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
---
Changes in v3:
-None

 drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_of.h     |  2 ++
 2 files changed, 50 insertions(+)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index d878d3a..238e8e5 100644
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
 	return backlight;
 }
 EXPORT_SYMBOL(drm_of_find_backlight);
+
+/**
+ * devm_drm_of_find_backlight_release - Release backlight device
+ * @dev: Device
+ *
+ * This is the release function corresponding to the devm_drm_of_find_backlight.
+ * Each devres entry is associated with a release function.
+ */
+static void devm_drm_of_find_backlight_release(void *data)
+{
+	put_device(data);
+}
+EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
+
+/**
+ * devm_drm_of_find_backlight - Find backlight device in device-tree
+ * devres version of the function
+ * @dev: Device
+ *
+ * This is the devres version of the function drm_of_find_backlight.
+ * Some drivers such as tinydrm use devres versions of functions for
+ * requiring device resources.
+ *
+ * Returns:
+ * NULL if there's no backlight property.
+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
+ * is found.
+ * If the backlight device is found, a pointer to the structure is returned.
+ */
+struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
+{
+	struct backlight_device *backlight;
+	int ret;
+
+	backlight = drm_of_find_backlight(dev);
+	if (IS_ERR_OR_NULL(backlight))
+		return backlight;
+
+	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
+			      &backlight->dev);
+	if (ret) {
+		put_device(&backlight->dev);
+		return ERR_PTR(ret);
+	}
+
+	return backlight;
+}
+EXPORT_SYMBOL(devm_drm_of_find_backlight);
diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
index e8fba5b..071fb3b 100644
--- a/include/drm/drm_of.h
+++ b/include/drm/drm_of.h
@@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
 				struct drm_panel **panel,
 				struct drm_bridge **bridge);
 struct backlight_device *drm_of_find_backlight(struct device *dev);
+struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
 #else
+static void devm_drm_of_find_backlight_release(void *data);
 static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
 						  struct device_node *port)
 {
-- 
2.7.4

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Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Noralf Trønnes]

Den 28.09.2017 11.15, skrev Meghana Madhyastha:
> Add devm_drm_of_find_backlight and the corresponding release
> function because some drivers such as tinydrm use devres versions
> of functions for requiring device resources.
>
> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> ---
> Changes in v3:
> -None
>
>   drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
>   include/drm/drm_of.h     |  2 ++
>   2 files changed, 50 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index d878d3a..238e8e5 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
>   	return backlight;
>   }
>   EXPORT_SYMBOL(drm_of_find_backlight);
> +
> +/**
> + * devm_drm_of_find_backlight_release - Release backlight device
> + * @dev: Device
> + *
> + * This is the release function corresponding to the devm_drm_of_find_backlight.
> + * Each devres entry is associated with a release function.
> + */

This is an internal function so no need for docs or exporting. I know
that some devm_ functions have explicit release functions, but I don't
think this is necessary since those users can just use
drm_of_find_backlight() directly instead.

> +static void devm_drm_of_find_backlight_release(void *data)
> +{
> +	put_device(data);
> +}
> +EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
> +
> +/**
> + * devm_drm_of_find_backlight - Find backlight device in device-tree
> + * devres version of the function
> + * @dev: Device
> + *
> + * This is the devres version of the function drm_of_find_backlight.
> + * Some drivers such as tinydrm use devres versions of functions for

No need to mention tinydrm here.

> + * requiring device resources.
> + *
> + * Returns:
> + * NULL if there's no backlight property.
> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> + * is found.
> + * If the backlight device is found, a pointer to the structure is returned.
> + */
> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
> +{
> +	struct backlight_device *backlight;
> +	int ret;
> +
> +	backlight = drm_of_find_backlight(dev);
> +	if (IS_ERR_OR_NULL(backlight))
> +		return backlight;
> +
> +	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
> +			      &backlight->dev);
> +	if (ret) {
> +		put_device(&backlight->dev);
> +		return ERR_PTR(ret);
> +	}
> +
> +	return backlight;
> +}
> +EXPORT_SYMBOL(devm_drm_of_find_backlight);
> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> index e8fba5b..071fb3b 100644
> --- a/include/drm/drm_of.h
> +++ b/include/drm/drm_of.h
> @@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>   				struct drm_panel **panel,
>   				struct drm_bridge **bridge);
>   struct backlight_device *drm_of_find_backlight(struct device *dev);
> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
>   #else

We need a dummy version of devm_drm_of_find_backlight() here that
returns NULL as in the previous patch.

> +static void devm_drm_of_find_backlight_release(void *data);

And this isn't needed as explained above.
>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>   						  struct device_node *port)
>   {

I'd appreciate if you could also switch mi0283qt over to this helper :-)

Noralf.

Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Noralf Trønnes]

Den 28.09.2017 11.15, skrev Meghana Madhyastha:
> Add devm_drm_of_find_backlight and the corresponding release
> function because some drivers such as tinydrm use devres versions
> of functions for requiring device resources.
>
> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> ---
> Changes in v3:
> -None
>
>   drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
>   include/drm/drm_of.h     |  2 ++
>   2 files changed, 50 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index d878d3a..238e8e5 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
>   	return backlight;
>   }
>   EXPORT_SYMBOL(drm_of_find_backlight);
> +
> +/**
> + * devm_drm_of_find_backlight_release - Release backlight device
> + * @dev: Device
> + *
> + * This is the release function corresponding to the devm_drm_of_find_backlight.
> + * Each devres entry is associated with a release function.
> + */

This is an internal function so no need for docs or exporting. I know
that some devm_ functions have explicit release functions, but I don't
think this is necessary since those users can just use
drm_of_find_backlight() directly instead.

> +static void devm_drm_of_find_backlight_release(void *data)
> +{
> +	put_device(data);
> +}
> +EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
> +
> +/**
> + * devm_drm_of_find_backlight - Find backlight device in device-tree
> + * devres version of the function
> + * @dev: Device
> + *
> + * This is the devres version of the function drm_of_find_backlight.
> + * Some drivers such as tinydrm use devres versions of functions for

No need to mention tinydrm here.

> + * requiring device resources.
> + *
> + * Returns:
> + * NULL if there's no backlight property.
> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> + * is found.
> + * If the backlight device is found, a pointer to the structure is returned.
> + */
> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
> +{
> +	struct backlight_device *backlight;
> +	int ret;
> +
> +	backlight = drm_of_find_backlight(dev);
> +	if (IS_ERR_OR_NULL(backlight))
> +		return backlight;
> +
> +	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
> +			      &backlight->dev);
> +	if (ret) {
> +		put_device(&backlight->dev);
> +		return ERR_PTR(ret);
> +	}
> +
> +	return backlight;
> +}
> +EXPORT_SYMBOL(devm_drm_of_find_backlight);
> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> index e8fba5b..071fb3b 100644
> --- a/include/drm/drm_of.h
> +++ b/include/drm/drm_of.h
> @@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>   				struct drm_panel **panel,
>   				struct drm_bridge **bridge);
>   struct backlight_device *drm_of_find_backlight(struct device *dev);
> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
>   #else

We need a dummy version of devm_drm_of_find_backlight() here that
returns NULL as in the previous patch.

> +static void devm_drm_of_find_backlight_release(void *data);

And this isn't needed as explained above.
>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>   						  struct device_node *port)
>   {

I'd appreciate if you could also switch mi0283qt over to this helper :-)

Noralf.


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Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Meghana Madhyastha]

On Thu, Sep 28, 2017 at 06:19:35PM +0200, Noralf Tr�nnes wrote:
> 
> Den 28.09.2017 11.15, skrev Meghana Madhyastha:
> >Add devm_drm_of_find_backlight and the corresponding release
> >function because some drivers such as tinydrm use devres versions
> >of functions for requiring device resources.
> >
> >Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >---
> >Changes in v3:
> >-None
> >
> >  drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_of.h     |  2 ++
> >  2 files changed, 50 insertions(+)
> >
> >diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >index d878d3a..238e8e5 100644
> >--- a/drivers/gpu/drm/drm_of.c
> >+++ b/drivers/gpu/drm/drm_of.c
> >@@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
> >  	return backlight;
> >  }
> >  EXPORT_SYMBOL(drm_of_find_backlight);
> >+
> >+/**
> >+ * devm_drm_of_find_backlight_release - Release backlight device
> >+ * @dev: Device
> >+ *
> >+ * This is the release function corresponding to the devm_drm_of_find_backlight.
> >+ * Each devres entry is associated with a release function.
> >+ */
> 
> This is an internal function so no need for docs or exporting. I know
> that some devm_ functions have explicit release functions, but I don't
> think this is necessary since those users can just use
> drm_of_find_backlight() directly instead.

I have a question here. devm_drm_of_find_backlight_release is a
wrapper around put_device which is passed as a parameter to
devm_add_action in devm_drm_of_find_backlight. So isn't the function
useful here ?

> >+static void devm_drm_of_find_backlight_release(void *data)
> >+{
> >+	put_device(data);
> >+}
> >+EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
> >+
> >+/**
> >+ * devm_drm_of_find_backlight - Find backlight device in device-tree
> >+ * devres version of the function
> >+ * @dev: Device
> >+ *
> >+ * This is the devres version of the function drm_of_find_backlight.
> >+ * Some drivers such as tinydrm use devres versions of functions for
> 
> No need to mention tinydrm here.
> 
> >+ * requiring device resources.
> >+ *
> >+ * Returns:
> >+ * NULL if there's no backlight property.
> >+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >+ * is found.
> >+ * If the backlight device is found, a pointer to the structure is returned.
> >+ */
> >+struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
> >+{
> >+	struct backlight_device *backlight;
> >+	int ret;
> >+
> >+	backlight = drm_of_find_backlight(dev);
> >+	if (IS_ERR_OR_NULL(backlight))
> >+		return backlight;
> >+
> >+	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
> >+			      &backlight->dev);
> >+	if (ret) {
> >+		put_device(&backlight->dev);
> >+		return ERR_PTR(ret);
> >+	}
> >+
> >+	return backlight;
> >+}
> >+EXPORT_SYMBOL(devm_drm_of_find_backlight);
> >diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >index e8fba5b..071fb3b 100644
> >--- a/include/drm/drm_of.h
> >+++ b/include/drm/drm_of.h
> >@@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >  				struct drm_panel **panel,
> >  				struct drm_bridge **bridge);
> >  struct backlight_device *drm_of_find_backlight(struct device *dev);
> >+struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
> >  #else
> 
> We need a dummy version of devm_drm_of_find_backlight() here that
> returns NULL as in the previous patch.
> 
> >+static void devm_drm_of_find_backlight_release(void *data);
> 
> And this isn't needed as explained above.
> >  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >  						  struct device_node *port)
> >  {
> 
> I'd appreciate if you could also switch mi0283qt over to this helper :-)
> 
> Noralf.
> 
> 

Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Meghana Madhyastha]

On Thu, Sep 28, 2017 at 06:19:35PM +0200, Noralf Trønnes wrote:
> 
> Den 28.09.2017 11.15, skrev Meghana Madhyastha:
> >Add devm_drm_of_find_backlight and the corresponding release
> >function because some drivers such as tinydrm use devres versions
> >of functions for requiring device resources.
> >
> >Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >---
> >Changes in v3:
> >-None
> >
> >  drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/drm/drm_of.h     |  2 ++
> >  2 files changed, 50 insertions(+)
> >
> >diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >index d878d3a..238e8e5 100644
> >--- a/drivers/gpu/drm/drm_of.c
> >+++ b/drivers/gpu/drm/drm_of.c
> >@@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
> >  	return backlight;
> >  }
> >  EXPORT_SYMBOL(drm_of_find_backlight);
> >+
> >+/**
> >+ * devm_drm_of_find_backlight_release - Release backlight device
> >+ * @dev: Device
> >+ *
> >+ * This is the release function corresponding to the devm_drm_of_find_backlight.
> >+ * Each devres entry is associated with a release function.
> >+ */
> 
> This is an internal function so no need for docs or exporting. I know
> that some devm_ functions have explicit release functions, but I don't
> think this is necessary since those users can just use
> drm_of_find_backlight() directly instead.

I have a question here. devm_drm_of_find_backlight_release is a
wrapper around put_device which is passed as a parameter to
devm_add_action in devm_drm_of_find_backlight. So isn't the function
useful here ?

> >+static void devm_drm_of_find_backlight_release(void *data)
> >+{
> >+	put_device(data);
> >+}
> >+EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
> >+
> >+/**
> >+ * devm_drm_of_find_backlight - Find backlight device in device-tree
> >+ * devres version of the function
> >+ * @dev: Device
> >+ *
> >+ * This is the devres version of the function drm_of_find_backlight.
> >+ * Some drivers such as tinydrm use devres versions of functions for
> 
> No need to mention tinydrm here.
> 
> >+ * requiring device resources.
> >+ *
> >+ * Returns:
> >+ * NULL if there's no backlight property.
> >+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >+ * is found.
> >+ * If the backlight device is found, a pointer to the structure is returned.
> >+ */
> >+struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
> >+{
> >+	struct backlight_device *backlight;
> >+	int ret;
> >+
> >+	backlight = drm_of_find_backlight(dev);
> >+	if (IS_ERR_OR_NULL(backlight))
> >+		return backlight;
> >+
> >+	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
> >+			      &backlight->dev);
> >+	if (ret) {
> >+		put_device(&backlight->dev);
> >+		return ERR_PTR(ret);
> >+	}
> >+
> >+	return backlight;
> >+}
> >+EXPORT_SYMBOL(devm_drm_of_find_backlight);
> >diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >index e8fba5b..071fb3b 100644
> >--- a/include/drm/drm_of.h
> >+++ b/include/drm/drm_of.h
> >@@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >  				struct drm_panel **panel,
> >  				struct drm_bridge **bridge);
> >  struct backlight_device *drm_of_find_backlight(struct device *dev);
> >+struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
> >  #else
> 
> We need a dummy version of devm_drm_of_find_backlight() here that
> returns NULL as in the previous patch.
> 
> >+static void devm_drm_of_find_backlight_release(void *data);
> 
> And this isn't needed as explained above.
> >  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >  						  struct device_node *port)
> >  {
> 
> I'd appreciate if you could also switch mi0283qt over to this helper :-)
> 
> Noralf.
> 
> 
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Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Noralf Trønnes]

Den 29.09.2017 05.17, skrev Meghana Madhyastha:
> On Thu, Sep 28, 2017 at 06:19:35PM +0200, Noralf Trønnes wrote:
>> Den 28.09.2017 11.15, skrev Meghana Madhyastha:
>>> Add devm_drm_of_find_backlight and the corresponding release
>>> function because some drivers such as tinydrm use devres versions
>>> of functions for requiring device resources.
>>>
>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>> ---
>>> Changes in v3:
>>> -None
>>>
>>>   drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
>>>   include/drm/drm_of.h     |  2 ++
>>>   2 files changed, 50 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>> index d878d3a..238e8e5 100644
>>> --- a/drivers/gpu/drm/drm_of.c
>>> +++ b/drivers/gpu/drm/drm_of.c
>>> @@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>   	return backlight;
>>>   }
>>>   EXPORT_SYMBOL(drm_of_find_backlight);
>>> +
>>> +/**
>>> + * devm_drm_of_find_backlight_release - Release backlight device
>>> + * @dev: Device
>>> + *
>>> + * This is the release function corresponding to the devm_drm_of_find_backlight.
>>> + * Each devres entry is associated with a release function.
>>> + */
>> This is an internal function so no need for docs or exporting. I know
>> that some devm_ functions have explicit release functions, but I don't
>> think this is necessary since those users can just use
>> drm_of_find_backlight() directly instead.
> I have a question here. devm_drm_of_find_backlight_release is a
> wrapper around put_device which is passed as a parameter to
> devm_add_action in devm_drm_of_find_backlight. So isn't the function
> useful here ?

We need the function for devm_add_action(), but no one outside of this 
file needs
it. Hence the static definition.

We can't use put_device directly:
     ret = devm_add_action(dev, put_device,
                   &backlight->dev);
because devm_add_action expects an argument like this: void 
(*action)(void *)
and put_device is: void put_device(struct device *dev)
They differ in their argument type: void * vs. struct device *
The compiler would complain.

So we need a wrapper.

>>> +static void devm_drm_of_find_backlight_release(void *data)
>>> +{
>>> +	put_device(data);
>>> +}
>>> +EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
>>> +
>>> +/**
>>> + * devm_drm_of_find_backlight - Find backlight device in device-tree
>>> + * devres version of the function
>>> + * @dev: Device
>>> + *
>>> + * This is the devres version of the function drm_of_find_backlight.
>>> + * Some drivers such as tinydrm use devres versions of functions for
>> No need to mention tinydrm here.
>>
>>> + * requiring device resources.
>>> + *
>>> + * Returns:
>>> + * NULL if there's no backlight property.
>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>> + * is found.
>>> + * If the backlight device is found, a pointer to the structure is returned.
>>> + */
>>> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
>>> +{
>>> +	struct backlight_device *backlight;
>>> +	int ret;
>>> +
>>> +	backlight = drm_of_find_backlight(dev);
>>> +	if (IS_ERR_OR_NULL(backlight))
>>> +		return backlight;
>>> +
>>> +	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
>>> +			      &backlight->dev);
>>> +	if (ret) {
>>> +		put_device(&backlight->dev);
>>> +		return ERR_PTR(ret);
>>> +	}
>>> +
>>> +	return backlight;
>>> +}
>>> +EXPORT_SYMBOL(devm_drm_of_find_backlight);
>>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>>> index e8fba5b..071fb3b 100644
>>> --- a/include/drm/drm_of.h
>>> +++ b/include/drm/drm_of.h
>>> @@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>   				struct drm_panel **panel,
>>>   				struct drm_bridge **bridge);
>>>   struct backlight_device *drm_of_find_backlight(struct device *dev);
>>> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
>>>   #else
>> We need a dummy version of devm_drm_of_find_backlight() here that
>> returns NULL as in the previous patch.
>>
>>> +static void devm_drm_of_find_backlight_release(void *data);
>> And this isn't needed as explained above.
>>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>>   						  struct device_node *port)
>>>   {
>> I'd appreciate if you could also switch mi0283qt over to this helper :-)
>>
>> Noralf.
>>
>>

Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Noralf Trønnes]

Den 29.09.2017 05.17, skrev Meghana Madhyastha:
> On Thu, Sep 28, 2017 at 06:19:35PM +0200, Noralf Trønnes wrote:
>> Den 28.09.2017 11.15, skrev Meghana Madhyastha:
>>> Add devm_drm_of_find_backlight and the corresponding release
>>> function because some drivers such as tinydrm use devres versions
>>> of functions for requiring device resources.
>>>
>>> Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
>>> ---
>>> Changes in v3:
>>> -None
>>>
>>>   drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
>>>   include/drm/drm_of.h     |  2 ++
>>>   2 files changed, 50 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
>>> index d878d3a..238e8e5 100644
>>> --- a/drivers/gpu/drm/drm_of.c
>>> +++ b/drivers/gpu/drm/drm_of.c
>>> @@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
>>>   	return backlight;
>>>   }
>>>   EXPORT_SYMBOL(drm_of_find_backlight);
>>> +
>>> +/**
>>> + * devm_drm_of_find_backlight_release - Release backlight device
>>> + * @dev: Device
>>> + *
>>> + * This is the release function corresponding to the devm_drm_of_find_backlight.
>>> + * Each devres entry is associated with a release function.
>>> + */
>> This is an internal function so no need for docs or exporting. I know
>> that some devm_ functions have explicit release functions, but I don't
>> think this is necessary since those users can just use
>> drm_of_find_backlight() directly instead.
> I have a question here. devm_drm_of_find_backlight_release is a
> wrapper around put_device which is passed as a parameter to
> devm_add_action in devm_drm_of_find_backlight. So isn't the function
> useful here ?

We need the function for devm_add_action(), but no one outside of this 
file needs
it. Hence the static definition.

We can't use put_device directly:
     ret = devm_add_action(dev, put_device,
                   &backlight->dev);
because devm_add_action expects an argument like this: void 
(*action)(void *)
and put_device is: void put_device(struct device *dev)
They differ in their argument type: void * vs. struct device *
The compiler would complain.

So we need a wrapper.

>>> +static void devm_drm_of_find_backlight_release(void *data)
>>> +{
>>> +	put_device(data);
>>> +}
>>> +EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
>>> +
>>> +/**
>>> + * devm_drm_of_find_backlight - Find backlight device in device-tree
>>> + * devres version of the function
>>> + * @dev: Device
>>> + *
>>> + * This is the devres version of the function drm_of_find_backlight.
>>> + * Some drivers such as tinydrm use devres versions of functions for
>> No need to mention tinydrm here.
>>
>>> + * requiring device resources.
>>> + *
>>> + * Returns:
>>> + * NULL if there's no backlight property.
>>> + * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
>>> + * is found.
>>> + * If the backlight device is found, a pointer to the structure is returned.
>>> + */
>>> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
>>> +{
>>> +	struct backlight_device *backlight;
>>> +	int ret;
>>> +
>>> +	backlight = drm_of_find_backlight(dev);
>>> +	if (IS_ERR_OR_NULL(backlight))
>>> +		return backlight;
>>> +
>>> +	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
>>> +			      &backlight->dev);
>>> +	if (ret) {
>>> +		put_device(&backlight->dev);
>>> +		return ERR_PTR(ret);
>>> +	}
>>> +
>>> +	return backlight;
>>> +}
>>> +EXPORT_SYMBOL(devm_drm_of_find_backlight);
>>> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
>>> index e8fba5b..071fb3b 100644
>>> --- a/include/drm/drm_of.h
>>> +++ b/include/drm/drm_of.h
>>> @@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
>>>   				struct drm_panel **panel,
>>>   				struct drm_bridge **bridge);
>>>   struct backlight_device *drm_of_find_backlight(struct device *dev);
>>> +struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
>>>   #else
>> We need a dummy version of devm_drm_of_find_backlight() here that
>> returns NULL as in the previous patch.
>>
>>> +static void devm_drm_of_find_backlight_release(void *data);
>> And this isn't needed as explained above.
>>>   static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
>>>   						  struct device_node *port)
>>>   {
>> I'd appreciate if you could also switch mi0283qt over to this helper :-)
>>
>> Noralf.
>>
>>

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Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 02:20:16PM +0200, Noralf Tr�nnes wrote:
> 
> Den 29.09.2017 05.17, skrev Meghana Madhyastha:
> >On Thu, Sep 28, 2017 at 06:19:35PM +0200, Noralf Tr�nnes wrote:
> >>Den 28.09.2017 11.15, skrev Meghana Madhyastha:
> >>>Add devm_drm_of_find_backlight and the corresponding release
> >>>function because some drivers such as tinydrm use devres versions
> >>>of functions for requiring device resources.
> >>>
> >>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>---
> >>>Changes in v3:
> >>>-None
> >>>
> >>>  drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> >>>  include/drm/drm_of.h     |  2 ++
> >>>  2 files changed, 50 insertions(+)
> >>>
> >>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>index d878d3a..238e8e5 100644
> >>>--- a/drivers/gpu/drm/drm_of.c
> >>>+++ b/drivers/gpu/drm/drm_of.c
> >>>@@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>  	return backlight;
> >>>  }
> >>>  EXPORT_SYMBOL(drm_of_find_backlight);
> >>>+
> >>>+/**
> >>>+ * devm_drm_of_find_backlight_release - Release backlight device
> >>>+ * @dev: Device
> >>>+ *
> >>>+ * This is the release function corresponding to the devm_drm_of_find_backlight.
> >>>+ * Each devres entry is associated with a release function.
> >>>+ */
> >>This is an internal function so no need for docs or exporting. I know
> >>that some devm_ functions have explicit release functions, but I don't
> >>think this is necessary since those users can just use
> >>drm_of_find_backlight() directly instead.
> >I have a question here. devm_drm_of_find_backlight_release is a
> >wrapper around put_device which is passed as a parameter to
> >devm_add_action in devm_drm_of_find_backlight. So isn't the function
> >useful here ?
> 
> We need the function for devm_add_action(), but no one outside of this file
> needs
> it. Hence the static definition.
> 
> We can't use put_device directly:
> ��� ret = devm_add_action(dev, put_device,
> ��� ��� ��� ����� &backlight->dev);
> because devm_add_action expects an argument like this: void (*action)(void
> *)
> and put_device is: void put_device(struct device *dev)
> They differ in their argument type: void * vs. struct device *
> The compiler would complain.
> 
> So we need a wrapper.

Yes this is what I thought. Okay, I misunderstood your previous
suggestion as removing the release function entirely which is why I
asked my question. Now it makes sense and I understood.

Thanks for the clarifications.

Regards,
Meghana
> >>>+static void devm_drm_of_find_backlight_release(void *data)
> >>>+{
> >>>+	put_device(data);
> >>>+}
> >>>+EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
> >>>+
> >>>+/**
> >>>+ * devm_drm_of_find_backlight - Find backlight device in device-tree
> >>>+ * devres version of the function
> >>>+ * @dev: Device
> >>>+ *
> >>>+ * This is the devres version of the function drm_of_find_backlight.
> >>>+ * Some drivers such as tinydrm use devres versions of functions for
> >>No need to mention tinydrm here.
> >>
> >>>+ * requiring device resources.
> >>>+ *
> >>>+ * Returns:
> >>>+ * NULL if there's no backlight property.
> >>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>+ * is found.
> >>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>+ */
> >>>+struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
> >>>+{
> >>>+	struct backlight_device *backlight;
> >>>+	int ret;
> >>>+
> >>>+	backlight = drm_of_find_backlight(dev);
> >>>+	if (IS_ERR_OR_NULL(backlight))
> >>>+		return backlight;
> >>>+
> >>>+	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
> >>>+			      &backlight->dev);
> >>>+	if (ret) {
> >>>+		put_device(&backlight->dev);
> >>>+		return ERR_PTR(ret);
> >>>+	}
> >>>+
> >>>+	return backlight;
> >>>+}
> >>>+EXPORT_SYMBOL(devm_drm_of_find_backlight);
> >>>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>>index e8fba5b..071fb3b 100644
> >>>--- a/include/drm/drm_of.h
> >>>+++ b/include/drm/drm_of.h
> >>>@@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>  				struct drm_panel **panel,
> >>>  				struct drm_bridge **bridge);
> >>>  struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>>+struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
> >>>  #else
> >>We need a dummy version of devm_drm_of_find_backlight() here that
> >>returns NULL as in the previous patch.
> >>
> >>>+static void devm_drm_of_find_backlight_release(void *data);
> >>And this isn't needed as explained above.
> >>>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>>  						  struct device_node *port)
> >>>  {
> >>I'd appreciate if you could also switch mi0283qt over to this helper :-)
> >>
> >>Noralf.
> >>
> >>
> 

Re: [PATCH v3 2/2] drm/tinydrm: Add devres versions of drm_of_find_backlight

[Meghana Madhyastha]

On Fri, Sep 29, 2017 at 02:20:16PM +0200, Noralf Trønnes wrote:
> 
> Den 29.09.2017 05.17, skrev Meghana Madhyastha:
> >On Thu, Sep 28, 2017 at 06:19:35PM +0200, Noralf Trønnes wrote:
> >>Den 28.09.2017 11.15, skrev Meghana Madhyastha:
> >>>Add devm_drm_of_find_backlight and the corresponding release
> >>>function because some drivers such as tinydrm use devres versions
> >>>of functions for requiring device resources.
> >>>
> >>>Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
> >>>---
> >>>Changes in v3:
> >>>-None
> >>>
> >>>  drivers/gpu/drm/drm_of.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
> >>>  include/drm/drm_of.h     |  2 ++
> >>>  2 files changed, 50 insertions(+)
> >>>
> >>>diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> >>>index d878d3a..238e8e5 100644
> >>>--- a/drivers/gpu/drm/drm_of.c
> >>>+++ b/drivers/gpu/drm/drm_of.c
> >>>@@ -304,3 +304,51 @@ struct backlight_device *drm_of_find_backlight(struct device *dev)
> >>>  	return backlight;
> >>>  }
> >>>  EXPORT_SYMBOL(drm_of_find_backlight);
> >>>+
> >>>+/**
> >>>+ * devm_drm_of_find_backlight_release - Release backlight device
> >>>+ * @dev: Device
> >>>+ *
> >>>+ * This is the release function corresponding to the devm_drm_of_find_backlight.
> >>>+ * Each devres entry is associated with a release function.
> >>>+ */
> >>This is an internal function so no need for docs or exporting. I know
> >>that some devm_ functions have explicit release functions, but I don't
> >>think this is necessary since those users can just use
> >>drm_of_find_backlight() directly instead.
> >I have a question here. devm_drm_of_find_backlight_release is a
> >wrapper around put_device which is passed as a parameter to
> >devm_add_action in devm_drm_of_find_backlight. So isn't the function
> >useful here ?
> 
> We need the function for devm_add_action(), but no one outside of this file
> needs
> it. Hence the static definition.
> 
> We can't use put_device directly:
>     ret = devm_add_action(dev, put_device,
>                   &backlight->dev);
> because devm_add_action expects an argument like this: void (*action)(void
> *)
> and put_device is: void put_device(struct device *dev)
> They differ in their argument type: void * vs. struct device *
> The compiler would complain.
> 
> So we need a wrapper.

Yes this is what I thought. Okay, I misunderstood your previous
suggestion as removing the release function entirely which is why I
asked my question. Now it makes sense and I understood.

Thanks for the clarifications.

Regards,
Meghana
> >>>+static void devm_drm_of_find_backlight_release(void *data)
> >>>+{
> >>>+	put_device(data);
> >>>+}
> >>>+EXPORT_SYMBOL(devm_drm_of_find_backlight_release);
> >>>+
> >>>+/**
> >>>+ * devm_drm_of_find_backlight - Find backlight device in device-tree
> >>>+ * devres version of the function
> >>>+ * @dev: Device
> >>>+ *
> >>>+ * This is the devres version of the function drm_of_find_backlight.
> >>>+ * Some drivers such as tinydrm use devres versions of functions for
> >>No need to mention tinydrm here.
> >>
> >>>+ * requiring device resources.
> >>>+ *
> >>>+ * Returns:
> >>>+ * NULL if there's no backlight property.
> >>>+ * Error pointer -EPROBE_DEFER if the DT node is found, but no backlight device
> >>>+ * is found.
> >>>+ * If the backlight device is found, a pointer to the structure is returned.
> >>>+ */
> >>>+struct backlight_device *devm_drm_of_find_backlight(struct device *dev)
> >>>+{
> >>>+	struct backlight_device *backlight;
> >>>+	int ret;
> >>>+
> >>>+	backlight = drm_of_find_backlight(dev);
> >>>+	if (IS_ERR_OR_NULL(backlight))
> >>>+		return backlight;
> >>>+
> >>>+	ret = devm_add_action(dev, devm_drm_of_find_backlight_release,
> >>>+			      &backlight->dev);
> >>>+	if (ret) {
> >>>+		put_device(&backlight->dev);
> >>>+		return ERR_PTR(ret);
> >>>+	}
> >>>+
> >>>+	return backlight;
> >>>+}
> >>>+EXPORT_SYMBOL(devm_drm_of_find_backlight);
> >>>diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> >>>index e8fba5b..071fb3b 100644
> >>>--- a/include/drm/drm_of.h
> >>>+++ b/include/drm/drm_of.h
> >>>@@ -30,7 +30,9 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> >>>  				struct drm_panel **panel,
> >>>  				struct drm_bridge **bridge);
> >>>  struct backlight_device *drm_of_find_backlight(struct device *dev);
> >>>+struct backlight_device *devm_drm_of_find_backlight(struct device *dev);
> >>>  #else
> >>We need a dummy version of devm_drm_of_find_backlight() here that
> >>returns NULL as in the previous patch.
> >>
> >>>+static void devm_drm_of_find_backlight_release(void *data);
> >>And this isn't needed as explained above.
> >>>  static inline uint32_t drm_of_find_possible_crtcs(struct drm_device *dev,
> >>>  						  struct device_node *port)
> >>>  {
> >>I'd appreciate if you could also switch mi0283qt over to this helper :-)
> >>
> >>Noralf.
> >>
> >>
> 
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