[PATCH 1/8] drm/probe-helper: warn about negative .get_modes()

[PATCH 1/8] drm/probe-helper: warn about negative .get_modes()

[Jani Nikula]

The .get_modes() callback is supposed to return the number of modes,
never a negative error code. If a negative value is returned, it'll just
be interpreted as a negative count, and added to previous calculations.

Document the rules, but handle the negative values gracefully with an
error message.

Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/drm_probe_helper.c       | 7 +++++++
 include/drm/drm_modeset_helper_vtables.h | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
index 4d60cc810b57..bf2dd1f46b6c 100644
--- a/drivers/gpu/drm/drm_probe_helper.c
+++ b/drivers/gpu/drm/drm_probe_helper.c
@@ -422,6 +422,13 @@ static int drm_helper_probe_get_modes(struct drm_connector *connector)
 
 	count = connector_funcs->get_modes(connector);
 
+	/* The .get_modes() callback should not return negative values. */
+	if (count < 0) {
+		drm_err(connector->dev, ".get_modes() returned %pe\n",
+			ERR_PTR(count));
+		count = 0;
+	}
+
 	/*
 	 * Fallback for when DDC probe failed in drm_get_edid() and thus skipped
 	 * override/firmware EDID.
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index 881b03e4dc28..9ed42469540e 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -898,7 +898,8 @@ struct drm_connector_helper_funcs {
 	 *
 	 * RETURNS:
 	 *
-	 * The number of modes added by calling drm_mode_probed_add().
+	 * The number of modes added by calling drm_mode_probed_add(). Return 0
+	 * on failures (no modes) instead of negative error codes.
 	 */
 	int (*get_modes)(struct drm_connector *connector);
 
-- 
2.39.2

[PATCH 2/8] drm/panel: do not return negative error codes from drm_panel_get_modes()

[Jani Nikula]

None of the callers of drm_panel_get_modes() expect it to return
negative error codes. Either they propagate the return value in their
struct drm_connector_helper_funcs .get_modes() hook (which is also not
supposed to return negative codes), or add it to other counts leading to
bogus values.

On the other hand, many of the struct drm_panel_funcs .get_modes() hooks
do return negative error codes, so handle them gracefully instead of
propagating further.

Return 0 for no modes, whatever the reason.

Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Jessica Zhang <quic_jesszhan@quicinc.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/drm_panel.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index e814020bbcd3..cfbe020de54e 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -274,19 +274,24 @@ EXPORT_SYMBOL(drm_panel_disable);
  * The modes probed from the panel are automatically added to the connector
  * that the panel is attached to.
  *
- * Return: The number of modes available from the panel on success or a
- * negative error code on failure.
+ * Return: The number of modes available from the panel on success, or 0 on
+ * failure (no modes).
  */
 int drm_panel_get_modes(struct drm_panel *panel,
 			struct drm_connector *connector)
 {
 	if (!panel)
-		return -EINVAL;
+		return 0;
 
-	if (panel->funcs && panel->funcs->get_modes)
-		return panel->funcs->get_modes(panel, connector);
+	if (panel->funcs && panel->funcs->get_modes) {
+		int num;
 
-	return -EOPNOTSUPP;
+		num = panel->funcs->get_modes(panel, connector);
+		if (num > 0)
+			return num;
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(drm_panel_get_modes);
 
-- 
2.39.2

Re: [PATCH 2/8] drm/panel: do not return negative error codes from drm_panel_get_modes()

[Jessica Zhang]

On 3/8/2024 8:03 AM, Jani Nikula wrote:
> None of the callers of drm_panel_get_modes() expect it to return
> negative error codes. Either they propagate the return value in their
> struct drm_connector_helper_funcs .get_modes() hook (which is also not
> supposed to return negative codes), or add it to other counts leading to
> bogus values.
> 
> On the other hand, many of the struct drm_panel_funcs .get_modes() hooks
> do return negative error codes, so handle them gracefully instead of
> propagating further.
> 
> Return 0 for no modes, whatever the reason.
> 
> Cc: Neil Armstrong <neil.armstrong@linaro.org>
> Cc: Jessica Zhang <quic_jesszhan@quicinc.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>   drivers/gpu/drm/drm_panel.c | 17 +++++++++++------
>   1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> index e814020bbcd3..cfbe020de54e 100644
> --- a/drivers/gpu/drm/drm_panel.c
> +++ b/drivers/gpu/drm/drm_panel.c
> @@ -274,19 +274,24 @@ EXPORT_SYMBOL(drm_panel_disable);
>    * The modes probed from the panel are automatically added to the connector
>    * that the panel is attached to.
>    *
> - * Return: The number of modes available from the panel on success or a
> - * negative error code on failure.
> + * Return: The number of modes available from the panel on success, or 0 on
> + * failure (no modes).
>    */
>   int drm_panel_get_modes(struct drm_panel *panel,
>   			struct drm_connector *connector)
>   {
>   	if (!panel)
> -		return -EINVAL;
> +		return 0;
>   
> -	if (panel->funcs && panel->funcs->get_modes)
> -		return panel->funcs->get_modes(panel, connector);
> +	if (panel->funcs && panel->funcs->get_modes) {
> +		int num;
>   
> -	return -EOPNOTSUPP;
> +		num = panel->funcs->get_modes(panel, connector);
> +		if (num > 0)
> +			return num;

Hi Jani,

The change LGTM:

Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>

Thanks,

Jessica Zhang

> +	}
> +
> +	return 0;
>   }
>   EXPORT_SYMBOL(drm_panel_get_modes);
>   
> -- 
> 2.39.2
> 

Re: [PATCH 2/8] drm/panel: do not return negative error codes from drm_panel_get_modes()

[Neil Armstrong]

On 08/03/2024 17:03, Jani Nikula wrote:
> None of the callers of drm_panel_get_modes() expect it to return
> negative error codes. Either they propagate the return value in their
> struct drm_connector_helper_funcs .get_modes() hook (which is also not
> supposed to return negative codes), or add it to other counts leading to
> bogus values.
> 
> On the other hand, many of the struct drm_panel_funcs .get_modes() hooks
> do return negative error codes, so handle them gracefully instead of
> propagating further.
> 
> Return 0 for no modes, whatever the reason.
> 
> Cc: Neil Armstrong <neil.armstrong@linaro.org>
> Cc: Jessica Zhang <quic_jesszhan@quicinc.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
> ---
>   drivers/gpu/drm/drm_panel.c | 17 +++++++++++------
>   1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
> index e814020bbcd3..cfbe020de54e 100644
> --- a/drivers/gpu/drm/drm_panel.c
> +++ b/drivers/gpu/drm/drm_panel.c
> @@ -274,19 +274,24 @@ EXPORT_SYMBOL(drm_panel_disable);
>    * The modes probed from the panel are automatically added to the connector
>    * that the panel is attached to.
>    *
> - * Return: The number of modes available from the panel on success or a
> - * negative error code on failure.
> + * Return: The number of modes available from the panel on success, or 0 on
> + * failure (no modes).
>    */
>   int drm_panel_get_modes(struct drm_panel *panel,
>   			struct drm_connector *connector)
>   {
>   	if (!panel)
> -		return -EINVAL;
> +		return 0;
>   
> -	if (panel->funcs && panel->funcs->get_modes)
> -		return panel->funcs->get_modes(panel, connector);
> +	if (panel->funcs && panel->funcs->get_modes) {
> +		int num;
>   
> -	return -EOPNOTSUPP;
> +		num = panel->funcs->get_modes(panel, connector);
> +		if (num > 0)
> +			return num;
> +	}
> +
> +	return 0;
>   }
>   EXPORT_SYMBOL(drm_panel_get_modes);
>   

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>

[PATCH 3/8] drm/exynos: do not return negative values from .get_modes()

[Jani Nikula]

The .get_modes() hooks aren't supposed to return negative error
codes. Return 0 for no modes, whatever the reason.

Cc: Inki Dae <inki.dae@samsung.com>
Cc: Seung-Woo Kim <sw0312.kim@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/exynos/exynos_drm_vidi.c | 4 ++--
 drivers/gpu/drm/exynos/exynos_hdmi.c     | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_vidi.c b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
index 00382f28748a..f5bbba9ad225 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_vidi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
@@ -316,14 +316,14 @@ static int vidi_get_modes(struct drm_connector *connector)
 	 */
 	if (!ctx->raw_edid) {
 		DRM_DEV_DEBUG_KMS(ctx->dev, "raw_edid is null.\n");
-		return -EFAULT;
+		return 0;
 	}
 
 	edid_len = (1 + ctx->raw_edid->extensions) * EDID_LENGTH;
 	edid = kmemdup(ctx->raw_edid, edid_len, GFP_KERNEL);
 	if (!edid) {
 		DRM_DEV_DEBUG_KMS(ctx->dev, "failed to allocate edid\n");
-		return -ENOMEM;
+		return 0;
 	}
 
 	drm_connector_update_edid_property(connector, edid);
diff --git a/drivers/gpu/drm/exynos/exynos_hdmi.c b/drivers/gpu/drm/exynos/exynos_hdmi.c
index 43bed6cbaaea..b1d02dec3774 100644
--- a/drivers/gpu/drm/exynos/exynos_hdmi.c
+++ b/drivers/gpu/drm/exynos/exynos_hdmi.c
@@ -887,11 +887,11 @@ static int hdmi_get_modes(struct drm_connector *connector)
 	int ret;
 
 	if (!hdata->ddc_adpt)
-		return -ENODEV;
+		return 0;
 
 	edid = drm_get_edid(connector, hdata->ddc_adpt);
 	if (!edid)
-		return -ENODEV;
+		return 0;
 
 	hdata->dvi_mode = !connector->display_info.is_hdmi;
 	DRM_DEV_DEBUG_KMS(hdata->dev, "%s : width[%d] x height[%d]\n",
-- 
2.39.2

[PATCH 4/8] drm/bridge: lt8912b: do not return negative values from .get_modes()

[Jani Nikula]

The .get_modes() hooks aren't supposed to return negative error
codes. Return 0 for no modes, whatever the reason.

Cc: Adrien Grassein <adrien.grassein@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/bridge/lontium-lt8912b.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt8912b.c b/drivers/gpu/drm/bridge/lontium-lt8912b.c
index e7c4bef74aa4..4b2ae27f0a57 100644
--- a/drivers/gpu/drm/bridge/lontium-lt8912b.c
+++ b/drivers/gpu/drm/bridge/lontium-lt8912b.c
@@ -441,23 +441,21 @@ lt8912_connector_mode_valid(struct drm_connector *connector,
 static int lt8912_connector_get_modes(struct drm_connector *connector)
 {
 	const struct drm_edid *drm_edid;
-	int ret = -1;
-	int num = 0;
 	struct lt8912 *lt = connector_to_lt8912(connector);
 	u32 bus_format = MEDIA_BUS_FMT_RGB888_1X24;
+	int ret, num;
 
 	drm_edid = drm_bridge_edid_read(lt->hdmi_port, connector);
 	drm_edid_connector_update(connector, drm_edid);
-	if (drm_edid) {
-		num = drm_edid_connector_add_modes(connector);
-	} else {
-		return ret;
-	}
+	if (!drm_edid)
+		return 0;
+
+	num = drm_edid_connector_add_modes(connector);
 
 	ret = drm_display_info_set_bus_formats(&connector->display_info,
 					       &bus_format, 1);
-	if (ret)
-		num = ret;
+	if (ret < 0)
+		num = 0;
 
 	drm_edid_free(drm_edid);
 	return num;
-- 
2.39.2

[PATCH 5/8] drm/imx/ipuv3: do not return negative values from .get_modes()

[Jani Nikula]

The .get_modes() hooks aren't supposed to return negative error
codes. Return 0 for no modes, whatever the reason.

Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/imx/ipuv3/parallel-display.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/imx/ipuv3/parallel-display.c b/drivers/gpu/drm/imx/ipuv3/parallel-display.c
index 70349739dd89..55dedd73f528 100644
--- a/drivers/gpu/drm/imx/ipuv3/parallel-display.c
+++ b/drivers/gpu/drm/imx/ipuv3/parallel-display.c
@@ -72,14 +72,14 @@ static int imx_pd_connector_get_modes(struct drm_connector *connector)
 		int ret;
 
 		if (!mode)
-			return -EINVAL;
+			return 0;
 
 		ret = of_get_drm_display_mode(np, &imxpd->mode,
 					      &imxpd->bus_flags,
 					      OF_USE_NATIVE_MODE);
 		if (ret) {
 			drm_mode_destroy(connector->dev, mode);
-			return ret;
+			return 0;
 		}
 
 		drm_mode_copy(mode, &imxpd->mode);
-- 
2.39.2

Re: [PATCH 5/8] drm/imx/ipuv3: do not return negative values from .get_modes()

[Philipp Zabel]

On Fr, 2024-03-08 at 18:03 +0200, Jani Nikula wrote:
> The .get_modes() hooks aren't supposed to return negative error
> codes. Return 0 for no modes, whatever the reason.
> 
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> Cc: stable@vger.kernel.org
> Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Acked-by: Philipp Zabel <p.zabel@pengutronix.de>

regards
Philipp

[PATCH 6/8] drm/vc4: hdmi: do not return negative values from .get_modes()

[Jani Nikula]

The .get_modes() hooks aren't supposed to return negative error
codes. Return 0 for no modes, whatever the reason.

Cc: Maxime Ripard <mripard@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 34f807ed1c31..d8751ea20303 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -509,7 +509,7 @@ static int vc4_hdmi_connector_get_modes(struct drm_connector *connector)
 	edid = drm_get_edid(connector, vc4_hdmi->ddc);
 	cec_s_phys_addr_from_edid(vc4_hdmi->cec_adap, edid);
 	if (!edid)
-		return -ENODEV;
+		return 0;
 
 	drm_connector_update_edid_property(connector, edid);
 	ret = drm_add_edid_modes(connector, edid);
-- 
2.39.2

Re: [PATCH 6/8] drm/vc4: hdmi: do not return negative values from .get_modes()

[Maxime Ripard]

On Fri, 8 Mar 2024 18:03:44 +0200, Jani Nikula wrote:
> The .get_modes() hooks aren't supposed to return negative error
> codes. Return 0 for no modes, whatever the reason.
> 
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: stable@vger.kernel.org
> 
> [ ... ]

Acked-by: Maxime Ripard <mripard@kernel.org>

Thanks!
Maxime