[PATCH 0/4] Add backlight registration notification and use it in acpi-video

[PATCH 0/4] Add backlight registration notification and use it in acpi-video

[Hans de Goede]

Hi all,

Here is a patch series to make video.use_native_backlight work on laptops
with nv gfx, at least on those were nv gfx have a raw backlight interface.

I've tried this on my own somewhat old nv equipped laptop, but that does
not have a raw backlight interface.

I'm currently doing a scratch build of the Fedora-20 kernel with this patches
for the user with an affected system to test.

Regards,

Hans

[PATCH 1/4] nouveau: Don't check acpi_video_backlight_support() before registering backlight

[Hans de Goede]

acpi_video_backlight_support() is supposed to be called by other (vendor
specific) firmware backlight controls, not by native / raw backlight controls
like nv_backlight.

Userspace will normally prefer firmware interfaces over raw interfaces, so
if acpi_video backlight support is present it will use that even if
nv_backlight is registered as well.

Except when video.use_native_backlight is present on the kernel cmdline
(or enabled through a dmi based quirk). As the name indicates the goal here
is to make only the raw interface available to userspace so that it will use
that (it only does this when it sees a win8 compliant bios).

This is done by:
1) Not registering any acpi_video# backlight devices; and
2) Making acpi_video_backlight_support() return true so that other firmware
drivers, ie acer_wmi, thinkpad_acpi, dell_laptop, etc. Don't register their
own vender specific interfaces.

Currently nouveau breaks this setup, as when acpi_video_backlight_support()
returns true, it does not register itself, resulting in no backlight control
at all.

This is esp. going to be a problem with 3.16 which will default to
video.use_native_backlight=1, and thus nouveau based laptops with a win8 bios
will get no backlight control at all.

This also likely explains why the previous attempt to make
video.use_native_backlight=1 the default was not a success, as without this
patch having a default of video.use_native_backlight=1 will cause regressions.

Note this effectively reverts commit 5bead799

Also see: https://bugzilla.redhat.com/show_bug.cgi?id\x1093171

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/gpu/drm/nouveau/nouveau_backlight.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c
index 630f6e8..2c1e4aa 100644
--- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
+++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
@@ -31,7 +31,6 @@
  */
 
 #include <linux/backlight.h>
-#include <linux/acpi.h>
 
 #include "nouveau_drm.h"
 #include "nouveau_reg.h"
@@ -222,14 +221,6 @@ nouveau_backlight_init(struct drm_device *dev)
 	struct nouveau_device *device = nv_device(drm->device);
 	struct drm_connector *connector;
 
-#ifdef CONFIG_ACPI
-	if (acpi_video_backlight_support()) {
-		NV_INFO(drm, "ACPI backlight interface available, "
-			     "not registering our own\n");
-		return 0;
-	}
-#endif
-
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
 		if (connector->connector_type != DRM_MODE_CONNECTOR_LVDS &&
 		    connector->connector_type != DRM_MODE_CONNECTOR_eDP)
-- 
1.9.0

[PATCH 2/4] backlight: Add backlight device (un)registration notification

[Hans de Goede]

Some firmware drivers, ie acpi-video want to get themselves out of the
way (in some cases) when their also is a raw backlight device available.

Due to module loading ordering being unknown, acpi-video cannot be certain
that the backlight_device_registered(BACKLIGHT_RAW) it does for this is
the final verdict wrt there being a BACKLIGHT_RAW device.

By adding notification acpi-video can listen for backlight devices showing
up after it has loaded, and unregister its backlight device if desired.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/video/backlight/backlight.c | 40 +++++++++++++++++++++++++++++++++++++
 include/linux/backlight.h           |  7 +++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index bd2172c..4280890 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -23,6 +23,7 @@
 
 static struct list_head backlight_dev_list;
 static struct mutex backlight_dev_list_mutex;
+static struct blocking_notifier_head backlight_notifier;
 
 static const char *const backlight_types[] = {
 	[BACKLIGHT_RAW] = "raw",
@@ -370,6 +371,9 @@ struct backlight_device *backlight_device_register(const char *name,
 	list_add(&new_bd->entry, &backlight_dev_list);
 	mutex_unlock(&backlight_dev_list_mutex);
 
+	blocking_notifier_call_chain(&backlight_notifier,
+				     BACKLIGHT_REGISTERED, new_bd);
+
 	return new_bd;
 }
 EXPORT_SYMBOL(backlight_device_register);
@@ -413,6 +417,10 @@ void backlight_device_unregister(struct backlight_device *bd)
 		pmac_backlight = NULL;
 	mutex_unlock(&pmac_backlight_mutex);
 #endif
+
+	blocking_notifier_call_chain(&backlight_notifier,
+				     BACKLIGHT_UNREGISTERED, bd);
+
 	mutex_lock(&bd->ops_lock);
 	bd->ops = NULL;
 	mutex_unlock(&bd->ops_lock);
@@ -438,6 +446,36 @@ static int devm_backlight_device_match(struct device *dev, void *res,
 }
 
 /**
+ * backlight_register_notifier - get notified of backlight (un)registration
+ * @nb: notifier block with the notifier to call on backlight (un)registration
+ *
+ * @return 0 on success, otherwise a negative error code
+ *
+ * Register a notifier to get notified when backlight devices get registered
+ * or unregistered.
+ */
+int backlight_register_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&backlight_notifier, nb);
+}
+EXPORT_SYMBOL(backlight_register_notifier);
+
+/**
+ * backlight_unregister_notifier - unregister a backlight notifier
+ * @nb: notifier block to unregister
+ *
+ * @return 0 on success, otherwise a negative error code
+ *
+ * Register a notifier to get notified when backlight devices get registered
+ * or unregistered.
+ */
+int backlight_unregister_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&backlight_notifier, nb);
+}
+EXPORT_SYMBOL(backlight_unregister_notifier);
+
+/**
  * devm_backlight_device_register - resource managed backlight_device_register()
  * @dev: the device to register
  * @name: the name of the device
@@ -544,6 +582,8 @@ static int __init backlight_class_init(void)
 	backlight_class->pm = &backlight_class_dev_pm_ops;
 	INIT_LIST_HEAD(&backlight_dev_list);
 	mutex_init(&backlight_dev_list_mutex);
+	BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);
+
 	return 0;
 }
 
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 7264742..adb14a8 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -40,6 +40,11 @@ enum backlight_type {
 	BACKLIGHT_TYPE_MAX,
 };
 
+enum backlight_notification {
+	BACKLIGHT_REGISTERED,
+	BACKLIGHT_UNREGISTERED,
+};
+
 struct backlight_device;
 struct fb_info;
 
@@ -133,6 +138,8 @@ extern void devm_backlight_device_unregister(struct device *dev,
 extern void backlight_force_update(struct backlight_device *bd,
 				   enum backlight_update_reason reason);
 extern bool backlight_device_registered(enum backlight_type type);
+extern int backlight_register_notifier(struct notifier_block *nb);
+extern int backlight_unregister_notifier(struct notifier_block *nb);
 
 #define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
 
-- 
1.9.0

[PATCH 3/4] acpi-video: Unregister the backlight device if a raw one shows up later

[Hans de Goede]

When video.use_native_backlight=1 and non intel gfx are in use, the raw
backlight device of the gfx driver will show up after acpi-video has done its
acpi_video_verify_backlight_support() check.

This causes video.use_native_backlight=1 to not have the desired result.

This patch fixes this by adding a backlight notifier and when a raw
backlight is registered or unregistered re-doing the
acpi_video_verify_backlight_support() check.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/acpi/video.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index aee85c4..123f919 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -151,6 +151,7 @@ struct acpi_video_enumerated_device {
 struct acpi_video_bus {
 	struct acpi_device *device;
 	bool backlight_registered;
+	bool backlight_notifier_registered;
 	u8 dos_setting;
 	struct acpi_video_enumerated_device *attached_array;
 	u8 attached_count;
@@ -162,6 +163,7 @@ struct acpi_video_bus {
 	struct input_dev *input;
 	char phys[32];	/* for input device */
 	struct notifier_block pm_nb;
+	struct notifier_block backlight_nb;
 };
 
 struct acpi_video_device_flags {
@@ -1836,6 +1838,9 @@ static int acpi_video_bus_register_backlight(struct acpi_video_bus *video)
 {
 	struct acpi_video_device *dev;
 
+	if (video->backlight_registered)
+		return 0;
+
 	if (!acpi_video_verify_backlight_support())
 		return 0;
 
@@ -1980,6 +1985,56 @@ static void acpi_video_bus_remove_notify_handler(struct acpi_video_bus *video)
 	video->input = NULL;
 }
 
+static int acpi_video_backlight_notify(struct notifier_block *nb,
+					unsigned long val, void *bd)
+{
+	struct backlight_device *backlight = bd;
+	struct acpi_video_bus *video;
+
+	/* acpi_video_verify_backlight_support only cares about raw devices */
+	if (backlight->props.type != BACKLIGHT_RAW)
+		return NOTIFY_DONE;
+
+	video = container_of(nb, struct acpi_video_bus, backlight_nb);
+
+	switch (val) {
+	case BACKLIGHT_REGISTERED:
+		if (!acpi_video_verify_backlight_support())
+			acpi_video_bus_unregister_backlight(video);
+		break;
+	case BACKLIGHT_UNREGISTERED:
+		acpi_video_bus_register_backlight(video);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static int acpi_video_bus_add_backlight_notify_handler(
+						struct acpi_video_bus *video)
+{
+	int error;
+
+	video->backlight_nb.notifier_call = acpi_video_backlight_notify;
+	video->backlight_nb.priority = 0;
+	error = backlight_register_notifier(&video->backlight_nb);
+	if (error = 0)
+		video->backlight_notifier_registered = true;
+
+	return error;
+}
+
+static int acpi_video_bus_remove_backlight_notify_handler(
+						struct acpi_video_bus *video)
+{
+	if (!video->backlight_notifier_registered)
+		return 0;
+
+	video->backlight_notifier_registered = false;
+
+	return backlight_unregister_notifier(&video->backlight_nb);
+}
+
 static int acpi_video_bus_put_devices(struct acpi_video_bus *video)
 {
 	struct acpi_video_device *dev, *next;
@@ -2061,6 +2116,7 @@ static int acpi_video_bus_add(struct acpi_device *device)
 
 	acpi_video_bus_register_backlight(video);
 	acpi_video_bus_add_notify_handler(video);
+	acpi_video_bus_add_backlight_notify_handler(video);
 
 	return 0;
 
@@ -2084,6 +2140,7 @@ static int acpi_video_bus_remove(struct acpi_device *device)
 
 	video = acpi_driver_data(device);
 
+	acpi_video_bus_remove_backlight_notify_handler(video);
 	acpi_video_bus_remove_notify_handler(video);
 	acpi_video_bus_unregister_backlight(video);
 	acpi_video_bus_put_devices(video);
-- 
1.9.0

[PATCH 4/4] acpi-video: Add use native backlight quirk for the ThinkPad W530

[Hans de Goede]

Like all of the other *30 ThinkPad models, the W530 has a broken acpi-video
backlight control. Note in order for this to actually fix things on the
ThinkPad W530 the commit titled:
"nouveau: Don't check acpi_video_backlight_support() before registering backlight"
is also needed.

https://bugzilla.redhat.com/show_bug.cgi?id\x1093171

Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 drivers/acpi/video.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 123f919..0fec70d 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -523,6 +523,14 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
 		},
 	},
 	{
+	 .callback = video_set_use_native_backlight,
+	 .ident = "ThinkPad W530",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad W530"),
+		},
+	},
+	{
 	.callback = video_set_use_native_backlight,
 	.ident = "ThinkPad X1 Carbon",
 	.matches = {
-- 
1.9.0