Merge tag 'backlight-detect-refactor-1' of...

Merge tag 'backlight-detect-refactor-1' of git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86 into drm-misc-next

Immutable backlight-detect-refactor branch between acpi, drm-* and pdx86

Tag (immutable branch) with v6.0-rc1 + the (acpi/x86) backlight
detect refactor work. For merging into the acpi, drm-* and pdx86
subsystems.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>

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# gpg: Signature made Mon 05 Sep 2022 09:25:44 AM IST
# gpg:                using RSA key BAF03B5D2718411A5E9E177E92EC4779440327DC
# gpg:                issuer "hdegoede@redhat.com"
# gpg: Can't check signature: No public key
From: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/261afe3d-7790-e945-adf6-a2c96c9b1eff@redhat.com

Documentation/gpu/todo.rst

@@ -679,6 +679,74 @@ Contact: Sam Ravnborg
 
 Level: Advanced
 
+Brightness handling on devices with multiple internal panels
+============================================================
+
+On x86/ACPI devices there can be multiple backlight firmware interfaces:
+(ACPI) video, vendor specific and others. As well as direct/native (PWM)
+register programming by the KMS driver.
+
+To deal with this backlight drivers used on x86/ACPI call
+acpi_video_get_backlight_type() which has heuristics (+quirks) to select
+which backlight interface to use; and backlight drivers which do not match
+the returned type will not register themselves, so that only one backlight
+device gets registered (in a single GPU setup, see below).
+
+At the moment this more or less assumes that there will only
+be 1 (internal) panel on a system.
+
+On systems with 2 panels this may be a problem, depending on
+what interface acpi_video_get_backlight_type() selects:
+
+1. native: in this case the KMS driver is expected to know which backlight
+   device belongs to which output so everything should just work.
+2. video: this does support controlling multiple backlights, but some work
+   will need to be done to get the output <-> backlight device mapping
+
+The above assumes both panels will require the same backlight interface type.
+Things will break on systems with multiple panels where the 2 panels need
+a different type of control. E.g. one panel needs ACPI video backlight control,
+where as the other is using native backlight control. Currently in this case
+only one of the 2 required backlight devices will get registered, based on
+the acpi_video_get_backlight_type() return value.
+
+If this (theoretical) case ever shows up, then supporting this will need some
+work. A possible solution here would be to pass a device and connector-name
+to acpi_video_get_backlight_type() so that it can deal with this.
+
+Note in a way we already have a case where userspace sees 2 panels,
+in dual GPU laptop setups with a mux. On those systems we may see
+either 2 native backlight devices; or 2 native backlight devices.
+
+Userspace already has code to deal with this by detecting if the related
+panel is active (iow which way the mux between the GPU and the panels
+points) and then uses that backlight device. Userspace here very much
+assumes a single panel though. It picks only 1 of the 2 backlight devices
+and then only uses that one.
+
+Note that all userspace code (that I know off) is currently hardcoded
+to assume a single panel.
+
+Before the recent changes to not register multiple (e.g. video + native)
+/sys/class/backlight devices for a single panel (on a single GPU laptop),
+userspace would see multiple backlight devices all controlling the same
+backlight.
+
+To deal with this userspace had to always picks one preferred device under
+/sys/class/backlight and will ignore the others. So to support brightness
+control on multiple panels userspace will need to be updated too.
+
+There are plans to allow brightness control through the KMS API by adding
+a "display brightness" property to drm_connector objects for panels. This
+solves a number of issues with the /sys/class/backlight API, including not
+being able to map a sysfs backlight device to a specific connector. Any
+userspace changes to add support for brightness control on devices with
+multiple panels really should build on top of this new KMS property.
+
+Contact: Hans de Goede
+
+Level: Advanced
+
 Outside DRM
 ===========
 

MAINTAINERS

@@ -14532,6 +14532,7 @@ M:	Daniel Dadap <ddadap@nvidia.com>
 L:	platform-driver-x86@vger.kernel.org
 S:	Supported
 F:	drivers/platform/x86/nvidia-wmi-ec-backlight.c
+F:	include/linux/platform_data/x86/nvidia-wmi-ec-backlight.h
 
 NVM EXPRESS DRIVER
 M:	Keith Busch <kbusch@kernel.org>

drivers/acpi/Kconfig

@@ -212,6 +212,7 @@ config ACPI_VIDEO
 	tristate "Video"
 	depends on BACKLIGHT_CLASS_DEVICE
 	depends on INPUT
+	depends on ACPI_WMI || !X86
 	select THERMAL
 	help
 	  This driver implements the ACPI Extensions For Display Adapters

drivers/acpi/acpi_video.c

@@ -73,6 +73,16 @@ module_param(device_id_scheme, bool, 0444);
 static int only_lcd = -1;
 module_param(only_lcd, int, 0444);
 
+/*
+ * Display probing is known to take up to 5 seconds, so delay the fallback
+ * backlight registration by 5 seconds + 3 seconds for some extra margin.
+ */
+static int register_backlight_delay = 8;
+module_param(register_backlight_delay, int, 0444);
+MODULE_PARM_DESC(register_backlight_delay,
+	"Delay in seconds before doing fallback (non GPU driver triggered) "
+	"backlight registration, set to 0 to disable.");
+
 static bool may_report_brightness_keys;
 static int register_count;
 static DEFINE_MUTEX(register_count_mutex);
@@ -81,7 +91,9 @@ static LIST_HEAD(video_bus_head);
 static int acpi_video_bus_add(struct acpi_device *device);
 static int acpi_video_bus_remove(struct acpi_device *device);
 static void acpi_video_bus_notify(struct acpi_device *device, u32 event);
-void acpi_video_detect_exit(void);
+static void acpi_video_bus_register_backlight_work(struct work_struct *ignored);
+static DECLARE_DELAYED_WORK(video_bus_register_backlight_work,
+			    acpi_video_bus_register_backlight_work);
 
 /*
  * Indices in the _BCL method response: the first two items are special,
@@ -1859,8 +1871,6 @@ static int acpi_video_bus_register_backlight(struct acpi_video_bus *video)
 	if (video->backlight_registered)
 		return 0;
 
-	acpi_video_run_bcl_for_osi(video);
-
 	if (acpi_video_get_backlight_type() != acpi_backlight_video)
 		return 0;
 
@@ -2086,7 +2096,11 @@ static int acpi_video_bus_add(struct acpi_device *device)
 	list_add_tail(&video->entry, &video_bus_head);
 	mutex_unlock(&video_list_lock);
 
-	acpi_video_bus_register_backlight(video);
+	/*
+	 * The userspace visible backlight_device gets registered separately
+	 * from acpi_video_register_backlight().
+	 */
+	acpi_video_run_bcl_for_osi(video);
 	acpi_video_bus_add_notify_handler(video);
 
 	return 0;
@@ -2111,20 +2125,25 @@ static int acpi_video_bus_remove(struct acpi_device *device)
 
 	video = acpi_driver_data(device);
 
-	acpi_video_bus_remove_notify_handler(video);
-	acpi_video_bus_unregister_backlight(video);
-	acpi_video_bus_put_devices(video);
-
 	mutex_lock(&video_list_lock);
 	list_del(&video->entry);
 	mutex_unlock(&video_list_lock);
 
+	acpi_video_bus_remove_notify_handler(video);
+	acpi_video_bus_unregister_backlight(video);
+	acpi_video_bus_put_devices(video);
+
 	kfree(video->attached_array);
 	kfree(video);
 
 	return 0;
 }
 
+static void acpi_video_bus_register_backlight_work(struct work_struct *ignored)
+{
+	acpi_video_register_backlight();
+}
+
 static int __init is_i740(struct pci_dev *dev)
 {
 	if (dev->device == 0x00D1)
@@ -2235,6 +2254,18 @@ int acpi_video_register(void)
 	 */
 	register_count = 1;
 
+	/*
+	 * acpi_video_bus_add() skips registering the userspace visible
+	 * backlight_device. The intend is for this to be registered by the
+	 * drm/kms driver calling acpi_video_register_backlight() *after* it is
+	 * done setting up its own native backlight device. The delayed work
+	 * ensures that acpi_video_register_backlight() always gets called
+	 * eventually, in case there is no drm/kms driver or it is disabled.
+	 */
+	if (register_backlight_delay)
+		schedule_delayed_work(&video_bus_register_backlight_work,
+				      register_backlight_delay * HZ);
+
 leave:
 	mutex_unlock(&register_count_mutex);
 	return ret;
@@ -2245,6 +2276,7 @@ void acpi_video_unregister(void)
 {
 	mutex_lock(&register_count_mutex);
 	if (register_count) {
+		cancel_delayed_work_sync(&video_bus_register_backlight_work);
 		acpi_bus_unregister_driver(&acpi_video_bus);
 		register_count = 0;
 		may_report_brightness_keys = false;
@@ -2253,19 +2285,16 @@ void acpi_video_unregister(void)
 }
 EXPORT_SYMBOL(acpi_video_unregister);
 
-void acpi_video_unregister_backlight(void)
+void acpi_video_register_backlight(void)
 {
 	struct acpi_video_bus *video;
 
-	mutex_lock(&register_count_mutex);
-	if (register_count) {
-		mutex_lock(&video_list_lock);
-		list_for_each_entry(video, &video_bus_head, entry)
-			acpi_video_bus_unregister_backlight(video);
-		mutex_unlock(&video_list_lock);
-	}
-	mutex_unlock(&register_count_mutex);
+	mutex_lock(&video_list_lock);
+	list_for_each_entry(video, &video_bus_head, entry)
+		acpi_video_bus_register_backlight(video);
+	mutex_unlock(&video_list_lock);
 }
+EXPORT_SYMBOL(acpi_video_register_backlight);
 
 bool acpi_video_handles_brightness_key_presses(void)
 {
@@ -2302,7 +2331,6 @@ static int __init acpi_video_init(void)
 
 static void __exit acpi_video_exit(void)
 {
-	acpi_video_detect_exit();
 	acpi_video_unregister();
 }
 

drivers/gpu/drm/Kconfig

@@ -235,6 +235,13 @@ config DRM_RADEON
 	select HWMON
 	select BACKLIGHT_CLASS_DEVICE
 	select INTERVAL_TREE
+	# radeon depends on ACPI_VIDEO when ACPI is enabled, for select to work
+	# ACPI_VIDEO's dependencies must also be selected.
+	select INPUT if ACPI
+	select ACPI_VIDEO if ACPI
+	# On x86 ACPI_VIDEO also needs ACPI_WMI
+	select X86_PLATFORM_DEVICES if ACPI && X86
+	select ACPI_WMI if ACPI && X86
 	help
 	  Choose this option if you have an ATI Radeon graphics card.  There
 	  are both PCI and AGP versions.  You don't need to choose this to
@@ -260,6 +267,13 @@ config DRM_AMDGPU
 	select BACKLIGHT_CLASS_DEVICE
 	select INTERVAL_TREE
 	select DRM_BUDDY
+	# amdgpu depends on ACPI_VIDEO when ACPI is enabled, for select to work
+	# ACPI_VIDEO's dependencies must also be selected.
+	select INPUT if ACPI
+	select ACPI_VIDEO if ACPI
+	# On x86 ACPI_VIDEO also needs ACPI_WMI
+	select X86_PLATFORM_DEVICES if ACPI && X86
+	select ACPI_WMI if ACPI && X86
 	help
 	  Choose this option if you have a recent AMD Radeon graphics card.
 

drivers/gpu/drm/amd/amdgpu/atombios_encoders.c

@@ -26,6 +26,8 @@
 
 #include <linux/pci.h>
 
+#include <acpi/video.h>
+
 #include <drm/drm_crtc_helper.h>
 #include <drm/amdgpu_drm.h>
 #include "amdgpu.h"
@@ -182,7 +184,12 @@ void amdgpu_atombios_encoder_init_backlight(struct amdgpu_encoder *amdgpu_encode
 		return;
 
 	if (!(adev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU))
-		return;
+		goto register_acpi_backlight;
+
+	if (!acpi_video_backlight_use_native()) {
+		drm_info(dev, "Skipping amdgpu atom DIG backlight registration\n");
+		goto register_acpi_backlight;
+	}
 
 	pdata = kmalloc(sizeof(struct amdgpu_backlight_privdata), GFP_KERNEL);
 	if (!pdata) {
@@ -218,6 +225,11 @@ void amdgpu_atombios_encoder_init_backlight(struct amdgpu_encoder *amdgpu_encode
 error:
 	kfree(pdata);
 	return;
+
+register_acpi_backlight:
+	/* Try registering an ACPI video backlight device instead. */
+	acpi_video_register_backlight();
+	return;
 }
 
 void

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -90,6 +90,8 @@
 #include <drm/drm_gem_atomic_helper.h>
 #include <drm/drm_plane_helper.h>
 
+#include <acpi/video.h>
+
 #include "ivsrcid/dcn/irqsrcs_dcn_1_0.h"
 
 #include "dcn/dcn_1_0_offset.h"
@@ -4032,6 +4034,13 @@ amdgpu_dm_register_backlight_device(struct amdgpu_display_manager *dm)
 	amdgpu_dm_update_backlight_caps(dm, dm->num_of_edps);
 	dm->brightness[dm->num_of_edps] = AMDGPU_MAX_BL_LEVEL;
 
+	if (!acpi_video_backlight_use_native()) {
+		drm_info(adev_to_drm(dm->adev), "Skipping amdgpu DM backlight registration\n");
+		/* Try registering an ACPI video backlight device instead. */
+		acpi_video_register_backlight();
+		return;
+	}
+
 	props.max_brightness = AMDGPU_MAX_BL_LEVEL;
 	props.brightness = AMDGPU_MAX_BL_LEVEL;
 	props.type = BACKLIGHT_RAW;

drivers/gpu/drm/gma500/Kconfig

@@ -7,6 +7,8 @@ config DRM_GMA500
 	select ACPI_VIDEO if ACPI
 	select BACKLIGHT_CLASS_DEVICE if ACPI
 	select INPUT if ACPI
+	select X86_PLATFORM_DEVICES if ACPI
+	select ACPI_WMI if ACPI
 	help
 	  Say yes for an experimental 2D KMS framebuffer driver for the
 	  Intel GMA500 (Poulsbo), Intel GMA600 (Moorestown/Oak Trail) and

drivers/gpu/drm/i915/Kconfig

@@ -23,6 +23,8 @@ config DRM_I915
 	# but for select to work, need to select ACPI_VIDEO's dependencies, ick
 	select BACKLIGHT_CLASS_DEVICE if ACPI
 	select INPUT if ACPI
+	select X86_PLATFORM_DEVICES if ACPI
+	select ACPI_WMI if ACPI
 	select ACPI_VIDEO if ACPI
 	select ACPI_BUTTON if ACPI
 	select SYNC_FILE

drivers/gpu/drm/i915/display/intel_acpi.c

@@ -7,6 +7,7 @@
 
 #include <linux/pci.h>
 #include <linux/acpi.h>
+#include <acpi/video.h>
 
 #include "i915_drv.h"
 #include "intel_acpi.h"
@@ -331,3 +332,29 @@ void intel_acpi_assign_connector_fwnodes(struct drm_i915_private *i915)
 	 */
 	fwnode_handle_put(fwnode);
 }
+
+void intel_acpi_video_register(struct drm_i915_private *i915)
+{
+	struct drm_connector_list_iter conn_iter;
+	struct drm_connector *connector;
+
+	acpi_video_register();
+
+	/*
+	 * If i915 is driving an internal panel without registering its native
+	 * backlight handler try to register the acpi_video backlight.
+	 * For panels not driven by i915 another GPU driver may still register
+	 * a native backlight later and acpi_video_register_backlight() should
+	 * only be called after any native backlights have been registered.
+	 */
+	drm_connector_list_iter_begin(&i915->drm, &conn_iter);
+	drm_for_each_connector_iter(connector, &conn_iter) {
+		struct intel_panel *panel = &to_intel_connector(connector)->panel;
+
+		if (panel->backlight.funcs && !panel->backlight.device) {
+			acpi_video_register_backlight();
+			break;
+		}
+	}
+	drm_connector_list_iter_end(&conn_iter);
+}

drivers/gpu/drm/i915/display/intel_acpi.h

@@ -14,6 +14,7 @@ void intel_unregister_dsm_handler(void);
 void intel_dsm_get_bios_data_funcs_supported(struct drm_i915_private *i915);
 void intel_acpi_device_id_update(struct drm_i915_private *i915);
 void intel_acpi_assign_connector_fwnodes(struct drm_i915_private *i915);
+void intel_acpi_video_register(struct drm_i915_private *i915);
 #else
 static inline void intel_register_dsm_handler(void) { return; }
 static inline void intel_unregister_dsm_handler(void) { return; }
@@ -23,6 +24,8 @@ static inline
 void intel_acpi_device_id_update(struct drm_i915_private *i915) { return; }
 static inline
 void intel_acpi_assign_connector_fwnodes(struct drm_i915_private *i915) { return; }
+static inline
+void intel_acpi_video_register(struct drm_i915_private *i915) { return; }
 #endif /* CONFIG_ACPI */
 
 #endif /* __INTEL_ACPI_H__ */

drivers/gpu/drm/i915/display/intel_backlight.c

@@ -8,6 +8,8 @@
 #include <linux/pwm.h>
 #include <linux/string_helpers.h>
 
+#include <acpi/video.h>
+
 #include "intel_backlight.h"
 #include "intel_connector.h"
 #include "intel_de.h"
@@ -950,6 +952,11 @@ int intel_backlight_device_register(struct intel_connector *connector)
 
 	WARN_ON(panel->backlight.max == 0);
 
+	if (!acpi_video_backlight_use_native()) {
+		drm_info(&i915->drm, "Skipping intel_backlight registration\n");
+		return 0;
+	}
+
 	memset(&props, 0, sizeof(props));
 	props.type = BACKLIGHT_RAW;
 

drivers/gpu/drm/i915/display/intel_display.c

@@ -9089,7 +9089,7 @@ void intel_display_driver_register(struct drm_i915_private *i915)
 
 	/* Must be done after probing outputs */
 	intel_opregion_register(i915);
-	acpi_video_register();
+	intel_acpi_video_register(i915);
 
 	intel_audio_init(i915);
 

drivers/gpu/drm/nouveau/nouveau_acpi.c

@@ -386,3 +386,13 @@ nouveau_acpi_edid(struct drm_device *dev, struct drm_connector *connector)
 
 	return kmemdup(edid, EDID_LENGTH, GFP_KERNEL);
 }
+
+bool nouveau_acpi_video_backlight_use_native(void)
+{
+	return acpi_video_backlight_use_native();
+}
+
+void nouveau_acpi_video_register_backlight(void)
+{
+	acpi_video_register_backlight();
+}

drivers/gpu/drm/nouveau/nouveau_acpi.h

@@ -11,6 +11,8 @@ void nouveau_register_dsm_handler(void);
 void nouveau_unregister_dsm_handler(void);
 void nouveau_switcheroo_optimus_dsm(void);
 void *nouveau_acpi_edid(struct drm_device *, struct drm_connector *);
+bool nouveau_acpi_video_backlight_use_native(void);
+void nouveau_acpi_video_register_backlight(void);
 #else
 static inline bool nouveau_is_optimus(void) { return false; };
 static inline bool nouveau_is_v1_dsm(void) { return false; };
@@ -18,6 +20,8 @@ static inline void nouveau_register_dsm_handler(void) {}
 static inline void nouveau_unregister_dsm_handler(void) {}
 static inline void nouveau_switcheroo_optimus_dsm(void) {}
 static inline void *nouveau_acpi_edid(struct drm_device *dev, struct drm_connector *connector) { return NULL; }
+static inline bool nouveau_acpi_video_backlight_use_native(void) { return true; }
+static inline void nouveau_acpi_video_register_backlight(void) {}
 #endif
 
 #endif

drivers/gpu/drm/nouveau/nouveau_backlight.c

@@ -38,6 +38,7 @@
 #include "nouveau_reg.h"
 #include "nouveau_encoder.h"
 #include "nouveau_connector.h"
+#include "nouveau_acpi.h"
 
 static struct ida bl_ida;
 #define BL_NAME_SIZE 15 // 12 for name + 2 for digits + 1 for '\0'
@@ -405,6 +406,11 @@ nouveau_backlight_init(struct drm_connector *connector)
 		goto fail_alloc;
 	}
 
+	if (!nouveau_acpi_video_backlight_use_native()) {
+		NV_INFO(drm, "Skipping nv_backlight registration\n");
+		goto fail_alloc;
+	}
+
 	if (!nouveau_get_backlight_name(backlight_name, bl)) {
 		NV_ERROR(drm, "Failed to retrieve a unique name for the backlight interface\n");
 		goto fail_alloc;
@@ -430,6 +436,13 @@ nouveau_backlight_init(struct drm_connector *connector)
 
 fail_alloc:
 	kfree(bl);
+	/*
+	 * If we get here we have an internal panel, but no nv_backlight,
+	 * try registering an ACPI video backlight device instead.
+	 */
+	if (ret == 0)
+		nouveau_acpi_video_register_backlight();
+
 	return ret;
 }
 

drivers/gpu/drm/radeon/atombios_encoders.c

@@ -32,6 +32,8 @@
 #include <drm/drm_file.h>
 #include <drm/radeon_drm.h>
 
+#include <acpi/video.h>
+
 #include "atom.h"
 #include "radeon_atombios.h"
 #include "radeon.h"
@@ -209,6 +211,11 @@ void radeon_atom_backlight_init(struct radeon_encoder *radeon_encoder,
 	if (!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_BL_CONTROLLED_BY_GPU))
 		return;
 
+	if (!acpi_video_backlight_use_native()) {
+		drm_info(dev, "Skipping radeon atom DIG backlight registration\n");
+		return;
+	}
+
 	pdata = kmalloc(sizeof(struct radeon_backlight_privdata), GFP_KERNEL);
 	if (!pdata) {
 		DRM_ERROR("Memory allocation failed\n");

drivers/gpu/drm/radeon/radeon_encoders.c

@@ -30,6 +30,8 @@
 #include <drm/drm_device.h>
 #include <drm/radeon_drm.h>
 
+#include <acpi/video.h>
+
 #include "radeon.h"
 #include "radeon_atombios.h"
 #include "radeon_legacy_encoders.h"
@@ -167,7 +169,7 @@ static void radeon_encoder_add_backlight(struct radeon_encoder *radeon_encoder,
 		return;
 
 	if (radeon_backlight == 0) {
-		return;
+		use_bl = false;
 	} else if (radeon_backlight == 1) {
 		use_bl = true;
 	} else if (radeon_backlight == -1) {
@@ -193,6 +195,13 @@ static void radeon_encoder_add_backlight(struct radeon_encoder *radeon_encoder,
 		else
 			radeon_legacy_backlight_init(radeon_encoder, connector);
 	}
+
+	/*
+	 * If there is no native backlight device (which may happen even when
+	 * use_bl==true) try registering an ACPI video backlight device instead.
+	 */
+	if (!rdev->mode_info.bl_encoder)
+		acpi_video_register_backlight();
 }
 
 void

drivers/gpu/drm/radeon/radeon_legacy_encoders.c

@@ -33,6 +33,8 @@
 #include <drm/drm_util.h>
 #include <drm/radeon_drm.h>
 
+#include <acpi/video.h>
+
 #include "radeon.h"
 #include "radeon_asic.h"
 #include "radeon_legacy_encoders.h"
@@ -387,6 +389,11 @@ void radeon_legacy_backlight_init(struct radeon_encoder *radeon_encoder,
 		return;
 #endif
 
+	if (!acpi_video_backlight_use_native()) {
+		drm_info(dev, "Skipping radeon legacy LVDS backlight registration\n");
+		return;
+	}
+
 	pdata = kmalloc(sizeof(struct radeon_backlight_privdata), GFP_KERNEL);
 	if (!pdata) {
 		DRM_ERROR("Memory allocation failed\n");

drivers/platform/x86/Kconfig

@@ -93,6 +93,7 @@ config PEAQ_WMI
 
 config NVIDIA_WMI_EC_BACKLIGHT
 	tristate "EC Backlight Driver for Hybrid Graphics Notebook Systems"
+	depends on ACPI_VIDEO
 	depends on ACPI_WMI
 	depends on BACKLIGHT_CLASS_DEVICE
 	help

drivers/platform/x86/acer-wmi.c

@@ -643,69 +643,6 @@ static const struct dmi_system_id non_acer_quirks[] __initconst = {
 	{}
 };
 
-static int __init
-video_set_backlight_video_vendor(const struct dmi_system_id *d)
-{
-	interface->capability &= ~ACER_CAP_BRIGHTNESS;
-	pr_info("Brightness must be controlled by generic video driver\n");
-	return 0;
-}
-
-static const struct dmi_system_id video_vendor_dmi_table[] __initconst = {
-	{
-		.callback = video_set_backlight_video_vendor,
-		.ident = "Acer TravelMate 4750",
-		.matches = {
-			DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
-			DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 4750"),
-		},
-	},
-	{
-		.callback = video_set_backlight_video_vendor,
-		.ident = "Acer Extensa 5235",
-		.matches = {
-			DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
-			DMI_MATCH(DMI_PRODUCT_NAME, "Extensa 5235"),
-		},
-	},
-	{
-		.callback = video_set_backlight_video_vendor,
-		.ident = "Acer TravelMate 5760",
-		.matches = {
-			DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
-			DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5760"),
-		},
-	},
-	{
-		.callback = video_set_backlight_video_vendor,
-		.ident = "Acer Aspire 5750",
-		.matches = {
-			DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
-			DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5750"),
-		},
-	},
-	{
-		.callback = video_set_backlight_video_vendor,
-		.ident = "Acer Aspire 5741",
-		.matches = {
-			DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
-			DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5741"),
-		},
-	},
-	{
-		/*
-		 * Note no video_set_backlight_video_vendor, we must use the
-		 * acer interface, as there is no native backlight interface.
-		 */
-		.ident = "Acer KAV80",
-		.matches = {
-			DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
-			DMI_MATCH(DMI_PRODUCT_NAME, "KAV80"),
-		},
-	},
-	{}
-};
-
 /* Find which quirks are needed for a particular vendor/ model pair */
 static void __init find_quirks(void)
 {
@@ -2477,9 +2414,6 @@ static int __init acer_wmi_init(void)
 
 	set_quirks();
 
-	if (dmi_check_system(video_vendor_dmi_table))
-		acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
-
 	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
 		interface->capability &= ~ACER_CAP_BRIGHTNESS;
 

drivers/platform/x86/apple-gmux.c

@@ -21,7 +21,6 @@
 #include <linux/delay.h>
 #include <linux/pci.h>
 #include <linux/vga_switcheroo.h>
-#include <acpi/video.h>
 #include <asm/io.h>
 
 /**
@@ -694,7 +693,6 @@ static int gmux_probe(struct pnp_dev *pnp, const struct pnp_device_id *id)
 	 * backlight control and supports more levels than other options.
 	 * Disable the other backlight choices.
 	 */
-	acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
 	apple_bl_unregister();
 
 	gmux_data->power_state = VGA_SWITCHEROO_ON;
@@ -804,7 +802,6 @@ static void gmux_remove(struct pnp_dev *pnp)
 	apple_gmux_data = NULL;
 	kfree(gmux_data);
 
-	acpi_video_register();
 	apple_bl_register();
 }
 

drivers/platform/x86/asus-nb-wmi.c

@@ -79,12 +79,10 @@ static struct quirk_entry quirk_asus_q500a = {
 
 /*
  * For those machines that need software to control bt/wifi status
- * and can't adjust brightness through ACPI interface
  * and have duplicate events(ACPI and WMI) for display toggle
  */
 static struct quirk_entry quirk_asus_x55u = {
 	.wapf = 4,
-	.wmi_backlight_power = true,
 	.wmi_backlight_set_devstate = true,
 	.no_display_toggle = true,
 };
@@ -99,11 +97,6 @@ static struct quirk_entry quirk_asus_x200ca = {
 	.wmi_backlight_set_devstate = true,
 };
 
-static struct quirk_entry quirk_asus_ux303ub = {
-	.wmi_backlight_native = true,
-	.wmi_backlight_set_devstate = true,
-};
-
 static struct quirk_entry quirk_asus_x550lb = {
 	.wmi_backlight_set_devstate = true,
 	.xusb2pr = 0x01D9,
@@ -147,11 +140,6 @@ static const struct dmi_system_id asus_quirks[] = {
 			DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 			DMI_MATCH(DMI_PRODUCT_NAME, "U32U"),
 		},
-		/*
-		 * Note this machine has a Brazos APU, and most Brazos Asus
-		 * machines need quirk_asus_x55u / wmi_backlight_power but
-		 * here acpi-video seems to work fine for backlight control.
-		 */
 		.driver_data = &quirk_asus_wapf4,
 	},
 	{
@@ -379,15 +367,6 @@ static const struct dmi_system_id asus_quirks[] = {
 		},
 		.driver_data = &quirk_asus_x200ca,
 	},
-	{
-		.callback = dmi_matched,
-		.ident = "ASUSTeK COMPUTER INC. UX303UB",
-		.matches = {
-			DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
-			DMI_MATCH(DMI_PRODUCT_NAME, "UX303UB"),
-		},
-		.driver_data = &quirk_asus_ux303ub,
-	},
 	{
 		.callback = dmi_matched,
 		.ident = "ASUSTeK COMPUTER INC. UX330UAK",

drivers/platform/x86/asus-wmi.c

@@ -3553,7 +3553,6 @@ static int asus_wmi_add(struct platform_device *pdev)
 	struct platform_driver *pdrv = to_platform_driver(pdev->dev.driver);
 	struct asus_wmi_driver *wdrv = to_asus_wmi_driver(pdrv);
 	struct asus_wmi *asus;
-	const char *chassis_type;
 	acpi_status status;
 	int err;
 	u32 result;
@@ -3635,18 +3634,6 @@ static int asus_wmi_add(struct platform_device *pdev)
 	if (asus->driver->quirks->wmi_force_als_set)
 		asus_wmi_set_als();
 
-	/* Some Asus desktop boards export an acpi-video backlight interface,
-	   stop this from showing up */
-	chassis_type = dmi_get_system_info(DMI_CHASSIS_TYPE);
-	if (chassis_type && !strcmp(chassis_type, "3"))
-		acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
-
-	if (asus->driver->quirks->wmi_backlight_power)
-		acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
-
-	if (asus->driver->quirks->wmi_backlight_native)
-		acpi_video_set_dmi_backlight_type(acpi_backlight_native);
-
 	if (asus->driver->quirks->xusb2pr)
 		asus_wmi_set_xusb2pr(asus);
 

drivers/platform/x86/asus-wmi.h

@@ -29,8 +29,6 @@ struct quirk_entry {
 	bool hotplug_wireless;
 	bool scalar_panel_brightness;
 	bool store_backlight_power;
-	bool wmi_backlight_power;
-	bool wmi_backlight_native;
 	bool wmi_backlight_set_devstate;
 	bool wmi_force_als_set;
 	bool use_kbd_dock_devid;

drivers/platform/x86/eeepc-wmi.c

@@ -96,11 +96,6 @@ static struct quirk_entry quirk_asus_et2012_type3 = {
 	.store_backlight_power = true,
 };
 
-static struct quirk_entry quirk_asus_x101ch = {
-	/* We need this when ACPI function doesn't do this well */
-	.wmi_backlight_power = true,
-};
-
 static struct quirk_entry *quirks;
 
 static void et2012_quirks(void)
@@ -151,25 +146,7 @@ static const struct dmi_system_id asus_quirks[] = {
 		},
 		.driver_data = &quirk_asus_unknown,
 	},
-	{
-		.callback = dmi_matched,
-		.ident = "ASUSTeK Computer INC. X101CH",
-		.matches = {
-			DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
-			DMI_MATCH(DMI_PRODUCT_NAME, "X101CH"),
-		},
-		.driver_data = &quirk_asus_x101ch,
-	},
-	{
-		.callback = dmi_matched,
-		.ident = "ASUSTeK Computer INC. 1015CX",
-		.matches = {
-			DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
-			DMI_MATCH(DMI_PRODUCT_NAME, "1015CX"),
-		},
-		.driver_data = &quirk_asus_x101ch,
-	},
-	{},
+	{}
 };
 
 static void eeepc_wmi_key_filter(struct asus_wmi_driver *asus_wmi, int *code,

drivers/platform/x86/nvidia-wmi-ec-backlight.c

@@ -7,73 +7,10 @@
 #include <linux/backlight.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
+#include <linux/platform_data/x86/nvidia-wmi-ec-backlight.h>
 #include <linux/types.h>
 #include <linux/wmi.h>
-
-/**
- * enum wmi_brightness_method - WMI method IDs
- * @WMI_BRIGHTNESS_METHOD_LEVEL:  Get/Set EC brightness level status
- * @WMI_BRIGHTNESS_METHOD_SOURCE: Get/Set EC Brightness Source
- */
-enum wmi_brightness_method {
-	WMI_BRIGHTNESS_METHOD_LEVEL = 1,
-	WMI_BRIGHTNESS_METHOD_SOURCE = 2,
-	WMI_BRIGHTNESS_METHOD_MAX
-};
-
-/**
- * enum wmi_brightness_mode - Operation mode for WMI-wrapped method
- * @WMI_BRIGHTNESS_MODE_GET:            Get the current brightness level/source.
- * @WMI_BRIGHTNESS_MODE_SET:            Set the brightness level.
- * @WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL:  Get the maximum brightness level. This
- *                                      is only valid when the WMI method is
- *                                      %WMI_BRIGHTNESS_METHOD_LEVEL.
- */
-enum wmi_brightness_mode {
-	WMI_BRIGHTNESS_MODE_GET = 0,
-	WMI_BRIGHTNESS_MODE_SET = 1,
-	WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL = 2,
-	WMI_BRIGHTNESS_MODE_MAX
-};
-
-/**
- * enum wmi_brightness_source - Backlight brightness control source selection
- * @WMI_BRIGHTNESS_SOURCE_GPU: Backlight brightness is controlled by the GPU.
- * @WMI_BRIGHTNESS_SOURCE_EC:  Backlight brightness is controlled by the
- *                             system's Embedded Controller (EC).
- * @WMI_BRIGHTNESS_SOURCE_AUX: Backlight brightness is controlled over the
- *                             DisplayPort AUX channel.
- */
-enum wmi_brightness_source {
-	WMI_BRIGHTNESS_SOURCE_GPU = 1,
-	WMI_BRIGHTNESS_SOURCE_EC = 2,
-	WMI_BRIGHTNESS_SOURCE_AUX = 3,
-	WMI_BRIGHTNESS_SOURCE_MAX
-};
-
-/**
- * struct wmi_brightness_args - arguments for the WMI-wrapped ACPI method
- * @mode:    Pass in an &enum wmi_brightness_mode value to select between
- *           getting or setting a value.
- * @val:     In parameter for value to set when using %WMI_BRIGHTNESS_MODE_SET
- *           mode. Not used in conjunction with %WMI_BRIGHTNESS_MODE_GET or
- *           %WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL mode.
- * @ret:     Out parameter returning retrieved value when operating in
- *           %WMI_BRIGHTNESS_MODE_GET or %WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL
- *           mode. Not used in %WMI_BRIGHTNESS_MODE_SET mode.
- * @ignored: Padding; not used. The ACPI method expects a 24 byte params struct.
- *
- * This is the parameters structure for the WmiBrightnessNotify ACPI method as
- * wrapped by WMI. The value passed in to @val or returned by @ret will be a
- * brightness value when the WMI method ID is %WMI_BRIGHTNESS_METHOD_LEVEL, or
- * an &enum wmi_brightness_source value with %WMI_BRIGHTNESS_METHOD_SOURCE.
- */
-struct wmi_brightness_args {
-	u32 mode;
-	u32 val;
-	u32 ret;
-	u32 ignored[3];
-};
+#include <acpi/video.h>
 
 /**
  * wmi_brightness_notify() - helper function for calling WMI-wrapped ACPI method
@@ -151,19 +88,10 @@ static int nvidia_wmi_ec_backlight_probe(struct wmi_device *wdev, const void *ct
 {
 	struct backlight_properties props = {};
 	struct backlight_device *bdev;
-	u32 source;
 	int ret;
 
-	ret = wmi_brightness_notify(wdev, WMI_BRIGHTNESS_METHOD_SOURCE,
-	                           WMI_BRIGHTNESS_MODE_GET, &source);
-	if (ret)
-		return ret;
-
-	/*
-	 * This driver is only to be used when brightness control is handled
-	 * by the EC; otherwise, the GPU driver(s) should control brightness.
-	 */
-	if (source != WMI_BRIGHTNESS_SOURCE_EC)
+	/* drivers/acpi/video_detect.c also checks that SOURCE == EC */
+	if (acpi_video_get_backlight_type() != acpi_backlight_nvidia_wmi_ec)
 		return -ENODEV;
 
 	/*
@@ -191,8 +119,6 @@ static int nvidia_wmi_ec_backlight_probe(struct wmi_device *wdev, const void *ct
 	return PTR_ERR_OR_ZERO(bdev);
 }
 
-#define WMI_BRIGHTNESS_GUID "603E9613-EF25-4338-A3D0-C46177516DB7"
-
 static const struct wmi_device_id nvidia_wmi_ec_backlight_id_table[] = {
 	{ .guid_string = WMI_BRIGHTNESS_GUID },
 	{ }

drivers/platform/x86/samsung-laptop.c

@@ -356,23 +356,13 @@ struct samsung_laptop {
 };
 
 struct samsung_quirks {
-	bool broken_acpi_video;
 	bool four_kbd_backlight_levels;
 	bool enable_kbd_backlight;
-	bool use_native_backlight;
 	bool lid_handling;
 };
 
 static struct samsung_quirks samsung_unknown = {};
 
-static struct samsung_quirks samsung_broken_acpi_video = {
-	.broken_acpi_video = true,
-};
-
-static struct samsung_quirks samsung_use_native_backlight = {
-	.use_native_backlight = true,
-};
-
 static struct samsung_quirks samsung_np740u3e = {
 	.four_kbd_backlight_levels = true,
 	.enable_kbd_backlight = true,
@@ -1540,76 +1530,6 @@ static const struct dmi_system_id samsung_dmi_table[] __initconst = {
 		},
 	},
 	/* Specific DMI ids for laptop with quirks */
-	{
-	 .callback = samsung_dmi_matched,
-	 .ident = "N150P",
-	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "N150P"),
-		DMI_MATCH(DMI_BOARD_NAME, "N150P"),
-		},
-	 .driver_data = &samsung_use_native_backlight,
-	},
-	{
-	 .callback = samsung_dmi_matched,
-	 .ident = "N145P/N250P/N260P",
-	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "N145P/N250P/N260P"),
-		DMI_MATCH(DMI_BOARD_NAME, "N145P/N250P/N260P"),
-		},
-	 .driver_data = &samsung_use_native_backlight,
-	},
-	{
-	 .callback = samsung_dmi_matched,
-	 .ident = "N150/N210/N220",
-	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "N150/N210/N220"),
-		DMI_MATCH(DMI_BOARD_NAME, "N150/N210/N220"),
-		},
-	 .driver_data = &samsung_broken_acpi_video,
-	},
-	{
-	 .callback = samsung_dmi_matched,
-	 .ident = "NF110/NF210/NF310",
-	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "NF110/NF210/NF310"),
-		DMI_MATCH(DMI_BOARD_NAME, "NF110/NF210/NF310"),
-		},
-	 .driver_data = &samsung_broken_acpi_video,
-	},
-	{
-	 .callback = samsung_dmi_matched,
-	 .ident = "X360",
-	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
-		DMI_MATCH(DMI_BOARD_NAME, "X360"),
-		},
-	 .driver_data = &samsung_broken_acpi_video,
-	},
-	{
-	 .callback = samsung_dmi_matched,
-	 .ident = "N250P",
-	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "N250P"),
-		DMI_MATCH(DMI_BOARD_NAME, "N250P"),
-		},
-	 .driver_data = &samsung_use_native_backlight,
-	},
-	{
-	 .callback = samsung_dmi_matched,
-	 .ident = "NC210",
-	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "NC210/NC110"),
-		DMI_MATCH(DMI_BOARD_NAME, "NC210/NC110"),
-		},
-	 .driver_data = &samsung_broken_acpi_video,
-	},
 	{
 	 .callback = samsung_dmi_matched,
 	 .ident = "730U3E/740U3E",
@@ -1654,15 +1574,8 @@ static int __init samsung_init(void)
 	samsung->handle_backlight = true;
 	samsung->quirks = quirks;
 
-#ifdef CONFIG_ACPI
-	if (samsung->quirks->broken_acpi_video)
-		acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
-	if (samsung->quirks->use_native_backlight)
-		acpi_video_set_dmi_backlight_type(acpi_backlight_native);
-
 	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
 		samsung->handle_backlight = false;
-#endif
 
 	ret = samsung_platform_init(samsung);
 	if (ret)

drivers/platform/x86/toshiba_acpi.c

@@ -271,14 +271,6 @@ static const struct key_entry toshiba_acpi_alt_keymap[] = {
 	{ KE_END, 0 },
 };
 
-/*
- * List of models which have a broken acpi-video backlight interface and thus
- * need to use the toshiba (vendor) interface instead.
- */
-static const struct dmi_system_id toshiba_vendor_backlight_dmi[] = {
-	{}
-};
-
 /*
  * Utility
  */
@@ -2881,14 +2873,6 @@ static int toshiba_acpi_setup_backlight(struct toshiba_acpi_dev *dev)
 		return 0;
 	}
 
-	/*
-	 * Tell acpi-video-detect code to prefer vendor backlight on all
-	 * systems with transflective backlight and on dmi matched systems.
-	 */
-	if (dev->tr_backlight_supported ||
-	    dmi_check_system(toshiba_vendor_backlight_dmi))
-		acpi_video_set_dmi_backlight_type(acpi_backlight_vendor);
-
 	if (acpi_video_get_backlight_type() != acpi_backlight_vendor)
 		return 0;
 

include/acpi/video.h

@@ -48,15 +48,18 @@ enum acpi_backlight_type {
 	acpi_backlight_video,
 	acpi_backlight_vendor,
 	acpi_backlight_native,
+	acpi_backlight_nvidia_wmi_ec,
+	acpi_backlight_apple_gmux,
 };
 
 #if IS_ENABLED(CONFIG_ACPI_VIDEO)
 extern int acpi_video_register(void);
 extern void acpi_video_unregister(void);
+extern void acpi_video_register_backlight(void);
 extern int acpi_video_get_edid(struct acpi_device *device, int type,
 			       int device_id, void **edid);
 extern enum acpi_backlight_type acpi_video_get_backlight_type(void);
-extern void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type);
+extern bool acpi_video_backlight_use_native(void);
 /*
  * Note: The value returned by acpi_video_handles_brightness_key_presses()
  * may change over time and should not be cached.
@@ -68,6 +71,7 @@ extern int acpi_video_get_levels(struct acpi_device *device,
 #else
 static inline int acpi_video_register(void) { return -ENODEV; }
 static inline void acpi_video_unregister(void) { return; }
+static inline void acpi_video_register_backlight(void) { return; }
 static inline int acpi_video_get_edid(struct acpi_device *device, int type,
 				      int device_id, void **edid)
 {
@@ -77,8 +81,9 @@ static inline enum acpi_backlight_type acpi_video_get_backlight_type(void)
 {
 	return acpi_backlight_vendor;
 }
-static inline void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
+static inline bool acpi_video_backlight_use_native(void)
 {
+	return true;
 }
 static inline bool acpi_video_handles_brightness_key_presses(void)
 {

include/linux/platform_data/x86/nvidia-wmi-ec-backlight.h

+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2020, NVIDIA CORPORATION.  All rights reserved.
+ */
+
+#ifndef __PLATFORM_DATA_X86_NVIDIA_WMI_EC_BACKLIGHT_H
+#define __PLATFORM_DATA_X86_NVIDIA_WMI_EC_BACKLIGHT_H
+
+#define WMI_BRIGHTNESS_GUID "603E9613-EF25-4338-A3D0-C46177516DB7"
+
+/**
+ * enum wmi_brightness_method - WMI method IDs
+ * @WMI_BRIGHTNESS_METHOD_LEVEL:  Get/Set EC brightness level status
+ * @WMI_BRIGHTNESS_METHOD_SOURCE: Get/Set EC Brightness Source
+ */
+enum wmi_brightness_method {
+	WMI_BRIGHTNESS_METHOD_LEVEL = 1,
+	WMI_BRIGHTNESS_METHOD_SOURCE = 2,
+	WMI_BRIGHTNESS_METHOD_MAX
+};
+
+/**
+ * enum wmi_brightness_mode - Operation mode for WMI-wrapped method
+ * @WMI_BRIGHTNESS_MODE_GET:            Get the current brightness level/source.
+ * @WMI_BRIGHTNESS_MODE_SET:            Set the brightness level.
+ * @WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL:  Get the maximum brightness level. This
+ *                                      is only valid when the WMI method is
+ *                                      %WMI_BRIGHTNESS_METHOD_LEVEL.
+ */
+enum wmi_brightness_mode {
+	WMI_BRIGHTNESS_MODE_GET = 0,
+	WMI_BRIGHTNESS_MODE_SET = 1,
+	WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL = 2,
+	WMI_BRIGHTNESS_MODE_MAX
+};
+
+/**
+ * enum wmi_brightness_source - Backlight brightness control source selection
+ * @WMI_BRIGHTNESS_SOURCE_GPU: Backlight brightness is controlled by the GPU.
+ * @WMI_BRIGHTNESS_SOURCE_EC:  Backlight brightness is controlled by the
+ *                             system's Embedded Controller (EC).
+ * @WMI_BRIGHTNESS_SOURCE_AUX: Backlight brightness is controlled over the
+ *                             DisplayPort AUX channel.
+ */
+enum wmi_brightness_source {
+	WMI_BRIGHTNESS_SOURCE_GPU = 1,
+	WMI_BRIGHTNESS_SOURCE_EC = 2,
+	WMI_BRIGHTNESS_SOURCE_AUX = 3,
+	WMI_BRIGHTNESS_SOURCE_MAX
+};
+
+/**
+ * struct wmi_brightness_args - arguments for the WMI-wrapped ACPI method
+ * @mode:    Pass in an &enum wmi_brightness_mode value to select between
+ *           getting or setting a value.
+ * @val:     In parameter for value to set when using %WMI_BRIGHTNESS_MODE_SET
+ *           mode. Not used in conjunction with %WMI_BRIGHTNESS_MODE_GET or
+ *           %WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL mode.
+ * @ret:     Out parameter returning retrieved value when operating in
+ *           %WMI_BRIGHTNESS_MODE_GET or %WMI_BRIGHTNESS_MODE_GET_MAX_LEVEL
+ *           mode. Not used in %WMI_BRIGHTNESS_MODE_SET mode.
+ * @ignored: Padding; not used. The ACPI method expects a 24 byte params struct.
+ *
+ * This is the parameters structure for the WmiBrightnessNotify ACPI method as
+ * wrapped by WMI. The value passed in to @val or returned by @ret will be a
+ * brightness value when the WMI method ID is %WMI_BRIGHTNESS_METHOD_LEVEL, or
+ * an &enum wmi_brightness_source value with %WMI_BRIGHTNESS_METHOD_SOURCE.
+ */
+struct wmi_brightness_args {
+	u32 mode;
+	u32 val;
+	u32 ret;
+	u32 ignored[3];
+};
+
+#endif