Merge tag 'backlight-detect-refactor-1' into review-hans

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.

3 files changed, 301 insertions, 192 deletions

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 7802d8846a8d..44ad4b6bd234 100644
--- a/drivers/acpi/Kconfig
+++ b/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
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 5cbe2196176d..a7c3d11e0dac 100644
--- a/drivers/acpi/acpi_video.c
+++ b/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();
 }
 
diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
index 5d7f38016a24..db2474fe58ac 100644
--- a/drivers/acpi/video_detect.c
+++ b/drivers/acpi/video_detect.c
@@ -17,8 +17,9 @@
  * Otherwise vendor specific drivers like thinkpad_acpi, asus-laptop,
  * sony_acpi,... can take care about backlight brightness.
  *
- * Backlight drivers can use acpi_video_get_backlight_type() to determine
- * which driver should handle the backlight.
+ * Backlight drivers can use acpi_video_get_backlight_type() to determine which
+ * driver should handle the backlight. RAW/GPU-driver backlight drivers must
+ * use the acpi_video_backlight_use_native() helper for this.
  *
  * If CONFIG_ACPI_VIDEO is neither set as "compiled in" (y) nor as a module (m)
  * this file will not be compiled and acpi_video_get_backlight_type() will
@@ -27,20 +28,16 @@
 
 #include <linux/export.h>
 #include <linux/acpi.h>
+#include <linux/apple-gmux.h>
 #include <linux/backlight.h>
 #include <linux/dmi.h>
 #include <linux/module.h>
 #include <linux/pci.h>
+#include <linux/platform_data/x86/nvidia-wmi-ec-backlight.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
 #include <acpi/video.h>
 
-void acpi_video_unregister_backlight(void);
-
-static bool backlight_notifier_registered;
-static struct notifier_block backlight_nb;
-static struct work_struct backlight_notify_work;
-
 static enum acpi_backlight_type acpi_backlight_cmdline = acpi_backlight_undef;
 static enum acpi_backlight_type acpi_backlight_dmi = acpi_backlight_undef;
 
@@ -78,6 +75,36 @@ find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
 	return AE_OK;
 }
 
+/* This depends on ACPI_WMI which is X86 only */
+#ifdef CONFIG_X86
+static bool nvidia_wmi_ec_supported(void)
+{
+	struct wmi_brightness_args args = {
+		.mode = WMI_BRIGHTNESS_MODE_GET,
+		.val = 0,
+		.ret = 0,
+	};
+	struct acpi_buffer buf = { (acpi_size)sizeof(args), &args };
+	acpi_status status;
+
+	status = wmi_evaluate_method(WMI_BRIGHTNESS_GUID, 0,
+				     WMI_BRIGHTNESS_METHOD_SOURCE, &buf, &buf);
+	if (ACPI_FAILURE(status))
+		return false;
+
+	/*
+	 * If brightness is handled by the EC then nvidia-wmi-ec-backlight
+	 * should be used, else the GPU driver(s) should be used.
+	 */
+	return args.ret == WMI_BRIGHTNESS_SOURCE_EC;
+}
+#else
+static bool nvidia_wmi_ec_supported(void)
+{
+	return false;
+}
+#endif
+
 /* Force to use vendor driver when the ACPI device is known to be
  * buggy */
 static int video_detect_force_vendor(const struct dmi_system_id *d)
@@ -105,63 +132,143 @@ static int video_detect_force_none(const struct dmi_system_id *d)
 }
 
 static const struct dmi_system_id video_detect_dmi_table[] = {
-	/* On Samsung X360, the BIOS will set a flag (VDRV) if generic
-	 * ACPI backlight device is used. This flag will definitively break
-	 * the backlight interface (even the vendor interface) until next
-	 * reboot. It's why we should prevent video.ko from being used here
-	 * and we can't rely on a later call to acpi_video_unregister().
-	 */
 	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1128309 */
 	 .callback = video_detect_force_vendor,
-	 /* X360 */
+	 /* Acer KAV80 */
 	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
-		DMI_MATCH(DMI_BOARD_NAME, "X360"),
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "KAV80"),
 		},
 	},
 	{
-	.callback = video_detect_force_vendor,
-	/* Asus UL30VT */
-	.matches = {
+	 .callback = video_detect_force_vendor,
+	 /* Asus UL30VT */
+	 .matches = {
 		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 		DMI_MATCH(DMI_PRODUCT_NAME, "UL30VT"),
 		},
 	},
 	{
-	.callback = video_detect_force_vendor,
-	/* Asus UL30A */
-	.matches = {
+	 .callback = video_detect_force_vendor,
+	 /* Asus UL30A */
+	 .matches = {
 		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
 		DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
 		},
 	},
 	{
-	.callback = video_detect_force_vendor,
-	/* GIGABYTE GB-BXBT-2807 */
-	.matches = {
+	 .callback = video_detect_force_vendor,
+	 /* Asus X55U */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "X55U"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Asus X101CH */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "X101CH"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Asus X401U */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "X401U"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Asus X501U */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "X501U"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Asus 1015CX */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "1015CX"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* GIGABYTE GB-BXBT-2807 */
+	 .matches = {
 		DMI_MATCH(DMI_SYS_VENDOR, "GIGABYTE"),
 		DMI_MATCH(DMI_PRODUCT_NAME, "GB-BXBT-2807"),
 		},
 	},
 	{
-	.callback = video_detect_force_vendor,
-	/* Sony VPCEH3U1E */
-	.matches = {
+	 .callback = video_detect_force_vendor,
+	 /* Samsung 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"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Samsung 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"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Samsung 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"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Sony VPCEH3U1E */
+	 .matches = {
 		DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
 		DMI_MATCH(DMI_PRODUCT_NAME, "VPCEH3U1E"),
 		},
 	},
 	{
-	.callback = video_detect_force_vendor,
-	/* Xiaomi Mi Pad 2 */
-	.matches = {
+	 .callback = video_detect_force_vendor,
+	 /* Xiaomi Mi Pad 2 */
+	 .matches = {
 			DMI_MATCH(DMI_SYS_VENDOR, "Xiaomi Inc"),
 			DMI_MATCH(DMI_PRODUCT_NAME, "Mipad2"),
 		},
 	},
 
 	/*
+	 * Toshiba models with Transflective display, these need to use
+	 * the toshiba_acpi vendor driver for proper Transflective handling.
+	 */
+	{
+	 .callback = video_detect_force_vendor,
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R500"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R600"),
+		},
+	},
+
+	/*
 	 * These models have a working acpi_video backlight control, and using
 	 * native backlight causes a regression where backlight does not work
 	 * when userspace is not handling brightness key events. Disable
@@ -390,130 +497,119 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 		},
 	},
 	{
-	 /* https://bugzilla.kernel.org/show_bug.cgi?id=207835 */
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1012674 */
 	 .callback = video_detect_force_native,
-	 /* Acer TravelMate 5735Z */
+	 /* Acer Aspire 5741 */
 	 .matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
-		DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5735Z"),
-		DMI_MATCH(DMI_BOARD_NAME, "BA51_MV"),
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5741"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	/* ASUSTeK COMPUTER INC. GA401 */
-	.matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "GA401"),
-		},
-	},
-	{
-	.callback = video_detect_force_native,
-	/* ASUSTeK COMPUTER INC. GA502 */
-	.matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "GA502"),
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=42993 */
+	 .callback = video_detect_force_native,
+	 /* Acer Aspire 5750 */
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5750"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	/* ASUSTeK COMPUTER INC. GA503 */
-	.matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
-		DMI_MATCH(DMI_PRODUCT_NAME, "GA503"),
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=42833 */
+	 .callback = video_detect_force_native,
+	 /* Acer Extensa 5235 */
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Extensa 5235"),
 		},
 	},
-	/*
-	 * Clevo NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2 have both a
-	 * working native and video interface. However the default detection
-	 * mechanism first registers the video interface before unregistering
-	 * it again and switching to the native interface during boot. This
-	 * results in a dangling SBIOS request for backlight change for some
-	 * reason, causing the backlight to switch to ~2% once per boot on the
-	 * first power cord connect or disconnect event. Setting the native
-	 * interface explicitly circumvents this buggy behaviour, by avoiding
-	 * the unregistering process.
-	 */
 	{
-	.callback = video_detect_force_native,
-	.ident = "Clevo NL5xRU",
-	.matches = {
-		DMI_MATCH(DMI_BOARD_NAME, "NL5xRU"),
+	 .callback = video_detect_force_native,
+	 /* Acer TravelMate 4750 */
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 4750"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "Clevo NL5xRU",
-	.matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
-		DMI_MATCH(DMI_BOARD_NAME, "AURA1501"),
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=207835 */
+	 .callback = video_detect_force_native,
+	 /* Acer TravelMate 5735Z */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5735Z"),
+		DMI_MATCH(DMI_BOARD_NAME, "BA51_MV"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "Clevo NL5xRU",
-	.matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
-		DMI_MATCH(DMI_BOARD_NAME, "EDUBOOK1502"),
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=36322 */
+	 .callback = video_detect_force_native,
+	 /* Acer TravelMate 5760 */
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 5760"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "Clevo NL5xNU",
-	.matches = {
-		DMI_MATCH(DMI_BOARD_NAME, "NL5xNU"),
+	 .callback = video_detect_force_native,
+	 /* ASUSTeK COMPUTER INC. GA401 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "GA401"),
 		},
 	},
-	/*
-	 * The TongFang PF5PU1G, PF4NU1F, PF5NU1G, and PF5LUXG/TUXEDO BA15 Gen10,
-	 * Pulse 14/15 Gen1, and Pulse 15 Gen2 have the same problem as the Clevo
-	 * NL5xRU and NL5xNU/TUXEDO Aura 15 Gen1 and Gen2. See the description
-	 * above.
-	 */
 	{
-	.callback = video_detect_force_native,
-	.ident = "TongFang PF5PU1G",
-	.matches = {
-		DMI_MATCH(DMI_BOARD_NAME, "PF5PU1G"),
+	 .callback = video_detect_force_native,
+	 /* ASUSTeK COMPUTER INC. GA502 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "GA502"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "TongFang PF4NU1F",
-	.matches = {
-		DMI_MATCH(DMI_BOARD_NAME, "PF4NU1F"),
+	 .callback = video_detect_force_native,
+	 /* ASUSTeK COMPUTER INC. GA503 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "GA503"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "TongFang PF4NU1F",
-	.matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
-		DMI_MATCH(DMI_BOARD_NAME, "PULSE1401"),
+	 .callback = video_detect_force_native,
+	 /* Asus UX303UB */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "UX303UB"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "TongFang PF5NU1G",
-	.matches = {
-		DMI_MATCH(DMI_BOARD_NAME, "PF5NU1G"),
+	 .callback = video_detect_force_native,
+	 /* Samsung N150P */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "N150P"),
+		DMI_MATCH(DMI_BOARD_NAME, "N150P"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "TongFang PF5NU1G",
-	.matches = {
-		DMI_MATCH(DMI_SYS_VENDOR, "TUXEDO"),
-		DMI_MATCH(DMI_BOARD_NAME, "PULSE1501"),
+	 .callback = video_detect_force_native,
+	 /* Samsung 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"),
 		},
 	},
 	{
-	.callback = video_detect_force_native,
-	.ident = "TongFang PF5LUXG",
-	.matches = {
-		DMI_MATCH(DMI_BOARD_NAME, "PF5LUXG"),
+	 .callback = video_detect_force_native,
+	 /* Samsung N250P */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "N250P"),
+		DMI_MATCH(DMI_BOARD_NAME, "N250P"),
 		},
 	},
+
 	/*
 	 * Desktops which falsely report a backlight and which our heuristics
 	 * for this do not catch.
@@ -537,43 +633,15 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
 	{ },
 };
 
-/* This uses a workqueue to avoid various locking ordering issues */
-static void acpi_video_backlight_notify_work(struct work_struct *work)
-{
-	if (acpi_video_get_backlight_type() != acpi_backlight_video)
-		acpi_video_unregister_backlight();
-}
-
-static int acpi_video_backlight_notify(struct notifier_block *nb,
-				       unsigned long val, void *bd)
-{
-	struct backlight_device *backlight = bd;
-
-	/* A raw bl registering may change video -> native */
-	if (backlight->props.type == BACKLIGHT_RAW &&
-	    val == BACKLIGHT_REGISTERED)
-		schedule_work(&backlight_notify_work);
-
-	return NOTIFY_OK;
-}
-
 /*
  * Determine which type of backlight interface to use on this system,
  * First check cmdline, then dmi quirks, then do autodetect.
- *
- * The autodetect order is:
- * 1) Is the acpi-video backlight interface supported ->
- *  no, use a vendor interface
- * 2) Is this a win8 "ready" BIOS and do we have a native interface ->
- *  yes, use a native interface
- * 3) Else use the acpi-video interface
- *
- * Arguably the native on win8 check should be done first, but that would
- * be a behavior change, which may causes issues.
  */
-enum acpi_backlight_type acpi_video_get_backlight_type(void)
+static enum acpi_backlight_type __acpi_video_get_backlight_type(bool native)
 {
 	static DEFINE_MUTEX(init_mutex);
+	static bool nvidia_wmi_ec_present;
+	static bool native_available;
 	static bool init_done;
 	static long video_caps;
 
@@ -585,48 +653,60 @@ enum acpi_backlight_type acpi_video_get_backlight_type(void)
 		acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
 				    ACPI_UINT32_MAX, find_video, NULL,
 				    &video_caps, NULL);
-		INIT_WORK(&backlight_notify_work,
-			  acpi_video_backlight_notify_work);
-		backlight_nb.notifier_call = acpi_video_backlight_notify;
-		backlight_nb.priority = 0;
-		if (backlight_register_notifier(&backlight_nb) == 0)
-			backlight_notifier_registered = true;
+		nvidia_wmi_ec_present = nvidia_wmi_ec_supported();
 		init_done = true;
 	}
+	if (native)
+		native_available = true;
 	mutex_unlock(&init_mutex);
 
+	/*
+	 * The below heuristics / detection steps are in order of descending
+	 * presedence. The commandline takes presedence over anything else.
+	 */
 	if (acpi_backlight_cmdline != acpi_backlight_undef)
 		return acpi_backlight_cmdline;
 
+	/* DMI quirks override any autodetection. */
 	if (acpi_backlight_dmi != acpi_backlight_undef)
 		return acpi_backlight_dmi;
 
-	if (!(video_caps & ACPI_VIDEO_BACKLIGHT))
-		return acpi_backlight_vendor;
+	/* Special cases such as nvidia_wmi_ec and apple gmux. */
+	if (nvidia_wmi_ec_present)
+		return acpi_backlight_nvidia_wmi_ec;
 
-	if (acpi_osi_is_win8() && backlight_device_get_by_type(BACKLIGHT_RAW))
-		return acpi_backlight_native;
+	if (apple_gmux_present())
+		return acpi_backlight_apple_gmux;
+
+	/* On systems with ACPI video use either native or ACPI video. */
+	if (video_caps & ACPI_VIDEO_BACKLIGHT) {
+		/*
+		 * Windows 8 and newer no longer use the ACPI video interface,
+		 * so it often does not work. If the ACPI tables are written
+		 * for win8 and native brightness ctl is available, use that.
+		 *
+		 * The native check deliberately is inside the if acpi-video
+		 * block on older devices without acpi-video support native
+		 * is usually not the best choice.
+		 */
+		if (acpi_osi_is_win8() && native_available)
+			return acpi_backlight_native;
+		else
+			return acpi_backlight_video;
+	}
 
-	return acpi_backlight_video;
+	/* No ACPI video (old hw), use vendor specific fw methods. */
+	return acpi_backlight_vendor;
 }
-EXPORT_SYMBOL(acpi_video_get_backlight_type);
 
-/*
- * Set the preferred backlight interface type based on DMI info.
- * This function allows DMI blacklists to be implemented by external
- * platform drivers instead of putting a big blacklist in video_detect.c
- */
-void acpi_video_set_dmi_backlight_type(enum acpi_backlight_type type)
+enum acpi_backlight_type acpi_video_get_backlight_type(void)
 {
-	acpi_backlight_dmi = type;
-	/* Remove acpi-video backlight interface if it is no longer desired */
-	if (acpi_video_get_backlight_type() != acpi_backlight_video)
-		acpi_video_unregister_backlight();
+	return __acpi_video_get_backlight_type(false);
 }
-EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
+EXPORT_SYMBOL(acpi_video_get_backlight_type);
 
-void __exit acpi_video_detect_exit(void)
+bool acpi_video_backlight_use_native(void)
 {
-	if (backlight_notifier_registered)
-		backlight_unregister_notifier(&backlight_nb);
+	return __acpi_video_get_backlight_type(true) == acpi_backlight_native;
 }
+EXPORT_SYMBOL(acpi_video_backlight_use_native);