v4.19.13 snapshot.
diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
new file mode 100644
index 0000000..43587ac
--- /dev/null
+++ b/drivers/acpi/video_detect.c
@@ -0,0 +1,434 @@
+/*
+ *  Copyright (C) 2015       Red Hat Inc.
+ *                           Hans de Goede <hdegoede@redhat.com>
+ *  Copyright (C) 2008       SuSE Linux Products GmbH
+ *                           Thomas Renninger <trenn@suse.de>
+ *
+ *  May be copied or modified under the terms of the GNU General Public License
+ *
+ * video_detect.c:
+ * After PCI devices are glued with ACPI devices
+ * acpi_get_pci_dev() can be called to identify ACPI graphics
+ * devices for which a real graphics card is plugged in
+ *
+ * Depending on whether ACPI graphics extensions (cmp. ACPI spec Appendix B)
+ * are available, video.ko should be used to handle the device.
+ *
+ * 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.
+ *
+ * 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
+ * always return acpi_backlight_vendor.
+ */
+
+#include <linux/export.h>
+#include <linux/acpi.h>
+#include <linux/backlight.h>
+#include <linux/dmi.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+#include <acpi/video.h>
+
+ACPI_MODULE_NAME("video");
+#define _COMPONENT		ACPI_VIDEO_COMPONENT
+
+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;
+
+static void acpi_video_parse_cmdline(void)
+{
+	if (!strcmp("vendor", acpi_video_backlight_string))
+		acpi_backlight_cmdline = acpi_backlight_vendor;
+	if (!strcmp("video", acpi_video_backlight_string))
+		acpi_backlight_cmdline = acpi_backlight_video;
+	if (!strcmp("native", acpi_video_backlight_string))
+		acpi_backlight_cmdline = acpi_backlight_native;
+	if (!strcmp("none", acpi_video_backlight_string))
+		acpi_backlight_cmdline = acpi_backlight_none;
+}
+
+static acpi_status
+find_video(acpi_handle handle, u32 lvl, void *context, void **rv)
+{
+	long *cap = context;
+	struct pci_dev *dev;
+	struct acpi_device *acpi_dev;
+
+	static const struct acpi_device_id video_ids[] = {
+		{ACPI_VIDEO_HID, 0},
+		{"", 0},
+	};
+	if (acpi_bus_get_device(handle, &acpi_dev))
+		return AE_OK;
+
+	if (!acpi_match_device_ids(acpi_dev, video_ids)) {
+		dev = acpi_get_pci_dev(handle);
+		if (!dev)
+			return AE_OK;
+		pci_dev_put(dev);
+		*cap |= acpi_is_video_device(handle);
+	}
+	return AE_OK;
+}
+
+/* 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)
+{
+	acpi_backlight_dmi = acpi_backlight_vendor;
+	return 0;
+}
+
+static int video_detect_force_video(const struct dmi_system_id *d)
+{
+	acpi_backlight_dmi = acpi_backlight_video;
+	return 0;
+}
+
+static int video_detect_force_native(const struct dmi_system_id *d)
+{
+	acpi_backlight_dmi = acpi_backlight_native;
+	return 0;
+}
+
+static int video_detect_force_none(const struct dmi_system_id *d)
+{
+	acpi_backlight_dmi = acpi_backlight_none;
+	return 0;
+}
+
+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) untill 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().
+	 */
+	{
+	 .callback = video_detect_force_vendor,
+	 .ident = "X360",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "X360"),
+		DMI_MATCH(DMI_BOARD_NAME, "X360"),
+		},
+	},
+	{
+	.callback = video_detect_force_vendor,
+	.ident = "Asus UL30VT",
+	.matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "UL30VT"),
+		},
+	},
+	{
+	.callback = video_detect_force_vendor,
+	.ident = "Asus UL30A",
+	.matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
+		},
+	},
+
+	/*
+	 * 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
+	 * native_backlight on these to fix this:
+	 * https://bugzilla.kernel.org/show_bug.cgi?id=81691
+	 */
+	{
+	 .callback = video_detect_force_video,
+	 .ident = "ThinkPad T420",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T420"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 .ident = "ThinkPad T520",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T520"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 .ident = "ThinkPad X201s",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201s"),
+		},
+	},
+        {
+         .callback = video_detect_force_video,
+         .ident = "ThinkPad X201T",
+         .matches = {
+                DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+                DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201T"),
+                },
+        },
+
+	/* The native backlight controls do not work on some older machines */
+	{
+	 /* https://bugs.freedesktop.org/show_bug.cgi?id=81515 */
+	 .callback = video_detect_force_video,
+	 .ident = "HP ENVY 15 Notebook",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "HP ENVY 15 Notebook PC"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 .ident = "SAMSUNG 870Z5E/880Z5E/680Z5E",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "870Z5E/880Z5E/680Z5E"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 .ident = "SAMSUNG 370R4E/370R4V/370R5E/3570RE/370R5V",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME,
+			  "370R4E/370R4V/370R5E/3570RE/370R5V"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1186097 */
+	 .callback = video_detect_force_video,
+	 .ident = "SAMSUNG 3570R/370R/470R/450R/510R/4450RV",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME,
+			  "3570R/370R/470R/450R/510R/4450RV"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1557060 */
+	 .callback = video_detect_force_video,
+	 .ident = "SAMSUNG 670Z5E",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "670Z5E"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1094948 */
+	 .callback = video_detect_force_video,
+	 .ident = "SAMSUNG 730U3E/740U3E",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "730U3E/740U3E"),
+		},
+	},
+	{
+	 /* https://bugs.freedesktop.org/show_bug.cgi?id=87286 */
+	 .callback = video_detect_force_video,
+	 .ident = "SAMSUNG 900X3C/900X3D/900X3E/900X4C/900X4D",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME,
+			  "900X3C/900X3D/900X3E/900X4C/900X4D"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1272633 */
+	 .callback = video_detect_force_video,
+	 .ident = "Dell XPS14 L421X",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "XPS L421X"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1163574 */
+	 .callback = video_detect_force_video,
+	 .ident = "Dell XPS15 L521X",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "XPS L521X"),
+		},
+	},
+	{
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=108971 */
+	 .callback = video_detect_force_video,
+	 .ident = "SAMSUNG 530U4E/540U4E",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "530U4E/540U4E"),
+		},
+	},
+
+	/* Non win8 machines which need native backlight nevertheless */
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1201530 */
+	 .callback = video_detect_force_native,
+	 .ident = "Lenovo Ideapad S405",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_BOARD_NAME, "Lenovo IdeaPad S405"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1187004 */
+	 .callback = video_detect_force_native,
+	 .ident = "Lenovo Ideapad Z570",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "102434U"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1217249 */
+	 .callback = video_detect_force_native,
+	 .ident = "Apple MacBook Pro 12,1",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro12,1"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 .ident = "Dell Vostro V131",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1123661 */
+	 .callback = video_detect_force_native,
+	 .ident = "Dell XPS 17 L702X",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Dell System XPS L702X"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 .ident = "Dell Precision 7510",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
+		},
+	},
+	{
+	 .callback = video_detect_force_none,
+	 .ident = "Dell OptiPlex 9020M",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 9020M"),
+		},
+	},
+	{ },
+};
+
+/* 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 DEFINE_MUTEX(init_mutex);
+	static bool init_done;
+	static long video_caps;
+
+	/* Parse cmdline, dmi and acpi only once */
+	mutex_lock(&init_mutex);
+	if (!init_done) {
+		acpi_video_parse_cmdline();
+		dmi_check_system(video_detect_dmi_table);
+		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;
+		init_done = true;
+	}
+	mutex_unlock(&init_mutex);
+
+	if (acpi_backlight_cmdline != acpi_backlight_undef)
+		return acpi_backlight_cmdline;
+
+	if (acpi_backlight_dmi != acpi_backlight_undef)
+		return acpi_backlight_dmi;
+
+	if (!(video_caps & ACPI_VIDEO_BACKLIGHT))
+		return acpi_backlight_vendor;
+
+	if (acpi_osi_is_win8() && backlight_device_get_by_type(BACKLIGHT_RAW))
+		return acpi_backlight_native;
+
+	return acpi_backlight_video;
+}
+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)
+{
+	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();
+}
+EXPORT_SYMBOL(acpi_video_set_dmi_backlight_type);
+
+void __exit acpi_video_detect_exit(void)
+{
+	if (backlight_notifier_registered)
+		backlight_unregister_notifier(&backlight_nb);
+}