Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 1090 insertions, 0 deletions

diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
new file mode 100644
index 000000000..e3b69f876
--- /dev/null
+++ b/drivers/acpi/video_detect.c
@@ -0,0 +1,1090 @@
+/*
+ *  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. 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
+ * always return acpi_backlight_vendor.
+ */
+
+#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/pnp.h>
+#include <linux/types.h>
+#include <linux/workqueue.h>
+#include <acpi/video.h>
+
+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("nvidia_wmi_ec", acpi_video_backlight_string))
+		acpi_backlight_cmdline = acpi_backlight_nvidia_wmi_ec;
+	if (!strcmp("apple_gmux", acpi_video_backlight_string))
+		acpi_backlight_cmdline = acpi_backlight_apple_gmux;
+	if (!strcmp("dell_uart", acpi_video_backlight_string))
+		acpi_backlight_cmdline = acpi_backlight_dell_uart;
+	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)
+{
+	struct acpi_device *acpi_dev = acpi_fetch_acpi_dev(handle);
+	long *cap = context;
+	struct pci_dev *dev;
+
+	if (acpi_dev_is_video_device(acpi_dev)) {
+		dev = acpi_dev_get_pci_dev(acpi_dev);
+		if (!dev)
+			return AE_OK;
+		pci_dev_put(dev);
+		*cap |= acpi_is_video_device(handle);
+	}
+	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)
+{
+	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_portege_r100(const struct dmi_system_id *d)
+{
+	struct pci_dev *dev;
+	/* Search for Trident CyberBlade XP4m32 to confirm Portégé R100 */
+	dev = pci_get_device(PCI_VENDOR_ID_TRIDENT, 0x2100, NULL);
+	if (dev) {
+		acpi_backlight_dmi = acpi_backlight_vendor;
+		pci_dev_put(dev);
+	}
+	return 0;
+}
+
+static const struct dmi_system_id video_detect_dmi_table[] = {
+	/*
+	 * Models which should use the vendor backlight interface,
+	 * because of broken ACPI video backlight control.
+	 */
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1128309 */
+	 .callback = video_detect_force_vendor,
+	 /* Acer KAV80 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "KAV80"),
+		},
+	},
+	{
+	 .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 = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "UL30A"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Asus X55U */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK COMPUTER INC."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "X55U"),
+		},
+	},
+	{
+	 /* https://bugs.launchpad.net/bugs/1000146 */
+	 .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"),
+		},
+	},
+	{
+	 /* https://bugs.launchpad.net/bugs/1000146 */
+	 .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,
+	 /* 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"),
+		},
+	},
+
+	/*
+	 * Models which should use the vendor backlight interface,
+	 * because of broken native backlight control.
+	 */
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Sony Vaio PCG-FRV35 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "PCG-FRV35"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Panasonic Toughbook CF-18 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Matsushita Electric Industrial"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "CF-18"),
+		},
+	},
+
+	/*
+	 * 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"),
+		},
+	},
+
+	/*
+	 * Toshiba Portégé R100 has working both acpi_video and toshiba_acpi
+	 * vendor driver. But none of them gets activated as it has a VGA with
+	 * no kernel driver (Trident CyberBlade XP4m32).
+	 * The DMI strings are generic so check for the VGA chip in callback.
+	 */
+	{
+	 .callback = video_detect_portege_r100,
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Portable PC"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "Version 1.0"),
+		DMI_MATCH(DMI_BOARD_NAME, "Portable PC")
+		},
+	},
+
+	/*
+	 * Models which need acpi_video backlight control where the GPU drivers
+	 * do not call acpi_video_register_backlight() because no internal panel
+	 * is detected. Typically these are all-in-ones (monitors with builtin
+	 * PC) where the panel connection shows up as regular DP instead of eDP.
+	 */
+	{
+	 .callback = video_detect_force_video,
+	 /* Apple iMac14,1 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "iMac14,1"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 /* Apple iMac14,2 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "iMac14,2"),
+		},
+	},
+
+	/*
+	 * 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,
+	 /* ThinkPad T420 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T420"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 /* ThinkPad T520 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad T520"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 /* ThinkPad X201s */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "ThinkPad X201s"),
+		},
+	},
+	{
+	 .callback = video_detect_force_video,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* 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,
+	 /* SAMSUNG 530U4E/540U4E */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "530U4E/540U4E"),
+		},
+	},
+	{
+	 /* https://bugs.launchpad.net/bugs/1894667 */
+	 .callback = video_detect_force_video,
+	 /* HP 635 Notebook */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "HP 635 Notebook PC"),
+		},
+	},
+
+	/* Non win8 machines which need native backlight nevertheless */
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1201530 */
+	 .callback = video_detect_force_native,
+	 /* Lenovo Ideapad S405 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_BOARD_NAME, "Lenovo IdeaPad S405"),
+		},
+	},
+	{
+	 /* https://bugzilla.suse.com/show_bug.cgi?id=1208724 */
+	 .callback = video_detect_force_native,
+	 /* Lenovo Ideapad Z470 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "IdeaPad Z470"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1187004 */
+	 .callback = video_detect_force_native,
+	 /* Lenovo Ideapad Z570 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "Ideapad Z570"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Lenovo E41-25 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "81FS"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Lenovo E41-45 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "82BK"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Lenovo Slim 7 16ARH7 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "82UX"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Lenovo ThinkPad X131e (3371 AMD version) */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "3371"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Apple iMac11,3 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "iMac11,3"),
+		},
+	},
+	{
+	 /* https://gitlab.freedesktop.org/drm/amd/-/issues/1838 */
+	 .callback = video_detect_force_native,
+	 /* Apple iMac12,1 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "iMac12,1"),
+		},
+	},
+	{
+	 /* https://gitlab.freedesktop.org/drm/amd/-/issues/2753 */
+	 .callback = video_detect_force_native,
+	 /* Apple iMac12,2 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "iMac12,2"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Apple MacBook Air 7,2 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookAir7,2"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Apple MacBook Air 9,1 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookAir9,1"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Apple MacBook Pro 9,2 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro9,2"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Apple MacBook Pro 11,2 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro11,2"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1217249 */
+	 .callback = video_detect_force_native,
+	 /* 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,
+	 /* Apple MacBook Pro 16,2 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Apple Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,2"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Dell Inspiron N4010 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Inspiron N4010"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* 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,
+	 /* 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,
+	 /* Dell Precision 7510 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Precision 7510"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Dell Studio 1569 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Studio 1569"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Acer Aspire 3830TG */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 3830TG"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Acer Aspire 4810T */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 4810T"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Acer Aspire 5738z */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5738"),
+		DMI_MATCH(DMI_BOARD_NAME, "JV50"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=1012674 */
+	 .callback = video_detect_force_native,
+	 /* Acer Aspire 5741 */
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5741"),
+		},
+	},
+	{
+	 /* 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"),
+		},
+	},
+	{
+	 /* 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"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Acer TravelMate 4750 */
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "TravelMate 4750"),
+		},
+	},
+	{
+	 /* 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"),
+		},
+	},
+	{
+	 /* 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,
+	 /* 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"),
+		},
+	},
+	{
+	 .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,
+	 /* Asus U46E */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "ASUSTeK Computer Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "U46E"),
+		},
+	},
+	{
+	 .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,
+	 /* HP EliteBook 8460p */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "HP EliteBook 8460p"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* HP Pavilion g6-1d80nr / B4U19UA */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Hewlett-Packard"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "HP Pavilion g6 Notebook PC"),
+		DMI_MATCH(DMI_PRODUCT_SKU, "B4U19UA"),
+		},
+	},
+	{
+	 .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,
+	 /* 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,
+	 /* Samsung N250P */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "SAMSUNG ELECTRONICS CO., LTD."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "N250P"),
+		DMI_MATCH(DMI_BOARD_NAME, "N250P"),
+		},
+	},
+	{
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=202401 */
+	 .callback = video_detect_force_native,
+	 /* Sony Vaio VPCEH3U1E */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "VPCEH3U1E"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Sony Vaio VPCY11S1E */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Sony Corporation"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "VPCY11S1E"),
+		},
+	},
+
+	/*
+	 * These Toshibas have a broken acpi-video interface for brightness
+	 * control. They also have an issue where the panel is off after
+	 * suspend until a special firmware call is made to turn it back
+	 * on. This is handled by the toshiba_acpi kernel module, so that
+	 * module must be enabled for these models to work correctly.
+	 */
+	{
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=21012 */
+	 .callback = video_detect_force_native,
+	 /* Toshiba Portégé R700 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "PORTEGE R700"),
+		},
+	},
+	{
+	 /* Portégé: https://bugs.freedesktop.org/show_bug.cgi?id=82634 */
+	 /* Satellite: https://bugzilla.kernel.org/show_bug.cgi?id=21012 */
+	 .callback = video_detect_force_native,
+	 /* Toshiba Satellite/Portégé R830 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "R830"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Toshiba Satellite/Portégé Z830 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "TOSHIBA"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Z830"),
+		},
+	},
+
+	/*
+	 * Dell AIO (All in Ones) which advertise an UART attached backlight
+	 * controller board in their ACPI tables (and may even have one), but
+	 * which need native backlight control nevertheless.
+	 */
+	{
+	 /* https://github.com/zabbly/linux/issues/26 */
+	 .callback = video_detect_force_native,
+	 /* Dell OptiPlex 5480 AIO */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 5480 AIO"),
+		},
+	},
+	{
+	 /* https://bugzilla.redhat.com/show_bug.cgi?id=2303936 */
+	 .callback = video_detect_force_native,
+	 /* Dell OptiPlex 7760 AIO */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 7760 AIO"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Dell OptiPlex 7770 AIO */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 7770 AIO"),
+		},
+	},
+
+	/*
+	 * Models which have nvidia-ec-wmi support, but should not use it.
+	 * Note this indicates a likely firmware bug on these models and should
+	 * be revisited if/when Linux gets support for dynamic mux mode.
+	 */
+	{
+	 .callback = video_detect_force_native,
+	 /* Dell G15 5515 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Dell G15 5515"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Vostro 15 3535"),
+		},
+	},
+	{
+	 /* https://gitlab.freedesktop.org/drm/amd/-/issues/4512 */
+	 .callback = video_detect_force_native,
+	 /* Lenovo Legion S7 15ACH6 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "LENOVO"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "82K8"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* HP OMEN Gaming Laptop 16-n0xxx */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "HP"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "OMEN by HP Gaming Laptop 16-n0xxx"),
+		},
+	},
+	{
+	 .callback = video_detect_force_native,
+	 /* Acer Nitro AN515-46 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Nitro AN515-46"),
+		},
+	},
+
+	/*
+	 * x86 android tablets which directly control the backlight through
+	 * an external backlight controller, typically TI's LP8557.
+	 * The backlight is directly controlled by the lp855x driver on these.
+	 * This setup means that neither i915's native nor acpi_video backlight
+	 * control works. Add a "vendor" quirk to disable both. Note these
+	 * devices do not use vendor control in the typical meaning of
+	 * vendor specific SMBIOS or ACPI calls being used.
+	 */
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Lenovo Yoga Book X90F / X90L */
+	 .matches = {
+		DMI_EXACT_MATCH(DMI_SYS_VENDOR, "Intel Corporation"),
+		DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "CHERRYVIEW D1 PLATFORM"),
+		DMI_EXACT_MATCH(DMI_PRODUCT_VERSION, "YETI-11"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /*
+	  * Lenovo Yoga Tablet 2 830F/L or 1050F/L (The 8" and 10"
+	  * Lenovo Yoga Tablet 2 use the same mainboard)
+	  */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Intel Corp."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "VALLEYVIEW C0 PLATFORM"),
+		DMI_MATCH(DMI_BOARD_NAME, "BYT-T FFD8"),
+		/* Partial match on beginning of BIOS version */
+		DMI_MATCH(DMI_BIOS_VERSION, "BLADE_21"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Lenovo Yoga Tab 3 Pro YT3-X90F */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Intel Corporation"),
+		DMI_MATCH(DMI_PRODUCT_VERSION, "Blade3-10A-001"),
+		},
+	},
+	{
+	 .callback = video_detect_force_vendor,
+	 /* Xiaomi Mi Pad 2 */
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Xiaomi Inc"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Mipad2"),
+		},
+	},
+	{ },
+};
+
+static bool google_cros_ec_present(void)
+{
+	return acpi_dev_found("GOOG0004") || acpi_dev_found("GOOG000C");
+}
+
+/*
+ * Windows 8 and newer no longer use the ACPI video interface, so it often
+ * does not work. So on win8+ systems prefer native brightness control.
+ * Chromebooks should always prefer native backlight control.
+ */
+static bool prefer_native_over_acpi_video(void)
+{
+	return acpi_osi_is_win8() || google_cros_ec_present();
+}
+
+/*
+ * Determine which type of backlight interface to use on this system,
+ * First check cmdline, then dmi quirks, then do autodetect.
+ */
+enum acpi_backlight_type __acpi_video_get_backlight_type(bool native, bool *auto_detect)
+{
+	static DEFINE_MUTEX(init_mutex);
+	static bool nvidia_wmi_ec_present;
+	static bool apple_gmux_present;
+	static bool dell_uart_present;
+	static bool native_available;
+	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);
+		nvidia_wmi_ec_present = nvidia_wmi_ec_supported();
+		apple_gmux_present = apple_gmux_detect(NULL, NULL);
+		dell_uart_present = acpi_dev_present("DELL0501", NULL, -1);
+		init_done = true;
+	}
+	if (native)
+		native_available = true;
+	mutex_unlock(&init_mutex);
+
+	if (auto_detect)
+		*auto_detect = false;
+
+	/*
+	 * 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 (auto_detect)
+		*auto_detect = true;
+
+	/* Special cases such as nvidia_wmi_ec and apple gmux. */
+	if (nvidia_wmi_ec_present)
+		return acpi_backlight_nvidia_wmi_ec;
+
+	if (apple_gmux_present)
+		return acpi_backlight_apple_gmux;
+
+	if (dell_uart_present)
+		return acpi_backlight_dell_uart;
+
+	/* Use ACPI video if available, except when native should be preferred. */
+	if ((video_caps & ACPI_VIDEO_BACKLIGHT) &&
+	     !(native_available && prefer_native_over_acpi_video()))
+		return acpi_backlight_video;
+
+	/* Use native if available */
+	if (native_available)
+		return acpi_backlight_native;
+
+	/*
+	 * The vendor specific BIOS interfaces are only necessary for
+	 * laptops from before ~2008.
+	 *
+	 * For laptops from ~2008 till ~2023 this point is never reached
+	 * because on those (video_caps & ACPI_VIDEO_BACKLIGHT) above is true.
+	 *
+	 * Laptops from after ~2023 no longer support ACPI_VIDEO_BACKLIGHT,
+	 * if this point is reached on those, this likely means that
+	 * the GPU kms driver which sets native_available has not loaded yet.
+	 *
+	 * Returning acpi_backlight_vendor in this case is known to sometimes
+	 * cause a non working vendor specific /sys/class/backlight device to
+	 * get registered.
+	 *
+	 * Return acpi_backlight_none on laptops with ACPI tables written
+	 * for Windows 8 (laptops from after ~2012) to avoid this problem.
+	 */
+	if (acpi_osi_is_win8())
+		return acpi_backlight_none;
+
+	/* No ACPI video/native (old hw), use vendor specific fw methods. */
+	return acpi_backlight_vendor;
+}
+EXPORT_SYMBOL(__acpi_video_get_backlight_type);