Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2308 insertions, 0 deletions

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
new file mode 100644
index 000000000..f7852fb75
--- /dev/null
+++ b/drivers/acpi/acpi_video.c
@@ -0,0 +1,2308 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  video.c - ACPI Video Driver
+ *
+ *  Copyright (C) 2004 Luming Yu <luming.yu@intel.com>
+ *  Copyright (C) 2004 Bruno Ducrot <ducrot@poupinou.org>
+ *  Copyright (C) 2006 Thomas Tuttle <linux-kernel@ttuttle.net>
+ */
+
+#define pr_fmt(fmt) "ACPI: video: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/input.h>
+#include <linux/backlight.h>
+#include <linux/thermal.h>
+#include <linux/sort.h>
+#include <linux/pci.h>
+#include <linux/pci_ids.h>
+#include <linux/slab.h>
+#include <linux/dmi.h>
+#include <linux/suspend.h>
+#include <linux/acpi.h>
+#include <acpi/video.h>
+#include <linux/uaccess.h>
+
+#define ACPI_VIDEO_BUS_NAME		"Video Bus"
+#define ACPI_VIDEO_DEVICE_NAME		"Video Device"
+
+#define MAX_NAME_LEN	20
+
+MODULE_AUTHOR("Bruno Ducrot");
+MODULE_DESCRIPTION("ACPI Video Driver");
+MODULE_LICENSE("GPL");
+
+static bool brightness_switch_enabled = true;
+module_param(brightness_switch_enabled, bool, 0644);
+
+/*
+ * By default, we don't allow duplicate ACPI video bus devices
+ * under the same VGA controller
+ */
+static bool allow_duplicates;
+module_param(allow_duplicates, bool, 0644);
+
+#define REPORT_OUTPUT_KEY_EVENTS		0x01
+#define REPORT_BRIGHTNESS_KEY_EVENTS		0x02
+static int report_key_events = -1;
+module_param(report_key_events, int, 0644);
+MODULE_PARM_DESC(report_key_events,
+	"0: none, 1: output changes, 2: brightness changes, 3: all");
+
+static int hw_changes_brightness = -1;
+module_param(hw_changes_brightness, int, 0644);
+MODULE_PARM_DESC(hw_changes_brightness,
+	"Set this to 1 on buggy hw which changes the brightness itself when "
+	"a hotkey is pressed: -1: auto, 0: normal 1: hw-changes-brightness");
+
+/*
+ * Whether the struct acpi_video_device_attrib::device_id_scheme bit should be
+ * assumed even if not actually set.
+ */
+static bool device_id_scheme = false;
+module_param(device_id_scheme, bool, 0444);
+
+static int only_lcd = -1;
+module_param(only_lcd, int, 0444);
+
+static int register_backlight_delay;
+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);
+static DEFINE_MUTEX(video_list_lock);
+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);
+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,
+ * the rest are all supported levels.
+ *
+ * See page 575 of the ACPI spec 3.0
+ */
+enum acpi_video_level_idx {
+	ACPI_VIDEO_AC_LEVEL,		/* level when machine has full power */
+	ACPI_VIDEO_BATTERY_LEVEL,	/* level when machine is on batteries */
+	ACPI_VIDEO_FIRST_LEVEL,		/* actual supported levels begin here */
+};
+
+static const struct acpi_device_id video_device_ids[] = {
+	{ACPI_VIDEO_HID, 0},
+	{"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, video_device_ids);
+
+static struct acpi_driver acpi_video_bus = {
+	.name = "video",
+	.class = ACPI_VIDEO_CLASS,
+	.ids = video_device_ids,
+	.ops = {
+		.add = acpi_video_bus_add,
+		.remove = acpi_video_bus_remove,
+		.notify = acpi_video_bus_notify,
+		},
+};
+
+struct acpi_video_bus_flags {
+	u8 multihead:1;		/* can switch video heads */
+	u8 rom:1;		/* can retrieve a video rom */
+	u8 post:1;		/* can configure the head to */
+	u8 reserved:5;
+};
+
+struct acpi_video_bus_cap {
+	u8 _DOS:1;		/* Enable/Disable output switching */
+	u8 _DOD:1;		/* Enumerate all devices attached to display adapter */
+	u8 _ROM:1;		/* Get ROM Data */
+	u8 _GPD:1;		/* Get POST Device */
+	u8 _SPD:1;		/* Set POST Device */
+	u8 _VPO:1;		/* Video POST Options */
+	u8 reserved:2;
+};
+
+struct acpi_video_device_attrib {
+	u32 display_index:4;	/* A zero-based instance of the Display */
+	u32 display_port_attachment:4;	/* This field differentiates the display type */
+	u32 display_type:4;	/* Describe the specific type in use */
+	u32 vendor_specific:4;	/* Chipset Vendor Specific */
+	u32 bios_can_detect:1;	/* BIOS can detect the device */
+	u32 depend_on_vga:1;	/* Non-VGA output device whose power is related to
+				   the VGA device. */
+	u32 pipe_id:3;		/* For VGA multiple-head devices. */
+	u32 reserved:10;	/* Must be 0 */
+
+	/*
+	 * The device ID might not actually follow the scheme described by this
+	 * struct acpi_video_device_attrib. If it does, then this bit
+	 * device_id_scheme is set; otherwise, other fields should be ignored.
+	 *
+	 * (but also see the global flag device_id_scheme)
+	 */
+	u32 device_id_scheme:1;
+};
+
+struct acpi_video_enumerated_device {
+	union {
+		u32 int_val;
+		struct acpi_video_device_attrib attrib;
+	} value;
+	struct acpi_video_device *bind_info;
+};
+
+struct acpi_video_bus {
+	struct acpi_device *device;
+	bool backlight_registered;
+	u8 dos_setting;
+	struct acpi_video_enumerated_device *attached_array;
+	u8 attached_count;
+	u8 child_count;
+	struct acpi_video_bus_cap cap;
+	struct acpi_video_bus_flags flags;
+	struct list_head video_device_list;
+	struct mutex device_list_lock;	/* protects video_device_list */
+	struct list_head entry;
+	struct input_dev *input;
+	char phys[32];	/* for input device */
+	struct notifier_block pm_nb;
+};
+
+struct acpi_video_device_flags {
+	u8 crt:1;
+	u8 lcd:1;
+	u8 tvout:1;
+	u8 dvi:1;
+	u8 bios:1;
+	u8 unknown:1;
+	u8 notify:1;
+	u8 reserved:1;
+};
+
+struct acpi_video_device_cap {
+	u8 _ADR:1;		/* Return the unique ID */
+	u8 _BCL:1;		/* Query list of brightness control levels supported */
+	u8 _BCM:1;		/* Set the brightness level */
+	u8 _BQC:1;		/* Get current brightness level */
+	u8 _BCQ:1;		/* Some buggy BIOS uses _BCQ instead of _BQC */
+	u8 _DDC:1;		/* Return the EDID for this device */
+};
+
+struct acpi_video_device {
+	unsigned long device_id;
+	struct acpi_video_device_flags flags;
+	struct acpi_video_device_cap cap;
+	struct list_head entry;
+	struct delayed_work switch_brightness_work;
+	int switch_brightness_event;
+	struct acpi_video_bus *video;
+	struct acpi_device *dev;
+	struct acpi_video_device_brightness *brightness;
+	struct backlight_device *backlight;
+	struct thermal_cooling_device *cooling_dev;
+};
+
+static void acpi_video_device_notify(acpi_handle handle, u32 event, void *data);
+static void acpi_video_device_rebind(struct acpi_video_bus *video);
+static void acpi_video_device_bind(struct acpi_video_bus *video,
+				   struct acpi_video_device *device);
+static int acpi_video_device_enumerate(struct acpi_video_bus *video);
+static int acpi_video_device_lcd_set_level(struct acpi_video_device *device,
+			int level);
+static int acpi_video_device_lcd_get_level_current(
+			struct acpi_video_device *device,
+			unsigned long long *level, bool raw);
+static int acpi_video_get_next_level(struct acpi_video_device *device,
+				     u32 level_current, u32 event);
+static void acpi_video_switch_brightness(struct work_struct *work);
+
+/* backlight device sysfs support */
+static int acpi_video_get_brightness(struct backlight_device *bd)
+{
+	unsigned long long cur_level;
+	int i;
+	struct acpi_video_device *vd = bl_get_data(bd);
+
+	if (acpi_video_device_lcd_get_level_current(vd, &cur_level, false))
+		return -EINVAL;
+	for (i = ACPI_VIDEO_FIRST_LEVEL; i < vd->brightness->count; i++) {
+		if (vd->brightness->levels[i] == cur_level)
+			return i - ACPI_VIDEO_FIRST_LEVEL;
+	}
+	return 0;
+}
+
+static int acpi_video_set_brightness(struct backlight_device *bd)
+{
+	int request_level = bd->props.brightness + ACPI_VIDEO_FIRST_LEVEL;
+	struct acpi_video_device *vd = bl_get_data(bd);
+
+	cancel_delayed_work(&vd->switch_brightness_work);
+	return acpi_video_device_lcd_set_level(vd,
+				vd->brightness->levels[request_level]);
+}
+
+static const struct backlight_ops acpi_backlight_ops = {
+	.get_brightness = acpi_video_get_brightness,
+	.update_status  = acpi_video_set_brightness,
+};
+
+/* thermal cooling device callbacks */
+static int video_get_max_state(struct thermal_cooling_device *cooling_dev,
+			       unsigned long *state)
+{
+	struct acpi_device *device = cooling_dev->devdata;
+	struct acpi_video_device *video = acpi_driver_data(device);
+
+	*state = video->brightness->count - ACPI_VIDEO_FIRST_LEVEL - 1;
+	return 0;
+}
+
+static int video_get_cur_state(struct thermal_cooling_device *cooling_dev,
+			       unsigned long *state)
+{
+	struct acpi_device *device = cooling_dev->devdata;
+	struct acpi_video_device *video = acpi_driver_data(device);
+	unsigned long long level;
+	int offset;
+
+	if (acpi_video_device_lcd_get_level_current(video, &level, false))
+		return -EINVAL;
+	for (offset = ACPI_VIDEO_FIRST_LEVEL; offset < video->brightness->count;
+	     offset++)
+		if (level == video->brightness->levels[offset]) {
+			*state = video->brightness->count - offset - 1;
+			return 0;
+		}
+
+	return -EINVAL;
+}
+
+static int
+video_set_cur_state(struct thermal_cooling_device *cooling_dev, unsigned long state)
+{
+	struct acpi_device *device = cooling_dev->devdata;
+	struct acpi_video_device *video = acpi_driver_data(device);
+	int level;
+
+	if (state >= video->brightness->count - ACPI_VIDEO_FIRST_LEVEL)
+		return -EINVAL;
+
+	state = video->brightness->count - state;
+	level = video->brightness->levels[state - 1];
+	return acpi_video_device_lcd_set_level(video, level);
+}
+
+static const struct thermal_cooling_device_ops video_cooling_ops = {
+	.get_max_state = video_get_max_state,
+	.get_cur_state = video_get_cur_state,
+	.set_cur_state = video_set_cur_state,
+};
+
+/*
+ * --------------------------------------------------------------------------
+ *                             Video Management
+ * --------------------------------------------------------------------------
+ */
+
+static int
+acpi_video_device_lcd_query_levels(acpi_handle handle,
+				   union acpi_object **levels)
+{
+	int status;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+
+
+	*levels = NULL;
+
+	status = acpi_evaluate_object(handle, "_BCL", NULL, &buffer);
+	if (ACPI_FAILURE(status))
+		return status;
+	obj = (union acpi_object *)buffer.pointer;
+	if (!obj || (obj->type != ACPI_TYPE_PACKAGE)) {
+		acpi_handle_info(handle, "Invalid _BCL data\n");
+		status = -EFAULT;
+		goto err;
+	}
+
+	*levels = obj;
+
+	return 0;
+
+err:
+	kfree(buffer.pointer);
+
+	return status;
+}
+
+static int
+acpi_video_device_lcd_set_level(struct acpi_video_device *device, int level)
+{
+	int status;
+	int state;
+
+	status = acpi_execute_simple_method(device->dev->handle,
+					    "_BCM", level);
+	if (ACPI_FAILURE(status)) {
+		acpi_handle_info(device->dev->handle, "_BCM evaluation failed\n");
+		return -EIO;
+	}
+
+	device->brightness->curr = level;
+	for (state = ACPI_VIDEO_FIRST_LEVEL; state < device->brightness->count;
+	     state++)
+		if (level == device->brightness->levels[state]) {
+			if (device->backlight)
+				device->backlight->props.brightness =
+					state - ACPI_VIDEO_FIRST_LEVEL;
+			return 0;
+		}
+
+	acpi_handle_info(device->dev->handle, "Current brightness invalid\n");
+	return -EINVAL;
+}
+
+/*
+ * For some buggy _BQC methods, we need to add a constant value to
+ * the _BQC return value to get the actual current brightness level
+ */
+
+static int bqc_offset_aml_bug_workaround;
+static int video_set_bqc_offset(const struct dmi_system_id *d)
+{
+	bqc_offset_aml_bug_workaround = 9;
+	return 0;
+}
+
+static int video_set_device_id_scheme(const struct dmi_system_id *d)
+{
+	device_id_scheme = true;
+	return 0;
+}
+
+static int video_enable_only_lcd(const struct dmi_system_id *d)
+{
+	only_lcd = true;
+	return 0;
+}
+
+static int video_set_report_key_events(const struct dmi_system_id *id)
+{
+	if (report_key_events == -1)
+		report_key_events = (uintptr_t)id->driver_data;
+	return 0;
+}
+
+static int video_hw_changes_brightness(
+	const struct dmi_system_id *d)
+{
+	if (hw_changes_brightness == -1)
+		hw_changes_brightness = 1;
+	return 0;
+}
+
+static const struct dmi_system_id video_dmi_table[] = {
+	/*
+	 * Broken _BQC workaround http://bugzilla.kernel.org/show_bug.cgi?id=13121
+	 */
+	{
+	 .callback = video_set_bqc_offset,
+	 .ident = "Acer Aspire 5720",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5720"),
+		},
+	},
+	{
+	 .callback = video_set_bqc_offset,
+	 .ident = "Acer Aspire 5710Z",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5710Z"),
+		},
+	},
+	{
+	 .callback = video_set_bqc_offset,
+	 .ident = "eMachines E510",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "EMACHINES"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "eMachines E510"),
+		},
+	},
+	{
+	 .callback = video_set_bqc_offset,
+	 .ident = "Acer Aspire 5315",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5315"),
+		},
+	},
+	{
+	 .callback = video_set_bqc_offset,
+	 .ident = "Acer Aspire 7720",
+	 .matches = {
+		DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 7720"),
+		},
+	},
+
+	/*
+	 * Some machine's _DOD IDs don't have bit 31(Device ID Scheme) set
+	 * but the IDs actually follow the Device ID Scheme.
+	 */
+	{
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=104121 */
+	 .callback = video_set_device_id_scheme,
+	 .ident = "ESPRIMO Mobile M9410",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "FUJITSU SIEMENS"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "ESPRIMO Mobile M9410"),
+		},
+	},
+	/*
+	 * Some machines have multiple video output devices, but only the one
+	 * that is the type of LCD can do the backlight control so we should not
+	 * register backlight interface for other video output devices.
+	 */
+	{
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=104121 */
+	 .callback = video_enable_only_lcd,
+	 .ident = "ESPRIMO Mobile M9410",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "FUJITSU SIEMENS"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "ESPRIMO Mobile M9410"),
+		},
+	},
+	/*
+	 * Some machines report wrong key events on the acpi-bus, suppress
+	 * key event reporting on these.  Note this is only intended to work
+	 * around events which are plain wrong. In some cases we get double
+	 * events, in this case acpi-video is considered the canonical source
+	 * and the events from the other source should be filtered. E.g.
+	 * by calling acpi_video_handles_brightness_key_presses() from the
+	 * vendor acpi/wmi driver or by using /lib/udev/hwdb.d/60-keyboard.hwdb
+	 */
+	{
+	 .callback = video_set_report_key_events,
+	 .driver_data = (void *)((uintptr_t)REPORT_OUTPUT_KEY_EVENTS),
+	 .ident = "Dell Vostro V131",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
+		},
+	},
+	{
+	 .callback = video_set_report_key_events,
+	 .driver_data = (void *)((uintptr_t)REPORT_BRIGHTNESS_KEY_EVENTS),
+	 .ident = "Dell Vostro 3350",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Vostro 3350"),
+		},
+	},
+	/*
+	 * Some machines change the brightness themselves when a brightness
+	 * hotkey gets pressed, despite us telling them not to. In this case
+	 * acpi_video_device_notify() should only call backlight_force_update(
+	 * BACKLIGHT_UPDATE_HOTKEY) and not do anything else.
+	 */
+	{
+	 /* https://bugzilla.kernel.org/show_bug.cgi?id=204077 */
+	 .callback = video_hw_changes_brightness,
+	 .ident = "Packard Bell EasyNote MZ35",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Packard Bell"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "EasyNote MZ35"),
+		},
+	},
+	{}
+};
+
+static unsigned long long
+acpi_video_bqc_value_to_level(struct acpi_video_device *device,
+			      unsigned long long bqc_value)
+{
+	unsigned long long level;
+
+	if (device->brightness->flags._BQC_use_index) {
+		/*
+		 * _BQC returns an index that doesn't account for the first 2
+		 * items with special meaning (see enum acpi_video_level_idx),
+		 * so we need to compensate for that by offsetting ourselves
+		 */
+		if (device->brightness->flags._BCL_reversed)
+			bqc_value = device->brightness->count -
+				ACPI_VIDEO_FIRST_LEVEL - 1 - bqc_value;
+
+		level = device->brightness->levels[bqc_value +
+						   ACPI_VIDEO_FIRST_LEVEL];
+	} else {
+		level = bqc_value;
+	}
+
+	level += bqc_offset_aml_bug_workaround;
+
+	return level;
+}
+
+static int
+acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
+					unsigned long long *level, bool raw)
+{
+	acpi_status status = AE_OK;
+	int i;
+
+	if (device->cap._BQC || device->cap._BCQ) {
+		char *buf = device->cap._BQC ? "_BQC" : "_BCQ";
+
+		status = acpi_evaluate_integer(device->dev->handle, buf,
+						NULL, level);
+		if (ACPI_SUCCESS(status)) {
+			if (raw) {
+				/*
+				 * Caller has indicated he wants the raw
+				 * value returned by _BQC, so don't furtherly
+				 * mess with the value.
+				 */
+				return 0;
+			}
+
+			*level = acpi_video_bqc_value_to_level(device, *level);
+
+			for (i = ACPI_VIDEO_FIRST_LEVEL;
+			     i < device->brightness->count; i++)
+				if (device->brightness->levels[i] == *level) {
+					device->brightness->curr = *level;
+					return 0;
+				}
+			/*
+			 * BQC returned an invalid level.
+			 * Stop using it.
+			 */
+			acpi_handle_info(device->dev->handle,
+					 "%s returned an invalid level", buf);
+			device->cap._BQC = device->cap._BCQ = 0;
+		} else {
+			/*
+			 * Fixme:
+			 * should we return an error or ignore this failure?
+			 * dev->brightness->curr is a cached value which stores
+			 * the correct current backlight level in most cases.
+			 * ACPI video backlight still works w/ buggy _BQC.
+			 * http://bugzilla.kernel.org/show_bug.cgi?id=12233
+			 */
+			acpi_handle_info(device->dev->handle,
+					 "%s evaluation failed", buf);
+			device->cap._BQC = device->cap._BCQ = 0;
+		}
+	}
+
+	*level = device->brightness->curr;
+	return 0;
+}
+
+static int
+acpi_video_device_EDID(struct acpi_video_device *device,
+		       union acpi_object **edid, ssize_t length)
+{
+	int status;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+	union acpi_object arg0 = { ACPI_TYPE_INTEGER };
+	struct acpi_object_list args = { 1, &arg0 };
+
+
+	*edid = NULL;
+
+	if (!device)
+		return -ENODEV;
+	if (length == 128)
+		arg0.integer.value = 1;
+	else if (length == 256)
+		arg0.integer.value = 2;
+	else
+		return -EINVAL;
+
+	status = acpi_evaluate_object(device->dev->handle, "_DDC", &args, &buffer);
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	obj = buffer.pointer;
+
+	if (obj && obj->type == ACPI_TYPE_BUFFER)
+		*edid = obj;
+	else {
+		acpi_handle_info(device->dev->handle, "Invalid _DDC data\n");
+		status = -EFAULT;
+		kfree(obj);
+	}
+
+	return status;
+}
+
+/* bus */
+
+/*
+ *  Arg:
+ *	video		: video bus device pointer
+ *	bios_flag	:
+ *		0.	The system BIOS should NOT automatically switch(toggle)
+ *			the active display output.
+ *		1.	The system BIOS should automatically switch (toggle) the
+ *			active display output. No switch event.
+ *		2.	The _DGS value should be locked.
+ *		3.	The system BIOS should not automatically switch (toggle) the
+ *			active display output, but instead generate the display switch
+ *			event notify code.
+ *	lcd_flag	:
+ *		0.	The system BIOS should automatically control the brightness level
+ *			of the LCD when:
+ *			- the power changes from AC to DC (ACPI appendix B)
+ *			- a brightness hotkey gets pressed (implied by Win7/8 backlight docs)
+ *		1.	The system BIOS should NOT automatically control the brightness
+ *			level of the LCD when:
+ *			- the power changes from AC to DC (ACPI appendix B)
+ *			- a brightness hotkey gets pressed (implied by Win7/8 backlight docs)
+ *  Return Value:
+ *		-EINVAL	wrong arg.
+ */
+
+static int
+acpi_video_bus_DOS(struct acpi_video_bus *video, int bios_flag, int lcd_flag)
+{
+	acpi_status status;
+
+	if (!video->cap._DOS)
+		return 0;
+
+	if (bios_flag < 0 || bios_flag > 3 || lcd_flag < 0 || lcd_flag > 1)
+		return -EINVAL;
+	video->dos_setting = (lcd_flag << 2) | bios_flag;
+	status = acpi_execute_simple_method(video->device->handle, "_DOS",
+					    (lcd_flag << 2) | bios_flag);
+	if (ACPI_FAILURE(status))
+		return -EIO;
+
+	return 0;
+}
+
+/*
+ * Simple comparison function used to sort backlight levels.
+ */
+
+static int
+acpi_video_cmp_level(const void *a, const void *b)
+{
+	return *(int *)a - *(int *)b;
+}
+
+/*
+ * Decides if _BQC/_BCQ for this system is usable
+ *
+ * We do this by changing the level first and then read out the current
+ * brightness level, if the value does not match, find out if it is using
+ * index. If not, clear the _BQC/_BCQ capability.
+ */
+static int acpi_video_bqc_quirk(struct acpi_video_device *device,
+				int max_level, int current_level)
+{
+	struct acpi_video_device_brightness *br = device->brightness;
+	int result;
+	unsigned long long level;
+	int test_level;
+
+	/* don't mess with existing known broken systems */
+	if (bqc_offset_aml_bug_workaround)
+		return 0;
+
+	/*
+	 * Some systems always report current brightness level as maximum
+	 * through _BQC, we need to test another value for them. However,
+	 * there is a subtlety:
+	 *
+	 * If the _BCL package ordering is descending, the first level
+	 * (br->levels[2]) is likely to be 0, and if the number of levels
+	 * matches the number of steps, we might confuse a returned level to
+	 * mean the index.
+	 *
+	 * For example:
+	 *
+	 *     current_level = max_level = 100
+	 *     test_level = 0
+	 *     returned level = 100
+	 *
+	 * In this case 100 means the level, not the index, and _BCM failed.
+	 * Still, if the _BCL package ordering is descending, the index of
+	 * level 0 is also 100, so we assume _BQC is indexed, when it's not.
+	 *
+	 * This causes all _BQC calls to return bogus values causing weird
+	 * behavior from the user's perspective.  For example:
+	 *
+	 * xbacklight -set 10; xbacklight -set 20;
+	 *
+	 * would flash to 90% and then slowly down to the desired level (20).
+	 *
+	 * The solution is simple; test anything other than the first level
+	 * (e.g. 1).
+	 */
+	test_level = current_level == max_level
+		? br->levels[ACPI_VIDEO_FIRST_LEVEL + 1]
+		: max_level;
+
+	result = acpi_video_device_lcd_set_level(device, test_level);
+	if (result)
+		return result;
+
+	result = acpi_video_device_lcd_get_level_current(device, &level, true);
+	if (result)
+		return result;
+
+	if (level != test_level) {
+		/* buggy _BQC found, need to find out if it uses index */
+		if (level < br->count) {
+			if (br->flags._BCL_reversed)
+				level = br->count - ACPI_VIDEO_FIRST_LEVEL - 1 - level;
+			if (br->levels[level + ACPI_VIDEO_FIRST_LEVEL] == test_level)
+				br->flags._BQC_use_index = 1;
+		}
+
+		if (!br->flags._BQC_use_index)
+			device->cap._BQC = device->cap._BCQ = 0;
+	}
+
+	return 0;
+}
+
+int acpi_video_get_levels(struct acpi_device *device,
+			  struct acpi_video_device_brightness **dev_br,
+			  int *pmax_level)
+{
+	union acpi_object *obj = NULL;
+	int i, max_level = 0, count = 0, level_ac_battery = 0;
+	union acpi_object *o;
+	struct acpi_video_device_brightness *br = NULL;
+	int result = 0;
+	u32 value;
+
+	if (ACPI_FAILURE(acpi_video_device_lcd_query_levels(device->handle, &obj))) {
+		acpi_handle_debug(device->handle,
+				  "Could not query available LCD brightness level\n");
+		result = -ENODEV;
+		goto out;
+	}
+
+	if (obj->package.count < ACPI_VIDEO_FIRST_LEVEL) {
+		result = -EINVAL;
+		goto out;
+	}
+
+	br = kzalloc(sizeof(*br), GFP_KERNEL);
+	if (!br) {
+		result = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * Note that we have to reserve 2 extra items (ACPI_VIDEO_FIRST_LEVEL),
+	 * in order to account for buggy BIOS which don't export the first two
+	 * special levels (see below)
+	 */
+	br->levels = kmalloc_array(obj->package.count + ACPI_VIDEO_FIRST_LEVEL,
+				   sizeof(*br->levels),
+				   GFP_KERNEL);
+	if (!br->levels) {
+		result = -ENOMEM;
+		goto out_free;
+	}
+
+	for (i = 0; i < obj->package.count; i++) {
+		o = (union acpi_object *)&obj->package.elements[i];
+		if (o->type != ACPI_TYPE_INTEGER) {
+			acpi_handle_info(device->handle, "Invalid data\n");
+			continue;
+		}
+		value = (u32) o->integer.value;
+		/* Skip duplicate entries */
+		if (count > ACPI_VIDEO_FIRST_LEVEL
+		    && br->levels[count - 1] == value)
+			continue;
+
+		br->levels[count] = value;
+
+		if (br->levels[count] > max_level)
+			max_level = br->levels[count];
+		count++;
+	}
+
+	/*
+	 * some buggy BIOS don't export the levels
+	 * when machine is on AC/Battery in _BCL package.
+	 * In this case, the first two elements in _BCL packages
+	 * are also supported brightness levels that OS should take care of.
+	 */
+	for (i = ACPI_VIDEO_FIRST_LEVEL; i < count; i++) {
+		if (br->levels[i] == br->levels[ACPI_VIDEO_AC_LEVEL])
+			level_ac_battery++;
+		if (br->levels[i] == br->levels[ACPI_VIDEO_BATTERY_LEVEL])
+			level_ac_battery++;
+	}
+
+	if (level_ac_battery < ACPI_VIDEO_FIRST_LEVEL) {
+		level_ac_battery = ACPI_VIDEO_FIRST_LEVEL - level_ac_battery;
+		br->flags._BCL_no_ac_battery_levels = 1;
+		for (i = (count - 1 + level_ac_battery);
+		     i >= ACPI_VIDEO_FIRST_LEVEL; i--)
+			br->levels[i] = br->levels[i - level_ac_battery];
+		count += level_ac_battery;
+	} else if (level_ac_battery > ACPI_VIDEO_FIRST_LEVEL)
+		acpi_handle_info(device->handle,
+				 "Too many duplicates in _BCL package");
+
+	/* Check if the _BCL package is in a reversed order */
+	if (max_level == br->levels[ACPI_VIDEO_FIRST_LEVEL]) {
+		br->flags._BCL_reversed = 1;
+		sort(&br->levels[ACPI_VIDEO_FIRST_LEVEL],
+		     count - ACPI_VIDEO_FIRST_LEVEL,
+		     sizeof(br->levels[ACPI_VIDEO_FIRST_LEVEL]),
+		     acpi_video_cmp_level, NULL);
+	} else if (max_level != br->levels[count - 1])
+		acpi_handle_info(device->handle,
+				 "Found unordered _BCL package");
+
+	br->count = count;
+	*dev_br = br;
+	if (pmax_level)
+		*pmax_level = max_level;
+
+out:
+	kfree(obj);
+	return result;
+out_free:
+	kfree(br);
+	goto out;
+}
+EXPORT_SYMBOL(acpi_video_get_levels);
+
+/*
+ *  Arg:
+ *	device	: video output device (LCD, CRT, ..)
+ *
+ *  Return Value:
+ *	Maximum brightness level
+ *
+ *  Allocate and initialize device->brightness.
+ */
+
+static int
+acpi_video_init_brightness(struct acpi_video_device *device)
+{
+	int i, max_level = 0;
+	unsigned long long level, level_old;
+	struct acpi_video_device_brightness *br = NULL;
+	int result;
+
+	result = acpi_video_get_levels(device->dev, &br, &max_level);
+	if (result)
+		return result;
+	device->brightness = br;
+
+	/* _BQC uses INDEX while _BCL uses VALUE in some laptops */
+	br->curr = level = max_level;
+
+	if (!device->cap._BQC)
+		goto set_level;
+
+	result = acpi_video_device_lcd_get_level_current(device,
+							 &level_old, true);
+	if (result)
+		goto out_free_levels;
+
+	result = acpi_video_bqc_quirk(device, max_level, level_old);
+	if (result)
+		goto out_free_levels;
+	/*
+	 * cap._BQC may get cleared due to _BQC is found to be broken
+	 * in acpi_video_bqc_quirk, so check again here.
+	 */
+	if (!device->cap._BQC)
+		goto set_level;
+
+	level = acpi_video_bqc_value_to_level(device, level_old);
+	/*
+	 * On some buggy laptops, _BQC returns an uninitialized
+	 * value when invoked for the first time, i.e.
+	 * level_old is invalid (no matter whether it's a level
+	 * or an index). Set the backlight to max_level in this case.
+	 */
+	for (i = ACPI_VIDEO_FIRST_LEVEL; i < br->count; i++)
+		if (level == br->levels[i])
+			break;
+	if (i == br->count || !level)
+		level = max_level;
+
+set_level:
+	result = acpi_video_device_lcd_set_level(device, level);
+	if (result)
+		goto out_free_levels;
+
+	acpi_handle_debug(device->dev->handle, "found %d brightness levels\n",
+			  br->count - ACPI_VIDEO_FIRST_LEVEL);
+
+	return 0;
+
+out_free_levels:
+	kfree(br->levels);
+	kfree(br);
+	device->brightness = NULL;
+	return result;
+}
+
+/*
+ *  Arg:
+ *	device	: video output device (LCD, CRT, ..)
+ *
+ *  Return Value:
+ *	None
+ *
+ *  Find out all required AML methods defined under the output
+ *  device.
+ */
+
+static void acpi_video_device_find_cap(struct acpi_video_device *device)
+{
+	if (acpi_has_method(device->dev->handle, "_ADR"))
+		device->cap._ADR = 1;
+	if (acpi_has_method(device->dev->handle, "_BCL"))
+		device->cap._BCL = 1;
+	if (acpi_has_method(device->dev->handle, "_BCM"))
+		device->cap._BCM = 1;
+	if (acpi_has_method(device->dev->handle, "_BQC")) {
+		device->cap._BQC = 1;
+	} else if (acpi_has_method(device->dev->handle, "_BCQ")) {
+		acpi_handle_info(device->dev->handle,
+				 "_BCQ is used instead of _BQC\n");
+		device->cap._BCQ = 1;
+	}
+
+	if (acpi_has_method(device->dev->handle, "_DDC"))
+		device->cap._DDC = 1;
+}
+
+/*
+ *  Arg:
+ *	device	: video output device (VGA)
+ *
+ *  Return Value:
+ *	None
+ *
+ *  Find out all required AML methods defined under the video bus device.
+ */
+
+static void acpi_video_bus_find_cap(struct acpi_video_bus *video)
+{
+	if (acpi_has_method(video->device->handle, "_DOS"))
+		video->cap._DOS = 1;
+	if (acpi_has_method(video->device->handle, "_DOD"))
+		video->cap._DOD = 1;
+	if (acpi_has_method(video->device->handle, "_ROM"))
+		video->cap._ROM = 1;
+	if (acpi_has_method(video->device->handle, "_GPD"))
+		video->cap._GPD = 1;
+	if (acpi_has_method(video->device->handle, "_SPD"))
+		video->cap._SPD = 1;
+	if (acpi_has_method(video->device->handle, "_VPO"))
+		video->cap._VPO = 1;
+}
+
+/*
+ * Check whether the video bus device has required AML method to
+ * support the desired features
+ */
+
+static int acpi_video_bus_check(struct acpi_video_bus *video)
+{
+	acpi_status status = -ENOENT;
+	struct pci_dev *dev;
+
+	if (!video)
+		return -EINVAL;
+
+	dev = acpi_get_pci_dev(video->device->handle);
+	if (!dev)
+		return -ENODEV;
+	pci_dev_put(dev);
+
+	/*
+	 * Since there is no HID, CID and so on for VGA driver, we have
+	 * to check well known required nodes.
+	 */
+
+	/* Does this device support video switching? */
+	if (video->cap._DOS || video->cap._DOD) {
+		if (!video->cap._DOS) {
+			pr_info(FW_BUG "ACPI(%s) defines _DOD but not _DOS\n",
+				acpi_device_bid(video->device));
+		}
+		video->flags.multihead = 1;
+		status = 0;
+	}
+
+	/* Does this device support retrieving a video ROM? */
+	if (video->cap._ROM) {
+		video->flags.rom = 1;
+		status = 0;
+	}
+
+	/* Does this device support configuring which video device to POST? */
+	if (video->cap._GPD && video->cap._SPD && video->cap._VPO) {
+		video->flags.post = 1;
+		status = 0;
+	}
+
+	return status;
+}
+
+/*
+ * --------------------------------------------------------------------------
+ *                               Driver Interface
+ * --------------------------------------------------------------------------
+ */
+
+/* device interface */
+static struct acpi_video_device_attrib *
+acpi_video_get_device_attr(struct acpi_video_bus *video, unsigned long device_id)
+{
+	struct acpi_video_enumerated_device *ids;
+	int i;
+
+	for (i = 0; i < video->attached_count; i++) {
+		ids = &video->attached_array[i];
+		if ((ids->value.int_val & 0xffff) == device_id)
+			return &ids->value.attrib;
+	}
+
+	return NULL;
+}
+
+static int
+acpi_video_get_device_type(struct acpi_video_bus *video,
+			   unsigned long device_id)
+{
+	struct acpi_video_enumerated_device *ids;
+	int i;
+
+	for (i = 0; i < video->attached_count; i++) {
+		ids = &video->attached_array[i];
+		if ((ids->value.int_val & 0xffff) == device_id)
+			return ids->value.int_val;
+	}
+
+	return 0;
+}
+
+static int acpi_video_bus_get_one_device(struct acpi_device *device, void *arg)
+{
+	struct acpi_video_bus *video = arg;
+	struct acpi_video_device_attrib *attribute;
+	struct acpi_video_device *data;
+	unsigned long long device_id;
+	acpi_status status;
+	int device_type;
+
+	status = acpi_evaluate_integer(device->handle, "_ADR", NULL, &device_id);
+	/* Skip devices without _ADR instead of failing. */
+	if (ACPI_FAILURE(status))
+		goto exit;
+
+	data = kzalloc(sizeof(struct acpi_video_device), GFP_KERNEL);
+	if (!data) {
+		dev_dbg(&device->dev, "Cannot attach\n");
+		return -ENOMEM;
+	}
+
+	strcpy(acpi_device_name(device), ACPI_VIDEO_DEVICE_NAME);
+	strcpy(acpi_device_class(device), ACPI_VIDEO_CLASS);
+	device->driver_data = data;
+
+	data->device_id = device_id;
+	data->video = video;
+	data->dev = device;
+	INIT_DELAYED_WORK(&data->switch_brightness_work,
+			  acpi_video_switch_brightness);
+
+	attribute = acpi_video_get_device_attr(video, device_id);
+
+	if (attribute && (attribute->device_id_scheme || device_id_scheme)) {
+		switch (attribute->display_type) {
+		case ACPI_VIDEO_DISPLAY_CRT:
+			data->flags.crt = 1;
+			break;
+		case ACPI_VIDEO_DISPLAY_TV:
+			data->flags.tvout = 1;
+			break;
+		case ACPI_VIDEO_DISPLAY_DVI:
+			data->flags.dvi = 1;
+			break;
+		case ACPI_VIDEO_DISPLAY_LCD:
+			data->flags.lcd = 1;
+			break;
+		default:
+			data->flags.unknown = 1;
+			break;
+		}
+		if (attribute->bios_can_detect)
+			data->flags.bios = 1;
+	} else {
+		/* Check for legacy IDs */
+		device_type = acpi_video_get_device_type(video, device_id);
+		/* Ignore bits 16 and 18-20 */
+		switch (device_type & 0xffe2ffff) {
+		case ACPI_VIDEO_DISPLAY_LEGACY_MONITOR:
+			data->flags.crt = 1;
+			break;
+		case ACPI_VIDEO_DISPLAY_LEGACY_PANEL:
+			data->flags.lcd = 1;
+			break;
+		case ACPI_VIDEO_DISPLAY_LEGACY_TV:
+			data->flags.tvout = 1;
+			break;
+		default:
+			data->flags.unknown = 1;
+		}
+	}
+
+	acpi_video_device_bind(video, data);
+	acpi_video_device_find_cap(data);
+
+	if (data->cap._BCM && data->cap._BCL)
+		may_report_brightness_keys = true;
+
+	mutex_lock(&video->device_list_lock);
+	list_add_tail(&data->entry, &video->video_device_list);
+	mutex_unlock(&video->device_list_lock);
+
+exit:
+	video->child_count++;
+	return 0;
+}
+
+/*
+ *  Arg:
+ *	video	: video bus device
+ *
+ *  Return:
+ *	none
+ *
+ *  Enumerate the video device list of the video bus,
+ *  bind the ids with the corresponding video devices
+ *  under the video bus.
+ */
+
+static void acpi_video_device_rebind(struct acpi_video_bus *video)
+{
+	struct acpi_video_device *dev;
+
+	mutex_lock(&video->device_list_lock);
+
+	list_for_each_entry(dev, &video->video_device_list, entry)
+		acpi_video_device_bind(video, dev);
+
+	mutex_unlock(&video->device_list_lock);
+}
+
+/*
+ *  Arg:
+ *	video	: video bus device
+ *	device	: video output device under the video
+ *		bus
+ *
+ *  Return:
+ *	none
+ *
+ *  Bind the ids with the corresponding video devices
+ *  under the video bus.
+ */
+
+static void
+acpi_video_device_bind(struct acpi_video_bus *video,
+		       struct acpi_video_device *device)
+{
+	struct acpi_video_enumerated_device *ids;
+	int i;
+
+	for (i = 0; i < video->attached_count; i++) {
+		ids = &video->attached_array[i];
+		if (device->device_id == (ids->value.int_val & 0xffff)) {
+			ids->bind_info = device;
+			acpi_handle_debug(video->device->handle, "%s: %d\n",
+					  __func__, i);
+		}
+	}
+}
+
+static bool acpi_video_device_in_dod(struct acpi_video_device *device)
+{
+	struct acpi_video_bus *video = device->video;
+	int i;
+
+	/*
+	 * If we have a broken _DOD or we have more than 8 output devices
+	 * under the graphics controller node that we can't proper deal with
+	 * in the operation region code currently, no need to test.
+	 */
+	if (!video->attached_count || video->child_count > 8)
+		return true;
+
+	for (i = 0; i < video->attached_count; i++) {
+		if ((video->attached_array[i].value.int_val & 0xfff) ==
+		    (device->device_id & 0xfff))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ *  Arg:
+ *	video	: video bus device
+ *
+ *  Return:
+ *	< 0	: error
+ *
+ *  Call _DOD to enumerate all devices attached to display adapter
+ *
+ */
+
+static int acpi_video_device_enumerate(struct acpi_video_bus *video)
+{
+	int status;
+	int count;
+	int i;
+	struct acpi_video_enumerated_device *active_list;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *dod = NULL;
+	union acpi_object *obj;
+
+	if (!video->cap._DOD)
+		return AE_NOT_EXIST;
+
+	status = acpi_evaluate_object(video->device->handle, "_DOD", NULL, &buffer);
+	if (ACPI_FAILURE(status)) {
+		acpi_handle_info(video->device->handle,
+				 "_DOD evaluation failed: %s\n",
+				 acpi_format_exception(status));
+		return status;
+	}
+
+	dod = buffer.pointer;
+	if (!dod || (dod->type != ACPI_TYPE_PACKAGE)) {
+		acpi_handle_info(video->device->handle, "Invalid _DOD data\n");
+		status = -EFAULT;
+		goto out;
+	}
+
+	acpi_handle_debug(video->device->handle, "Found %d video heads in _DOD\n",
+			  dod->package.count);
+
+	active_list = kcalloc(1 + dod->package.count,
+			      sizeof(struct acpi_video_enumerated_device),
+			      GFP_KERNEL);
+	if (!active_list) {
+		status = -ENOMEM;
+		goto out;
+	}
+
+	count = 0;
+	for (i = 0; i < dod->package.count; i++) {
+		obj = &dod->package.elements[i];
+
+		if (obj->type != ACPI_TYPE_INTEGER) {
+			acpi_handle_info(video->device->handle,
+					 "Invalid _DOD data in element %d\n", i);
+			continue;
+		}
+
+		active_list[count].value.int_val = obj->integer.value;
+		active_list[count].bind_info = NULL;
+
+		acpi_handle_debug(video->device->handle,
+				  "_DOD element[%d] = %d\n", i,
+				  (int)obj->integer.value);
+
+		count++;
+	}
+
+	kfree(video->attached_array);
+
+	video->attached_array = active_list;
+	video->attached_count = count;
+
+out:
+	kfree(buffer.pointer);
+	return status;
+}
+
+static int
+acpi_video_get_next_level(struct acpi_video_device *device,
+			  u32 level_current, u32 event)
+{
+	int min, max, min_above, max_below, i, l, delta = 255;
+	max = max_below = 0;
+	min = min_above = 255;
+	/* Find closest level to level_current */
+	for (i = ACPI_VIDEO_FIRST_LEVEL; i < device->brightness->count; i++) {
+		l = device->brightness->levels[i];
+		if (abs(l - level_current) < abs(delta)) {
+			delta = l - level_current;
+			if (!delta)
+				break;
+		}
+	}
+	/* Adjust level_current to closest available level */
+	level_current += delta;
+	for (i = ACPI_VIDEO_FIRST_LEVEL; i < device->brightness->count; i++) {
+		l = device->brightness->levels[i];
+		if (l < min)
+			min = l;
+		if (l > max)
+			max = l;
+		if (l < min_above && l > level_current)
+			min_above = l;
+		if (l > max_below && l < level_current)
+			max_below = l;
+	}
+
+	switch (event) {
+	case ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS:
+		return (level_current < max) ? min_above : min;
+	case ACPI_VIDEO_NOTIFY_INC_BRIGHTNESS:
+		return (level_current < max) ? min_above : max;
+	case ACPI_VIDEO_NOTIFY_DEC_BRIGHTNESS:
+		return (level_current > min) ? max_below : min;
+	case ACPI_VIDEO_NOTIFY_ZERO_BRIGHTNESS:
+	case ACPI_VIDEO_NOTIFY_DISPLAY_OFF:
+		return 0;
+	default:
+		return level_current;
+	}
+}
+
+static void
+acpi_video_switch_brightness(struct work_struct *work)
+{
+	struct acpi_video_device *device = container_of(to_delayed_work(work),
+			     struct acpi_video_device, switch_brightness_work);
+	unsigned long long level_current, level_next;
+	int event = device->switch_brightness_event;
+	int result = -EINVAL;
+
+	/* no warning message if acpi_backlight=vendor or a quirk is used */
+	if (!device->backlight)
+		return;
+
+	if (!device->brightness)
+		goto out;
+
+	result = acpi_video_device_lcd_get_level_current(device,
+							 &level_current,
+							 false);
+	if (result)
+		goto out;
+
+	level_next = acpi_video_get_next_level(device, level_current, event);
+
+	result = acpi_video_device_lcd_set_level(device, level_next);
+
+	if (!result)
+		backlight_force_update(device->backlight,
+				       BACKLIGHT_UPDATE_HOTKEY);
+
+out:
+	if (result)
+		acpi_handle_info(device->dev->handle,
+				 "Failed to switch brightness\n");
+}
+
+int acpi_video_get_edid(struct acpi_device *device, int type, int device_id,
+			void **edid)
+{
+	struct acpi_video_bus *video;
+	struct acpi_video_device *video_device;
+	union acpi_object *buffer = NULL;
+	acpi_status status;
+	int i, length;
+
+	if (!device || !acpi_driver_data(device))
+		return -EINVAL;
+
+	video = acpi_driver_data(device);
+
+	for (i = 0; i < video->attached_count; i++) {
+		video_device = video->attached_array[i].bind_info;
+		length = 256;
+
+		if (!video_device)
+			continue;
+
+		if (!video_device->cap._DDC)
+			continue;
+
+		if (type) {
+			switch (type) {
+			case ACPI_VIDEO_DISPLAY_CRT:
+				if (!video_device->flags.crt)
+					continue;
+				break;
+			case ACPI_VIDEO_DISPLAY_TV:
+				if (!video_device->flags.tvout)
+					continue;
+				break;
+			case ACPI_VIDEO_DISPLAY_DVI:
+				if (!video_device->flags.dvi)
+					continue;
+				break;
+			case ACPI_VIDEO_DISPLAY_LCD:
+				if (!video_device->flags.lcd)
+					continue;
+				break;
+			}
+		} else if (video_device->device_id != device_id) {
+			continue;
+		}
+
+		status = acpi_video_device_EDID(video_device, &buffer, length);
+
+		if (ACPI_FAILURE(status) || !buffer ||
+		    buffer->type != ACPI_TYPE_BUFFER) {
+			length = 128;
+			status = acpi_video_device_EDID(video_device, &buffer,
+							length);
+			if (ACPI_FAILURE(status) || !buffer ||
+			    buffer->type != ACPI_TYPE_BUFFER) {
+				continue;
+			}
+		}
+
+		*edid = buffer->buffer.pointer;
+		return length;
+	}
+
+	return -ENODEV;
+}
+EXPORT_SYMBOL(acpi_video_get_edid);
+
+static int
+acpi_video_bus_get_devices(struct acpi_video_bus *video,
+			   struct acpi_device *device)
+{
+	/*
+	 * There are systems where video module known to work fine regardless
+	 * of broken _DOD and ignoring returned value here doesn't cause
+	 * any issues later.
+	 */
+	acpi_video_device_enumerate(video);
+
+	return acpi_dev_for_each_child(device, acpi_video_bus_get_one_device, video);
+}
+
+/* acpi_video interface */
+
+/*
+ * Win8 requires setting bit2 of _DOS to let firmware know it shouldn't
+ * perform any automatic brightness change on receiving a notification.
+ */
+static int acpi_video_bus_start_devices(struct acpi_video_bus *video)
+{
+	return acpi_video_bus_DOS(video, 0,
+				  acpi_osi_is_win8() ? 1 : 0);
+}
+
+static int acpi_video_bus_stop_devices(struct acpi_video_bus *video)
+{
+	return acpi_video_bus_DOS(video, 0,
+				  acpi_osi_is_win8() ? 0 : 1);
+}
+
+static void acpi_video_bus_notify(struct acpi_device *device, u32 event)
+{
+	struct acpi_video_bus *video = acpi_driver_data(device);
+	struct input_dev *input;
+	int keycode = 0;
+
+	if (!video || !video->input)
+		return;
+
+	input = video->input;
+
+	switch (event) {
+	case ACPI_VIDEO_NOTIFY_SWITCH:	/* User requested a switch,
+					 * most likely via hotkey. */
+		keycode = KEY_SWITCHVIDEOMODE;
+		break;
+
+	case ACPI_VIDEO_NOTIFY_PROBE:	/* User plugged in or removed a video
+					 * connector. */
+		acpi_video_device_enumerate(video);
+		acpi_video_device_rebind(video);
+		keycode = KEY_SWITCHVIDEOMODE;
+		break;
+
+	case ACPI_VIDEO_NOTIFY_CYCLE:	/* Cycle Display output hotkey pressed. */
+		keycode = KEY_SWITCHVIDEOMODE;
+		break;
+	case ACPI_VIDEO_NOTIFY_NEXT_OUTPUT:	/* Next Display output hotkey pressed. */
+		keycode = KEY_VIDEO_NEXT;
+		break;
+	case ACPI_VIDEO_NOTIFY_PREV_OUTPUT:	/* previous Display output hotkey pressed. */
+		keycode = KEY_VIDEO_PREV;
+		break;
+
+	default:
+		acpi_handle_debug(device->handle, "Unsupported event [0x%x]\n",
+				  event);
+		break;
+	}
+
+	if (acpi_notifier_call_chain(device, event, 0))
+		/* Something vetoed the keypress. */
+		keycode = 0;
+
+	if (keycode && (report_key_events & REPORT_OUTPUT_KEY_EVENTS)) {
+		input_report_key(input, keycode, 1);
+		input_sync(input);
+		input_report_key(input, keycode, 0);
+		input_sync(input);
+	}
+}
+
+static void brightness_switch_event(struct acpi_video_device *video_device,
+				    u32 event)
+{
+	if (!brightness_switch_enabled)
+		return;
+
+	video_device->switch_brightness_event = event;
+	schedule_delayed_work(&video_device->switch_brightness_work, HZ / 10);
+}
+
+static void acpi_video_device_notify(acpi_handle handle, u32 event, void *data)
+{
+	struct acpi_video_device *video_device = data;
+	struct acpi_device *device = NULL;
+	struct acpi_video_bus *bus;
+	struct input_dev *input;
+	int keycode = 0;
+
+	if (!video_device)
+		return;
+
+	device = video_device->dev;
+	bus = video_device->video;
+	input = bus->input;
+
+	if (hw_changes_brightness > 0) {
+		if (video_device->backlight)
+			backlight_force_update(video_device->backlight,
+					       BACKLIGHT_UPDATE_HOTKEY);
+		acpi_notifier_call_chain(device, event, 0);
+		return;
+	}
+
+	switch (event) {
+	case ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS:	/* Cycle brightness */
+		brightness_switch_event(video_device, event);
+		keycode = KEY_BRIGHTNESS_CYCLE;
+		break;
+	case ACPI_VIDEO_NOTIFY_INC_BRIGHTNESS:	/* Increase brightness */
+		brightness_switch_event(video_device, event);
+		keycode = KEY_BRIGHTNESSUP;
+		break;
+	case ACPI_VIDEO_NOTIFY_DEC_BRIGHTNESS:	/* Decrease brightness */
+		brightness_switch_event(video_device, event);
+		keycode = KEY_BRIGHTNESSDOWN;
+		break;
+	case ACPI_VIDEO_NOTIFY_ZERO_BRIGHTNESS:	/* zero brightness */
+		brightness_switch_event(video_device, event);
+		keycode = KEY_BRIGHTNESS_ZERO;
+		break;
+	case ACPI_VIDEO_NOTIFY_DISPLAY_OFF:	/* display device off */
+		brightness_switch_event(video_device, event);
+		keycode = KEY_DISPLAY_OFF;
+		break;
+	default:
+		acpi_handle_debug(handle, "Unsupported event [0x%x]\n", event);
+		break;
+	}
+
+	if (keycode)
+		may_report_brightness_keys = true;
+
+	acpi_notifier_call_chain(device, event, 0);
+
+	if (keycode && (report_key_events & REPORT_BRIGHTNESS_KEY_EVENTS)) {
+		input_report_key(input, keycode, 1);
+		input_sync(input);
+		input_report_key(input, keycode, 0);
+		input_sync(input);
+	}
+}
+
+static int acpi_video_resume(struct notifier_block *nb,
+				unsigned long val, void *ign)
+{
+	struct acpi_video_bus *video;
+	struct acpi_video_device *video_device;
+	int i;
+
+	switch (val) {
+	case PM_POST_HIBERNATION:
+	case PM_POST_SUSPEND:
+	case PM_POST_RESTORE:
+		video = container_of(nb, struct acpi_video_bus, pm_nb);
+
+		dev_info(&video->device->dev, "Restoring backlight state\n");
+
+		for (i = 0; i < video->attached_count; i++) {
+			video_device = video->attached_array[i].bind_info;
+			if (video_device && video_device->brightness)
+				acpi_video_device_lcd_set_level(video_device,
+						video_device->brightness->curr);
+		}
+
+		return NOTIFY_OK;
+	}
+	return NOTIFY_DONE;
+}
+
+static acpi_status
+acpi_video_bus_match(acpi_handle handle, u32 level, void *context,
+			void **return_value)
+{
+	struct acpi_device *device = context;
+	struct acpi_device *sibling;
+
+	if (handle == device->handle)
+		return AE_CTRL_TERMINATE;
+
+	sibling = acpi_fetch_acpi_dev(handle);
+	if (!sibling)
+		return AE_OK;
+
+	if (!strcmp(acpi_device_name(sibling), ACPI_VIDEO_BUS_NAME))
+			return AE_ALREADY_EXISTS;
+
+	return AE_OK;
+}
+
+static void acpi_video_dev_register_backlight(struct acpi_video_device *device)
+{
+	struct backlight_properties props;
+	struct pci_dev *pdev;
+	acpi_handle acpi_parent;
+	struct device *parent = NULL;
+	int result;
+	static int count;
+	char *name;
+
+	result = acpi_video_init_brightness(device);
+	if (result)
+		return;
+
+	name = kasprintf(GFP_KERNEL, "acpi_video%d", count);
+	if (!name)
+		return;
+	count++;
+
+	if (ACPI_SUCCESS(acpi_get_parent(device->dev->handle, &acpi_parent))) {
+		pdev = acpi_get_pci_dev(acpi_parent);
+		if (pdev) {
+			parent = &pdev->dev;
+			pci_dev_put(pdev);
+		}
+	}
+
+	memset(&props, 0, sizeof(struct backlight_properties));
+	props.type = BACKLIGHT_FIRMWARE;
+	props.max_brightness =
+		device->brightness->count - ACPI_VIDEO_FIRST_LEVEL - 1;
+	device->backlight = backlight_device_register(name,
+						      parent,
+						      device,
+						      &acpi_backlight_ops,
+						      &props);
+	kfree(name);
+	if (IS_ERR(device->backlight)) {
+		device->backlight = NULL;
+		return;
+	}
+
+	/*
+	 * Save current brightness level in case we have to restore it
+	 * before acpi_video_device_lcd_set_level() is called next time.
+	 */
+	device->backlight->props.brightness =
+			acpi_video_get_brightness(device->backlight);
+
+	device->cooling_dev = thermal_cooling_device_register("LCD",
+				device->dev, &video_cooling_ops);
+	if (IS_ERR(device->cooling_dev)) {
+		/*
+		 * Set cooling_dev to NULL so we don't crash trying to free it.
+		 * Also, why the hell we are returning early and not attempt to
+		 * register video output if cooling device registration failed?
+		 * -- dtor
+		 */
+		device->cooling_dev = NULL;
+		return;
+	}
+
+	dev_info(&device->dev->dev, "registered as cooling_device%d\n",
+		 device->cooling_dev->id);
+	result = sysfs_create_link(&device->dev->dev.kobj,
+			&device->cooling_dev->device.kobj,
+			"thermal_cooling");
+	if (result)
+		pr_info("sysfs link creation failed\n");
+
+	result = sysfs_create_link(&device->cooling_dev->device.kobj,
+			&device->dev->dev.kobj, "device");
+	if (result)
+		pr_info("Reverse sysfs link creation failed\n");
+}
+
+static void acpi_video_run_bcl_for_osi(struct acpi_video_bus *video)
+{
+	struct acpi_video_device *dev;
+	union acpi_object *levels;
+
+	mutex_lock(&video->device_list_lock);
+	list_for_each_entry(dev, &video->video_device_list, entry) {
+		if (!acpi_video_device_lcd_query_levels(dev->dev->handle, &levels))
+			kfree(levels);
+	}
+	mutex_unlock(&video->device_list_lock);
+}
+
+static bool acpi_video_should_register_backlight(struct acpi_video_device *dev)
+{
+	/*
+	 * Do not create backlight device for video output
+	 * device that is not in the enumerated list.
+	 */
+	if (!acpi_video_device_in_dod(dev)) {
+		dev_dbg(&dev->dev->dev, "not in _DOD list, ignore\n");
+		return false;
+	}
+
+	if (only_lcd)
+		return dev->flags.lcd;
+	return true;
+}
+
+static int acpi_video_bus_register_backlight(struct acpi_video_bus *video)
+{
+	struct acpi_video_device *dev;
+
+	if (video->backlight_registered)
+		return 0;
+
+	if (acpi_video_get_backlight_type() != acpi_backlight_video)
+		return 0;
+
+	mutex_lock(&video->device_list_lock);
+	list_for_each_entry(dev, &video->video_device_list, entry) {
+		if (acpi_video_should_register_backlight(dev))
+			acpi_video_dev_register_backlight(dev);
+	}
+	mutex_unlock(&video->device_list_lock);
+
+	video->backlight_registered = true;
+
+	video->pm_nb.notifier_call = acpi_video_resume;
+	video->pm_nb.priority = 0;
+	return register_pm_notifier(&video->pm_nb);
+}
+
+static void acpi_video_dev_unregister_backlight(struct acpi_video_device *device)
+{
+	if (device->backlight) {
+		backlight_device_unregister(device->backlight);
+		device->backlight = NULL;
+	}
+	if (device->brightness) {
+		kfree(device->brightness->levels);
+		kfree(device->brightness);
+		device->brightness = NULL;
+	}
+	if (device->cooling_dev) {
+		sysfs_remove_link(&device->dev->dev.kobj, "thermal_cooling");
+		sysfs_remove_link(&device->cooling_dev->device.kobj, "device");
+		thermal_cooling_device_unregister(device->cooling_dev);
+		device->cooling_dev = NULL;
+	}
+}
+
+static int acpi_video_bus_unregister_backlight(struct acpi_video_bus *video)
+{
+	struct acpi_video_device *dev;
+	int error;
+
+	if (!video->backlight_registered)
+		return 0;
+
+	error = unregister_pm_notifier(&video->pm_nb);
+
+	mutex_lock(&video->device_list_lock);
+	list_for_each_entry(dev, &video->video_device_list, entry)
+		acpi_video_dev_unregister_backlight(dev);
+	mutex_unlock(&video->device_list_lock);
+
+	video->backlight_registered = false;
+
+	return error;
+}
+
+static void acpi_video_dev_add_notify_handler(struct acpi_video_device *device)
+{
+	acpi_status status;
+	struct acpi_device *adev = device->dev;
+
+	status = acpi_install_notify_handler(adev->handle, ACPI_DEVICE_NOTIFY,
+					     acpi_video_device_notify, device);
+	if (ACPI_FAILURE(status))
+		dev_err(&adev->dev, "Error installing notify handler\n");
+	else
+		device->flags.notify = 1;
+}
+
+static int acpi_video_bus_add_notify_handler(struct acpi_video_bus *video)
+{
+	struct input_dev *input;
+	struct acpi_video_device *dev;
+	int error;
+
+	video->input = input = input_allocate_device();
+	if (!input) {
+		error = -ENOMEM;
+		goto out;
+	}
+
+	error = acpi_video_bus_start_devices(video);
+	if (error)
+		goto err_free_input;
+
+	snprintf(video->phys, sizeof(video->phys),
+			"%s/video/input0", acpi_device_hid(video->device));
+
+	input->name = acpi_device_name(video->device);
+	input->phys = video->phys;
+	input->id.bustype = BUS_HOST;
+	input->id.product = 0x06;
+	input->dev.parent = &video->device->dev;
+	input->evbit[0] = BIT(EV_KEY);
+	set_bit(KEY_SWITCHVIDEOMODE, input->keybit);
+	set_bit(KEY_VIDEO_NEXT, input->keybit);
+	set_bit(KEY_VIDEO_PREV, input->keybit);
+	set_bit(KEY_BRIGHTNESS_CYCLE, input->keybit);
+	set_bit(KEY_BRIGHTNESSUP, input->keybit);
+	set_bit(KEY_BRIGHTNESSDOWN, input->keybit);
+	set_bit(KEY_BRIGHTNESS_ZERO, input->keybit);
+	set_bit(KEY_DISPLAY_OFF, input->keybit);
+
+	error = input_register_device(input);
+	if (error)
+		goto err_stop_dev;
+
+	mutex_lock(&video->device_list_lock);
+	list_for_each_entry(dev, &video->video_device_list, entry)
+		acpi_video_dev_add_notify_handler(dev);
+	mutex_unlock(&video->device_list_lock);
+
+	return 0;
+
+err_stop_dev:
+	acpi_video_bus_stop_devices(video);
+err_free_input:
+	input_free_device(input);
+	video->input = NULL;
+out:
+	return error;
+}
+
+static void acpi_video_dev_remove_notify_handler(struct acpi_video_device *dev)
+{
+	if (dev->flags.notify) {
+		acpi_remove_notify_handler(dev->dev->handle, ACPI_DEVICE_NOTIFY,
+					   acpi_video_device_notify);
+		dev->flags.notify = 0;
+	}
+}
+
+static void acpi_video_bus_remove_notify_handler(struct acpi_video_bus *video)
+{
+	struct acpi_video_device *dev;
+
+	mutex_lock(&video->device_list_lock);
+	list_for_each_entry(dev, &video->video_device_list, entry)
+		acpi_video_dev_remove_notify_handler(dev);
+	mutex_unlock(&video->device_list_lock);
+
+	acpi_video_bus_stop_devices(video);
+	input_unregister_device(video->input);
+	video->input = NULL;
+}
+
+static int acpi_video_bus_put_devices(struct acpi_video_bus *video)
+{
+	struct acpi_video_device *dev, *next;
+
+	mutex_lock(&video->device_list_lock);
+	list_for_each_entry_safe(dev, next, &video->video_device_list, entry) {
+		list_del(&dev->entry);
+		kfree(dev);
+	}
+	mutex_unlock(&video->device_list_lock);
+
+	return 0;
+}
+
+static int instance;
+
+static int acpi_video_bus_add(struct acpi_device *device)
+{
+	struct acpi_video_bus *video;
+	bool auto_detect;
+	int error;
+	acpi_status status;
+
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE,
+				acpi_dev_parent(device)->handle, 1,
+				acpi_video_bus_match, NULL,
+				device, NULL);
+	if (status == AE_ALREADY_EXISTS) {
+		pr_info(FW_BUG
+			"Duplicate ACPI video bus devices for the"
+			" same VGA controller, please try module "
+			"parameter \"video.allow_duplicates=1\""
+			"if the current driver doesn't work.\n");
+		if (!allow_duplicates)
+			return -ENODEV;
+	}
+
+	video = kzalloc(sizeof(struct acpi_video_bus), GFP_KERNEL);
+	if (!video)
+		return -ENOMEM;
+
+	/* a hack to fix the duplicate name "VID" problem on T61 */
+	if (!strcmp(device->pnp.bus_id, "VID")) {
+		if (instance)
+			device->pnp.bus_id[3] = '0' + instance;
+		instance++;
+	}
+	/* a hack to fix the duplicate name "VGA" problem on Pa 3553 */
+	if (!strcmp(device->pnp.bus_id, "VGA")) {
+		if (instance)
+			device->pnp.bus_id[3] = '0' + instance;
+		instance++;
+	}
+
+	video->device = device;
+	strcpy(acpi_device_name(device), ACPI_VIDEO_BUS_NAME);
+	strcpy(acpi_device_class(device), ACPI_VIDEO_CLASS);
+	device->driver_data = video;
+
+	acpi_video_bus_find_cap(video);
+	error = acpi_video_bus_check(video);
+	if (error)
+		goto err_free_video;
+
+	mutex_init(&video->device_list_lock);
+	INIT_LIST_HEAD(&video->video_device_list);
+
+	error = acpi_video_bus_get_devices(video, device);
+	if (error)
+		goto err_put_video;
+
+	pr_info("%s [%s] (multi-head: %s  rom: %s  post: %s)\n",
+	       ACPI_VIDEO_DEVICE_NAME, acpi_device_bid(device),
+	       video->flags.multihead ? "yes" : "no",
+	       video->flags.rom ? "yes" : "no",
+	       video->flags.post ? "yes" : "no");
+	mutex_lock(&video_list_lock);
+	list_add_tail(&video->entry, &video_bus_head);
+	mutex_unlock(&video_list_lock);
+
+	/*
+	 * If backlight-type auto-detection is used then a native backlight may
+	 * show up later and this may change the result from video to native.
+	 * Therefor normally the userspace visible /sys/class/backlight device
+	 * gets registered separately by the GPU driver calling
+	 * acpi_video_register_backlight() when an internal panel is detected.
+	 * Register the backlight now when not using auto-detection, so that
+	 * when the kernel cmdline or DMI-quirks are used the backlight will
+	 * get registered even if acpi_video_register_backlight() is not called.
+	 */
+	acpi_video_run_bcl_for_osi(video);
+	if (__acpi_video_get_backlight_type(false, &auto_detect) == acpi_backlight_video &&
+	    !auto_detect)
+		acpi_video_bus_register_backlight(video);
+
+	acpi_video_bus_add_notify_handler(video);
+
+	return 0;
+
+err_put_video:
+	acpi_video_bus_put_devices(video);
+	kfree(video->attached_array);
+err_free_video:
+	kfree(video);
+	device->driver_data = NULL;
+
+	return error;
+}
+
+static int acpi_video_bus_remove(struct acpi_device *device)
+{
+	struct acpi_video_bus *video = NULL;
+
+
+	if (!device || !acpi_driver_data(device))
+		return -EINVAL;
+
+	video = acpi_driver_data(device);
+
+	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)
+		return 1;
+	if (dev->device == 0x7000)
+		return 1;
+	return 0;
+}
+
+static int __init intel_opregion_present(void)
+{
+	int opregion = 0;
+	struct pci_dev *dev = NULL;
+	u32 address;
+
+	for_each_pci_dev(dev) {
+		if ((dev->class >> 8) != PCI_CLASS_DISPLAY_VGA)
+			continue;
+		if (dev->vendor != PCI_VENDOR_ID_INTEL)
+			continue;
+		/* We don't want to poke around undefined i740 registers */
+		if (is_i740(dev))
+			continue;
+		pci_read_config_dword(dev, 0xfc, &address);
+		if (!address)
+			continue;
+		opregion = 1;
+	}
+	return opregion;
+}
+
+/* Check if the chassis-type indicates there is no builtin LCD panel */
+static bool dmi_is_desktop(void)
+{
+	const char *chassis_type;
+	unsigned long type;
+
+	chassis_type = dmi_get_system_info(DMI_CHASSIS_TYPE);
+	if (!chassis_type)
+		return false;
+
+	if (kstrtoul(chassis_type, 10, &type) != 0)
+		return false;
+
+	switch (type) {
+	case 0x03: /* Desktop */
+	case 0x04: /* Low Profile Desktop */
+	case 0x05: /* Pizza Box */
+	case 0x06: /* Mini Tower */
+	case 0x07: /* Tower */
+	case 0x10: /* Lunch Box */
+	case 0x11: /* Main Server Chassis */
+		return true;
+	}
+
+	return false;
+}
+
+/*
+ * We're seeing a lot of bogus backlight interfaces on newer machines
+ * without a LCD such as desktops, servers and HDMI sticks. Checking the
+ * lcd flag fixes this, enable this by default on any machines which are:
+ * 1.  Win8 ready (where we also prefer the native backlight driver, so
+ *     normally the acpi_video code should not register there anyways); *and*
+ * 2.1 Report a desktop/server DMI chassis-type, or
+ * 2.2 Are an ACPI-reduced-hardware platform (and thus won't use the EC for
+       backlight control)
+ */
+static bool should_check_lcd_flag(void)
+{
+	if (!acpi_osi_is_win8())
+		return false;
+
+	if (dmi_is_desktop())
+		return true;
+
+	if (acpi_reduced_hardware())
+		return true;
+
+	return false;
+}
+
+/*
+ * At least one graphics driver has reported that no LCD is connected
+ * via the native interface. cancel the registration for fallback acpi_video0.
+ * If another driver still deems this necessary, it can explicitly register it.
+ */
+void acpi_video_report_nolcd(void)
+{
+	cancel_delayed_work(&video_bus_register_backlight_work);
+}
+EXPORT_SYMBOL(acpi_video_report_nolcd);
+
+int acpi_video_register(void)
+{
+	int ret = 0;
+
+	mutex_lock(&register_count_mutex);
+	if (register_count) {
+		/*
+		 * if the function of acpi_video_register is already called,
+		 * don't register the acpi_video_bus again and return no error.
+		 */
+		goto leave;
+	}
+
+	if (only_lcd == -1)
+		only_lcd = should_check_lcd_flag();
+
+	dmi_check_system(video_dmi_table);
+
+	ret = acpi_bus_register_driver(&acpi_video_bus);
+	if (ret)
+		goto leave;
+
+	/*
+	 * When the acpi_video_bus is loaded successfully, increase
+	 * the counter reference.
+	 */
+	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;
+}
+EXPORT_SYMBOL(acpi_video_register);
+
+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;
+	}
+	mutex_unlock(&register_count_mutex);
+}
+EXPORT_SYMBOL(acpi_video_unregister);
+
+void acpi_video_register_backlight(void)
+{
+	struct acpi_video_bus *video;
+
+	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)
+{
+	return may_report_brightness_keys &&
+	       (report_key_events & REPORT_BRIGHTNESS_KEY_EVENTS);
+}
+EXPORT_SYMBOL(acpi_video_handles_brightness_key_presses);
+
+/*
+ * This is kind of nasty. Hardware using Intel chipsets may require
+ * the video opregion code to be run first in order to initialise
+ * state before any ACPI video calls are made. To handle this we defer
+ * registration of the video class until the opregion code has run.
+ */
+
+static int __init acpi_video_init(void)
+{
+	/*
+	 * Let the module load even if ACPI is disabled (e.g. due to
+	 * a broken BIOS) so that i915.ko can still be loaded on such
+	 * old systems without an AcpiOpRegion.
+	 *
+	 * acpi_video_register() will report -ENODEV later as well due
+	 * to acpi_disabled when i915.ko tries to register itself afterwards.
+	 */
+	if (acpi_disabled)
+		return 0;
+
+	if (intel_opregion_present())
+		return 0;
+
+	return acpi_video_register();
+}
+
+static void __exit acpi_video_exit(void)
+{
+	acpi_video_unregister();
+}
+
+module_init(acpi_video_init);
+module_exit(acpi_video_exit);