// 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/auxiliary_bus.h>
#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>
#include <linux/string_choices.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;
module_param(only_lcd, int, 0444);

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_probe(struct auxiliary_device *aux_dev,
                                const struct auxiliary_device_id *id);
static void acpi_video_bus_remove(struct auxiliary_device *aux);
static void acpi_video_bus_notify(acpi_handle handle, u32 event, void *data);

/*
 * 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 auxiliary_device_id video_bus_auxiliary_id_table[] = {
        { .name = "acpi.video_bus" },
        {},
};
MODULE_DEVICE_TABLE(auxiliary, video_bus_auxiliary_id_table);

static struct auxiliary_driver acpi_video_bus = {
        .probe = acpi_video_bus_probe,
        .remove = acpi_video_bus_remove,
        .id_table = video_bus_auxiliary_id_table,
};

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_video_device *video = cooling_dev->devdata;

        *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_video_device *video = cooling_dev->devdata;
        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_video_device *video = cooling_dev->devdata;
        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"),
                },
        },
        {
         .callback = video_set_report_key_events,
         .driver_data = (void *)((uintptr_t)REPORT_BRIGHTNESS_KEY_EVENTS),
         .ident = "COLORFUL X15 AT 23",
         .matches = {
                DMI_MATCH(DMI_SYS_VENDOR, "COLORFUL"),
                DMI_MATCH(DMI_PRODUCT_NAME, "X15 AT 23"),
                },
        },
        /*
         * 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;
}

/**
 * acpi_video_device_EDID() - Get EDID from ACPI _DDC
 * @device: video output device (LCD, CRT, ..)
 * @edid: address for returned EDID pointer
 * @length: _DDC length to request (must be a multiple of 128)
 *
 * Get EDID from ACPI _DDC. On success, a pointer to the EDID data is written
 * to the @edid address, and the length of the EDID is returned. The caller is
 * responsible for freeing the edid pointer.
 *
 * Return the length of EDID (positive value) on success or error (negative
 * value).
 */
static int
acpi_video_device_EDID(struct acpi_video_device *device, void **edid, int length)
{
        acpi_status 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 };
        int ret;

        *edid = NULL;

        if (!device)
                return -ENODEV;
        if (!length || (length % 128))
                return -EINVAL;

        arg0.integer.value = length / 128;

        status = acpi_evaluate_object(device->dev->handle, "_DDC", &args, &buffer);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        obj = buffer.pointer;

        /*
         * Some buggy implementations incorrectly return the EDID buffer in an ACPI package.
         * In this case, extract the buffer from the package.
         */
        if (obj && obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 1)
                obj = &obj->package.elements[0];

        if (obj && obj->type == ACPI_TYPE_BUFFER) {
                *edid = kmemdup(obj->buffer.pointer, obj->buffer.length, GFP_KERNEL);
                ret = *edid ? obj->buffer.length : -ENOMEM;
        } else {
                acpi_handle_debug(device->dev->handle,
                                 "Invalid _DDC data for length %d\n", length);
                ret = -EFAULT;
        }

        kfree(buffer.pointer);
        return ret;
}

/* 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_obj(*br);
        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_objs(*br->levels,
                                  obj->package.count + ACPI_VIDEO_FIRST_LEVEL);
        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;
        int device_type;
        u64 device_id;

        /* Skip devices without _ADR instead of failing. */
        if (acpi_get_local_u64_address(device->handle, &device_id))
                goto exit;

        data = kzalloc_obj(struct acpi_video_device);
        if (!data) {
                dev_dbg(&device->dev, "Cannot attach\n");
                return -ENOMEM;
        }

        strscpy(acpi_device_name(device), ACPI_VIDEO_DEVICE_NAME);
        strscpy(acpi_device_class(device), ACPI_VIDEO_CLASS);

        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 = kzalloc_objs(struct acpi_video_enumerated_device,
                                   1 + dod->package.count);
        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;
        int i, length, ret;

        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;

                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;
                }

                for (length = 512; length > 0; length -= 128) {
                        ret = acpi_video_device_EDID(video_device, edid, length);
                        if (ret > 0)
                                return ret;
                }
        }

        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(acpi_handle handle, u32 event, void *data)
{
        struct acpi_video_bus *video = data;
        struct acpi_device *device = video->device;
        struct input_dev *input;
        int keycode = 0;

        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,
                                                              &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 device *parent)
{
        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 = parent;
        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);
                cancel_delayed_work_sync(&dev->switch_brightness_work);
        }
        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_probe(struct auxiliary_device *aux_dev,
                                const struct auxiliary_device_id *id_unused)
{
        struct acpi_device *device = ACPI_COMPANION(&aux_dev->dev);
        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_obj(struct acpi_video_bus);
        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++;
        }

        auxiliary_set_drvdata(aux_dev, video);

        video->device = device;
        strscpy(acpi_device_name(device), ACPI_VIDEO_BUS_NAME);
        strscpy(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;

        /*
         * HP ZBook Fury 16 G10 requires ACPI video's child devices have _PS0
         * evaluated to have functional panel brightness control.
         */
        acpi_device_fix_up_power_children(device);

        pr_info("%s [%s] (multi-head: %s  rom: %s  post: %s)\n",
               ACPI_VIDEO_DEVICE_NAME, acpi_device_bid(device),
               str_yes_no(video->flags.multihead),
               str_yes_no(video->flags.rom),
               str_yes_no(video->flags.post));
        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);

        error = acpi_video_bus_add_notify_handler(video, &aux_dev->dev);
        if (error)
                goto err_del;

        error = acpi_dev_install_notify_handler(device, ACPI_DEVICE_NOTIFY,
                                                acpi_video_bus_notify, video);
        if (error)
                goto err_remove;

        return 0;

err_remove:
        acpi_video_bus_remove_notify_handler(video);
err_del:
        mutex_lock(&video_list_lock);
        list_del(&video->entry);
        mutex_unlock(&video_list_lock);
        acpi_video_bus_unregister_backlight(video);
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 void acpi_video_bus_remove(struct auxiliary_device *aux_dev)
{
        struct acpi_video_bus *video = auxiliary_get_drvdata(aux_dev);
        struct acpi_device *device = ACPI_COMPANION(&aux_dev->dev);

        acpi_dev_remove_notify_handler(device, ACPI_DEVICE_NOTIFY,
                                       acpi_video_bus_notify);

        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);
        device->driver_data = NULL;
}

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;
}

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;
        }

        dmi_check_system(video_dmi_table);

        ret = auxiliary_driver_register(&acpi_video_bus);
        if (ret)
                goto leave;

        /*
         * When the acpi_video_bus is loaded successfully, increase
         * the counter reference.
         */
        register_count = 1;

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) {
                auxiliary_driver_unregister(&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);