This driver implement the ACPI Extensions For Display Adapters
for integrated graphics devices on motherboard, as specified in
ACPI 2.0 Specification, Appendix B, allowing to perform some basic
control like defining the video POST device, retrieving EDID information
or to setup a video output, etc.  Note that this is an ref. implementation only.
It may or may not work for your integrated video device.

Interfaces exposed to userland through /proc/acpi/video:

VGA/info : display the supported video bus device capability like ,Video ROM, CRT/LCD/TV.
VGA/ROM :  Used to get a copy of the display devices' ROM data (up to 4k).
VGA/POST_info : Used to determine what options are implemented.
VGA/POST : Used to get/set POST device.
VGA/DOS : Used to get/set ownership of output switching:
	Please refer ACPI spec B.4.1 _DOS
VGA/CRT : CRT output
VGA/LCD : LCD output
VGA/TV : TV output 
VGA/*/brightness : Used to get/set brightness of output device

Notify event through /proc/acpi/event:

#define ACPI_VIDEO_NOTIFY_SWITCH        0x80
#define ACPI_VIDEO_NOTIFY_PROBE         0x81
#define ACPI_VIDEO_NOTIFY_CYCLE         0x82
#define ACPI_VIDEO_NOTIFY_NEXT_OUTPUT   0x83
#define ACPI_VIDEO_NOTIFY_PREV_OUTPUT   0x84

#define ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS      0x82
#define ACPI_VIDEO_NOTIFY_INC_BRIGHTNESS        0x83
#define ACPI_VIDEO_NOTIFY_DEC_BRIGHTNESS        0x84
#define ACPI_VIDEO_NOTIFY_ZERO_BRIGHTNESS       0x85
#define ACPI_VIDEO_NOTIFY_DISPLAY_OFF           0x86