linux/Documentation/power/video_extension.txt
Linus Torvalds 1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00

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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