linux/Documentation/power/video_extension.txt
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   1ACPI video extensions
   2~~~~~~~~~~~~~~~~~~~~~
   3
   4This driver implement the ACPI Extensions For Display Adapters for
   5integrated graphics devices on motherboard, as specified in ACPI 2.0
   6Specification, Appendix B, allowing to perform some basic control like
   7defining the video POST device, retrieving EDID information or to
   8setup a video output, etc.  Note that this is an ref. implementation
   9only.  It may or may not work for your integrated video device.
  10
  11Interfaces exposed to userland through /proc/acpi/video:
  12
  13VGA/info : display the supported video bus device capability like Video ROM, CRT/LCD/TV.
  14VGA/ROM :  Used to get a copy of the display devices' ROM data (up to 4k).
  15VGA/POST_info : Used to determine what options are implemented.
  16VGA/POST : Used to get/set POST device.
  17VGA/DOS : Used to get/set ownership of output switching:
  18        Please refer ACPI spec B.4.1 _DOS
  19VGA/CRT : CRT output
  20VGA/LCD : LCD output
  21VGA/TVO : TV output
  22VGA/*/brightness : Used to get/set brightness of output device
  23
  24Notify event through /proc/acpi/event:
  25
  26#define ACPI_VIDEO_NOTIFY_SWITCH        0x80
  27#define ACPI_VIDEO_NOTIFY_PROBE         0x81
  28#define ACPI_VIDEO_NOTIFY_CYCLE         0x82
  29#define ACPI_VIDEO_NOTIFY_NEXT_OUTPUT   0x83
  30#define ACPI_VIDEO_NOTIFY_PREV_OUTPUT   0x84
  31
  32#define ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS      0x82
  33#define ACPI_VIDEO_NOTIFY_INC_BRIGHTNESS        0x83
  34#define ACPI_VIDEO_NOTIFY_DEC_BRIGHTNESS        0x84
  35#define ACPI_VIDEO_NOTIFY_ZERO_BRIGHTNESS       0x85
  36#define ACPI_VIDEO_NOTIFY_DISPLAY_OFF           0x86
  37
  38
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