Documentation/ABI/stable/sysfs-class-backlight

   1 What:           /sys/class/backlight/<backlight>/bl_power
   2 Date:           April 2005
   3 KernelVersion:  2.6.12
   4 Contact:        Richard Purdie <rpurdie@rpsys.net>
   5 Description:
   6                 Control BACKLIGHT power, values are FB_BLANK_* from fb.h
   7                  - FB_BLANK_UNBLANK (0)   : power on.
   8                  - FB_BLANK_POWERDOWN (4) : power off
   9 Users:          HAL
  10
  11 What:           /sys/class/backlight/<backlight>/brightness
  12 Date:           April 2005
  13 KernelVersion:  2.6.12
  14 Contact:        Richard Purdie <rpurdie@rpsys.net>
  15 Description:
  16                 Control the brightness for this <backlight>. Values
  17                 are between 0 and max_brightness. This file will also
  18                 show the brightness level stored in the driver, which
  19                 may not be the actual brightness (see actual_brightness).
  20 Users:          HAL
  21
  22 What:           /sys/class/backlight/<backlight>/actual_brightness
  23 Date:           March 2006
  24 KernelVersion:  2.6.17
  25 Contact:        Richard Purdie <rpurdie@rpsys.net>
  26 Description:
  27                 Show the actual brightness by querying the hardware.
  28 Users:          HAL
  29
  30 What:           /sys/class/backlight/<backlight>/max_brightness
  31 Date:           April 2005
  32 KernelVersion:  2.6.12
  33 Contact:        Richard Purdie <rpurdie@rpsys.net>
  34 Description:
  35                 Maximum brightness for <backlight>.
  36 Users:          HAL
  37
  38 What:           /sys/class/backlight/<backlight>/type
  39 Date:           September 2010
  40 KernelVersion:  2.6.37
  41 Contact:        Matthew Garrett <mjg@redhat.com>
  42 Description:
  43                 The type of interface controlled by <backlight>.
  44                 "firmware": The driver uses a standard firmware interface
  45                 "platform": The driver uses a platform-specific interface
  46                 "raw": The driver controls hardware registers directly
  47
  48                 In the general case, when multiple backlight
  49                 interfaces are available for a single device, firmware
  50                 control should be preferred to platform control should
  51                 be preferred to raw control. Using a firmware
  52                 interface reduces the probability of confusion with
  53                 the hardware and the OS independently updating the
  54                 backlight state. Platform interfaces are mostly a
  55                 holdover from pre-standardisation of firmware
  56                 interfaces.