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