Documentation/ABI/testing/sysfs-class-backlight

   1 What:           /sys/class/backlight/<backlight>/scale
   2 Date:           July 2019
   3 KernelVersion:  5.4
   4 Contact:        Daniel Thompson <daniel.thompson@linaro.org>
   5 Description:
   6                 Description of the scale of the brightness curve.
   7
   8                 The human eye senses brightness approximately logarithmically,
   9                 hence linear changes in brightness are perceived as being
  10                 non-linear. To achieve a linear perception of brightness changes
  11                 controls like sliders need to apply a logarithmic mapping for
  12                 backlights with a linear brightness curve.
  13
  14                 Possible values of the attribute are:
  15
  16                 unknown
  17                   The scale of the brightness curve is unknown.
  18
  19                 linear
  20                   The brightness changes linearly with each step. Brightness
  21                   controls should apply a logarithmic mapping for a linear
  22                   perception.
  23
  24                 non-linear
  25                   The brightness changes non-linearly with each step. Brightness
  26                   controls should use a linear mapping for a linear perception.
  27
  28 What:           /sys/class/backlight/<backlight>/ambient_light_level
  29 Date:           Apr, 2010
  30 KernelVersion:  v2.6.35
  31 Contact:        Michael Hennerich <michael.hennerich@analog.com>
  32 Description:
  33                 (RO) Get conversion value of the light sensor.
  34
  35                 The value is automatically updated every 80 ms when the
  36                 light sensor is enabled.
  37
  38                 The value range is device-driver specific:
  39
  40                 For ADP8870:
  41
  42                   It returns integer between 0 (dark) and 8000 (max ambient
  43                   brightness).
  44
  45                 For ADP8860:
  46
  47                   It returns a 13-bits integer.
  48
  49 What:           /sys/class/backlight/<backlight>/ambient_light_zone
  50 Date:           Apr, 2010
  51 KernelVersion:  v2.6.35
  52 Contact:        Michael Hennerich <michael.hennerich@analog.com>,
  53                 device-drivers-devel@blackfin.uclinux.org
  54
  55 Description:
  56                 (RW) Read or write the specific brightness level at which the
  57                 backlight operates.
  58
  59                 The value meaning is device-driver specific:
  60
  61                 For ADP8860:
  62
  63                   ==    ==========================
  64                    0    Off: Backlight set to 0 mA
  65                    1    Level 1: daylight
  66                    2    Level 2: bright
  67                    3    Level 3: dark
  68                   ==    ==========================
  69
  70                 For ADP8870:
  71
  72                   ==    ==========================
  73                    0    Off: Backlight set to 0 mA
  74                    1    Level 1: daylight
  75                    2    Level 2: bright
  76                    3    Level 3: office
  77                    4    Level 4: indoor
  78                    5    Level 5: dark
  79                   ==    ==========================
  80
  81                 Writing 0 returns to normal/automatic ambient light level
  82                 operation.
  83
  84                 It can be enabled by writing the value stored in
  85                 /sys/class/backlight/<backlight>/max_brightness to
  86                 /sys/class/backlight/<backlight>/brightness.