[Ubuntu Wiki] Update of "Kernel/Debugging/Backlight" by jnikula

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The "Kernel/Debugging/Backlight" page has been changed by jnikula:
http://wiki.ubuntu.com/Kernel/Debugging/Backlight?action=diff&rev1=30&rev2=31

Comment:
link to sysfs backlight interface documentation

  
  The file {{{actual_brightness}}} contains the currently set brightness level. Reading {{{brightness}}} results in the same number. In {{{max_brightness}}} is the maximum number allowed to be written into {{{brightness}}}. While the ACPI {{{/proc}}} interface uses percentage levels, the ''sysfs'' interface uses index numbers between 0 and the maximum brightness.
  
- /!\ TODO: might be that actual_brightness queries the values on read, while brightness only returns the value written last. bl_power has no effect, what is it supposed to do?
+ See the kernel documentation of [[http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/ABI/stable/sysfs-class-backlight|sysfs class backlight]] interface for the definitive description of the attributes.
  
  {{{
  #> grep . /sys/class/backlight/acpi_video0/*