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[Bug 527157] Re: Brightness controls skips Levels.

 

Seems odd to me that this bug is a low priority. The results are pretty
poor UX.

There are 3 interesting solutions here.
http://askubuntu.com/questions/208331/brightness-control-increments-brightness-by-4-instead-of-1

Fix 1 is a partial fix that worked for me right away. Still looking into
the others.

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https://bugs.launchpad.net/bugs/527157

Title:
  Brightness controls skips Levels.

Status in Gnome Settings Daemon:
  New
Status in “gnome-power-manager” package in Ubuntu:
  Invalid
Status in “gnome-power-manager” package in Arch Linux:
  New

Bug description:
  Binary package hint: gnome-power-manager

  Expected:
  Hitting brightness up key or brightness down key changes brightness by one level out of 15.

  Actual: 
  Hitting brightness up key or brightness down key changes brightness by two or three levels out of 15.

  
  When I use the brightness control keys from a fresh install, the brightness jumps THREE increments.
  By creating /etc/modprobe.d/video.conf and setting
  options video brightness_switch_enabled = 0
  I reduce this to consistently TWO brightness events, but this is still double the normal events.  If I kill gnome-power-manager, it returns to single brightness events.

  when hitting brightness up/down with gnome-power-manager, udevmonitor shows
  UDEV - the event which udev sends out after rule processing
  KERNEL - the kernel uevent

  KERNEL[1267026969.897008] change   /devices/virtual/backlight/acpi_video0 (backlight)
  UDEV  [1267026969.898270] change   /devices/virtual/backlight/acpi_video0 (backlight)
  KERNEL[1267026969.903078] change   /devices/virtual/backlight/acpi_video0 (backlight)
  UDEV  [1267026969.903842] change   /devices/virtual/backlight/acpi_video0 (backlight)
  KERNEL[1267026971.355970] change   /devices/virtual/backlight/acpi_video0 (backlight)
  UDEV  [1267026971.357418] change   /devices/virtual/backlight/acpi_video0 (backlight)

  
  with gnome-power-manager not running, it shows no events.

  Before:
  cat /proc/acpi/video/IGD0/LCD/brightness 
  levels:  25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
  current: 25

  Brightness up pressed:
  cat /proc/acpi/video/IGD0/LCD/brightness 
  levels:  25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
  current: 40

  With options video brightness_switch_enabled = 0:
  cat /proc/acpi/video/IGD0/LCD/brightness 
  levels:  25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
  current: 25

  Brightness up pressed:
  cat /proc/acpi/video/IGD0/LCD/brightness 
  levels:  25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
  current: 35

  With brightness_switch_enabled=0 and gnome-power-manager not running:
  cat /proc/acpi/video/IGD0/LCD/brightness 
  levels:  25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
  current: 25

  Brightness up pressed:
  cat /proc/acpi/video/IGD0/LCD/brightness 
  levels:  25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
  current: 30



  Description:	Ubuntu lucid (development branch)
  Release:	10.04

  xserver-xorg-video-intel:
    Installed: 2:2.9.1-1ubuntu1
    Candidate: 2:2.9.1-1ubuntu1
    Version table:
   *** 2:2.9.1-1ubuntu1 0
          500 http://archive.linux.duke.edu lucid/main Packages
          100 /var/lib/dpkg/status

  gnome-power-manager:
    Installed: 2.29.1-0ubuntu2
    Candidate: 2.29.1-0ubuntu2
    Version table:
   *** 2.29.1-0ubuntu2 0
          500 http://archive.linux.duke.edu lucid/main Packages
          100 /var/lib/dpkg/status

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