← Back to team overview

kernel-packages team mailing list archive

[Bug 1054298] Re: xbacklight doesn't work, but xrandr does and so does /sys/class/backlight


for ubuntu 16.04 on HP pavilion dv6 and Nvidia Graphic driver,
the problem is the same. 

xbacklight -set 100                                           ----> NOT WORKS
xrandr --output LVDS-0 --set Backlight 100                    ----> NOT WORKS
xrandr --output LVDS-0 --brightness 1                         ----> WORKS(IT HAS A DIFFERENT EFFECT!)
echo 1 |sudo tee /sys/class/backlight/acpi_video0/brightness  ----> WORKS

You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.

  xbacklight doesn't work, but xrandr does and so does

Status in linux package in Ubuntu:

Bug description:
  Sony Vaio P
  Ubuntu Precise and Quantal
  kernel 3.5.0
  gma500_gfx kernel driver
  modesetting xorg driver
  Assume the current quantal & quantal-proposed versions of everything.

  xbacklight doesn't work. No backlight change, and no output from the program.
  "xbacklight" and "xbacklight -get" show nothing, no output from the program at all.
  "xbacklight -set50" and "xbacklight-d :0 -set 50" does nothing nor prints any output.

  However both sysfs and xrandr work fine.

  xrandr --verbose lists outputs and shows the main screen has backlight property,
  and "xrandr --output LVDS-0 --set backlight 50" changes the backlight brightness.


  "cat /sys/class/backlight/psb-bl/actual_brightness" shows the current brightness, and
  "echo 50 >/sys/class/backlight/psb-bl/brightness" changes the brightness.

  I have written the following script to use in place of xbacklight:

  This script, both the sysfs and xrandr methods of it, works fine for me on the same machine.
  (for sysfs, I had to make a udev rule to allow users to write to the sysfs files, as noted on that page and in the --help output of the script)
  It requires zenity for the user interactive options. Not needed for the non-interactive options.


To manage notifications about this bug go to: