Ubuntu
linux package

  1. Bug #1069357
  2. Comment #0

Comment 0 for bug 1069357

Revision history for this message
Rafał Ochmański (rmopl) wrote : Hardware keys change backlight brightness in much larger increments/steps than expected

SInce the upgrade to Ubuntu 12.10, hardware keys for regulating backlight brightness (fn+f4, fn+f5) change brightness in large increments, even though much finer control is available both through the Brightness and Lock dialog in Settings and by just setting the value in /sys/class/backlight/acpi_video0/brightness, for example:

# echo 1 > /sys/class/backlight/acpi_video0/brightness

/sys/class/backlight/acpi_video0/brightness accepts values 0-15, the default step seems to be 3 instead of 1 as expected, and as it was in Ubuntu 12.04.

Partial workaround is to disable brightness switch

# echo -n 0 > /sys/module/video/parameters/brightness_switch_enabled

which cuts the step to 2. Moreover, adding kernel parameters "acpi_osi=Linux acpi_backlight=legacy" allows for even finer control in the Brightness and Lock dialog in Settings (finer than those 16 settings, backlight including completely turning the backlight via the brightness slider) but breaks the hardware keys functionality completely.

# lsb_release -rd
Description: Ubuntu 12.10
Release: 12.10