Comment 0 for bug 1041846

When I originally installed Ubuntu 12.04 it came with kernel 3.2.0-23 and the screen brightness controls on my Samsung NP530U3C worked out-of-the-box.

However after I applied the updates and rebooted into the latest kernel (3.2.0-29) the screen brightness controls no longer work.

Symptoms:
Press screen brightness function keys to either increase or decrease brightness OR try changing the screen brightness in either KDE or GNOME with the 'slider' in the respective power management GUI programs

Expected Result and Result with kernel 3.2.0-23:
Screen brightness increases or decreases accordingly

Actual Result with kernel 3.2.0-29:
Screen flickers a bit but the brightness level seems 'stuck' and won't change.

Workaround:
The funny thing is that manipulating the /sys/class/backlight/acpi_video0 files directly works, so:
echo 47 | sudo tee /sys/class/backlight/acpi_video0/brightness # set brightness to approx 50% of the maximum