Comment # 1 on bug 907368 from Takashi Iwai

To see whether it's a kernel issue, try the following:
- Install evtest package
- Go to Linux console (e.g. VT1), be root.
- Run evtest /dev/input/by-path/platform-i8042-serio-0-event-kbd 
  (the device path might be different, but you must have a similar one.)
- Press brightness up/down key.

If this shows the proper key events (KEY_BRIGHTNESSUP and KEY_BRIGHTNESSDOWN),
then the kernel reports correctly.  The problem is rather in the upper layer,
either X or KDE.  If the keys aren't reported, then it's a kernel problem.