I have a Fujitsu E756 which has two brightness keys, accessible through a Fn-Key (Fn+F6, Fn+F7).
They don't work.

These two keys don't have a scancode, according to showkey --scancodes or xev. How can I get the keys to work?

I'm working with a Kubuntu 14 - based distribution and Kernel 4.2.0-30-generic.

1.) Do keys for acpi-function always have a scancode at all? Can it be normal that the keys don't show a scancode in showkey?
2.) Which kernel module is resposible for the keyboard?
3.) Any other ideas?

Thank you very much.

I searched for "kde enable brightness keys" and got a few hits which might help, like
https://docs.kde.org/stable5/en/kde-...eys/index.html
https://www.linux.com/news/customize...oard-x-and-kde
http://askubuntu.com/questions/57236...-lenovo-laptop

I don't think this is a KDE related problem. I have found that a i8042 is used for the keyboard. I could enable debugging messages with Kernel Parameters i8042.debug=1 and i8042.unmask_kbd_data=1 . Then I see all keyboard presses in /var/log/kern.log, but not those on the brightness keys.
The "disable touchpad button" on Fn+F4 exibits the same behaviour.
I have a Fujitsu E754 where all buttons work and have scancodes, even though it also seems to have that i8042.

Somebody else solved this problem:

http://www.spinics.net/lists/platfor.../msg09005.html