Comment 8 for bug 264947

I've found that the laptop_panel.brightness_in_hardware key has no effect in this bug.
It's fixed for me by commenting the following lines in /usr/share/hotkey-setup/dell.hk:

setkeycodes e005 $KEY_BRIGHTNESSDOWN # Fn+Down Brightness Down (e005)
setkeycodes e006 $KEY_BRIGHTNESSUP # Fn+Up Brightness Up (e006)