Comment 15 for bug 140782

I think that's correct for laptops with keys that only send a keypress event, but there're laptops who change brightness by hardware (probably by sending some signal to the BIOS).
It's not desktop environment specific, since I can change brightness with hotkeys in grub menu, but not after the acpi video module is loaded.
Probably, when gnome-power-manager (or its kde counterpart) is loaded, it gets the keypress and change brightness, but I don't see why shouldn't I be able to change brightness when g-p-m is not loaded, since I can do it when no OS is loaded.