[arch-general] xbacklight, gnome brightness slider don't work, but changing rightness within /sys will

as per subject, whenever i try to change my brightness with xbacklight -set, it doesnt work. it does not change the brightness. the same thing happenes in gnome, with the brightness slider on the top right menu. what does work is (as root) going into /sys/class/backlight/intel_backlight, and changing the value in the brightness folder. there are no other folders in /sys/class/backlight.