There was no problem with Ubuntu 12.10 but after upgrading to 13.04 I can't change the brightness level of my Dell 3721 laptop anymore. Nothing happend if I use the hardware keys or ubuntu system control. If I use the command "echo xxxx | sudo tee /sys/class/backlight/intel_backlight/brightness" display brightness will change, but its very uncomfortable to use the terminal to change the brightness level. Is there any solution to reactivate the hardware keys?
VGA compatible controller : Intel Corporation 3rd Gen Core processor Graphics Controller [8086:0166] (rev 09)"