Up until yesterday I was running Ubuntu 12.10 on my Dell Latitude E6530. Recently I played around with the nvidia settings, which caused my brightness control to stop working. However, I could fix it by adding
Option "RegistryDwords" "EnableBrightnessControl=1" to
/etc/X11/xorg.conf as advised in .
Now, last night I upgraded to Ubuntu 13.04 because I needed are newer kernel. After that, the brightness control once again stopped working. But this time,  doesn't help. I have also tried the methods in :
echo $SOME_VALUE | sudo tee /sys/class/backlight/dell_backlight/brightness
None of them are working, the brightness just doesn't change, but that's about all I could find for this problem. Any ideas on how I can get my brightness control back?