I installed Ubuntu 13.10 on my
Vaio nr21s but cannot adjust brightness levels. The fn keys work, but they don't change a thing, brightness remains at max level.
Thought I should choose a repository nvidia driver, but I believe it makes it worse, because the screens during boot are all messed up. So I got back to the nouveau.
Video card is
nvidia 8400m gt gpu.
I know that there are plenty of threads stating the same issues, but none of the suggested solutions worked out for me.