I am a very unfortunate owner of a sony vaio VPCEL22FX laptop. I purchased it a few years ago with Windows 7, but Windows 7 never booted. So I ditched Windows and loaded ubuntu 11.10 and struggled for several days to get the brightness hot keys working. Now that ubuntu 11.10 has reached its end of life, it was time to upgrade to ubuntu 12.04 LTS. I postponed it for as long as I could, until I could find a day or two to work on it.
I got ubuntu 12.04 ISO image loaded on a thumb drive with LiLi USB creator and did a completely new install of ubuntu 12.04. To my horror I saw that the brightness hot keys i.e. FN+F5, Fn+F6 were not working. So started my google search for the problem and I was so happy that I could find a solution quickly.
I don’t know if this will work for all laptops. But it worked on my Sony VAIO VPCEL22FX with ubuntu 12.04.2 LTS.
From the unity dash, click on SYSTEM SETTINGS. Then select ADDITIONAL DRIVERS from within the system settings menu. I got 3 options and I how to download kik on pc selected “ATI/AMD proprietary FGLRX graphics driver (post-release updates)” from it and installed it. Then I restarted my computer and voila! The brightness hot keys are working like a charm. I don’t mind even if ubuntu forgets the brightness settings and next time I restart my laptop it will start with max brightness. I am so happy that the brightness is now adjustible with the hot keys and I can save my eyes!