Never
knew that the problem that haunted me for years would be related to
something I never ever had thought at. Being a software engineer
based in Nepal, Loadshedding problem is very common for me. Long
hours of loadshedding demands you to have support for longer battery
life. Controlling brightness of monitor is very important to prolong
battery life. I have HP Pavillion Dv3 system which I bought two years
ago. My first step after buying was to install Ubuntu by replacing
Vista which accompanied with it. But, I noticed immediately
afterwards that ubuntu was not supporting changing screen brightness.
After searching for solution I found it out as a general problem.
But, I was not able to solve it even after trying various means. I
tried this for every time I updated my ubuntu to a newer version till
now (12.04).
So,
if you also face from same problem, Here are the steps you need to do
to fix it. It is related to grub. So, here are the steps
gksudo gedit /etc/default/grub
Change GRUB_CMDLINE_LINUX from "” to "acpi_osi=Linux"
Change GRUB_CMDLINE_LINUX_DEFAULT from (”” or "quiet splash") to “quiet splash acpi_backlight=vendor”
Close gedit
run sudo update-grub
reboot your system
I got it working after doing (I couldn't believe it did!!) and here are the links that gave me that solution. Hope it worked for you too.
http://livinginjava.blogspot.de/2010/11/ubuntu-1010-brightness-problem-in-acer.html
http://askubuntu.com/questions/139796/cannot-adjust-brightness-on-my-packard-bell-easynote-ts11hr-127ge-laptop