I recently purchased a new laptop HP DV6121tx and installed linux on it. Apart from the muxless switchable graphics and openGL (HP will release a BIOS update to fix it soon), and brightness control, everything worked. I couldn’t change the brightness using the Fn Hotkeys. They displayed the brightness applet on pressing but nothing happened.
After scavenging, what seemed like the whole WWW, I finally found a modified kernel by Kamal Mostafa which fixed the issue. You can see the bug reports and patch here.
The issue seemed to be with i915 kernel module and how it handled brightness on certain laptops which had different ACPI implementation.
Only install this kernel if you are using i915 kernel module. You can check if its active by executing:
lsmod | grep i915
If it gives you output, it means you’re using the i915 kernel module and you can proceed further. If it doesn’t give any output, you should leave this page.
Fix the brightness issue by installing kernel debs provided in Kamal’s PPA.
sudo add-apt-repository ppa:kamalmostafa/linux-kamal-mjgbacklight sudo apt-get update sudo apt-get dist-upgrade
This will install the modified kernel. Alternatively, you could do (not recommended):
sudo add-apt-repository ppa:kamalmostafa/linux-kamal-mjgbacklight sudo apt-get update sudo apt-get install linux-headers-2.6.38-10 linux-headers-2.6.38-10-generic linux-image-2.6.38-10-generic linux-libc-dev
Reboot into the modified kernel to confirm the brightness keys work. Cheers!