That's my first post and I would try to be the more precise I could.
I've got an HP Pavilion dv7 and just installed Linux mint. I got ubuntu before and got the same issue.
When I press the volume up or volume down keys it works well but when I try to adjust the brightness it doesn't works.
The slider appears and changes but it takes no effect. That's the graphic card:
PavimintX ~ # lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09)
01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Seymour [Radeon HD 6400M Series]
I've tried adding this on /etc/X11/xorg.conf
Option "RegistryDwords" "EnableBrightnessControl=1"
and this on grub.cfg
But no result. Help me please.