I want to report my success in finally enabling the brightness control of my LCD screen on
HP Pavilion dv6-6192sl.
I make use of Debian/Sid and a custom 3.1.4 kernel. It didn't worked before until I modified grub and passed the
option to the kernel at boot as told in other posts.
Thank to all that contributed with their experience and to Kamal Mostafa for the patches to Linux.