Linux :Ubuntu fix for Fn (Functional) Brightness keys issue

tags:
Ubuntu 12.04, 12.10, 13.04, Linux, Opensource,lenovo, acer, Acer
Aspire, Brightness fix, Cannot reduce Brightness,

open /etc/default/grub

sudo gedit /etc/default/grub
and change

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

then do
sudo update-grub

and reboot the system.