sid@prosid ~ $ ls /sys/class/backlight/ acpi_video0 intel_backlight
edit /etc/default/grub and add “video.use_native_backlight=1″ in GRUB_CMDLINE_LINUX_DEFAULT
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash video.use_native_backlight=1"
reboot & check
sid@prosid ~ $ ls /sys/class/backlight/ intel_backlight