insert acpi_backlight=vendor option into grub.

update-grub2

GRUB_DEFAULT=0

GRUB_HIDDEN_TIMEOUT=0

GRUB_HIDDEN_TIMEOUT_QUIET=true

GRUB_TIMEOUT=10

GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor”

GRUB_CMDLINE_LINUX=””