@Vladimir Kravets: If there's acer-wmi present in your /sys/classes/backlight (and in my case it is when I'm booting with acpi_backlight=vendor parameter), you might want to blacklist acer_wmi module
@Vladimir Kravets: If there's acer-wmi present in your /sys/classes/ backlight (and in my case it is when I'm booting with acpi_backlight= vendor parameter), you might want to blacklist acer_wmi module