https://bugzilla.kernel.org/show_bug.cgi?id=115011

Alex Deucher alexdeucher@gmail.com changed:

What |Removed |Added ---------------------------------------------------------------------------- CC| |alexdeucher@gmail.com

--- Comment #10 from Alex Deucher alexdeucher@gmail.com --- (In reply to Luya Tshimbalanga from comment #7)

Created attachment 210281 [details] dmesg with 4.6.0-0.rc0.git13.1

dmesg report using latest git kernel i.e. 4.6.0-0. Same result:

[ 7.498283] [drm:radeon_acpi_init [radeon]] *ERROR* Cannot find a backlight controller

This message is harmless. Your laptop has two GPUs. The ATIF ACPI method is used to notify the driver of backlight change events so the driver checks to see if it exists. Depending on the board configuration, the secondary GPU may or may not have access to the backlight controller. In this case it does not.