Comment # 67 on bug 899879 from Freek de Kruijf

(In reply to Egbert Eich from comment #65)
> If you want to try a newer user space driver without getting all the
> annoying messages (which make things really slow), you can use a different
> repo I've created: 
> http://download.opensuse.org/repositories/home:/eeich:/Test:/Intel-NoDebug/
> openSUSE_Tumbleweed/
> 
> But at least we got somewhere and did make some progress: we did find that
> the backlight is the culprit.
> Fist thing I need from you is 
> 1. What you get when you do: 
>    systemctl list-units | grep backlight

# systemctl list-units | grep backlight
 
sys-devices-pci0000:00-0000:00:02.0-drm-card0-card0\x2deDP\x2d1-intel_backlight.device
     loaded active plugged  
/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-eDP-1/intel_backlight
  systemd-backlight@backlight:intel_backlight.service                          
              loaded active exited    Load/Save Screen Backlight Brightness of
backlight:intel_backlight
  system-systemd\x2dbacklight.slice                                            
              loaded active active    system-systemd\x2dbacklight.slice

> 2. What you get by doing:
>    ls /var/lib/systemd/backlight/

# ls /var/lib/systemd/backlight/
pci-0000:00:02.0:backlight:intel_backlight

> 3. Determine if you get a somewhat linear behaviour between 0 and 4687.

No. 0 is black and even 1 is bright. It looks like values above 4687 make a
difference in brightness.