As the mentioned fix is in the ATI driver, it would be good if I actually could
build and use it. Expected it to be in the radeon/radeonsi driver and concluded
the missing xf86-video-ati wont be a problem.

==  Processing:  "driver/xf86-video-ati"
==        configuration options:
make: *** Keine Targets angegeben und keine »make«-Steuerdatei gefunden. 
Schluss.
build.sh: "make " failed on driver/xf86-video-ati

***** Failed components *****
    driver/xf86-video-v4l
    driver/xf86-video-ati
Everything else could be build.