To anyone checking, this is still an issue with versions: Kernel 4.18.16, LLVM 8.0.0, Mesa 18.3.0-devel, XOrg 1.20.2. Monitor is connected, but powered off: Screen 0: minimum 320 x 200, current 1024 x 768, maximum 16384 x 16384 DisplayPort-0 disconnected primary (normal left inverted right x axis y axis) DisplayPort-1 disconnected (normal left inverted right x axis y axis) HDMI-A-0 disconnected (normal left inverted right x axis y axis) HDMI-A-1 disconnected (normal left inverted right x axis y axis) DVI-D-0 disconnected (normal left inverted right x axis y axis)