desktop@steamos:/var/log$ DISPLAY=:1 xrandr --prop
Screen 0: minimum 8 x 8, current 3840 x 2160, maximum 32767 x 32767
DP1 disconnected (normal left inverted right x axis y axis)
	Broadcast RGB: Automatic
		supported: Automatic, Full, Limited 16:235
	audio: auto
		supported: force-dvi, off, auto, on
DP2 connected primary 3840x2160+0+0 (normal left inverted right x axis y axis) 1600mm x 900mm
	EDID:
		00ffffffffffff0011ee460001010101
		0019010380a05a780aee91a3544c9926
		0f5054a1080031404540614071408180
		010101010101023a801871382d40582c
		450040846300001e023a801871382d40
		582c4500c48e2100001e000000fc0044
		454e4f4e2d4156520a202020000000fd
		003a3e1e5310000a202020202020018b
		020351f154109f041305140302122021
		2215015d5e5f626364293d06c0150750
		095707830100007f030c002500b83c20
		c0910102030401410e3c081018100610
		16102810666800e50e60616566e30607
		01011d8018711c1620582c2500408463
		00009e00000000000000000000000000
		000000000000000000000000000000a9
	_MUTTER_PRESENTATION_OUTPUT: 0
	Broadcast RGB: Automatic
		supported: Automatic, Full, Limited 16:235
	audio: auto
		supported: force-dvi, off, auto, on
   1920x1080     60.00 +  50.00    59.94    30.00    25.00    24.00    29.97    23.98
   4096x2160     24.00    23.98
   3840x2160     30.00*   25.00    24.00    29.97    23.98
   1920x1080i    60.00    50.00    59.94
   1280x1024     60.02
   1152x864      59.97
   1280x720      60.00    50.00    59.94
   1024x768      60.00
   800x600       60.32
   720x576       50.00
   720x480       60.00    59.94
   640x480       60.00    59.94
   720x400       70.08
HDMI1 disconnected (normal left inverted right x axis y axis)
	aspect ratio: Automatic
		supported: Automatic, 4:3, 16:9
	Broadcast RGB: Automatic
		supported: Automatic, Full, Limited 16:235
	audio: auto
		supported: force-dvi, off, auto, on
HDMI2 disconnected (normal left inverted right x axis y axis)
	aspect ratio: Automatic
		supported: Automatic, 4:3, 16:9
	Broadcast RGB: Automatic
		supported: Automatic, Full, Limited 16:235
	audio: auto
		supported: force-dvi, off, auto, on
HDMI3 disconnected (normal left inverted right x axis y axis)
	aspect ratio: Automatic
		supported: Automatic, 4:3, 16:9
	Broadcast RGB: Automatic
		supported: Automatic, Full, Limited 16:235
	audio: auto
		supported: force-dvi, off, auto, on
VIRTUAL1 disconnected (normal left inverted right x axis y axis)
desktop@steamos:/var/log$ uname -a
Linux steamos 4.5.0-997-generic #201603142201 SMP Tue Mar 15 02:03:35 UTC 2016 x86_64 GNU/Linux