Have a Rasberry Pi 3 B+ running Ubuntu Mate 16.04.2
I have a two USB 2.0 to DVI adapters connected to the Pi and both work separately but never together.
xrandr -q gives the following:
:~$ xrandr -q
Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 2048 x 2048
DVI-I-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 299mm
1920x1080 60.00*+
1680x1050 59.88
1600x900 60.00
1280x1024 75.02 60.02
1440x900 59.90
1280x800 59.91
1152x864 75.00
1280x720 60.00
1024x768 75.03 70.07 60.00
832x624 74.55
800x600 72.19 75.00 60.32 56.25
640x480 75.00 72.81 66.67 59.94
720x400 70.08
Here is an except from the lshq -numeric command showing the two USB adpters
lshw -numeric
*-usb:3
description: Generic USB device
product: USB to DVI-17 [17E9:360]
vendor: DisplayLink [17E9]
physical id: 4
bus info: usb@1:1.4
version: 1.11
serial: 624867
capabilities: usb-2.00
configuration: driver=udl maxpower=500mA speed=480Mbit/s
*-usb:4
description: Generic USB device
product: USB to DVI-17 [17E9:360]
vendor: DisplayLink [17E9]
physical id: 5
bus info: usb@1:1.5
version: 1.11
serial: 621252
capabilities: usb-2.00
configuration: driver=udl maxpower=500mA speed=480Mbit/s
Then two more pieces from /var/log/Xorg.0.log showing the two DVI adapters showing up
/var/log/Xorg.0.log
[ 13.085] (II) modeset(0): Output DVI-I-1 has no monitor section
[ 13.163] (II) modeset(0): EDID for output DVI-I-1
[ 13.163] (II) modeset(0): Manufacturer: SAM Model: ca1 Serial#: 808792371
[ 13.163] (II) modeset(0): Year: 2016 Week: 49
[ 13.163] (II) modeset(0): EDID Version: 1.3
[ 13.163] (II) modeset(0): Digital Display Input
[ 13.163] (II) modeset(0): Max Image Size [cm]: horiz.: 53 vert.: 30
[ 13.163] (II) modeset(0): Gamma: 2.20
[ 13.163] (II) modeset(0): DPMS capabilities: Off
[ 13.163] (II) modeset(0): Supported color encodings: RGB 4:4:4 YCrCb 4:4:4
[ 13.163] (II) modeset(0): First detailed timing is preferred mode
[ 13.163] (II) modeset(0): redX: 0.638 redY: 0.348 greenX: 0.334 greenY: 0.608
[ 13.163] (II) modeset(0): blueX: 0.150 blueY: 0.057 whiteX: 0.312 whiteY: 0.329
[ 13.328] (II) modeset(G0): Output DVI-I-1-2 has no monitor section
[ 13.468] (II) modeset(G0): EDID for output DVI-I-1-2
[ 13.468] (II) modeset(G0): Manufacturer: SAM Model: ca1 Serial#: 808792371
[ 13.468] (II) modeset(G0): Year: 2017 Week: 27
[ 13.468] (II) modeset(G0): EDID Version: 1.3
[ 13.468] (II) modeset(G0): Digital Display Input
[ 13.468] (II) modeset(G0): Max Image Size [cm]: horiz.: 53 vert.: 30
[ 13.468] (II) modeset(G0): Gamma: 2.20
[ 13.468] (II) modeset(G0): DPMS capabilities: Off
[ 13.468] (II) modeset(G0): Supported color encodings: RGB 4:4:4 YCrCb 4:4:4
[ 13.468] (II) modeset(G0): First detailed timing is preferred mode
[ 13.468] (II) modeset(G0): redX: 0.638 redY: 0.348 greenX: 0.334 greenY: 0.608
[ 13.468] (II) modeset(G0): blueX: 0.150 blueY: 0.057 whiteX: 0.312 whiteY: 0.329
It looks like they are both detecting in the OS but xrandr isnt seeing both at the same time. I assume I need to edit a config that works between the OS and Xrandr but not sure what that is.