UDL device cannot get its own screen

Pekka Paalanen ppaalanen at gmail.com
Wed Oct 23 07:42:25 UTC 2019

On Tue, 22 Oct 2019 17:50:21 +0200
Böszörményi Zoltán <zboszor at pr.hu> wrote:

> Hi,
> I have the below configuration for an Intel based POS system that,
> while advertises 3 outputs (DP1, VGA1 and HDMI1 with xf86-video-intel),
> only two are usable. DP1 for the built-in touchscreen and VGA1 for
> the external VGA connector.
> I wanted to use an USB DisplayLink device as the 3rd output, with all
> three output using its own Screen number, i.e. :0.0 :0.1 and :0.2.


> The third observation is that while I am using this configuration below,
> so the UDL device should be assigned to :0.2 (and active!), it is really
> assigned to :0[.0] as an inactive output. See that there's no "*" indicator
> set for any of the supported modes on DVI-I-1-1.
> How can I set up 3 different Screens correctly for 3 separate fullscreen
> applications?
> I am using Xorg 1.20.4 patched with the "autobind GPUs to the screen"
> patch from Dave Airlie that at least wakes up the UDL device and makes
> it visible without extra magic with providers/sinks.


for your specific use case, auto-bind is exactly what you do not want.
So drop the patch or (since the patch is in upstream master already)
use the option it adds to stop auto-binding.

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