Any HINTS how to debug this? - USB okay, X11 display not... what are the steps???

[jamesreinders]

Can anyone give me hints on how to debug this?

I think it would help me a lot to understand the steps that should be happening
between the USB device being recognized (working) for a DisplayLink,
and X11 deciding it is a display (only happening to the FIRST USB
device). I do not understand how to debug this... so I can't figure out why it is failing.

I have two DisplayLinks hooked to Ubuntu.

Both are recognized as USB devices, but only one becomes a display for
X11 (which ever is plugged in first, even if I change which USB
sockets I plug into... it is always the DisplayLink that is plugged in
first that becomes a display for X11 - both of them clearly work
hardware wise!)

Here is a sample of what I see...

ls /dev/displaylink/by-id
usb-002-003-DisplayLink_Displaylink_USB3.0_Display_PCT13600000 014
usb-002-005-DisplayLink_Displaylink_USB3.0_Display_PCT13600000 014

xrandr --listproviders
Providers: number : 2
Provider 0: id: 0x7b cap: 0x9, Source Output, Sink Offload crtcs: 2 outputs: 7 associated providers: 1 name:modesetting
Provider 1: id: 0x41 cap: 0x2, Sink Output crtcs: 1 outputs: 1 associated providers: 1 name:modesetting

Frankly - I'm not sure how to read that... I have one working monitor (a DELL) and two DisplayLinks via USB.


This is a laptop, with a VGA monitor connected, the lid closed. The
DisplayLink USB devices definitely both work as monitors - but only one at a time.

How can I get X11 to see and use both of them???

Can anyone help me understand the steps that should be happening
between the USB device being recognized (working) for a DisplayLink,
and X11 deciding it is a display (only happening to the FIRST USB
device).

Output from the DLSupportTool is available at
https://displaylink.org/forum/attach...2&d=1567618658