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Old 11-04-2017, 09:34 AM   #1
JeromeK
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Join Date: Nov 2017
Posts: 2
Default Multi seat on Debian9

Dear support,
I am trying to build a double-seat system with one of the screens connected via a DisplayLink adapter (from Kensington, still in USB2, it is a DL165).

The operating system is debian9 on a SSD with 2 seats defined:
seat0:
Nvidia 9300 GPU with the Nouveau driver (works great)
+ keyboard + mouse + everything else

Seat1: DisplayLink adapter + keyboard + mouse
seat1
Sessions: *c1
Devices:
├─/sys/devices/pci0000:00/0000:00:1a.1/usb2/2-1/2-1:1.0/0003:413C:301A.0004/input/input7
│ input:input7 "PixArt Dell MS116 USB Optical Mouse"
├─/sys/devices/pci0000:00/0000:00:1a.7/usb6/6-4/6-4.4/6-4.4:1.0/drm/card0
│ [MASTER] drm:card0
│ └─/sys/devices/pci0000:00/0000:00:1a.7/usb6/6-4/6-4.4/6-4.4:1.0/drm/card0/card0-DVI-I-1
│ [MASTER] drm:card0-DVI-I-1
├─/sys/devices/pci0000:00/0000:00:1a.7/usb6/6-4/6-4.4/6-4.4:1.0/graphics/fb0
│ [MASTER] graphics:fb0 "udldrmfb"
├─/sys/devices/pci0000:00/0000:00:1a.7/usb6/6-4/6-4.5/6-4.5:1.0/0003:413C:2107.000A/input/input13
│ input:input13 "DELL Dell USB Entry Keyboard"
├─/sys/devices/pci0000:00/0000:00:1d.2/usb5/5-2/5-2:1.0/0003:0A81:0205.0005/input/input8
│ input:input8 "CHESEN PS2 to USB Converter"
└─/sys/devices/pci0000:00/0000:00:1d.2/usb5/5-2/5-2:1.1/0003:0A81:0205.0006/input/input9
input:input9 "CHESEN PS2 to USB Converter"

The Xorg server has been launched by lightdm and is running but the screen is not active (no login screen)
/usr/lib/xorg/Xorg -sharevts :0 -layout SecondLayout -seat seat1 -auth /var/run/lightdm/root/:0 -nolisten tcp

Nothing special in the Xorg.0.log file, apparently everything is "working" except the screen which behaves "strangly".
For example
* There are still messages from the boot on the screen while lightdm is supposed to ask for login.
*When I login (blindly) the splash screen appears with a mouse pointer but it is static and stays like this forever
* the desktop manager (xfce4) is properly launched but unusable.

Do you have any idea in which direction to look at ?
Thanks for your help

Jerome Kieffer
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Old 11-14-2017, 08:56 PM   #2
JeromeK
Junior Member
 
Join Date: Nov 2017
Posts: 2
Smile Found the solution

Hi,

I found the solution:
  1. Remove all the closed source crap from display-link, including their kernel drivers.
  2. Remove the udlfb driver from blacklist
  3. Configure the udlfb modules to be loaded with the proper option (in /etc/modprobe.d)
  4. ensure nouveau and udlfb are always loaded in the same order in /etc/modules
  5. re-create the seat1 which points to the right /dev/fbX, i.e. the displaylink one
  6. re-configure the /etc/X11/xorg.conf for the seat1/second layout with the fbdev driver pointing to the proper /dev/fbX

Apparently this stopped working with the newer USB3 display-link devices ... it is a bit sad as it is exactly MY use-case. At least I will not spend money on a new device
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