Xephyr Input is broken

[Julian Rendell]

I'm using Xephyr for a multiseat system (4 GPUs -> up to 12 screens; using VirtualGL for 3D acceleration.)

The eventual command line that LightDM ends up running is:

Xephyr -fullscreen :0 -seat seat5 -auth /var/run/lightdm/root/:0 -nolisten tcp

In 18.04 and earlier this works great.

Important note: There is a strong chance my system had the version of Xephyr from the Multiseat PPA with Evdev support patches (https://launchpad.net/~ubuntu-multiseat/+archive/ubuntu/xephyr/+packages).

In 19.04 I get:

root@redstone-server:~# DISPLAY=:200.1 Xephyr -fullscreen -seat seat6 :20
Pointer option key (_source) of value (server/udev) not assigned!
Pointer option key (major) of value (13) not assigned!
Pointer option key (minor) of value (80) not assigned!
Pointer option key (config_info) of value (udev:/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.5/2-1.5.5/2-1.5.5.3/2-1.5.5.3.1/2-1.5.5.3.1:1.0/0003:045E:0083.001D/input/input58/event16) not assigned!
Pointer option key (GrabDevice) of value (on) not assigned!
couldn't find driver for pointer device "Microsoft Basic Optical Mouse" (/dev/input/event16)
Pointer option key (_source) of value (server/udev) not assigned!
Pointer option key (major) of value (13) not assigned!
Pointer option key (minor) of value (32) not assigned!
Pointer option key (config_info) of value (udev:/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.5/2-1.5.5/2-1.5.5.3/2-1.5.5.3.1/2-1.5.5.3.1:1.0/0003:045E:0083.001D/input/input58/mouse0) not assigned!
Pointer option key (GrabDevice) of value (on) not assigned!
couldn't find driver for pointer device "Microsoft Basic Optical Mouse" (/dev/input/mouse0)
Kbd option key (_source) of value (server/udev) not assigned!
Kbd option key (major) of value (13) not assigned!
Kbd option key (minor) of value (93) not assigned!
Kbd option key (config_info) of value (udev:/sys/devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1.5/2-1.5.5/2-1.5.5.3/2-1.5.5.3.2/2-1.5.5.3.2:1.0/0003:045E:0752.001E/input/input59/event29) not assigned!
Kbd option key (GrabDevice) of value (on) not assigned!
couldn't find driver for keyboard device "Microsoft Wired Keyboard 400" (/dev/input/event29)

The display is correct, but no user input (mouse or keyboard) works.

It looks like Xephyr can't find any input drivers. I also tried specifying drivers (eg Evdev, libinput, keyboard, mouse, ...) Nothing worked.

Extracting the version of Xephyr from https://launchpad.net/~ubuntu-multiseat/+archive/ubuntu/xephyr/+packages runs correctly.

Required details:

lsb_release -rd
Description: Ubuntu 19.04
Release: 19.04

apt-cache policy xserver-xephyr
xserver-xephyr:
  Installed: 2:1.20.4-1ubuntu3
  Candidate: 2:1.20.4-1ubuntu3
  Version table:
 *** 2:1.20.4-1ubuntu3 500
        500 http://ca.archive.ubuntu.com/ubuntu disco/main amd64 Packages
        100 /var/lib/dpkg/status

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Sebastien Bacher (seb128)]

Is that still an issue in newer series?

[Julian Rendell (julianrendell)]

Absolutely.

I believe it's an issue in upstream; I did spend a little time trying to investigate/recompile/figure out which set of changes removed/broke this functionality, but ran out of time.

At present to make multi-seat work I have to manually install and pin the old version of Xephyr.

It's a shame as multi-seat works incredibly well (once set up.)

[Sebastien Bacher (seb128)]

Thanks, it would be worth reporting upstream even if you don't have the debug cycles to investigate

[Julian Rendell (julianrendell)]

From memory, there were bugs reported, but it seems it's:

- almost abandoned
- breaking change is by design; I don't think Xorg wants to support this kind of configuration. Again, from memory, it's been changed so that it can only work with xevents from the "master" XServer.

Sad, but I think this avenue (multiseat in general) is pretty much abandonware.

It was amazing to see an i7 with 3 GPUs drive 14 instances of Minecraft ;-)

[Prashant (vulcrine)]

Sebastien Bacher , pls also tell what's the alternate software/method to do multiseat.
After Xephyr, their seems no hope. I run a computer lab for poor people, but without multiseat it's not possible. What's the alternate.

[Daniel van Vugt (vanvugt)]

Ubuntu 19.04 is no longer supported but the issue continues in bug 1988275.