X.Org: invoking xinput --disable [ || --enable] <device_xID> kills gdm user session

[Cedric Bhihe]

Hi folks,

[Background info: host OS is Arch linux 5.11.12 with gdm 40.0.1 on xorg]

  For the past 4 days, I have this weird mix-up between issuing either 
of the following cmds in a `tmux` terminal:

      $ /usr/bin/xinput --disable <xID>
or
      $ /usr/bin/xinput --enable <xID>

where <xID> is my Touchpad xorg device ID (=14) on a Dell XPS15, 
obtained with
      $ /usr/bin/xinput --list --short

Issuing either one of the above cmds instantly kills my gdm user 
session, along with all that was going on in it. Next it lands me on the 
gdm user login frame, where I can start a new user session as if nothing 
had happened. Everything else seems completely normal.

The touchpad's driver is: xf86-input-synaptics 1.9.1-2 (could not find a 
reference to a recent update)
The xorg-xinput version is 1.6.3-2, upgraded from 1.6.3-1 on 2020.05.19 
(way before the issue appeared)
On the other hand, gdm + the linux kernel and headers were upgraded 
recently (from /var/log/pacman.log):
     - [2021-04-09T08:29:29+0200] [ALPM] upgraded linux (5.11.11.arch1-1 
-> 5.11.12.arch1-1)
     - [2021-04-09T08:29:30+0200] [ALPM] upgraded gdm (3.38.2.1-1 -> 40.0-1)

I have looked up FAQs, misc FAQs and extra FAQs and all I could on get 
my eyes on at xorg, as well as the knowledge base on StackExchange, in 
addition to having scanned the web, by I found absolutely no chatter on 
anything similar to that issue.

I'm stumped in part because I've used the above cli cmds for years to 
activate/deactivate my laptop's touchpad on the fly (on the same box) 
and I never had an issue.

I'm stumped and would be grateful for any pointer.

PS: I have not cross posted on gdm yet. Will do so in a few days only if 
needed or recommended by someone deeper than me on the issue.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.x.org/archives/xorg/attachments/20210411/5141139c/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: OpenPGP_signature
Type: application/pgp-signature
Size: 236 bytes
Desc: OpenPGP digital signature
URL: <https://lists.x.org/archives/xorg/attachments/20210411/5141139c/attachment.sig>