Arch Linux

Any xorg configs?

Attached is /etc/X11/xorg.conf.d/50-synaptics.conf, can't recall having any other custom configuration. Let me know if there are specific files you'd like me to post.

Can you try without xf86-video-intel driver?

No change in behaviour without xf86-video-intel.

I can confirm that freshly installing latest arch linux also has the same issue.
Using nvidia/nouveau or intel driver (laptop has both).

The following lines seem like a problem?

[ 22.002] (II) config/udev: Adding input device (unnamed) (/dev/ttyS0)
[ 22.002] (**) (unnamed): Applying InputClass "touchpad"
[ 22.002] (II) Using input driver 'libinput' for '(unnamed)'
[ 22.002] (EE) systemd-logind: failed to take device /dev/ttyS0: No such device
[ 22.002] (**) (unnamed): always reports core events
[ 22.002] (**) Option "Device" "/dev/ttyS0"
[ 22.002] (**) Option "_source" "server/udev"
[ 22.002] (II) ttyS0 - failed to create input device '/dev/ttyS0'.
[ 22.002] (EE) libinput: (unnamed): Failed to create a device for /dev/ttyS0
[ 22.002] (EE) PreInit returned 2 for "(unnamed)"
[ 22.002] (II) UnloadModule: "libinput"

X seems to think that /dev/ttyS0 is a touchpad? Maybe add the following line to your 50-synaptics.conf?

MatchIsTouchpad "yes"

edit: It seems to assume *everything* is a touchpad which I would expect to cause all sorts of havoc:

[ 43.389] (EE) systemd-logind: failed to take device /dev/tty: Connection was disconnected before a reply was received
...
[ 43.389] (EE) systemd-logind: failed to take device /dev/tty0: Connection is closed
...
[ 43.390] (EE) xf86OpenSerial: Cannot open device /dev/tty0
Permission denied

MatchIsTouchpad "yes" did the trick -- thanks! All good on my end. If the same works for Petar, I guess it's a wrap.

I checked the wiki and MatchIsTouchpad is present in examples there, so I guess my config was just outdated.

The fact that your configuration worked previously could still mean that a problem was introduced in 1.19.6. The following change might be related?

https://patchwork.freedesktop.org/patch/178833/

Might still be worth it to follow up on this issue.

In fact, I think there really is an issue here.

$ udevadm info --name=/dev/ttyS0
P: /devices/platform/serial8250/tty/ttyS0
N: ttyS0
E: DEVNAME=/dev/ttyS0
E: DEVPATH=/devices/platform/serial8250/tty/ttyS0
E: ID_MM_CANDIDATE=1
E: MAJOR=4
E: MINOR=64
E: SUBSYSTEM=tty
E: TAGS=:systemd:
E: USEC_INITIALIZED=11004582

$ grep ttyS0 /var/log/Xorg.0.log | grep Adding
[ 18.325] (II) config/udev: Adding input device (unnamed) (/dev/ttyS0)

This is weird. From the code in
https://cgit.freedesktop.org/xorg/xserver/tree/config/udev.c?h=server-1.19-branch
I would not expect this to happen, because there is this block in device_added:

value = udev_device_get_property_value(udev_device, "ID_INPUT");
if (value && !strcmp(value, "0")) {
LogMessageVerb(X_INFO, 10,
"config/udev: ignoring device %s without "
"property ID_INPUT set\n", path);
return;
}
...

LogMessage(X_INFO, "config/udev: Adding input device %s (%s)\n",
name, path);

It is not supposed to reach this line if ID_INPUT is unset. I think it should return for value==NULL as well, not just for (value && ...)!

Old code checks for !udev_device_get_property_value(..)
New code checks value is not null and value is 0.

It should be if (value == NULL || strcmp(value, "0") == 0) instead.

Is somebody going to take this upstream?

Why don't you take it upstream, as you're the one who spotted it? :)

Done:

https://bugs.freedesktop.org/show_bug.cgi?id=104382

For now I've reverted the upstream udev changes in 1.19.6-2 until we have a proper fix.