[systemd-devel] [multiseat] Attach virtual input to seat1

[Lennart Poettering]

On So, 03.09.23 00:46, LuKaRo (lists at lrose.de) wrote:

>
> $ sudo loginctl attach seat1 /sys/devices/virtual/input/input43
> Could not attach device: No such device
> $ sudo loginctl attach seat1 /sys/devices/virtual/input/input44
> Could not attach device: No such device
> $ sudo loginctl attach seat1 /sys/devices/virtual/input/input23
> Could not attach device: No such device
> $ sudo loginctl attach seat1 /sys/devices/virtual/input/input22
> Could not attach device: No such device
> $ sudo loginctl attach seat1 /sys/devices/virtual/input/input21
> Could not attach device: No such device
>
> Any idea why all of them fail, and what could be a possible
> workaround?

See my reply here:

https://lists.freedesktop.org/archives/systemd-devel/2023-September/049470.html

The key is that the udev property ID_FOR_SEAT is not set for these
devices. (We should definitely generate a more useful error in that
case.) Only devices that have that property set can be assigned to seats.

ID_FOR_SEAT is supposed to carry some form of stable ID string we can
identify the device with, that remains the same between reboots. We
currently set ID_FOR_SEAT to useful values for PCI and USB devices,
but not on other busses. In particular virtual devices are not
covered. "input23" is not useful as an identifier string in
ID_FOR_SEAT, because they are assigned in the order of probing, which
typically is not stable.

it should suffice setting the udev property via some udev rule to
something reasonable, for the devices you add... I have no idea how
that looks like for your specific type of devices.

Lennart

--
Lennart Poettering, Berlin