evdev: libinput ignores the events because tablet resolution is missing

[skadge]

Step to reproduce on Ubuntu 19.10, running wayland:

• start remouse like that:

$ sudo remouse --evdev --key ~/.ssh/remarkable
Created virtual input device '/dev/input/event5'

• no virtual tablet is created/visible

• Running libinput list-devices return the following error:

$ sudo libinput list-devices
event5  - reMarkable tablet: libinput bug: missing tablet capabilities: resolution. Ignoring this device.

According to libinput documentation, we need to specify the resolution of the tablet in a 60-evdev.hwdb entry.

[skadge]

Adding the following lines to /lib/udev/hwdb.d/60-evdev.hwdb:

evdev:input:b0018v056Ap0000*
 EVDEV_ABS_00=::20
 EVDEV_ABS_01=::20

Followed by:

$ sudo systemd-hwdb update
$ sudo udevadm trigger /dev/input/event5

And finally restarting remouse fixes the problem.

Two important notes:

• the value after evdev:input is the modalias of the tablet. You might want to check how it appears on your system: cat /sys/devices/virtual/input/input58/modalias
• I'm not sure about the actual resolution of the tablet, but 20 units/mm seems not too far off (the resulting behaviour of the tablet was ok)

[chabad360]

I hate to be a bother, but I'm having this issue as well and it's been a while since this was touched.

[Evidlo]

Maybe something like this is the right approach?

Can someome try adding this in evdev.py?

device.absinfo[libevdev.EV_ABS.ABS_X] = InputAbsInfo(resolution=2531)
device.absinfo[libevdev.EV_ABS.ABS_Y] = InputAbsInfo(resolution=2531)

Not sure if these resolutions are correct. In the example it seems like the resolution is in dpi, which I manually computed. Does the error go away at least?

[chabad360]

Where would I put it?

[Evidlo]

After `device` is created and before it is returned.

…

On Oct 22, 2020 7:29 PM, "Mendel Greenberg" ***@***.***> wrote: Where would I put it? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#18 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABJT7YKVNNIZUPAWFQHPEMLSMDFABANCNFSM4KJ2EJRA> .

[chabad360]

I stuck it over here:

...
   # Enable position, tilt, distance and pressure change events
    device.enable(
        libevdev.EV_ABS.ABS_X,
        libevdev.InputAbsInfo(
            minimum=0,
            maximum=MAX_ABS_X,
            resolution=2531 # <----
        )
    )
    device.enable(
        libevdev.EV_ABS.ABS_Y,
        libevdev.InputAbsInfo(
            minimum=0,
            maximum=MAX_ABS_Y,
            resolution=2531 # <----
        )
    )
...

[chabad360]

Further testing revealed a slight lack of alignment, but that was fixed with --mode fill. So it seems to have worked (yay)!

[chabad360]

@Evidlo mmm... it seems like the alignment issues persist, so either the resolution is wrong, or there is something wrong with remap()