Re: Requesting your attention and expertise regarding a Tablet/Kernel issue

[Benjamin Tissoires]

On Thu, Nov 9, 2023 at 12:56 PM Benjamin Tissoires
<benjamin.tissoires@xxxxxxxxxx> wrote:
>
> Hi David,
>
> On Thu, Nov 9, 2023 at 1:32 AM David Revoy <davidrevoy@xxxxxxxxxxxxxx> wrote:
> >
> > Hi Benjamin,
> >
> > > Alright, I made quite some progress so far:
> > > - regressions tests have been written (branch wip/xp-pen of my fork on
> > > freedesktop[0])
> > > that branch can not go in directly as it just adds the tests, and
> > > thus is failing
> > > - I made the fixes through HID-BPF[1]
> > >
> > > Anyone using those 2 tablets and using Fedora should be able to just
> > > grab the artifact at [2], uncompress it and run `sudo ./install.sh --verbose`.
> > > This will install the bpf programs in /lib/firmware/hid/bpf/ and will
> > > automatically load them when the device is connected.
> > >
> > > For those not using Fedora, the binary might work (or not, not sure),
> > > but you can always decompress it, and check if running
> > > `udev-hid-bpf_0.1.0/bin/udev-hid-bpf --version` returns the correct
> > > version or just fails. If you get "udev-hid-bpf 0.1.0", then running
> > > `sudo ./install.sh --verbose` should work, as long as the kernel has
> > > CONFIG_HID_BPF set to 'Y'.
> > > [...]
> > > [0] https://gitlab.freedesktop.org/bentiss/hid/-/tree/wip/xp-pen?ref_type=heads
> > > [1] https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/27
> > > [2] https://gitlab.freedesktop.org/bentiss/udev-hid-bpf/-/jobs/51350589/artifacts/raw/udev-hid-bpf_0.1.0.tar.xz
> >
> > Thank you for this package.
> >
> > I was able to test it even though the link in (2) at the bottom of your email returned a blank page. I was able to find my way after manually visiting gitlab.freedesktop.org [1] and then manually downloading the article from 51350589. I unzipped it and ran `sudo ./install.sh --verbose`. Everything looks like it was successful [2]. I then rebooted my Fedora 38 'Linux workstation 6.5.8-200.fc38.x86_64' kernel (the one I blamed in my post) and tested both tablets.
>
> Weird that you had to manually retrieve it. It works here, but maybe
> because I am logged in on gitlab.fd.o.
>
> Also, just FYI, you shouldn't have to reboot. Just unplug/replug and
> you are good. In the same way, if you uninstall the package, you can
> just unplug/replug to not have the programs loaded.

I've pushed an update of the file[0], turns out I made several mistakes.
As a general rule of thumb, you can follow the MR I've opened at [1],
click on the pipeline, open the last job ("make release"), then browse
the artifacts and pull the file from there.

>
> >
> > Here are my observation:
> >
> > XPPEN Artist Pro 24
> > ===================
> > Nothing changed for this device (it's the one with two buttons and no 'eraser tip'). Nor my hwdb/udev rules or `xsetwacom set "UGTABLET 24 inch PenDisplay eraser" button 1 3` affects the upper button of the stylus: if I hold it hover the canvas, Krita switch the tool and cursor for an eraser. If I click on the canvas with the pen tip while holding the upper button pressed, I get the right-click Pop-up Palette (but not all the time, probably Krita has hard time to triage Eraser or Right-click).
>
> As I mentioned in another reply, the more I think of it, the more I
> think I should get rid of the "eraser mode". In that Artist Pro 24 I
> can detect it through the same mechanics as the HID_QUIRK_NOINVERT
> from Illia's patch. But instead of trying to force the device into the
> eraser mode, we should just say "this is actually BUTTON_STYLUS_2".
>
> So I'm going to amend the bpf program to do this and hopefully you
> won't need the hwdb/udev rule at all.

I've fixed that one normally. There were a couple of issues:
- the PID in use was the one from the pro 16 gen2, which explained why
no change was appearing
- I've now decided to not export the second button as an eraser, as
mentioned above.

>
> >
> > XPPEN Artist Pro 16 (Gen2)
> > ==========================
> > Something changed. `xsetwacom set "UGTABLET Artist Pro 16 (Gen2) eraser" button 1 3` successfully affected the upper button of the stylus. Now if I click it while hovering the canvas, Krita shows the right click Pop-up Palette.
>
> I'm surprised you need to teach the wacom driver that BTN_STYLUS_2 is
> the right click.
>
> > On the downside; the real eraser tip when I flip the stylus bugs. When I flip the stylus on eraser hovering the canvas, Krita shows the Eraser icon and switch tool. As soon as I draw with the eraser tip, Krita will also show a right-click color palette and with also not a 100% consistency, as if the event were mixed.
>
> I'll investigate. Maybe I messed up with my event flow patch.

Definitely my mistake: both the bpf programs I wrote were attached to
the same device. Thus, the 2 fixes were stacking on each other,
leading to some interesting side effects.

You can check that the bpf are properly loaded by having a look at the
report descriptor when you replug the device:
if you see "Secondary Barrel Switch" at offset 16 instead of "Eraser"
on both of your tablets (with hid-recorder), you should have
successfully patched your devices.

Cheers,
Benjamin

>
> But just to be sure, you don't have a custom configuration in place
> for that tablet device?
>

[0] https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/jobs/51399392/artifacts/file/udev-hid-bpf_0.1.0.tar.xz
[1] https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/27