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

[David Revoy]

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. 

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).

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.
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.

[1] https://gitlab.freedesktop.org/bentiss/udev-hid-bpf/-/artifacts  
[2] https://www.peppercarrot.com/extras/temp/2023-11-09_screenshot_005214_net.jpg


On Wednesday, November 8th, 2023 at 19:21, Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx> wrote:


> On Wed, Nov 8, 2023 at 10:34 AM Benjamin Tissoires
> benjamin.tissoires@xxxxxxxxxx wrote:
> 
> > On Wed, Nov 8, 2023 at 10:23 AM José Expósito jose.exposito89@xxxxxxxxx wrote:
> > 
> > > Hi Benjamin,
> > > 
> > > On Wed, Nov 08, 2023 at 10:04:30AM +0100, Benjamin Tissoires wrote:
> > > [...]
> > > 
> > > > > So, the behavior probably breaks the specs, but sincerely I'm happy to
> > > > > have the "eraser" button independent of the "rubber eraser", which
> > > > > makes the stylus a somewhat 4-buttons stylus (tip, button1, button2,
> > > > > rubber), and I would like to keep this.
> > > > 
> > > > Yes, and I'd like to keep it that way, even if 6.6 and 6.5.8
> > > > apparently broke it.
> > > > 
> > > > So, to me:
> > > > - 276e14e6c3993317257e1787e93b7166fbc30905 is wrong: this is a
> > > > firmware bug (reporting invert through eraser) and should not be
> > > > tackled at the generic level, thus it should be reverted
> > > > - both of these tablets are forwarding the useful information, but not
> > > > correctly, which confuses the kernel
> > > > - I should now be able to write regression tests
> > > > - I should be able to provide HID-BPF fixes for those tablets so that
> > > > we can keep them working with or without
> > > > 276e14e6c3993317257e1787e93b7166fbc30905
> > > > reverted (hopefully)
> > > > - problem is I still don't have the mechanics to integrate the HID-BPF
> > > > fixes directly in the kernel tree, so maybe I'll have to write a
> > > > driver for XP-Pen while these internals are set (it shouldn't
> > > > interfere with the HID-BPF out of the tree).
> > > 
> > > I already added support for a few XP-Pen devices on the UCLogic driver
> > > and I was planning to start working on this one during the weekend in
> > > my DIGImend fork (to simplify testing).
> > > 
> > > Let me know if you prefer to add it yourself or if you want me to ping
> > > you in the DIGImend discussion.
> > 
> > So far, I really have to work on this now. It's a good use case for
> > HID-BPF and it's a regression that I'd like to be fixed ASAP.
> > I'd appreciate any reviews :)
> 
> 
> 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'.
> 
> > Also, good to know that I can probably piggyback on hid-uclogic for
> > fixing those 2 devices in the kernel.
> 
> 
> Next step will be to fix them using a kernel driver, but it seems that
> the uclogic driver is doing more than just report descriptor fixups,
> so maybe I'll have to use a different driver.
> But the point is, in theory, if you are affected by those bugs, using
> the udev-hid-bpf should fix the issue, and this should also be
> resilient to further kernel updates.
> 
> I'd appreciate testing when I got the full kernel series up and ready,
> of course.
> 
> Cheers,
> Benjamin
> 
> [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