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Date:   Fri, 19 Aug 2022 16:15:34 +0200
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From:   Benjamin Tissoires <benjamin.tissoires@redhat.com>
Subject: Re: PROBLEM: Regression likely in hid_uclogic driver breaks Huion
 Inspiroy H640 drawing tablet
To:     =?UTF-8?B?Sm9zw6kgRXhww7NzaXRv?= <jose.exposito89@gmail.com>
Cc:     Stefan Hansson <newbie13xd@gmail.com>,
        Jiri Kosina <jikos@kernel.org>,
        Ping Cheng <ping.cheng@wacom.com>,
        Peter Hutterer <peter.hutterer@who-t.net>,
        "open list:HID CORE LAYER" <linux-input@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
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On Sat, Aug 13, 2022 at 1:09 PM José Expósito <jose.exposito89@gmail.com> wrote:
>
> Hi Benjamin,
>
> On Thu, Aug 11, 2022 at 05:23:52PM +0200, Benjamin Tissoires wrote:
> > On Thu, Aug 4, 2022 at 8:24 PM José Expósito <jose.exposito89@gmail.com> wrote:
> > >
> > > Hi again,
> > >
> > > On 2022-07-26 18:48, José Expósito wrote:
> > > > The first bad commit is 87562fcd1342 ("HID: input: remove the need for
> > > > HID_QUIRK_INVERT"):
> > > > https://lore.kernel.org/all/20220203143226.4023622-11-benjamin.tissoires@redhat.com/
> > > > (CCing the folks whose email is in the patch tags)
> > > >
> > > > I reverted the patch on hid/for-next and, after fixing a tiny conflict,
> > > > I can confirm that the tablet works again as expected.
> > > >
> > > > I'd need to investigate a bit more over the weekend, but I think that
> > > > all HUION tablets with the latest firmware (internally, v2) are
> > > > affected.
> > >
> > > Indeed, it looks like v2 devices are affected. Similar reports:
> > >
> > >  - https://github.com/DIGImend/digimend-kernel-drivers/issues/626
> > >  - https://bugzilla.kernel.org/show_bug.cgi?id=216106
> > >
> > > Kindly sending this thread back to your inbox to see if we could fix
> > > this regression.
> >
> > [sorry, I was out on vacation the past 2 weeks and this week was the
> > usual "urgent" thing I have to day for yesterday]
>
> No problem, I hope you enjoyed your holidays :D
>
> > Ideally, I'd like to not revert that commit. It solves a bunch of
> > issues on many devices, so that's maybe not the way forward.
> >
> > FWIW, it was quite painful to tweak and that was a solution that
> > matches the hid-multitouch devices I could find.
> >
> > I tried to process your email when you described the succession of
> > events without much success.
> >
> > Would you mind dumping a hid-record when exposing the bug?
>
> Sure, I added as an attachment in the existing report in bugzilla:
> https://bugzilla.kernel.org/show_bug.cgi?id=216106#c2
>
> I hope it helps you to debug the issue. Let me know if you need more
> recordings, help testing patches or any other information.
>
> In future changes to tablet code, feel free to cc me. I have a bunch of
> non Wacom devices and I'll help you testing your changes.

FWIW, I found the issue: the hid-uclogic driver is emitting input data
behind hid-input, and the state between the 2 is desynchronized.

The following patch seems to be working (with the Huion v1 protocol I
have here that I have tweaked to resemble a v2):
---
 From aeedd318e6cb4dbee551f67616302cc7c4308c58 Mon Sep 17 00:00:00 2001
From: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Date: Thu, 18 Aug 2022 15:09:25 +0200
Subject: [PATCH] Fix uclogic

---
  drivers/hid/hid-input.c | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index c6b27aab9041..a3e2397bb3a7 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -1530,7 +1530,10 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
  			 * assume ours
  			 */
  			if (!report->tool)
-				hid_report_set_tool(report, input, usage->code);
+				report->tool = usage->code;
+
+			/* drivers may have changed the value behind our back, resend it */
+			hid_report_set_tool(report, input, report->tool);
  		} else {
  			hid_report_release_tool(report, input, usage->code);
  		}
-- 
2.36.1

---

Can someone with an affected device test it?

Cheers,
Benjamin

>
> Best wishes,
> Jose
>
> > Cheers,
> > Benjamin
> >
> >
> > >
> > > Best wishes,
> > > Jose
> > >
> > > > Those tablets do not set the inrange bit (UCLOGIC_PARAMS_PEN_INRANGE_NONE).
> > > > The driver sets it and uses a timer to remove it.
> > > > See drivers/hid/hid-uclogic-core.c, function uclogic_raw_event_pen().
> > > > [...]
> > >
> >
>