Date:   Tue, 26 Jul 2022 13:58:24 -0400
From:   Stefan Hansson <newbie13xd@...il.com>
To:     José Expósito <jose.exposito89@...il.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Ping Cheng <ping.cheng@...om.com>,
        Peter Hutterer <peter.hutterer@...-t.net>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: PROBLEM: Regression likely in hid_uclogic driver breaks Huion
 Inspiroy H640 drawing tablet

Hi again!

On 2022-07-25 18:48, José Expósito wrote:
> Hi everyone,
> 
> On Sun, Jul 24, 2022 at 01:48:49PM +0200, José Expósito wrote:
>> On Fri, 22 Jul 2022, Stefan Hansson wrote:
>>> Hi!
>>>
>>> Somewhere between Linux 5.17.6 and 5.18.11 the Huion tablet I have stopped
>>> working properly. In GNOME Control Center it is identified as Huion New 1060
>>> Plus, however that's a different tablet than the one I have. Mine is a Huion
>>> Inspiroy H640, and it uses the hid_uclogic driver.
>>>
>>> With Linux 5.17.6, the tablet works as expected with all the buttons being
>>> detected and the stylus being usable. With 5.18.11, the buttons work fine but
>>> the stylus does not work correctly. The first time I approach the tablet with
>>> the stylus it works properly, i.e., the cursor on my screen moves around and
>>> follows the stylus around the tablet as expected. It continues working like
>>> this until I remove the stylus from the tablet. After I remove it from the
>>> tablet, the cursor never gets controlled by the stylus again. I can see that
>>> the tablet detects the stylus (it has a small indicator light), but the cursor
>>> doesn't move when I approach the tablet again. To clarify, with Linux 5.17.6,
>>> the cursor moves around just fine when I remove and then put it back to the
>>> tablet, just as you would expected.
>>>
>>> It may also be worth noting that it worked fine when I previously used it
>>> around six months ago, although I'm not sure what version of Linux I was using
>>> at that time (whatever Fedora shipped back then). I also tried reproducing it
>>> with yesterday's linux-next and Linux 5.19.0-RC7, and the behaviour was the
>>> same as 5.18.11. I am currently trying to bisect this, but it's not going very
>>> fast as I currently only have access to a dual core laptop from 2014, so
>>> building Linux takes a good while.
>>
>> Thanks a lot for reporting the issue.
>>
>> HUION and other non-Wacom tablets are handled by the UCLogic driver.
>> This driver is present in the kernel but its changes were deployed
>> and tested first in the DIGImend driver:
>> https://github.com/DIGImend/digimend-kernel-drivers
>>
>> A while ago, I started including in the kernel the code present in
>> DIGImend. At this moment, 5.19.0-RC7 and DIGImend have the same code
>> (well, 5.19 has more features, but they don't affect your tablet).
>>
>> I'm telling you this because it might be easier for you to bisect the
>> changes in the DIGImend driver as it builds way faster than the kernel.
>> Let me know if you need help bisecting it and I'll do my best to help
>> you.
>>
>> Is this your device?
>> https://www.huion.com/pen_tablet/Inspiroy/H640P.html

Yes :)

>> It is affordable, so I ordered it. I don't have any HUION devices to
>> debug and this is a good excuse to buy one ;)
>> I'll let you know how it goes once I receive it.
> 
> The tablet arrived today and it is a bank holiday in Spain, so I had
> some time to bisect the bug.
> 
> 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.

Thanks for looking into this! Bisecting has been slow on my end 
unfortunately. I built today's linux-next (20220726) with your proposed 
patch below and my drawing tablet curiously still does not work as 
expected. The stylus works a couple of times, but eventually stops 
working (unlike prior where it always seemed to only work once). Do I 
need both your revert and this diff for it to work properly?

Also, do you know whether the revert be backported to stable 5.18?

> 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.
> 
> 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().
> 
> However, at least the Huion Inspiroy H640, sends a 0x00 byte when the
> tool is removed, making it possible to fix it in the driver [1].
> 
> Unfortunately, the affected code path is used by many tablets and I
> can not test them, so I'd prefer to hear Benjamin's opinion and see if
> this should be fixed in hid-input rather than in the driver before
> sending a fix.
> 
> Best wishes,
> José Expósito
> 
> [1] Diff of a possible fix:
> 
> diff --git a/drivers/hid/hid-uclogic-core.c b/drivers/hid/hid-uclogic-core.c
> index 47a17375c7fc..bdcbbd57d0fc 100644
> --- a/drivers/hid/hid-uclogic-core.c
> +++ b/drivers/hid/hid-uclogic-core.c
> @@ -316,8 +316,11 @@ static int uclogic_raw_event_pen(struct uclogic_drvdata *drvdata,
>          }
>          /* If we need to emulate in-range detection */
>          if (pen->inrange == UCLOGIC_PARAMS_PEN_INRANGE_NONE) {
>                  /* Set in-range bit */
> -               data[1] |= 0x40;
> +               if (data[1])
> +                       data[1] |= 0x40;
> +
>                  /* (Re-)start in-range timeout */
>                  mod_timer(&drvdata->inrange_timer,
>                                  jiffies + msecs_to_jiffies(100));
Regards,
Stefan Hansson

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