Date:   Sat, 18 Mar 2023 22:54:48 +0700
From:   msizanoen <msizanoen@...labs.xyz>
To:     Linux regressions mailing list <regressions@...ts.linux.dev>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        barry@...sagefor.me.uk
Subject: Re: [regression] focaltech touchpad driver misbehaves due to "kbuild:
 treat char as always unsigned"

Seems like the AlpsPS/2 driver also got hit with the exact same issue: 
https://gitlab.freedesktop.org/libinput/libinput/-/issues/871#note_1829296

I submitted a patch for that: 
https://lore.kernel.org/linux-input/20230318144206.14309-1-msizanoen@qtmlabs.xyz/

On 3/18/23 19:08, Linux regression tracking (Thorsten Leemhuis) wrote:
> Hi, Thorsten here, the Linux kernel's regression tracker.
>
> I noticed a regression report in bugzilla.kernel.org. Jason, apparently
> it's caused by a change of yours (3bc753c06dd0 ("kbuild: treat char as
> always unsigned")), which apparently caused a problem in
> drivers/input/mouse/focaltech.c to surface. Someone provided a patch
> already to fix it here: https://bugs.archlinux.org/task/77733?getfile=22498
>
> Back to the bug. As many (most?) kernel developer don't keep an eye on
> bugzilla, I decided to forward it by mail. Quoting from
> https://bugzilla.kernel.org/show_bug.cgi?id=217211 :
>
>> Barry 2023-03-17 13:51:10 UTC
>>
>> Created attachment 303972 [details] Kernel bisect result
>>
>> O/S: Archlinux.
>>
>> On any kernel release from 6.2 onwards I have found that the touchpad
>> doesn't respond to multi finger touches properly. The pad works fine for
>> single finger movement and single finger tap to click. If I click and
>> hold the pad button and then use another finger to move such as for text
>> selection, drag and drop, moving or resizing a window etc. Or if I try
>> to use 2 finger scrolling then the mouse pointer jumps to the top or
>> right or into the top right of the screen. All of this functionality
>> worked as expected up to kernel 6.1.19.
>>
>> I have bisected the kernel and got the attached result.
>>
>>
>> I have checked out kernel 6.2.6 and removed the `-funsigned-char` from
>> the Makefile. Kernel 6.2.6 built with the modified Makefile restores the
>> correct functionality. I believe the touchpad uses the psmouse driver so
>> maybe the new build option has broken this driver.>
>> I have bisected the kernel and got the attached result.
>>
>>
>> I have checked out kernel 6.2.6 and removed the `-funsigned-char`
>> from the Makefile. Kernel 6.2.6 built with the modified Makefile
>> restores the correct functionality. I believe the touchpad uses the
>> psmouse driver so maybe the new build option has broken this driver.
>>
>> [...]
>>
>> barry@...sagefor.me.uk 2023-03-18 11:49:27 UTC
>>
>> Hi. If you check this link which is my report of the same bug on the
>> arch bug tracker there is a patch attached which fixes the issue.
>>
>> https://bugs.archlinux.org/task/77733#comment216336
> See the ticket for more details.
>
>
> [TLDR for the rest of this mail: I'm adding this report to the list of
> tracked Linux kernel regressions; the text you find below is based on a
> few templates paragraphs you might have encountered already in similar
> form.]
>
> BTW, let me use this mail to also add the report to the list of tracked
> regressions to ensure it's doesn't fall through the cracks:
>
> #regzbot introduced: 3bc753c06dd0
> https://bugzilla.kernel.org/show_bug.cgi?id=217211
> #regzbot title: kbuild/input: focaltech touchpad driver misbehaves due
> to a checke how to treat char
> #regzbot ignore-activity
>
> This isn't a regression? This issue or a fix for it are already
> discussed somewhere else? It was fixed already? You want to clarify when
> the regression started to happen? Or point out I got the title or
> something else totally wrong? Then just reply and tell me -- ideally
> while also telling regzbot about it, as explained by the page listed in
> the footer of this mail.
>
> Developers: When fixing the issue, remember to add 'Link:' tags pointing
> to the report (e.g. the buzgzilla ticket and maybe this mail as well, if
> this thread sees some discussion). See page linked in footer for details.
>
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> --
> Everything you wanna know about Linux kernel regression tracking:
> https://linux-regtracking.leemhuis.info/about/#tldr
> If I did something stupid, please tell me, as explained on that page.
>

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