Bug#1114557: linux-image-6.12.43+deb13-amd64: Jieli touchscreen and stylus no longer supported

[Salvatore Bonaccorso <carnil@debian.org>]

Control: tags -1 + moreinfo

Hi Staffan,

On Sat, Sep 06, 2025 at 04:36:55PM +0200, Staffan Melin wrote:
> Package: src:linux
> Version: 6.12.43-1
> Severity: important
> X-Debbugs-Cc: staffan.melin@oscillator.se
> 
> Dear Maintainer,
> 
> *** Reporter, please consider answering these questions, where appropriate ***
> 
>    * What led up to the situation? I installed a clean Debian 13 Stable/Trixie and the touchscreen on my GPD DUO worked. After doing a sudo apt upgrade the kernel was upgraded from 6.12.38 to 6.12.43 and the touchscreen stopped working. The touchscreen not working is on the upper screen and is of make Jieli.
>    * What exactly did you do (or not do) that was effective (or
>      ineffective)? Booting again with kernel 6.12.38 made the touchscreen work again.
>    * What was the outcome of this action? The newer kernel does not support the Jieli touchscreen.
>    * What outcome did you expect instead? That the touchscreen continued working.

Thanks for reorting the issue. I have two questions:

Can you please test the kernel from unstable and see if the problem
persists there was well? If so this might indicate a upstream
regression still present in mainline.

Next, as this is a reegression in 6.12.38 to 6.12.43, can you bisect
the changes? That would involve compiling and testing a few kernels:

    git clone --single-branch -b linux-6.12.y https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
    cd linux-stable
    git checkout v6.12.38
    cp /boot/config-$(uname -r) .config
    yes '' | make localmodconfig
    make savedefconfig
    mv defconfig arch/x86/configs/my_defconfig

    # test 6.12.38 to ensure this is "good"
    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install the resulting .deb package and confirm it successfully boots / problem does not exist

    # test 6.12.43 to ensure this is "bad"
    git checkout v6.12.43
    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install the resulting .deb package and confirm it fails to boot / problem exists

With that confirmed, the bisection can start:

    git bisect start
    git bisect good v6.12.38
    git bisect bad v6.12.43

In each bisection step git checks out a state between the oldest
known-bad and the newest known-good commit. In each step test using:

    make my_defconfig
    make -j $(nproc) bindeb-pkg
    ... install, try to boot / verify if problem exists

and if the problem is hit run:

    git bisect bad

and if the problem doesn't trigger run:

    git bisect good

. Please pay attention to always select the just built kernel for
booting, it won't always be the default kernel picked up by grub.

Iterate until git announces to have identified the first bad commit.

Then provide the output of

    git bisect log

In the course of the bisection you might have to uninstall previous
kernels again to not exhaust the disk space in /boot. Also in the end
uninstall all self-built kernels again.

Can you report back please?

Regards,
Salvatore