Re: hid_multitouch - random non-responsive, multitouch, scrolling and zooming

["Benjamin Tissoires" <benjamin.tissoires@gmail.com>]

On Fri, Oct 10, 2025, at 2:21 PM, Steven Haigh wrote:
> On 7/10/25 20:10, Benjamin Tissoires wrote:
>> On Tue, Oct 7, 2025, at 3:42 AM, Steven Haigh wrote:
>>> I ran `libinput record -o recording.yml /dev/event/input6` and have
>>> attached the compressed output. Annoyingly, it seems like the touchpad
>>> is working fine at the moment - so it may confirm the hardware
>>> information, but not a recording of the problem right now.
>> 
>> Yeah, same on one of the Dell laptops I have here. I know it has the bug, but whenever I try to reproduce it it never shows meaning I was never able to pin point the issue :(
>
> So, "good" news is that I managed to grab a recording today when the 
> touchpad started to play up. When using two-fingers to scroll, I ended 
> up zooming etc.

Unfortunately, this is a recording after the kernel processing, so all I can do is check that we have ghost fingers (and even that is trciky because I'm not sure if what we see are the expected events or not).

>
> I tried to make the recording as short as possible, but still include 
> examples of clicking, scrolling etc.
>
> Attached for reference.
>
> As for which way to approach a fix - I'm happy for you to suggest what 
> path we take - a BPF, kernel patch backport, or something else.

Great, thanks!

>
> You tell me which one gives the most value and is likely to help more 
> people in the long run.

Right now the most valuable would be to test the series at
https://lore.kernel.org/linux-input/20251008-fix-sticky-fingers-v1-0-760f1f26fce3@kernel.org/T/#m0fba507cbd43acd36bef28151ecb90b7077606a4

If this work and you want a quick and dirty fix you can then return to the default kernel, and use the BPF from https://gitlab.freedesktop.org/libevdev/udev-hid-bpf/-/merge_requests/204, the latest version should be compatible with your device, just re-download and install it again.

But definitely a tested-by on the kernel patch would be appreciated :)

Cheers,
Benjamin

>
> -- 
> Steven Haigh
>
> 📧 netwiz@crc.id.au
> 💻 https://crc.id.au
> Attachments:
> * recording.yml.xz