linux-kernel - [PATCH 0/2] HID: multitouch: fix sticky-fingers quirks

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Message-Id: <20251008-fix-sticky-fingers-v1-0-760f1f26fce3@kernel.org>
Date: Wed, 08 Oct 2025 16:06:57 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Jiri Kosina <jikos@...nel.org>, Shuah Khan <shuah@...nel.org>
Cc: Peter Hutterer <peter.hutterer@...-t.net>, linux-input@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Benjamin Tissoires <bentiss@...nel.org>, stable@...r.kernel.org
Subject: [PATCH 0/2] HID: multitouch: fix sticky-fingers quirks

According to Peter, we've had for a very long time an issue on some
mutltiouch touchpads where the fingers were stuck in a scrolling mode,
or 3 fingers gesture mode. I was unable to debug it because it was
rather hard to reproduce.

Recently, some people raised the issue again on libinput, and this time
added a recording of the actual bug.

It turns out that the sticky finger quirk that was introduced back in
2017 was only checking the last report, and that those missing releases
also happen when moving from 3 to 1 finger (only 1 is released instead
of 2).

This solution seems to me to be the most sensible, because we could also
add the NSMU quirk to win8 multitouch touchpads, but this would involve
a lot more computations at each report for rather annoying corner cases.

Link: https://gitlab.freedesktop.org/libinput/libinput/-/issues/1194
Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>
---
Benjamin Tissoires (2):
      HID: multitouch: fix sticky fingers
      selftests/hid: add tests for missing release on the Dell Synaptics

 drivers/hid/hid-multitouch.c                       | 27 ++++++-----
 .../testing/selftests/hid/tests/test_multitouch.py | 55 ++++++++++++++++++++++
 2 files changed, 69 insertions(+), 13 deletions(-)
---
base-commit: 54ba6d9b1393a0061600c0e49c8ebef65d60a8b2
change-id: 20250926-fix-sticky-fingers-8ae88436ae82

Best regards,
-- 
Benjamin Tissoires <bentiss@...nel.org>