From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D71D2DB7B0; Mon, 12 Jan 2026 14:58:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768229932; cv=none; b=t1zWarNgqtIoYQZ9Gm4Nn7t0wTtRvyYiZBK8fPbG3RyrOQ22FxPeQ46kMIGj7sw8+PrmZ86mjcKqzFfUPVAnlo4ZNWWsy6YXSWzqO5Myxw28W3bym7SzSAEdsKmK96SJLmtl8GXsA4ixNfsoVA3awVrabJttc+10YNwI8hHaTG4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768229932; c=relaxed/simple; bh=tmveYG3MYrcIOx8fgo5jQ0uyIL+4rJEKzFawxuWWjgY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=iXaARuNwsRMGS00IUrVC615xtp9WrsRN0w/lGDZ7CmHIIs+y06jG+SKbGd2KltHBH4W7vy3T1EFVl1Fj495P4dOFb40YH9ZO/DJEmw4o0M5IYUH/ceiS6dshbdyFdvYMHXPEaRAZp4JFK6XiM1te4Qg024dxkZXaW6Gez+kwd6Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lckl+44M; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lckl+44M" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 231CFC19422; Mon, 12 Jan 2026 14:58:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768229931; bh=tmveYG3MYrcIOx8fgo5jQ0uyIL+4rJEKzFawxuWWjgY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lckl+44Mbe8FW04Gi084rW/NR2OCxWbFu3Iw4YjwFx/0XA+Cnc+HMPDGrn2XZZ/jB b3jp6VFVcGGTtJ8590pm8xoAHf8fH/j+1RuXYrn8S4H21dBxFbW9qPYyE8UmvihOVT e5ER4SPUC42d4RBMyNht1B9CE+PLy1rIwEJtQUwupP7dQXe+z0/6WEoRkic6s0jYU6 4/vKhXxWzrF+oXMqTQtktHGYJH/nVDrIyMws5d0UQ1e8RCLl383rS5YaGR/jzvgtju zG1z2ZpS/TXpzx0YjsAUFt47z0rYtfPUQkj+fzTjggYJWA3lkKcux/Tr5bsBwh581B xmOivLHrlF+eA== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: DaytonCL , Benjamin Tissoires , Benjamin Tissoires , Sasha Levin , jikos@kernel.org, linux-input@vger.kernel.org Subject: [PATCH AUTOSEL 6.18-5.10] HID: multitouch: add MT_QUIRK_STICKY_FINGERS to MT_CLS_VTL Date: Mon, 12 Jan 2026 09:58:09 -0500 Message-ID: <20260112145840.724774-8-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260112145840.724774-1-sashal@kernel.org> References: <20260112145840.724774-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.18.5 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: DaytonCL [ Upstream commit ff3f234ff1dcd6d626a989151db067a1b7f0f215 ] Some VTL-class touchpads (e.g. TOPS0102:00 35CC:0104) intermittently fail to release a finger contact. A previous slot remains logically active, accompanied by stale BTN_TOOL_DOUBLETAP state, causing gestures to stay latched and resulting in stuck two-finger scrolling and false right-clicks. Apply MT_QUIRK_STICKY_FINGERS to handle the unreleased contact correctly. Link: https://gitlab.freedesktop.org/libinput/libinput/-/issues/1225 Suggested-by: Benjamin Tissoires Tested-by: DaytonCL Signed-off-by: DaytonCL Signed-off-by: Benjamin Tissoires Signed-off-by: Sasha Levin --- LLM Generated explanations, may be completely bogus: ## Analysis of HID Multitouch Quirk Addition ### 1. COMMIT MESSAGE ANALYSIS The commit clearly describes a **real user-visible bug**: - VTL-class touchpads (specifically TOPS0102:00 35CC:0104) intermittently fail to release finger contacts - This causes gestures to stay latched - stuck two-finger scrolling and false right-clicks - Links to a libinput bug report: https://gitlab.freedesktop.org/libinput/libinput/-/issues/1225 - Has `Tested-by:` from the reporter and `Suggested-by:` from Benjamin Tissoires (HID maintainer) - Signed off by the maintainer (Benjamin Tissoires) ### 2. CODE CHANGE ANALYSIS The change is **extremely minimal** - adding one line: ```c MT_QUIRK_STICKY_FINGERS | ``` to the existing `MT_CLS_VTL` class definition. This enables an already- existing quirk flag (`MT_QUIRK_STICKY_FINGERS`) for VTL-class devices. The quirk mechanism handles cases where a touchpad firmware fails to properly report when a finger has been lifted. Without it, the system thinks the finger is still touching, causing "sticky" gestures. The quirk infrastructure already exists and is well-tested - this commit just enables it for another device class. ### 3. CLASSIFICATION This falls squarely into the **QUIRKS and WORKAROUNDS exception category**: - Hardware-specific quirk for buggy/non-compliant devices - The quirk code already exists in mainline - only enabling it for VTL class - Fixes real-world hardware behavior issues This is NOT: - A new feature or API - A new driver - Code refactoring ### 4. SCOPE AND RISK ASSESSMENT | Factor | Assessment | |--------|------------| | Lines changed | 1 | | Files touched | 1 | | Complexity | Trivially low | | Subsystem | HID multitouch (mature, stable) | | Risk | Very low | The worst case scenario: if the quirk somehow caused issues on a specific VTL device, it would only affect that device class. But the current behavior is already broken for affected users, so this is a clear improvement. ### 5. USER IMPACT - **Affected users**: Anyone with VTL-class touchpads - **Symptoms**: Stuck two-finger scrolling, false right-clicks - these are highly disruptive daily-use issues - **Severity**: Medium-high for affected users (makes touchpad unreliable) - **Evidence of real impact**: Linked bug report from libinput tracker ### 6. STABILITY INDICATORS - `Tested-by:` tag from the reporter who experienced the issue - Suggested and signed off by HID subsystem maintainer - The `MT_QUIRK_STICKY_FINGERS` quirk has existed since ~Linux 3.15 - The `MT_CLS_VTL` class has existed since ~Linux 4.13 - Well-established quirk pattern used by many other device classes (FLATFROG, LG, ASUS, etc.) ### 7. DEPENDENCY CHECK - **No dependencies** on other commits - Both the quirk flag and VTL class exist in all recent stable trees - Should apply cleanly without modification ### STABLE KERNEL RULES ASSESSMENT | Criterion | Met? | |-----------|------| | Obviously correct and tested | ✅ Yes - trivial change, has Tested-by | | Fixes a real bug | ✅ Yes - documented hardware issue with bug report | | Important issue | ✅ Yes - stuck gestures/false clicks affect daily use | | Small and contained | ✅ Yes - 1 line in 1 file | | No new features | ✅ Yes - uses existing quirk mechanism | | Applies cleanly | ✅ Yes - no dependencies | ### CONCLUSION This is an **ideal stable backport candidate**: 1. **Minimal risk**: Single-line addition of an existing, well-tested quirk flag 2. **Real user benefit**: Fixes stuck gestures and false clicks on VTL touchpads 3. **Proper testing**: Has Tested-by tag and maintainer approval 4. **Falls under hardware quirk exception**: Hardware quirks/workarounds are explicitly allowed in stable even though they add code 5. **Self-contained**: No dependencies, applies cleanly to stable trees The fix is small, surgical, obviously correct, and addresses a real user-visible hardware issue. This is exactly the type of hardware quirk addition that stable trees should accept. **YES** drivers/hid/hid-multitouch.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c index 179dc316b4b51..a0c1ad5acb670 100644 --- a/drivers/hid/hid-multitouch.c +++ b/drivers/hid/hid-multitouch.c @@ -393,6 +393,7 @@ static const struct mt_class mt_classes[] = { { .name = MT_CLS_VTL, .quirks = MT_QUIRK_ALWAYS_VALID | MT_QUIRK_CONTACT_CNT_ACCURATE | + MT_QUIRK_STICKY_FINGERS | MT_QUIRK_FORCE_GET_FEATURE, }, { .name = MT_CLS_GOOGLE, -- 2.51.0