linux-kernel - Re: [PATCH] x86/Mouse: thinkpad_acpi/Trackpoint: Trackpoint Doubletap handling

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Message-ID: <5jgix7znkfrkopmwnmwkxx35dj2ovvdpplhadcozbpejm32o2j@yxnbfvmealtl>
Date: Thu, 26 Jun 2025 22:14:25 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Vishnu Sankar <vishnuocv@...il.com>
Cc: pali@...nel.org, hmh@....eng.br, hansg@...nel.org, 
	ilpo.jarvinen@...ux.intel.com, tglx@...utronix.de, mingo@...nel.org, jon_xie@...art.com, 
	jay_lee@...art.com, zhoubinbin@...ngson.cn, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org, ibm-acpi-devel@...ts.sourceforge.net, 
	platform-driver-x86@...r.kernel.org, vsankar@...ovo.com, Mark Pearson <mpearson-lenovo@...ebb.ca>
Subject: Re: [PATCH] x86/Mouse: thinkpad_acpi/Trackpoint: Trackpoint
 Doubletap handling

Hi Vishnu,

On Fri, Jun 20, 2025 at 09:42:08AM +0900, Vishnu Sankar wrote:
> Newer ThinkPads have a doubletap feature that needs to be turned
> ON/OFF via the trackpoint registers.
> Systems released from 2023 have doubletap disabled by default and
> need the feature enabling to be useful.
> 
> This patch introduces support for exposing and controlling the
> trackpoint doubletap feature via a sysfs attribute.
> /sys/devices/platform/thinkpad_acpi/tp_doubletap
> This can be toggled by an "enable" or a "disable".
> 
> With this implemented we can remove the masking of events, and rely on
> HW control instead, when the feature is disabled.
> 
> Note - Early Thinkpads (pre 2015) used the same register for hysteris
> control, Check the FW IDs to make sure these are not affected.
> 
> trackpoint.h is moved to linux/input/.

No, please keep everything private to trackpoint.c and do not involve
thinkpad_acpi driver. By doing so you are introducing unwanted
dependencies (for both module loading, driver initialization, and
operation) and unsafe use of non-owned pointers/dangling pointers, etc.

Thanks.

-- 
Dmitry