Hi Pali,

On Mon, Jun 30, 2025 at 5:51 AM Pali Rohár [off-list ref] wrote:

On Monday 30 June 2025 05:42:45 Mark Pearson wrote:

quoted

Hi Dmitry,

On Fri, Jun 27, 2025, at 2:14 PM, Dmitry Torokhov wrote:

quoted

Hi Vishnu,

On Fri, Jun 20, 2025 at 09:42:08AM +0900, Vishnu Sankar wrote:

quoted

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.

Do you have recommendations on how to handle this case then?

This is a Thinkpad specific feature and hence the logic for involving thinkpad_acpi. There are Thinkpad hotkeys that will enable/disable the trackpoint doubletap feature - so there is some linkage. I'm not sure how to avoid that.

Is there a cleaner way to do this that you'd recommend we look at using? It's a feature (albeit a minor one) on the laptops that we'd like to make available to Linux users.

Mark

Hello, I do not know what is doubletap and patch description does not
explain it. But for laptop / mouse interface, I'm just giving example
that dell-laptop.c for some particular laptop can enable/disable
touchpad led and uses PS/2 interface for it. See touchpad_led_init().
I do not know if it is ideal or preferred solution, just writing to let
you know, maybe it can be useful.

FYR, please find the previous commits regarding Doubletap support for
Trackpoint below:

https://github.com/torvalds/linux/commit/a9b0b1ee59a79d0d3853cba9a4b7376ea15be21f
https://github.com/torvalds/linux/commit/fd1e3344d13f1eedb862804dd1d2d5e184cf8eae

Sorry if details are missing in the commit. I can add those.

To be more precise, Thinkpad_acpi handles hotkeys, including Fn+G for doubletap.
To make that work, we need an integration point.

Thinkpad_acpi.c
Fn + G Hotkey - Enable/Disable the Trackpoint Double Tap.
DoubleTap on Trackpoint - Generates a DoubleTap ACPI Event

trackpoint.c
Enable/Disable the Doubletap functionality

To enable (this is decided based on Fn + G toggle key) the Trackpoint
Doubletap, we need to write to the Trackpoint extended register.
Therefore, the event to enable or disable the double tap will be
handled inside Thinkpad_acpi, but the actual write to the register is
in trackpoint.c.

I will check dell-laptop.c to understand the LED handling.

-- 

Regards,

      Vishnu Sankar
     +817015150407 (Japan)