Re: [PATCH v7 1/3] input: trackpoint - Enable doubletap by default on capable devices

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Mon, 9 Feb 2026, Vishnu Sankar wrote:

> Enable doubletap functionality by default on TrackPoint devices that
> support it. The feature is detected using firmware ID pattern matching
> (PNP: LEN03xxx) with a deny list of incompatible devices.
> 
> This provides immediate doubletap functionality without requiring
> userspace configuration. The hardware is enabled during device
> detection, while event filtering continues to be handled by the
> thinkpad_acpi driver as before.
> 
> Signed-off-by: Vishnu Sankar <vishnuocv@gmail.com>
> Suggested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
> Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> ---
> Changes in v7:
> - Removed unwanted comments
> - Removed psmouse_info ()
> 
> Changes in v6:
> - No Changes
> 
> Changes in v5:
> - Renamed function to trackpoint_is_dt_capable()
> - Simplified string comparison without sscanf()
> - Removed wrapper function as suggested
> - Fixed missing period in comment
> 
> Changes in v4:
> - Simplified approach: removed all sysfs attributes and user interface
> - Enable doubletap by default during device detection
> - Removed global variables and complex attribute infrastructure
> - Uses minimal firmware ID detection with deny list
> - Follows KISS principle as suggested by reviewers
> 
> Changes in v3:
> - No changes
> 
> Changes in v2:
> - Improve commit messages
> - Sysfs attributes moved to trackpoint.c
> - Removed unnecessary comments
> - Removed unnecessary debug messages
> - Using strstarts() instead of strcmp()
> - is_trackpoint_dt_capable() modified
> - Removed _BIT suffix and used BIT() define
> - Reverse the trackpoint_doubletap_status() logic to return error first
> - Removed export functions as a result of the design change
> - Changed trackpoint_dev->psmouse to parent_psmouse
> - The path of trackpoint.h is not changed
> ---
>  drivers/input/mouse/trackpoint.c | 45 ++++++++++++++++++++++++++++++++
>  drivers/input/mouse/trackpoint.h |  5 ++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/drivers/input/mouse/trackpoint.c b/drivers/input/mouse/trackpoint.c
> index 5f6643b69a2c..e12d76350252 100644
> --- a/drivers/input/mouse/trackpoint.c
> +++ b/drivers/input/mouse/trackpoint.c
> @@ -393,6 +393,45 @@ static int trackpoint_reconnect(struct psmouse *psmouse)
>  	return 0;
>  }
>  
> +/* List of known incapable device PNP IDs */
> +static const char * const dt_incompatible_devices[] = {
> +	"LEN0304",
> +	"LEN0306",
> +	"LEN0317",
> +	"LEN031A",
> +	"LEN031B",
> +	"LEN031C",
> +	"LEN031D",
> +};
> +
> +/*
> + * Checks if it's a doubletap capable device.
> + * The PNP ID format is "PNP: LEN030d PNP0f13".
> + */
> +static bool trackpoint_is_dt_capable(const char *pnp_id)
> +{
> +	size_t i;
> +
> +	if (!pnp_id)
> +		return false;
> +
> +	/* Must start with "PNP: LEN03" */
> +	if (!strstarts(pnp_id, "PNP: LEN03"))

Missing include.

> +		return false;
> +
> +	/* Ensure enough length before comparing */
> +	if (strlen(pnp_id) < 12)
> +		return false;
> +
> +	/* Check deny-list */
> +	for (i = 0; i < ARRAY_SIZE(dt_incompatible_devices); i++) {

Missing include for ARRAY_SIZE().

> +		if (!strncmp(pnp_id + 5,
> +			     dt_incompatible_devices[i], 7))

Fits to one line.

> +			return false;
> +	}
> +	return true;
> +}
> +
>  int trackpoint_detect(struct psmouse *psmouse, bool set_properties)
>  {
>  	struct ps2dev *ps2dev = &psmouse->ps2dev;
> @@ -470,6 +509,12 @@ int trackpoint_detect(struct psmouse *psmouse, bool set_properties)
>  		     psmouse->vendor, firmware_id,
>  		     (button_info & 0xf0) >> 4, button_info & 0x0f);
>  
> +	if (trackpoint_is_dt_capable(ps2dev->serio->firmware_id)) {
> +		error = trackpoint_write(ps2dev, TP_DOUBLETAP, TP_DOUBLETAP_ENABLE);
> +		if (error)
> +			psmouse_warn(psmouse, "Failed to enable doubletap: %d\n", error);
> +	}
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/input/mouse/trackpoint.h b/drivers/input/mouse/trackpoint.h
> index eb5412904fe0..3e03cdb39449 100644
> --- a/drivers/input/mouse/trackpoint.h
> +++ b/drivers/input/mouse/trackpoint.h
> @@ -69,6 +69,8 @@
>  					/* (how hard it is to drag */
>  					/* with Z-axis pressed) */
>  
> +#define TP_DOUBLETAP		0x58	/* TrackPoint doubletap register */
> +
>  #define TP_MINDRAG		0x59	/* Minimum amount of force needed */
>  					/* to trigger dragging */
>  
> @@ -110,6 +112,9 @@
>  					   external device will be forced to 1 */
>  #define TP_MASK_EXT_TAG			0x04
>  
> +/* Doubletap register values */
> +#define TP_DOUBLETAP_ENABLE	0xFF	/* Enable value */
> +#define TP_DOUBLETAP_DISABLE	0xFE	/* Disable value */
>  
>  /* Power on Self Test Results */
>  #define TP_POR_SUCCESS		0x3B
> 

-- 
 i.