Re: [PATCH] Input: synaptics - disable InterTouch on ThinkPad T440p (board id 2722)

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Hi Raphaël,

On Tue, Jun 16, 2026 at 01:11:36PM -0400, Raphaël Larocque wrote:
> The Lenovo ThinkPad T440p (PNP ID LEN0036, board id 2722) has a
> Synaptics touchpad whose SMBus companion is not ready at boot and
> takes roughly 200 seconds to appear. During this window the touchpad
> and TrackPoint are completely unresponsive on approximately 50% of
> boots, making the machine unusable until the companion finally
> registers.
> 
> The device is in the topbuttonpad_pnp_ids[] SMBus allowlist, so the
> kernel attempts to use SMBus/RMI4 mode by default. When the companion
> is not ready, psmouse_smbus_init() leaves breadcrumbs and returns
> -EAGAIN, the PS/2 fallback path is taken, but the device does not
> function properly until the companion appears and RMI4 takes over.
> 
> Disable SMBus InterTouch for board id 2722 so the touchpad and
> TrackPoint work immediately via PS/2 from boot. Users can still force
> SMBus with psmouse.synaptics_intertouch=1 if needed.

Is this board ID unique to T440p? Or it may be used in other devices as
well?

I also wonder, if you try loading psmouse later in the initialization
cycle, after SMBus has been loaded, if that would help it detect the
touchpad quicker? Is there anything interested in DTS regarding device
interconnect/hierarchy that we might be missing?

> 
> Tested-by: Raphaël Larocque <rlarocque@disroot.org>
> Signed-off-by: Raphaël Larocque <rlarocque@disroot.org>
> ---
>  drivers/input/mouse/synaptics.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> index c70502e24031..8f38bc498798 100644
> --- a/drivers/input/mouse/synaptics.c
> +++ b/drivers/input/mouse/synaptics.c
> @@ -1837,6 +1837,14 @@ static int synaptics_setup_intertouch(struct psmouse *psmouse,
>  
>  			return -ENXIO;
>  		}
> +
> +		/* Disable intertouch on known-broken board revisions */
> +		if (info->board_id == 2722) {
> +			psmouse_info(psmouse,
> +				     "Disabling intertouch for board id %d\n",
> +				     info->board_id);
> +			return -ENXIO;
> +		}
>  	}
>  
>  	psmouse_info(psmouse, "Trying to set up SMBus access\n");

Thanks.

-- 
Dmitry