linux-kernel - Re: [PATCH] Input - synaptics: use dmax in input_mt_assign

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Date:	Tue, 3 Feb 2015 15:40:59 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:	Henrik Rydberg <rydberg@...math.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Peter Hutterer <peter.hutterer@...-t.net>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input - synaptics: use dmax in input_mt_assign_slots

On Mon, Feb 02, 2015 at 02:15:58PM -0500, Benjamin Tissoires wrote:
> When tapping a clickpad with two fingers, there is a chance that the
> sensor sees first only one finger, and at the next scan only the
> second one.
> In this case, the sensors says that there has been only one finger
> on the clickpad, which moved really fast between two scans.
> 
> We can try to counter this by adding a limit to what an actual finger
> can move between 2 scans.
> A distance of 1cm between two scans for one finger seems reasonable.
> 
> However, this is not really accurate because the resolution in X and in Y
> differs. But heh, that's how the in-kernel tracking works right now, and
> its job is quite good, even with this approximation.
> 
> This parameter solves most of the jumps observed, not all of them however.
> But this is a hardware defect, and we might not be able to get something
> better without much heavier computations.
> 
> Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=76722
> 
> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

Applied, thank you.

> ---
>  drivers/input/mouse/synaptics.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/input/mouse/synaptics.c b/drivers/input/mouse/synaptics.c
> index a3692e3..bee0387 100644
> --- a/drivers/input/mouse/synaptics.c
> +++ b/drivers/input/mouse/synaptics.c
> @@ -67,6 +67,9 @@
>  #define X_MAX_POSITIVE 8176
>  #define Y_MAX_POSITIVE 8176
>  
> +/* maximum ABS_MT_POSITION displacement (in mm) */
> +#define DMAX 10
> +
>  /*****************************************************************************
>   *	Stuff we need even when we do not want native Synaptics support
>   ****************************************************************************/
> @@ -809,7 +812,7 @@ static void synaptics_report_mt_data(struct psmouse *psmouse,
>  		pos[i].y = synaptics_invert_y(hw[i]->y);
>  	}
>  
> -	input_mt_assign_slots(dev, slot, pos, nsemi, 0);
> +	input_mt_assign_slots(dev, slot, pos, nsemi, DMAX * priv->x_res);
>  
>  	for (i = 0; i < nsemi; i++) {
>  		input_mt_slot(dev, slot[i]);
> -- 
> 2.1.0
> 

-- 
Dmitry
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