Re: [PATCH] Input: mms114: don't report 0 pressure while still tracking contact(s)

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

Hi Denis,

On Sat, Jun 06, 2020 at 05:50:17AM +0200, Denis 'GNUtoo' Carikli wrote:
> In the middle of a sliding gesture, we manage to have events
> that look like that:
>     Event: time 1571859641.595517, -------------- SYN_REPORT ------------
>     Event: time 1571859641.606593, type 3 (EV_ABS), code 54 (ABS_MT_POSITION_Y), value 1193
>     Event: time 1571859641.606593, type 3 (EV_ABS), code 48 (ABS_MT_TOUCH_MAJOR), value 21
>     Event: time 1571859641.606593, type 3 (EV_ABS), code 58 (ABS_MT_PRESSURE), value 0
>     Event: time 1571859641.606593, type 3 (EV_ABS), code 1 (ABS_Y), value 1193
>     Event: time 1571859641.606593, type 3 (EV_ABS), code 24 (ABS_PRESSURE), value 0
>     Event: time 1571859641.606593, -------------- SYN_REPORT ------------
> 
> In such cases, we still have a valid ABS_MT_TRACKING_ID along
> with an ABS_MT_TOUCH_MAJOR that is > 0, which both indicates
> that the sliding is still in progress.
> 
> However in Documentation/input/multi-touch-protocol.rst, we
> have:
>     ABS_MT_PRESSURE
>         The pressure, in arbitrary units, on the contact
>         area. May be used instead of TOUCH and WIDTH for
>         pressure-based devices or any device with a spatial
>         signal intensity distribution.
> 
> Because of that userspace may consider an ABS_MT_PRESSURE
> of 0 as an indication that the sliding stopped. This has
> side effects such as making it difficult to unlock the
> screen under Android.
> 
> This fix was tested on the following devices:
> - GT-I9300 with a glass screen protection
> - GT-I9300 without any screen protection
> - GT-N7105 with a glass screen protection
> 
> Reported-by: Javi Ferrer <javi.f.o@gmail.com>
> Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>
> ---
>  drivers/input/touchscreen/mms114.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/input/touchscreen/mms114.c b/drivers/input/touchscreen/mms114.c
> index 2ef1adaed9af..adc18cd9a437 100644
> --- a/drivers/input/touchscreen/mms114.c
> +++ b/drivers/input/touchscreen/mms114.c
> @@ -183,7 +183,10 @@ static void mms114_process_mt(struct mms114_data *data, struct mms114_touch *tou
>  	if (touch->pressed) {
>  		touchscreen_report_pos(input_dev, &data->props, x, y, true);
>  		input_report_abs(input_dev, ABS_MT_TOUCH_MAJOR, touch->width);
> -		input_report_abs(input_dev, ABS_MT_PRESSURE, touch->strength);
> +		if (touch->strength) {
> +			input_report_abs(input_dev, ABS_MT_PRESSURE,
> +					 touch->strength);

So this will result in userspace believing that pressure is unchanged
from the previous packet. I wonder if we should report

		input_report_abs(input_dev, ABS_MT_PRESSURE,
				 max(touch->strength, 1));

instead.

Could you please post longer sequence from evtest leading to the packet
with 0 pressure?

Thanks.

-- 
Dmitry