linux-kernel - Re: [PATCH] Input: synaptics-rmi4 - Report slot as inactive when contact is a palm

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Date:   Fri, 17 Mar 2017 10:58:05 +1000
From:   Peter Hutterer <peter.hutterer@...-t.net>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Andrew Duggan <aduggan@...aptics.com>, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Cameron Gutman <aicommander@...il.com>,
        Thorsten Leemhuis <linux@...mhuis.info>,
        Christopher Heiny <cheiny@...aptics.com>,
        Nick Dyer <nick@...anahar.org>
Subject: Re: [PATCH] Input: synaptics-rmi4 - Report slot as inactive when
 contact is a palm

On Thu, Mar 16, 2017 at 05:04:50PM -0700, Dmitry Torokhov wrote:
> On Thu, Mar 16, 2017 at 04:56:31PM -0700, Andrew Duggan wrote:
> > When the firmware identifies a contact as a palm the driver sets the tool
> > type to MT_TOOL_PALM, but sets the slot state as active. Reporting the
> > palm as active results in userspace input libraries considering the palm
> > as a valid contact. Touchpads which previously were using hid-multitouch
> > are now not suppressing palms when switching to the RMI4 driver. This
> > change fixes palm rejection when using the RMI4 driver.
> > 
> > Signed-off-by: Andrew Duggan <aduggan@...aptics.com>
> > Tested-by: Cameron Gutman <aicommander@...il.com>
> > ---
> >  drivers/input/rmi4/rmi_2d_sensor.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/input/rmi4/rmi_2d_sensor.c b/drivers/input/rmi4/rmi_2d_sensor.c
> > index 8bb866c..8d1f295 100644
> > --- a/drivers/input/rmi4/rmi_2d_sensor.c
> > +++ b/drivers/input/rmi4/rmi_2d_sensor.c
> > @@ -80,7 +80,8 @@ void rmi_2d_sensor_abs_report(struct rmi_2d_sensor *sensor,
> >  		input_mt_slot(input, slot);
> >  
> >  	input_mt_report_slot_state(input, obj->mt_tool,
> > -				   obj->type != RMI_2D_OBJECT_NONE);
> > +				   (obj->type != RMI_2D_OBJECT_NONE)
> > +				   && (obj->type != RMI_2D_OBJECT_PALM));
> >  
> >  	if (obj->type != RMI_2D_OBJECT_NONE) {
> >  		obj->x = sensor->tracking_pos[slot].x;
> 
> If we are relying on hardware to do palm rejection, then we should not
> be reporting the rest of the events for palm either (i.e. the condition
> in the if statement above should also be updated).
> 
> But I do not understand why userspace doe snot do the right thing? Yes,
> the slot is active, but reported contact type is MT_TOOL_PALM, so it
> knows what it deals with.

oops, filed: https://bugs.freedesktop.org/show_bug.cgi?id=100243
until RMI4 we had no drivers setting that tool type and we still don't have
rull RMI4 in the released kernels, so it was a simple oversight.

mind you, that only applies for libinput, not hedging my bets on the
synaptics driver here.

Cheers,
   Peter