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

[Andrew Duggan]

On 03/16/2017 05:04 PM, 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@xxxxxxxxxxxxx>
> > Tested-by: Cameron Gutman <aicommander@xxxxxxxxx>
> > ---
> >   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.
>
> Thanks.
My intent is to notify userspace that there is a palm present. But, if 
userspace does not have code which explicitly handles the MT_TOOL_PALM 
type it won't be considered a finger. I think it is only recently that 
drivers have started reporting MT_TOOL_PALM to userspace so I'm not sure 
if libraries like libinput make use of it yet.

Starting with v4.11 some touchpads will be switching from hid-multitouch 
to the RMI4 driver and reporting palms as active results in unsuppressed 
palms. I want to avoid users from upgrading and experiencing a 
degradation in usability. In which case I can update the if statement 
and resubmit. This is basically how hid-multitouch is handling it. Maybe 
in the future we can add a parameter to enable reporting palms to userspace.

Andrew