Support for additional properties in touchscreen.h

Support for additional properties in touchscreen.h

[Gregor Riepl]

Hi,

I was discussing jitter problems with a Silead touchscreen user today.
This is a general issue that should be solved on the hardware or firmware
level, but as we don't have a way to modify either for Silead controllers, I
was thinking that there might be a way to apply interpolation in the driver.

input_set_abs_params has fuzz and flat parameters, perhaps these can be used
for that purpose? Is there a better way to do interpolation?

Would it make sense to add corresponding jitter_x and jitter_y parameters to
include/linux/input/touchscreen.h ?

Regards,
Greg

Re: Support for additional properties in touchscreen.h

[Dmitry Torokhov]

Hi Gregor,

On Sat, Nov 11, 2017 at 6:34 AM, Gregor Riepl <onitake@gmail.com> wrote:
> Hi,
>
> I was discussing jitter problems with a Silead touchscreen user today.
> This is a general issue that should be solved on the hardware or firmware
> level, but as we don't have a way to modify either for Silead controllers, I
> was thinking that there might be a way to apply interpolation in the driver.
>
> input_set_abs_params has fuzz and flat parameters, perhaps these can be used
> for that purpose? Is there a better way to do interpolation?
>
> Would it make sense to add corresponding jitter_x and jitter_y parameters to
> include/linux/input/touchscreen.h ?

The fuzz (smoothing the output coordinates) is done in input core and
the touchscreen properties parsing code already handles
touchscreen-fuzz-x and touchscreen-fuzz-y parameters. The only thing
that is needed is to pass these parameters through DT or ACPI or
static properties, based on particular device.

Thanks.

-- 
Dmitry

Re: Support for additional properties in touchscreen.h

[Gregor Riepl]

> The fuzz (smoothing the output coordinates) is done in input core and
> the touchscreen properties parsing code already handles
> touchscreen-fuzz-x and touchscreen-fuzz-y parameters. The only thing
> that is needed is to pass these parameters through DT or ACPI or
> static properties, based on particular device.

Thanks for the clarification, Dmitry.

So do I understand correctly that it would suffice to add these parameters to
a DMI match in drivers/platform/x86/silead_dmi.c ?

Something like:

static const struct property_entry my_imaginary_tablet_props[] = {
	PROPERTY_ENTRY_U32("touchscreen-size-x", 1920),
	PROPERTY_ENTRY_U32("touchscreen-size-y", 1080),
	PROPERTY_ENTRY_U32("touchscreen-fuzz-x", 10),
	PROPERTY_ENTRY_U32("touchscreen-fuzz-y", 10),
	PROPERTY_ENTRY_STRING("firmware-name", "gsl1680-my-imaginary-tablet.fw"),
	PROPERTY_ENTRY_U32("silead,max-fingers", 10),
	{ }
};

Re: Support for additional properties in touchscreen.h

[Dmitry Torokhov]

On Tue, Nov 14, 2017 at 08:55:01AM +0100, Gregor Riepl wrote:
> > The fuzz (smoothing the output coordinates) is done in input core and
> > the touchscreen properties parsing code already handles
> > touchscreen-fuzz-x and touchscreen-fuzz-y parameters. The only thing
> > that is needed is to pass these parameters through DT or ACPI or
> > static properties, based on particular device.
> 
> Thanks for the clarification, Dmitry.
> 
> So do I understand correctly that it would suffice to add these parameters to
> a DMI match in drivers/platform/x86/silead_dmi.c ?
> 
> Something like:
> 
> static const struct property_entry my_imaginary_tablet_props[] = {
> 	PROPERTY_ENTRY_U32("touchscreen-size-x", 1920),
> 	PROPERTY_ENTRY_U32("touchscreen-size-y", 1080),
> 	PROPERTY_ENTRY_U32("touchscreen-fuzz-x", 10),
> 	PROPERTY_ENTRY_U32("touchscreen-fuzz-y", 10),
> 	PROPERTY_ENTRY_STRING("firmware-name", "gsl1680-my-imaginary-tablet.fw"),
> 	PROPERTY_ENTRY_U32("silead,max-fingers", 10),
> 	{ }
> };

Yes, and you'd need to add a new entry to silead_ts_dmi_table.

Thanks.

-- 
Dmitry