Re: [PATCH v3] Input: rename INPUT_PROP_HAPTIC_TOUCHPAD to INPUT_PROP_PRESSUREPAD

[Peter Hutterer <peter.hutterer@who-t.net>]

Dmitry - gentle ping?

Cheers,
  Peter

On Thu, Nov 06, 2025 at 03:32:56PM +0100, Benjamin Tissoires wrote:
> On Nov 06 2025, Peter Hutterer wrote:
> > And expand it to encompass all pressure pads.
> > 
> > Definition: "pressure pad" as used here as includes all touchpads that
> > use physical pressure to convert to click, without physical hinges. Also
> > called haptic touchpads in general parlance, Synaptics calls them
> > ForcePads.
> > 
> > Most (all?) pressure pads are currently advertised as
> > INPUT_PROP_BUTTONPAD. The suggestion to identify them as pressure pads
> > by defining the resolution on ABS_MT_PRESSURE has been in the docs since
> > commit 20ccc8dd38a3 ("Documentation: input: define
> > ABS_PRESSURE/ABS_MT_PRESSURE resolution as grams") but few devices
> > provide this information.
> > 
> > In userspace it's thus impossible to determine whether a device is a
> > true pressure pad (pressure equals pressure) or a normal clickpad with
> > (pressure equals finger size).
> > 
> > Commit 7075ae4ac9db ("Input: add INPUT_PROP_HAPTIC_TOUCHPAD") introduces
> > INPUT_PROP_HAPTIC_TOUCHPAD but restricted it to those touchpads that
> > have support for userspace-controlled effects. Let's expand and rename
> > that definition to include all pressure pad touchpads since those that
> > do support FF effects can be identified by the presence of the
> > FF_HAPTIC bit.
> > 
> > This means:
> > - clickpad: INPUT_PROP_BUTTONPAD
> > - pressurepad: INPUT_PROP_BUTTONPAD + INPUT_PROP_PRESSUREPAD
> > - pressurepad with configurable haptics:
> >   INPUT_PROP_BUTTONPAD + INPUT_PROP_PRESSUREPAD + FF_HAPTIC
> > 
> > Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
> 
> Acked-by: Benjamin Tissoires <bentiss@kernel.org>
> 
> Unless Jiri has any problem with it, I guess this would be fine going
> through your tree Dmitry.
> 
> Cheers,
> Benjamin
> 
> 
> > ---
> > ftr, I picked PRESSUREPAD over Dmitry's PRESSURE_TOUCHPAD suggestion
> > because it matches better with the existing BUTTONPAD.
> > 
> > Changes to v1: extra empty lines to render the lists as lists
> > Changes to v2: rename to PRESSUREPAD and rename it in the instances
> >   where it's used in the code
> > 
> > v1: https://lore.kernel.org/linux-input/20251030011735.GA969565@quokka/T/#u
> > v2: https://lore.kernel.org/linux-input/20251030011735.GA969565@quokka/T/#m9504de27b02d00a55d540fd9fec9aed3edd0133c
> > 
> >  Documentation/input/event-codes.rst    | 25 ++++++++++++++++++-------
> >  drivers/hid/hid-haptic.c               |  2 +-
> >  include/uapi/linux/input-event-codes.h |  2 +-
> >  3 files changed, 20 insertions(+), 9 deletions(-)
> > 
> > diff --git a/Documentation/input/event-codes.rst b/Documentation/input/event-codes.rst
> > index 1ead9bb8d9c6..4424cbff251f 100644
> > --- a/Documentation/input/event-codes.rst
> > +++ b/Documentation/input/event-codes.rst
> > @@ -400,19 +400,30 @@ can report through the rotational axes (absolute and/or relative rx, ry, rz).
> >  All other axes retain their meaning. A device must not mix
> >  regular directional axes and accelerometer axes on the same event node.
> >  
> > -INPUT_PROP_HAPTIC_TOUCHPAD
> > ---------------------------
> > +INPUT_PROP_PRESSUREPAD
> > +----------------------
> > +
> > +The INPUT_PROP_PRESSUREPAD property indicates that the device provides
> > +simulated haptic feedback (e.g. a vibrator motor situated below the surface)
> > +instead of physical haptic feedback (e.g. a hinge). This property is only set
> > +if the device:
> >  
> > -The INPUT_PROP_HAPTIC_TOUCHPAD property indicates that device:
> > -- supports simple haptic auto and manual triggering
> >  - can differentiate between at least 5 fingers
> >  - uses correct resolution for the X/Y (units and value)
> > -- reports correct force per touch, and correct units for them (newtons or grams)
> >  - follows the MT protocol type B
> >  
> > +If the simulated haptic feedback is controllable by userspace the device must:
> > +
> > +- support simple haptic auto and manual triggering, and
> > +- report correct force per touch, and correct units for them (newtons or grams), and
> > +- provide the EV_FF FF_HAPTIC force feedback effect.
> > +
> >  Summing up, such devices follow the MS spec for input devices in
> > -Win8 and Win8.1, and in addition support the Simple haptic controller HID table,
> > -and report correct units for the pressure.
> > +Win8 and Win8.1, and in addition may support the Simple haptic controller HID
> > +table, and report correct units for the pressure.
> > +
> > +Where applicable, this property is set in addition to INPUT_PROP_BUTTONPAD, it
> > +does not replace that property.
> >  
> >  Guidelines
> >  ==========
> > diff --git a/drivers/hid/hid-haptic.c b/drivers/hid/hid-haptic.c
> > index aa090684c1f2..fc8a9997f815 100644
> > --- a/drivers/hid/hid-haptic.c
> > +++ b/drivers/hid/hid-haptic.c
> > @@ -86,7 +86,7 @@ int hid_haptic_input_configured(struct hid_device *hdev,
> >  	if (hi->application == HID_DG_TOUCHPAD) {
> >  		if (haptic->auto_trigger_report &&
> >  		    haptic->manual_trigger_report) {
> > -			__set_bit(INPUT_PROP_HAPTIC_TOUCHPAD, hi->input->propbit);
> > +			__set_bit(INPUT_PROP_PRESSUREPAD, hi->input->propbit);
> >  			return 1;
> >  		}
> >  		return 0;
> > diff --git a/include/uapi/linux/input-event-codes.h b/include/uapi/linux/input-event-codes.h
> > index 8ba48590bd2c..d21172c6a266 100644
> > --- a/include/uapi/linux/input-event-codes.h
> > +++ b/include/uapi/linux/input-event-codes.h
> > @@ -27,7 +27,7 @@
> >  #define INPUT_PROP_TOPBUTTONPAD		0x04	/* softbuttons at top of pad */
> >  #define INPUT_PROP_POINTING_STICK	0x05	/* is a pointing stick */
> >  #define INPUT_PROP_ACCELEROMETER	0x06	/* has accelerometer */
> > -#define INPUT_PROP_HAPTIC_TOUCHPAD	0x07	/* is a haptic touchpad */
> > +#define INPUT_PROP_PRESSUREPAD		0x07	/* pressure triggers clicks */
> >  
> >  #define INPUT_PROP_MAX			0x1f
> >  #define INPUT_PROP_CNT			(INPUT_PROP_MAX + 1)
> > -- 
> > 2.51.1
> >