Input: add INPUT_PROP_HAPTIC_TOUCHPAD

INPUT_PROP_HAPTIC_TOUCHPAD property is to be set for a device with simple
haptic capabilities.

Signed-off-by: Angela Czubak <aczubak@google.com>
Co-developed-by: Jonathan Denose <jdenose@google.com>
Signed-off-by: Jonathan Denose <jdenose@google.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

Documentation/input/event-codes.rst

@@ -400,6 +400,20 @@ 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
+--------------------------
+
+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
+
+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.
+
 Guidelines
 ==========
 

include/uapi/linux/input-event-codes.h

@@ -27,6 +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_MAX			0x1f
 #define INPUT_PROP_CNT			(INPUT_PROP_MAX + 1)