HID: multitouch: support for hovering devices

Win8 devices supporting hovering must provides InRange HID field.
The information that the finger is here but is not touching the surface
is sent to the user space through ABS_MT_DISTANCE as required by the
multitouch protocol.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Reviewed-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index e86fbf4..0a04893 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -53,11 +53,13 @@
 #define MT_QUIRK_SLOT_IS_CONTACTID_MINUS_ONE	(1 << 8)
 #define MT_QUIRK_NO_AREA		(1 << 9)
 #define MT_QUIRK_IGNORE_DUPLICATES	(1 << 10)
+#define MT_QUIRK_HOVERING		(1 << 11)
 
 struct mt_slot {
 	__s32 x, y, cx, cy, p, w, h;
 	__s32 contactid;	/* the device ContactID assigned to this slot */
 	bool touch_state;	/* is the touch valid? */
+	bool inrange_state;	/* is the finger in proximity of the sensor? */
 };
 
 struct mt_class {
@@ -391,6 +393,12 @@
 	case HID_UP_DIGITIZER:
 		switch (usage->hid) {
 		case HID_DG_INRANGE:
+			if (cls->quirks & MT_QUIRK_HOVERING) {
+				hid_map_usage(hi, usage, bit, max,
+					EV_ABS, ABS_MT_DISTANCE);
+				input_set_abs_params(hi->input,
+					ABS_MT_DISTANCE, 0, 1, 0, 0);
+			}
 			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
@@ -520,9 +528,9 @@
 
 		input_mt_slot(input, slotnum);
 		input_mt_report_slot_state(input, MT_TOOL_FINGER,
-			s->touch_state);
-		if (s->touch_state) {
-			/* this finger is on the screen */
+			s->touch_state || s->inrange_state);
+		if (s->touch_state || s->inrange_state) {
+			/* this finger is in proximity of the sensor */
 			int wide = (s->w > s->h);
 			/* divided by two to match visual scale of touch */
 			int major = max(s->w, s->h) >> 1;
@@ -532,6 +540,8 @@
 			input_event(input, EV_ABS, ABS_MT_POSITION_Y, s->y);
 			input_event(input, EV_ABS, ABS_MT_TOOL_X, s->cx);
 			input_event(input, EV_ABS, ABS_MT_TOOL_Y, s->cy);
+			input_event(input, EV_ABS, ABS_MT_DISTANCE,
+				!s->touch_state);
 			input_event(input, EV_ABS, ABS_MT_ORIENTATION, wide);
 			input_event(input, EV_ABS, ABS_MT_PRESSURE, s->p);
 			input_event(input, EV_ABS, ABS_MT_TOUCH_MAJOR, major);
@@ -564,6 +574,8 @@
 		case HID_DG_INRANGE:
 			if (quirks & MT_QUIRK_VALID_IS_INRANGE)
 				td->curvalid = value;
+			if (quirks & MT_QUIRK_HOVERING)
+				td->curdata.inrange_state = value;
 			break;
 		case HID_DG_TIPSWITCH:
 			if (quirks & MT_QUIRK_NOT_SEEN_MEANS_UP)