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>

drivers/hid/hid-multitouch.c

@@ -53,11 +53,13 @@ MODULE_LICENSE("GPL");
 #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 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 	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 @@ static void mt_complete_slot(struct mt_device *td, struct input_dev *input)
 
 		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 @@ static void mt_complete_slot(struct mt_device *td, struct input_dev *input)
 			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 @@ static int mt_event(struct hid_device *hid, struct hid_field *field,
 		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)