HID: hid-multitouch: fix wrong protocol detection

The previous implementation introduced a randomness in the splitting
of the different touches reported by the device. This version is more
robust as we don't rely on hi->input->absbit, but on our own structure.

This also prepares hid-multitouch to better support Win8 devices.

[Jiri Kosina <jkosina@suse.cz>: fix build]
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@enac.fr>
Acked-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-multitouch.c

@@ -70,9 +70,16 @@ struct mt_class {
 	bool is_indirect;	/* true for touchpads */
 };
 
+struct mt_fields {
+	unsigned usages[HID_MAX_FIELDS];
+	unsigned int length;
+};
+
 struct mt_device {
 	struct mt_slot curdata;	/* placeholder of incoming data */
 	struct mt_class mtclass;	/* our mt device class */
+	struct mt_fields *fields;	/* temporary placeholder for storing the
+					   multitouch fields */
 	unsigned last_field_index;	/* last field index of the report */
 	unsigned last_slot_field;	/* the last field of a slot */
 	__s8 inputmode;		/* InputMode HID feature, -1 if non-existent */
@@ -278,11 +285,15 @@ static void set_abs(struct input_dev *input, unsigned int code,
 	input_set_abs_params(input, code, fmin, fmax, fuzz, 0);
 }
 
-static void set_last_slot_field(struct hid_usage *usage, struct mt_device *td,
+static void mt_store_field(struct hid_usage *usage, struct mt_device *td,
 		struct hid_input *hi)
 {
-	if (!test_bit(usage->hid, hi->input->absbit))
-		td->last_slot_field = usage->hid;
+	struct mt_fields *f = td->fields;
+
+	if (f->length >= HID_MAX_FIELDS)
+		return;
+
+	f->usages[f->length++] = usage->hid;
 }
 
 static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
@@ -333,7 +344,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 				cls->sn_move);
 			/* touchscreen emulation */
 			set_abs(hi->input, ABS_X, field, cls->sn_move);
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		case HID_GD_Y:
@@ -343,7 +354,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 				cls->sn_move);
 			/* touchscreen emulation */
 			set_abs(hi->input, ABS_Y, field, cls->sn_move);
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		}
@@ -352,24 +363,24 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 	case HID_UP_DIGITIZER:
 		switch (usage->hid) {
 		case HID_DG_INRANGE:
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONFIDENCE:
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_TIPSWITCH:
 			hid_map_usage(hi, usage, bit, max, EV_KEY, BTN_TOUCH);
 			input_set_capability(hi->input, EV_KEY, BTN_TOUCH);
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONTACTID:
 			if (!td->maxcontacts)
 				td->maxcontacts = MT_DEFAULT_MAXCONTACT;
 			input_mt_init_slots(hi->input, td->maxcontacts);
-			td->last_slot_field = usage->hid;
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			td->touches_by_report++;
 			return 1;
@@ -378,7 +389,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 					EV_ABS, ABS_MT_TOUCH_MAJOR);
 			set_abs(hi->input, ABS_MT_TOUCH_MAJOR, field,
 				cls->sn_width);
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_HEIGHT:
@@ -388,7 +399,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 				cls->sn_height);
 			input_set_abs_params(hi->input,
 					ABS_MT_ORIENTATION, 0, 1, 0, 0);
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_TIPPRESSURE:
@@ -399,7 +410,7 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 			/* touchscreen emulation */
 			set_abs(hi->input, ABS_PRESSURE, field,
 				cls->sn_pressure);
-			set_last_slot_field(usage, td, hi);
+			mt_store_field(usage, td, hi);
 			td->last_field_index = field->index;
 			return 1;
 		case HID_DG_CONTACTCOUNT:
@@ -653,6 +664,16 @@ static void mt_post_parse_default_settings(struct mt_device *td)
 	td->mtclass.quirks = quirks;
 }
 
+static void mt_post_parse(struct mt_device *td)
+{
+	struct mt_fields *f = td->fields;
+
+	if (td->touches_by_report > 0) {
+		int field_count_per_touch = f->length / td->touches_by_report;
+		td->last_slot_field = f->usages[field_count_per_touch - 1];
+	}
+}
+
 static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 {
 	int ret, i;
@@ -683,6 +704,13 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	td->maxcontact_report_id = -1;
 	hid_set_drvdata(hdev, td);
 
+	td->fields = kzalloc(sizeof(struct mt_fields), GFP_KERNEL);
+	if (!td->fields) {
+		dev_err(&hdev->dev, "cannot allocate multitouch fields data\n");
+		ret = -ENOMEM;
+		goto fail;
+	}
+
 	ret = hid_parse(hdev);
 	if (ret != 0)
 		goto fail;
@@ -691,6 +719,8 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	if (ret)
 		goto fail;
 
+	mt_post_parse(td);
+
 	if (id->vendor == HID_ANY_ID && id->product == HID_ANY_ID)
 		mt_post_parse_default_settings(td);
 
@@ -708,9 +738,13 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	mt_set_maxcontacts(hdev);
 	mt_set_input_mode(hdev);
 
+	kfree(td->fields);
+	td->fields = NULL;
+
 	return 0;
 
 fail:
+	kfree(td->fields);
 	kfree(td);
 	return ret;
 }