[PATCH 5.12 109/161] HID: multitouch: require Finger field to mark Win8 reports as MT

From: Ahelenia Ziemiańska <redacted>

commit a2353e3b26012ff43bcdf81d37a3eaddd7ecdbf3 upstream.

This effectively changes collection_is_mt from
  contact ID in report->field
to
  (device is Win8 => collection is finger) && contact ID in report->field

Some devices erroneously report Pen for fingers, and Win8 stylus-on-touchscreen
devices report contact ID, but mark the accompanying touchscreen device's
collection correctly

Cc: stable@vger.kernel.org
Signed-off-by: Ahelenia Ziemiańska <redacted>
Acked-by: Benjamin Tissoires <redacted>
Signed-off-by: Jiri Kosina <redacted>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/hid/hid-multitouch.c |   10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c

@@ -604,9 +604,13 @@ static struct mt_report_data *mt_allocat
 		if (!(HID_MAIN_ITEM_VARIABLE & field->flags))
 			continue;
 
-		for (n = 0; n < field->report_count; n++) {
-			if (field->usage[n].hid == HID_DG_CONTACTID)
-				rdata->is_mt_collection = true;
+		if (field->logical == HID_DG_FINGER || td->hdev->group != HID_GROUP_MULTITOUCH_WIN_8) {
+			for (n = 0; n < field->report_count; n++) {
+				if (field->usage[n].hid == HID_DG_CONTACTID) {
+					rdata->is_mt_collection = true;
+					break;
+				}
+			}
 		}
 	}