[PATCH] USB: HID: Fix fields from pen report ID being interpreted for multitouch.

[Brent Adam <brentadamdev@gmail.com>]

Fields like HID_DG_CONTACTCOUNT are outside of the physical collection,
but within the application collection and report ID.  Make sure to catch
those fields that are not part of the mt_report_id and return 0 so they
can be processed with the pen.  Otherwise, the wrong HID_DG_CONTACTCOUNT
will be applied to cc_index and result in dereferencing a null pointer in
mt_touch_report.

Signed-off-by: Brent Adam <brentadam@smarttech.com>
---
 drivers/hid/hid-multitouch.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 6a9b05b..2ee8800 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -781,6 +781,9 @@ static int mt_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 	 */
 	if (field->physical == HID_DG_STYLUS)
 		return 0;
+	else if ((field->physical == 0) &&
+		 (field->report->id != td->mt_report_id))
+		return 0;
 
 	if (field->application == HID_DG_TOUCHSCREEN ||
 	    field->application == HID_DG_TOUCHPAD)
-- 
2.1.4