From: Benjamin Tissoires <redacted>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit e24d0d399b2fce71b627043e900ef28283850482 upstream.

The Microsoft Surface Type/Touch Cover 2 is a fancy device which advertised
itself as a multitouch device but with constant input reports.
This way, hid_scan_report() gives the group MULTITOUCH to it, but
hid-multitouch can not handle it due to the constant collection ignored
by hid-input.

To prevent such crap in the future, and while we do not fix this particular
device, make the scan_report coherent with hid-input.c, and ignore constant
input reports.

Signed-off-by: Benjamin Tissoires <redacted>
Signed-off-by: Jiri Kosina <redacted>
Signed-off-by: Jiri Slaby <redacted>
---
 drivers/hid/hid-core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 30abb14ff618..0335f86502c2 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c

@@ -718,6 +718,9 @@ static int hid_scan_main(struct hid_parser *parser, struct hid_item *item)
 	case HID_MAIN_ITEM_TAG_END_COLLECTION:
 		break;
 	case HID_MAIN_ITEM_TAG_INPUT:
+		/* ignore constant inputs, they will be ignored by hid-input */
+		if (data & HID_MAIN_ITEM_CONSTANT)
+			break;
 		for (i = 0; i < parser->local.usage_index; i++)
 			hid_scan_input_usage(parser, parser->local.usage[i]);
 		break;

-- 
1.9.3