[PATCH v3 3/9] HID: multitouch: support getting the contact ID from HID_DG_TRANSDUCER_INDEX fields

[Aditya Garg <gargaditya08@live.com>]

From: Kerem Karabay <kekrby@gmail.com>

This is needed to support Apple Touch Bars, where the contact ID is
contained in fields with the HID_DG_TRANSDUCER_INDEX usage.

Signed-off-by: Kerem Karabay <kekrby@gmail.com>
Signed-off-by: Aditya Garg <gargaditya08@live.com>
---
 drivers/hid/hid-multitouch.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 56fc78841..3e92789ed 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -635,7 +635,9 @@ static struct mt_report_data *mt_allocate_report_data(struct mt_device *td,
 
 		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) {
+				unsigned int hid = field->usage[n].hid;
+
+				if (hid == HID_DG_CONTACTID || hid == HID_DG_TRANSDUCER_INDEX) {
 					rdata->is_mt_collection = true;
 					break;
 				}
@@ -814,6 +816,7 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 			MT_STORE_FIELD(tip_state);
 			return 1;
 		case HID_DG_CONTACTID:
+		case HID_DG_TRANSDUCER_INDEX:
 			MT_STORE_FIELD(contactid);
 			app->touches_by_report++;
 			return 1;
-- 
2.43.0