linux-kernel - [PATCH 1/5] HID: multitouch: Get the contact ID from HID_DG_TRANSDUCER

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Message-ID: <C1E82928-1646-438E-AE94-7E91BAE0D689@live.com>
Date: Thu, 27 Feb 2025 17:33:56 +0000
From: Aditya Garg <gargaditya08@...e.com>
To: Jiri Kosina <jikos@...nel.org>, "jkosina@...e.com" <jkosina@...e.com>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>, "bentiss@...nel.org"
	<bentiss@...nel.org>
CC: Kerem Karabay <kekrby@...il.com>, Linux Kernel Mailing List
	<linux-kernel@...r.kernel.org>, "linux-input@...r.kernel.org"
	<linux-input@...r.kernel.org>
Subject: [PATCH 1/5] HID: multitouch: Get the contact ID from
 HID_DG_TRANSDUCER_INDEX fields in case of Apple Touch Bar

From: Kerem Karabay <kekrby@...il.com>

In Apple Touch Bar, the contact ID is contained in fields with the
HID_DG_TRANSDUCER_INDEX usage rather than HID_DG_CONTACTID, thus differing
from the HID spec. Add a quirk for the same.

Signed-off-by: Kerem Karabay <kekrby@...il.com>
Co-developed-by: Aditya Garg <gargaditya08@...e.com>
Signed-off-by: Aditya Garg <gargaditya08@...e.com>
---
 drivers/hid/hid-multitouch.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index e50887a6d..6e7f34a47 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -73,6 +73,7 @@ MODULE_LICENSE("GPL");
 #define MT_QUIRK_FORCE_MULTI_INPUT	BIT(20)
 #define MT_QUIRK_DISABLE_WAKEUP		BIT(21)
 #define MT_QUIRK_ORIENTATION_INVERT	BIT(22)
+#define MT_QUIRK_APPLE_TOUCHBAR		BIT(23)
 
 #define MT_INPUTMODE_TOUCHSCREEN	0x02
 #define MT_INPUTMODE_TOUCHPAD		0x03
@@ -625,6 +626,7 @@ static struct mt_application *mt_find_application(struct mt_device *td,
 static struct mt_report_data *mt_allocate_report_data(struct mt_device *td,
 						      struct hid_report *report)
 {
+	struct mt_class *cls = &td->mtclass;
 	struct mt_report_data *rdata;
 	struct hid_field *field;
 	int r, n;
@@ -649,7 +651,11 @@ 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 ||
+				   (cls->quirks & MT_QUIRK_APPLE_TOUCHBAR &&
+				   hid == HID_DG_TRANSDUCER_INDEX)) {
 					rdata->is_mt_collection = true;
 					break;
 				}
@@ -827,6 +833,14 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 						     EV_KEY, BTN_TOUCH);
 			MT_STORE_FIELD(tip_state);
 			return 1;
+		case HID_DG_TRANSDUCER_INDEX:
+			/*
+			 * Contact ID in case of Apple Touch Bars is contained
+			 * in fields with HID_DG_TRANSDUCER_INDEX usage.
+			 */
+			if (!(cls->quirks & MT_QUIRK_APPLE_TOUCHBAR))
+				return 0;
+			fallthrough;
 		case HID_DG_CONTACTID:
 			MT_STORE_FIELD(contactid);
 			app->touches_by_report++;
-- 
2.43.0