linux-kernel - [PATCH v2 2/5] HID: multitouch: support getting the tip state from HID_DG

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Message-ID: <20250325180138.15113-3-gargaditya08@live.com>
Date: Tue, 25 Mar 2025 17:57:25 +0000
From: adityagarg1208@...il.com
To: jikos@...nel.org,
	jkosina@...e.com,
	bentiss@...nel.org,
	benjamin.tissoires@...hat.com
Cc: gargaditya08@...e.com,
	kekrby@...il.com,
	orlandoch.dev@...il.com,
	admin@...eit.net,
	linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/5] HID: multitouch: support getting the tip state from HID_DG_TOUCH fields in Apple Touch Bar

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

In Apple Touch Bar, the tip state is contained in fields with the
HID_DG_TOUCH usage. This feature is gated by a quirk in order to
prevent breaking other devices, see commit c2ef8f21ea8f
("HID: multitouch: add support for trackpads").

Acked-by: Benjamin Tissoires <bentiss@...nel.org>
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 | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 6e7f34a47..70fdd8cf9 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -827,6 +827,17 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 
 			MT_STORE_FIELD(confidence_state);
 			return 1;
+		case HID_DG_TOUCH:
+			/*
+			 * Legacy devices use TIPSWITCH and not TOUCH.
+			 * One special case here is of the Apple Touch Bars.
+			 * In these devices, the tip state is contained in
+			 * fields with the HID_DG_TOUCH usage.
+			 * Let's just ignore this field for other devices.
+			 */
+			if (!(cls->quirks & MT_QUIRK_APPLE_TOUCHBAR))
+				return -1;
+			fallthrough;
 		case HID_DG_TIPSWITCH:
 			if (field->application != HID_GD_SYSTEM_MULTIAXIS)
 				input_set_capability(hi->input,
@@ -897,10 +908,6 @@ static int mt_touch_input_mapping(struct hid_device *hdev, struct hid_input *hi,
 		case HID_DG_CONTACTMAX:
 			/* contact max are global to the report */
 			return -1;
-		case HID_DG_TOUCH:
-			/* Legacy devices use TIPSWITCH and not TOUCH.
-			 * Let's just ignore this field. */
-			return -1;
 		}
 		/* let hid-input decide for the others */
 		return 0;
-- 
2.49.0