linux-kernel - [PATCH 2/2] HID: multitouch: Toggle touch surface on Elan touchpad on lid event

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Message-ID: <20251030-lid-switch-notifier-v1-2-c58dc9b1439d@google.com>
Date: Thu, 30 Oct 2025 14:10:41 +0000
From: Jonathan Denose <jdenose@...gle.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>, Jiri Kosina <jikos@...nel.org>, 
	Benjamin Tissoires <bentiss@...nel.org>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Jonathan Denose <jdenose@...gle.com>
Subject: [PATCH 2/2] HID: multitouch: Toggle touch surface on Elan touchpad on
 lid event

Many touchpad modules have a pin which is expected to be connected to the
lid angle sensor in laptops. The pin sends a signal to the touchpad module
about the lid state and each touchpad vendor handles this notification in
their firmware.

The Elan touchpad with VID 323b does not always have this aforementioned
pin, which then causes interference between the lid and the touchpad when
the lid is closed. This interference causes a few seconds delay before the
touchpad works again, or it causes it to be come completely unresponsive.
To circumvent this hardware issue in software, implement a device quirk
which will allow the hid-multitouch driver to register a notifier_block
to listen for lid switch events and turn the touchpad surface on and off
triggering a recalibration of the touchpad. This recalibration resolves
interference issues when the lid is closed.

Signed-off-by: Jonathan Denose <jdenose@...gle.com>
---
 drivers/hid/hid-multitouch.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
index 2879e65cf303b1456311ac06115adda5a78a2600..feb0a0b65b6355cc412fcf8ea88132dc5bdc6a26 100644
--- a/drivers/hid/hid-multitouch.c
+++ b/drivers/hid/hid-multitouch.c
@@ -35,6 +35,7 @@
 #include <linux/device.h>
 #include <linux/hid.h>
 #include <linux/module.h>
+#include <linux/notifier.h>
 #include <linux/slab.h>
 #include <linux/input/mt.h>
 #include <linux/jiffies.h>
@@ -76,6 +77,7 @@ MODULE_LICENSE("GPL");
 #define MT_QUIRK_DISABLE_WAKEUP		BIT(21)
 #define MT_QUIRK_ORIENTATION_INVERT	BIT(22)
 #define MT_QUIRK_APPLE_TOUCHBAR		BIT(23)
+#define MT_QUIRK_REGISTER_INPUT_NOTIFIER BIT(24)
 
 #define MT_INPUTMODE_TOUCHSCREEN	0x02
 #define MT_INPUTMODE_TOUCHPAD		0x03
@@ -183,6 +185,8 @@ struct mt_device {
 	struct list_head reports;
 };
 
+static struct hid_device *lid_notify_hdev;
+
 static void mt_post_parse_default_settings(struct mt_device *td,
 					   struct mt_application *app);
 static void mt_post_parse(struct mt_device *td, struct mt_application *app);
@@ -227,6 +231,7 @@ static void mt_post_parse(struct mt_device *td, struct mt_application *app);
 #define MT_CLS_SMART_TECH			0x0113
 #define MT_CLS_APPLE_TOUCHBAR			0x0114
 #define MT_CLS_SIS				0x0457
+#define MT_CLS_REGISTER_INPUT_NOTIFIER 0x0115
 
 #define MT_DEFAULT_MAXCONTACT	10
 #define MT_MAX_MAXCONTACT	250
@@ -327,7 +332,9 @@ static const struct mt_class mt_classes[] = {
 			MT_QUIRK_CONTACT_CNT_ACCURATE |
 			MT_QUIRK_WIN8_PTP_BUTTONS,
 		.export_all_inputs = true },
-
+	{ .name = MT_CLS_REGISTER_INPUT_NOTIFIER,
+		.quirks = MT_QUIRK_REGISTER_INPUT_NOTIFIER,
+		.export_all_inputs = true },
 	/*
 	 * vendor specific classes
 	 */
@@ -1840,6 +1847,20 @@ static void mt_expired_timeout(struct timer_list *t)
 	clear_bit_unlock(MT_IO_FLAGS_RUNNING, &td->mt_io_flags);
 }
 
+static int mt_input_notifier(struct notifier_block *nb, unsigned long action, void *dev)
+{
+	if (action == LID_SWITCH_CLOSE)
+		mt_set_modes(lid_notify_hdev, HID_LATENCY_NORMAL, TOUCHPAD_REPORT_NONE);
+	else if (action == LID_SWITCH_OPEN)
+		mt_set_modes(lid_notify_hdev, HID_LATENCY_NORMAL, TOUCHPAD_REPORT_ALL);
+
+	return 0;
+}
+
+static struct notifier_block mt_notifier_block = {
+	.notifier_call = mt_input_notifier
+};
+
 static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 {
 	int ret, i;
@@ -1920,6 +1941,11 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
 	if (hdev->vendor == USB_VENDOR_ID_SIS_TOUCH)
 		hdev->quirks |= HID_QUIRK_NOGET;
 
+	if (mtclass->quirks & MT_CLS_REGISTER_INPUT_NOTIFIER) {
+		lid_notify_hdev = hdev;
+		register_input_notifier(&mt_notifier_block);
+	}
+
 	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
 	if (ret)
 		return ret;
@@ -2150,6 +2176,10 @@ static const struct hid_device_id mt_devices[] = {
 		HID_DEVICE(BUS_I2C, HID_GROUP_MULTITOUCH_WIN_8,
 			USB_VENDOR_ID_ELAN, 0x32ae) },
 
+	{ .driver_data = MT_CLS_REGISTER_INPUT_NOTIFIER,
+		HID_DEVICE(BUS_I2C, HID_GROUP_MULTITOUCH_WIN_8,
+			USB_VENDOR_ID_ELAN, 0x323b) },
+
 	/* Elitegroup panel */
 	{ .driver_data = MT_CLS_SERIAL,
 		MT_USB_DEVICE(USB_VENDOR_ID_ELITEGROUP,

-- 
2.51.1.851.g4ebd6896fd-goog