[PATCH v2 2/2] HID: multitouch: Toggle touch surface on Elan touchpad on lid event

[Jonathan Denose <jdenose@google.com>]

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. When the lid switch closes, the
touchpad surface will be turned off and when the lid switch opens, the
touchpad surgace will be turned on. This triggers recalibration which
resolves interference issues when the lid is closed.

Signed-off-by: Jonathan Denose <jdenose@google.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..9a89913c193bc110a0a821a901aebd97892c66bd 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_LID_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_LID_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_LID_NOTIFIER,
+		.quirks = MT_QUIRK_REGISTER_LID_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)
+		mt_set_modes(lid_notify_hdev, HID_LATENCY_NORMAL, TOUCHPAD_REPORT_NONE);
+	else if (!action)
+		mt_set_modes(lid_notify_hdev, HID_LATENCY_NORMAL, TOUCHPAD_REPORT_ALL);
+
+	return 0;
+}
+
+static struct notifier_block mt_lid_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_LID_NOTIFIER) {
+		lid_notify_hdev = hdev;
+		register_lid_notifier(&mt_lid_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_LID_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,

-- 
2.51.2.1041.gc1ab5b90ca-goog