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

[Dmitry Torokhov]

Hi Jonathan,

On Tue, Nov 11, 2025 at 09:34:07PM +0000, Jonathan Denose wrote:
> 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@xxxxxxxxxx>
> ---
>  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;

This should really be per-device.

> +
>  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) },

The need to have special handling of LID events is a quirk of board
design, not quire of a controller. So I think it needs to be triggered
by DMI quirk.

> +
>  	/* Elitegroup panel */
>  	{ .driver_data = MT_CLS_SERIAL,
>  		MT_USB_DEVICE(USB_VENDOR_ID_ELITEGROUP,
> 

Thanks.

-- 
Dmitry