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

Dmitry Torokhov
2025-11-11T22:37:47Z

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@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;

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