linux-kernel - Re: [PATCH v3] hid/hid-multitouch: Keep latency normal on deactivate for reactivation gesture

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Message-ID: <ae75b604-9bdb-430a-bd4d-8e1e669cf4d8@tuxedocomputers.com>
Date: Wed, 12 Nov 2025 16:51:48 +0100
From: Werner Sembach <wse@...edocomputers.com>
To: Jiri Kosina <jikos@...nel.org>, Benjamin Tissoires <bentiss@...nel.org>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] hid/hid-multitouch: Keep latency normal on deactivate
 for reactivation gesture


Am 12.11.25 um 15:47 schrieb Werner Sembach:
> Uniwill devices have a built in gesture in the touchpad to de- and
> reactivate it by double taping the upper left corner. This gesture stops
> working when latency is set to high, so this patch keeps the latency on
> normal.
>
> Signed-off-by: Werner Sembach <wse@...edocomputers.com>
> Cc: stable@...r.kernel.org
> ---
> V1->V2: Use a quirk to narrow down the devices this is applied to.
> V2->V3: Fix this patch breaking touchpads on some devices.
>          Add another device ID.
>
> I have three Uniwill devices at hand right now that have at least two
> physically different touchpads, but same Vendor + Product ID combination.
> Maybe the vendor uses this product ID for all i2c connected touchpads, or
> it is used as some kind of subvendor ID to indicate Uniwill?
>
> To be able to really narrow it down to Uniwill only devices I would need to
> check DMI strings, but then I will probably narrow it down to much as I
> only know what we at TUXEDO use there.
>
>   drivers/hid/hid-multitouch.c | 26 +++++++++++++++++++++++++-
>   1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
> index 179dc316b4b51..ed9eb4e0d5038 100644
> --- a/drivers/hid/hid-multitouch.c
> +++ b/drivers/hid/hid-multitouch.c
> @@ -76,6 +76,7 @@ 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_KEEP_LATENCY_ON_CLOSE	BIT(24)
>   
>   #define MT_INPUTMODE_TOUCHSCREEN	0x02
>   #define MT_INPUTMODE_TOUCHPAD		0x03
> @@ -211,6 +212,7 @@ static void mt_post_parse(struct mt_device *td, struct mt_application *app);
>   #define MT_CLS_WIN_8_DISABLE_WAKEUP		0x0016
>   #define MT_CLS_WIN_8_NO_STICKY_FINGERS		0x0017
>   #define MT_CLS_WIN_8_FORCE_MULTI_INPUT_NSMU	0x0018
> +#define MT_CLS_WIN_8_KEEP_LATENCY_ON_CLOSE	0x0019
A college realized that at some points in the code some, but not all, of the 
MT_CLS_WIN_8* classes are checked for directly. Should I add my new class there 
too?
>   
>   /* vendor specific classes */
>   #define MT_CLS_3M				0x0101
> @@ -330,6 +332,15 @@ static const struct mt_class mt_classes[] = {
>   			MT_QUIRK_CONTACT_CNT_ACCURATE |
>   			MT_QUIRK_WIN8_PTP_BUTTONS,
>   		.export_all_inputs = true },
> +	{ .name = MT_CLS_WIN_8_KEEP_LATENCY_ON_CLOSE,
> +		.quirks = MT_QUIRK_ALWAYS_VALID |
> +			MT_QUIRK_IGNORE_DUPLICATES |
> +			MT_QUIRK_HOVERING |
> +			MT_QUIRK_CONTACT_CNT_ACCURATE |
> +			MT_QUIRK_STICKY_FINGERS |
> +			MT_QUIRK_WIN8_PTP_BUTTONS |
> +			MT_QUIRK_KEEP_LATENCY_ON_CLOSE,
> +		.export_all_inputs = true },
>   
>   	/*
>   	 * vendor specific classes
> @@ -1998,7 +2009,12 @@ static void mt_on_hid_hw_open(struct hid_device *hdev)
>   
>   static void mt_on_hid_hw_close(struct hid_device *hdev)
>   {
> -	mt_set_modes(hdev, HID_LATENCY_HIGH, TOUCHPAD_REPORT_NONE);
> +	struct mt_device *td = hid_get_drvdata(hdev);
> +
> +	if (td->mtclass.quirks & MT_QUIRK_KEEP_LATENCY_ON_CLOSE)
> +		mt_set_modes(hdev, HID_LATENCY_NORMAL, TOUCHPAD_REPORT_NONE);
> +	else
> +		mt_set_modes(hdev, HID_LATENCY_HIGH, TOUCHPAD_REPORT_NONE);
>   }
>   
>   /*
> @@ -2375,6 +2391,14 @@ static const struct hid_device_id mt_devices[] = {
>   		MT_USB_DEVICE(USB_VENDOR_ID_UNITEC,
>   			USB_DEVICE_ID_UNITEC_USB_TOUCH_0A19) },
>   
> +	/* Uniwill touchpads */
> +	{ .driver_data = MT_CLS_WIN_8_KEEP_LATENCY_ON_CLOSE,
> +		HID_DEVICE(BUS_I2C, HID_GROUP_MULTITOUCH_WIN_8,
> +			USB_VENDOR_ID_PIXART, 0x0255) },
> +	{ .driver_data = MT_CLS_WIN_8_KEEP_LATENCY_ON_CLOSE,
> +		HID_DEVICE(BUS_I2C, HID_GROUP_MULTITOUCH_WIN_8,
> +			USB_VENDOR_ID_PIXART, 0x0274) },
> +
>   	/* VTL panels */
>   	{ .driver_data = MT_CLS_VTL,
>   		MT_USB_DEVICE(USB_VENDOR_ID_VTL,