Re: [PATCH 2/2] HID: wacom: Setup SW_MUTE_DEVICE according to the order of input registration

[Lee Jones <lee@kernel.org>]

On Tue, 22 Sep 2026, Ping Cheng wrote:

> From: Ping Cheng <ping.cheng@wacom.com>
> 
> The refactored SW_MUTE_DEVICE code assumed that stylus will be
> the first regiestered input. In reality, touch can be registered
> before stylus, such as the Wacom Cintiq Pro 13 and 16.
> 
> This patch covers both touch-first and stylus-first cases.
> 
> Cc: stable@vger.kernel.org
> Fixes: ba16e5ffbaa1 ("HID: wacom: Advertise SW_MUTE_DEVICE capability prior to registration")
> Reviewed-by: Lee Jones <lee@kernel.org>

I did not review this patch!

> Signed-off-by: Ping Cheng <ping.cheng@wacom.com>
> ---
>  drivers/hid/wacom_wac.c | 22 +++++++++++++++++++---
>  1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hid/wacom_wac.c b/drivers/hid/wacom_wac.c
> index c4cd87b781c4..9520296cb349 100644
> --- a/drivers/hid/wacom_wac.c
> +++ b/drivers/hid/wacom_wac.c
> @@ -3977,10 +3977,12 @@ int wacom_setup_touch_input_capabilities(struct input_dev *input_dev,
>  
>  	if (features->type == HID_GENERIC) {
>  		hid_dbg(hdev, "generic touch setup\n");
> -		if (wacom_wac->has_mute_touch_switch ||
> -		    (wacom_wac->shared && READ_ONCE(wacom_wac->shared->has_mute_touch_switch))) {
> +
> +		/* setup touch switch for those devices that report pen interface first
> +		 * can only be done here since we only call this routine once
> +		 */

This is the incorrect multi-line comment format.

Sentences start with uppercase chars.

> +		if (wacom_wac->shared && READ_ONCE(wacom_wac->shared->has_mute_touch_switch)) {
>  			input_set_capability(input_dev, EV_SW, SW_MUTE_DEVICE);
> -			wacom_wac->has_mute_touch_switch = true;
>  		}
>  		/* setup has already been done */
>  		return 0;
> @@ -4403,7 +4405,21 @@ int wacom_setup_pad_input_capabilities(struct input_dev *input_dev,
>  		break;
>  
>  	case INTUOSHT3_BT:
> +		break;
> +
>  	case HID_GENERIC:
> +		if (wacom_wac->shared) {
> +			/*
> +			 * setup touch switch capability can only be done here
> +			 * for those devices that have touch input registered
> +			 * before stylus and pad inputs.

It might be worth explaining the limitation.

What happens if those prerequisites are not satisfied?

> +			 */
> +			if (wacom_wac->has_mute_touch_switch &&
> +			    wacom_wac->shared->touch_input) {
> +				input_set_capability(wacom_wac->shared->touch_input,
> +				    EV_SW, SW_MUTE_DEVICE);
> +			}
> +		}
>  		break;
>  
>  	default:
> -- 
> 2.55.0
> 

-- 
Lee Jones