linux-kernel - Re: [PATCH 2/3] media: uvcvideo: Do not send events for not changed controls

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Message-ID: <20250223171005.GC2821@pendragon.ideasonboard.com>
Date: Sun, 23 Feb 2025 19:10:05 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Hans de Goede <hdegoede@...hat.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	stable@...nel.org
Subject: Re: [PATCH 2/3] media: uvcvideo: Do not send events for not changed
 controls

Hi Ricardo,

Thank you for the patch.

On Tue, Dec 10, 2024 at 10:22:23PM +0000, Ricardo Ribalda wrote:
> Only send events for controls that have actually changed.
> E.g.: We are changing entities A, B and C. If we get an error while
> we change B we do not continue setting C. But the current code sends an
> event also for C.

Does it ? If uvc_ctrl_commit_entity() fails the 'goto done' statement
skips over uvc_ctrl_send_events().

> Due to the fact that the controls are grouped by entities, and the user
> might group them in different orders, we cannot send the events at the
> end, but when we change an entity.
> 
> Cc: stable@...nel.org
> Fixes: b4012002f3a3 ("[media] uvcvideo: Add support for control events")
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index 7e2fc97c9f43..9496ac970267 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1669,7 +1669,9 @@ static bool uvc_ctrl_xctrls_has_control(const struct v4l2_ext_control *xctrls,
>  }
>  
>  static void uvc_ctrl_send_events(struct uvc_fh *handle,
> -	const struct v4l2_ext_control *xctrls, unsigned int xctrls_count)
> +				 struct uvc_entity *entity,
> +				 const struct v4l2_ext_control *xctrls,
> +				 unsigned int xctrls_count)
>  {
>  	struct uvc_control_mapping *mapping;
>  	struct uvc_control *ctrl;
> @@ -1680,6 +1682,9 @@ static void uvc_ctrl_send_events(struct uvc_fh *handle,
>  	for (i = 0; i < xctrls_count; ++i) {
>  		ctrl = uvc_find_control(handle->chain, xctrls[i].id, &mapping);
>  
> +		if (ctrl->entity != entity)
> +			continue;
> +
>  		if (ctrl->info.flags & UVC_CTRL_FLAG_ASYNCHRONOUS)
>  			/* Notification will be sent from an Interrupt event. */
>  			continue;
> @@ -1911,11 +1916,12 @@ int __uvc_ctrl_commit(struct uvc_fh *handle, int rollback,
>  					uvc_ctrl_find_ctrl_idx(entity, ctrls,
>  							       err_ctrl);
>  			goto done;
> +		} else if (ret > 0 && !rollback) {
> +			uvc_ctrl_send_events(handle, entity,
> +					     ctrls->controls, ctrls->count);
>  		}
>  	}
>  
> -	if (!rollback)
> -		uvc_ctrl_send_events(handle, ctrls->controls, ctrls->count);
>  done:
>  	mutex_unlock(&chain->ctrl_mutex);
>  	return ret < 0 ? ret : 0;

-- 
Regards,

Laurent Pinchart