linux-kernel - Re: [PATCH 1/3] media: uvcvideo: Refactor uvc_queue

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Message-ID: <5b2c5e93-3e5d-497e-aef5-89f3474be2c7@xs4all.nl>
Date: Mon, 2 Jun 2025 09:32:08 +0200
From: Hans Verkuil <hverkuil@...all.nl>
To: Ricardo Ribalda <ribalda@...omium.org>,
 Laurent Pinchart <laurent.pinchart@...asonboard.com>,
 Hans de Goede <hdegoede@...hat.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] media: uvcvideo: Refactor uvc_queue_streamon

On 22/05/2025 19:58, Ricardo Ribalda wrote:
> Do uvc_pm_get before we call uvc_queue_streamon. Although the current
> code is correct, uvc_ioctl_streamon is allways called after uvc_pm_get,

allways -> always

> this change makes the code more resiliant to future changes.

I would add that this change also avoids calling streamoff, which is
a rather ugly thing to do.

> 
> Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>

Reviewed-by: Hans Verkuil <hverkuil@...all.nl>

Regards,

	Hans

> ---
>  drivers/media/usb/uvc/uvc_v4l2.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index 668a4e9d772c6d91f045ca75e2744b3a6c69da6b..862b4e34e5b629cf324479a9bb59ebe8784ccd5d 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -853,15 +853,16 @@ static int uvc_ioctl_streamon(struct file *file, void *fh,
>  	if (handle->is_streaming)
>  		return 0;
>  
> -	ret = uvc_queue_streamon(&stream->queue, type);
> +	ret = uvc_pm_get(stream->dev);
>  	if (ret)
>  		return ret;
>  
> -	ret = uvc_pm_get(stream->dev);
> +	ret = uvc_queue_streamon(&stream->queue, type);
>  	if (ret) {
> -		uvc_queue_streamoff(&stream->queue, type);
> +		uvc_pm_put(stream->dev);
>  		return ret;
>  	}
> +
>  	handle->is_streaming = true;
>  
>  	return 0;
>