Re: [PATCH v4 4/5] media: uvcvideo: Make power management granular

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 26-Feb-25 15:23, Ricardo Ribalda wrote:
> Now that every ioctl takes care of their power management we can remove
> the "global" power management.
> 
> Despite its size, this is a relatively big change. We hope that there
> are no size effects of it. If there are some specific devices that
> miss-behave, we can add a small quirk for them.
> 
> This patch introduces a behavioral change for the uvc "trigger" button.
> It will not work unless the camera is streaming. We consider that this
> the most common (if not the only) usecase and therefore we do not consider
> it a regression.

You may want to expand this part of the commit message a bit and make it
clear that before the "trigger" button would work as long as an open has
/dev/video# open and now it only works when the camera is actually
streaming.

I agree that in practice this is not an issue since apps only open
the /dev/video# node for a longer period at a time (vs short open
for query/probe) when they actually want to stream.

Otherwise the patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@redhat.com>

Regards,

Hans




> 
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_v4l2.c | 8 --------
>  1 file changed, 8 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index 1c9ac72be58a..6af93e00b304 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -652,7 +652,6 @@ static int uvc_v4l2_open(struct file *file)
>  {
>  	struct uvc_streaming *stream;
>  	struct uvc_fh *handle;
> -	int ret = 0;
>  
>  	stream = video_drvdata(file);
>  	uvc_dbg(stream->dev, CALLS, "%s\n", __func__);
> @@ -662,12 +661,6 @@ static int uvc_v4l2_open(struct file *file)
>  	if (!handle)
>  		return -ENOMEM;
>  
> -	ret = uvc_pm_get(stream->dev);
> -	if (ret) {
> -		kfree(handle);
> -		return ret;
> -	}
> -
>  	v4l2_fh_init(&handle->vfh, &stream->vdev);
>  	v4l2_fh_add(&handle->vfh);
>  	handle->chain = stream->chain;
> @@ -701,7 +694,6 @@ static int uvc_v4l2_release(struct file *file)
>  	kfree(handle);
>  	file->private_data = NULL;
>  
> -	uvc_pm_put(stream->dev);
>  	return 0;
>  }
>  
>