Re: [PATCH] media: uvcvideo: Fail probe when no video device is registered

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Wed, Nov 04, 2026 at 10:21:46AM +0800, Chen Changcheng wrote:
> When a UVC device is unbound while userspace still holds the video
> device open, the VS interface claims are released only after the last
> file descriptor is closed.  Rebinding before that fails to claim the VS
> interfaces, leaving the VC interface bound without a usable video
> device:
> 
>   [ 3229.189556] uvcvideo: Probing generic UVC device 1
>   [ 3229.190496] uvcvideo: device 2 interface 1 is already claimed
>   ...
>   [ 3229.193758] uvcvideo: Scanning UVC chain: OT 4 <- XU 3 <- PU 2 <- IT 1
>   [ 3229.193766] uvcvideo: Found a valid video chain (1 -> 4).
>   [ 3229.193771] usb 9-1: No streaming interface found for terminal 4.
> 
> Check after registering all video chains that at least one video device
> was registered, and fail the probe with -ENODEV otherwise.

That's a workaround, it doesn't fix the root cause.

> Devices with no usable streaming interface at all will now also stay
> unbound instead of being bound without any video device.
> 
> Signed-off-by: Chen Changcheng <chenchangcheng@kylinos.cn>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index e289cc71ba98..0943db4eae07 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -2156,6 +2156,19 @@ static int uvc_register_terms(struct uvc_device *dev,
>  	return 0;
>  }
>  
> +static int uvc_has_video_node(struct uvc_device *dev)
> +{
> +	struct uvc_streaming *stream;
> +
> +	list_for_each_entry(stream, &dev->streams, list)
> +		if (video_is_registered(&stream->queue.vdev))
> +			return 0;
> +
> +	dev_info(&dev->intf->dev,
> +		 "No usable streaming interface found\n");
> +	return -ENODEV;
> +}
> +
>  static int uvc_register_chains(struct uvc_device *dev)
>  {
>  	struct uvc_video_chain *chain;
> @@ -2174,7 +2187,7 @@ static int uvc_register_chains(struct uvc_device *dev)
>  #endif
>  	}
>  
> -	return 0;
> +	return uvc_has_video_node(dev);
>  }
>  
>  /* ------------------------------------------------------------------------
> 
> base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222

-- 
Regards,

Laurent Pinchart