Re: [PATCHv3 1/6] media: core: v4l2-async.c: unreg subdev if asc_list is empty

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Hans,

Thanks for the patch.

On Mon, Jun 29, 2026 at 08:55:49AM +0200, Hans Verkuil wrote:
> In v4l2_device_unregister_subdev(), if sd->asc_list is empty,
> then v4l2_device_unregister_subdev() is never called, but that
> should still happen.
> 
> This causes crashes with em28xx that uses tvp5150: that i2c
> module uses v4l2_async, but em28xx does not as it predates
> v4l2_async.

Isn't the sub-device unregistered via v4l2_device_unregister() or do I miss
something? em28xx_v4l2_fini() calls it.

Or do you mean the issue happens at tvp5150 unbind time?

> 
> So if sd->asc_list is empty, then just call
> v4l2_device_unregister_subdev().
> 
> Fixes: 28a1295795d8 ("media: v4l: async: Allow multiple connections between entities")
> Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
> ---
>  drivers/media/v4l2-core/v4l2-async.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 888a2e213b08..d7437c958028 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -898,9 +898,13 @@ void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
>  	sd->subdev_notifier = NULL;
>  
>  	if (sd->asc_list.next) {
> -		list_for_each_entry_safe(asc, asc_tmp, &sd->asc_list,
> -					 asc_subdev_entry) {
> -			v4l2_async_unbind_subdev_one(asc->notifier, asc);
> +		if (list_empty(&sd->asc_list)) {
> +			v4l2_device_unregister_subdev(sd);
> +		} else {
> +			list_for_each_entry_safe(asc, asc_tmp, &sd->asc_list,
> +						 asc_subdev_entry) {
> +				v4l2_async_unbind_subdev_one(asc->notifier, asc);
> +			}
>  		}
>  	}
>  

-- 
Kind regards,

Sakari Ailus