Hi Laurent,
On 07/01/2021 22:54, Laurent Pinchart wrote:
> From: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
>
> Make the V4L2 async framework a bit more robust by allowing to
> unregister a non-registered async subdev. Otherwise the
> v4l2_async_cleanup() will attempt to delete the async subdev from the
> subdev_list with the corresponding list_head not initialized.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/v4l2-core/v4l2-async.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 8bde33c21ce4..fc4525c4a75f 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -750,6 +750,9 @@ EXPORT_SYMBOL(v4l2_async_register_subdev);
>
> void v4l2_async_unregister_subdev(struct v4l2_subdev *sd)
> {
> + if (!sd->async_list.next)
> + return;
This is a bit opaque for anyone reading the code alone.
It could easily read as:
"If we don't have a following item in the async list - then don't
unregister?", which seems a bit nonsensical.
Hopefully that would make someone question what it's actually checking
but still.
I think I've seen you reference this pattern a couple of times so
perhaps having a way to check if a list is initialised would be worth
having as a helper in the list.
Otherwise, at least a comment to say that we're using the initialisation
of the list to determine if the async subdevice is already registered or
not. (perhaps a bit more briefly ;D)
Anyway, with that all in mind - I always like being able to simplify
error and clean up paths, so
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> +
> mutex_lock(&list_lock);
>
> __v4l2_async_notifier_unregister(sd->subdev_notifier);
>
