Re: [PATCH] media: v4l2-async: fix binding async subdevs with multiple source ports

[Philipp Zabel <p.zabel@pengutronix.de>]

Hi,

On Wed, Aug 10, 2022 at 12:48:48PM +0200, Philipp Zabel wrote:
> Asynchronous subdevice probing on imx-media with imx6-mipi-csi2 is
> broken since commit 1f391df44607 ("media: v4l2-async: Use endpoints in
> __v4l2_async_nf_add_fwnode_remote()").
> 
> This is a side effect of imx6-mipi-csi2 having a single subdevice with
> four separate source ports connected to different subdevices. Before,
> the imx-media-csi and video-mux devices registered async sub-devices
> via device fwnode that matched the imx6-mipi-csi2 device on their
> respective notifiers. This caused the first asd to be put on the
> notifier waiting list, and the other three to return -EEXIST and be
> ignored.
> 
> With async subdev registration via endpoint fwnode, all four asds are
> distinct and three of them keep dangling on their notifiers after the
> first one is bound.
> 
> This patch modifies __v4l2_async_nf_has_async_subdev() to consider
> asds matching different fwnode endpoints of the same sub-device equal
> if the latter is already bound and matches via device fwnode. Further,
> v4l2_async_register_subdev() is modified to remove dangling duplicate
> asds that were registered before the sub-device was available to check
> its fwnode.
> 
> Fixes: 1f391df44607 ("media: v4l2-async: Use endpoints in __v4l2_async_nf_add_fwnode_remote()")
> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

Any comments on this? The issue persists on v6.2-rc3.

> ---
>  drivers/media/v4l2-core/v4l2-async.c | 43 ++++++++++++++++++++++++++++
>  1 file changed, 43 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 2f1b718a9189..b24220ed7077 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -452,6 +452,22 @@ __v4l2_async_nf_has_async_subdev(struct v4l2_async_notifier *notifier,
>  
>  		if (asd_equal(asd, sd->asd))
>  			return true;
> +
> +		/*
> +		 * If the asd matches an endpoint fwnode, handle sub-devices
> +		 * with device fwnode that were already matched by another asd
> +		 * with a different endpoint fwnode on the same device.
> +		 */
> +		if (asd->match_type == V4L2_ASYNC_MATCH_FWNODE &&
> +		    fwnode_graph_is_endpoint(asd->match.fwnode) &&
> +		    sd->fwnode && !fwnode_graph_is_endpoint(sd->fwnode)) {
> +			struct fwnode_handle *devnode;
> +
> +			devnode = fwnode_graph_get_port_parent(asd->match.fwnode);
> +			fwnode_handle_put(devnode);
> +			if (devnode == sd->fwnode)
> +				return true;
> +		}
>  	}
>  
>  	return false;
> @@ -749,6 +765,24 @@ __v4l2_async_nf_add_i2c(struct v4l2_async_notifier *notifier, int adapter_id,
>  }
>  EXPORT_SYMBOL_GPL(__v4l2_async_nf_add_i2c);
>  
> +static void v4l2_async_remove_duplicate_matches(struct v4l2_subdev *sd)
> +{
> +	struct v4l2_async_notifier *notifier;
> +
> +	lockdep_assert_held(&list_lock);
> +
> +	list_for_each_entry(notifier, &notifier_list, list) {
> +		struct v4l2_async_subdev *asd;
> +
> +		asd = v4l2_async_find_match(notifier, sd);
> +		if (!asd)
> +			continue;
> +
> +		/* Remove from the waiting list */
> +		list_del(&asd->list);
> +	}
> +}
> +
>  int v4l2_async_register_subdev(struct v4l2_subdev *sd)
>  {
>  	struct v4l2_async_notifier *subdev_notifier;
> @@ -783,6 +817,15 @@ int v4l2_async_register_subdev(struct v4l2_subdev *sd)
>  		if (ret)
>  			goto err_unbind;
>  
> +		/*
> +		 * At this point the asd is removed from the notifier wait list.
> +		 * There might be other notifiers with asds matching different
> +		 * fwnode endpoints of the same sd remaining. If the sd matches
> +		 * by device fwnode, remove the dangling asds.
> +		 */
> +		if (sd->fwnode && !fwnode_graph_is_endpoint(sd->fwnode))
> +			v4l2_async_remove_duplicate_matches(sd);
> +
>  		ret = v4l2_async_nf_try_complete(notifier);
>  		if (ret)
>  			goto err_unbind;
> -- 
> 2.30.2
> 
> 

regards
Philipp