Re: [PATCH] media: v4l2-async: Accept endpoints and devices for fwnode matching

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

Hi Laurent,

Thanks for the patch.

On Sun, Mar 15, 2020 at 02:55:11PM +0200, Laurent Pinchart wrote:
> fwnode matching was designed to match on nodes corresponding to a
> device. Some drivers, however, needed to match on endpoints, and have
> passed endpoint fwnodes to v4l2-async. This works when both the subdev
> and the notifier use the same fwnode types (endpoint or device), but
> makes drivers that use different types incompatible.
> 
> Fix this by extending the fwnode match to handle fwnodes of different
> types. When the types (deduced from the node name) are different,
> retrieve the device fwnode for the side that provides an endpoint
> fwnode, and compare it with the device fwnode provided by the other
> side. This allows interoperability between all drivers, regardless of
> which type of fwnode they use for matching.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> ---
> This has been compile-tested only. Prabhakar, could you check if it
> fixes your issue ?
> 
>  drivers/media/v4l2-core/v4l2-async.c | 42 +++++++++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 8bde33c21ce4..995e5464cba7 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -71,7 +71,47 @@ static bool match_devname(struct v4l2_subdev *sd,
>  
>  static bool match_fwnode(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
>  {
> -	return sd->fwnode == asd->match.fwnode;
> +	struct fwnode_handle *other_fwnode;
> +	struct fwnode_handle *dev_fwnode;
> +	bool asd_fwnode_is_ep;
> +	bool sd_fwnode_is_ep;
> +	const char *name;
> +
> +	/*
> +	 * Both the subdev and the async subdev can provide either an endpoint
> +	 * fwnode or a device fwnode. Start with the simple case of direct
> +	 * fwnode matching.
> +	 */
> +	if (sd->fwnode == asd->match.fwnode)
> +		return true;
> +
> +	/*
> +	 * Otherwise, check if the sd fwnode and the asd fwnode refer to an
> +	 * endpoint or a device. If they're of the same type, there's no match.
> +	 */
> +	name = fwnode_get_name(sd->fwnode);
> +	sd_fwnode_is_ep = name && strstarts(name, "endpoint");
> +	name = fwnode_get_name(asd->match.fwnode);
> +	asd_fwnode_is_ep = name && strstarts(name, "endpoint");

Apart from the fact that you're parsing graph node names here, this looks
good.

How about checking instead that calling
fwnode_graph_get_remote_endpoint(fwnode_graph_get_remote_endpoint()) yields
the same node? That would ensure you're dealing with endpoint nodes without
explicitly parsing the graph in any way.

Just remember to drop the references.

> +
> +	if (sd_fwnode_is_ep == asd_fwnode_is_ep)
> +		return false;
> +
> +	/*
> +	 * The sd and asd fwnodes are of different types. Get the device fwnode
> +	 * parent of the endpoint fwnode, and compare it with the other fwnode.
> +	 */
> +	if (sd_fwnode_is_ep) {
> +		dev_fwnode = fwnode_graph_get_port_parent(sd->fwnode);
> +		other_fwnode = asd->match.fwnode;
> +	} else {
> +		dev_fwnode = fwnode_graph_get_port_parent(asd->match.fwnode);
> +		other_fwnode = sd->fwnode;
> +	}
> +
> +	fwnode_handle_put(dev_fwnode);
> +
> +	return dev_fwnode == other_fwnode;
>  }
>  
>  static bool match_custom(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)

-- 
Kind regards,

Sakari Ailus