Re: [PATCH v3 1/3] media: v4l2-async: Accept endpoints and devices for fwnode matching

[Sakari Ailus <sakari.ailus@iki.fi>]

Hi Laurent,

On Sun, Jun 21, 2020 at 03:00:26AM +0300, 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 presence of remote endpoints)
> 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>
> Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
> Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> ---
> Changes since v2:
> 
> - Add comment to explain that we're matching connecting endpoints
> - Don't check fwnode name to detect endpoint
> ---
>  drivers/media/v4l2-core/v4l2-async.c | 45 +++++++++++++++++++++++++++-
>  1 file changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 8bde33c21ce4..f82e0a32647d 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -71,7 +71,50 @@ 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;
> +
> +	/*
> +	 * 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.
> +	 * Technically speaking this checks if the nodes refer to a connected
> +	 * endpoint, which is the simplest check that works for both OF and
> +	 * ACPI. This won't make a difference, as drivers should not try to
> +	 * match unconnected endpoints.
> +	 */
> +	sd_fwnode_is_ep = fwnode_property_present(sd->fwnode,
> +						  "remote-endpoint");
> +	asd_fwnode_is_ep = fwnode_property_present(asd->match.fwnode,
> +						   "remote-endpoint");

Please don't try parsing graph bindings outside the main parsers.

There's no API function to do just this, but you could go and check for the
port parent right away. The code might be even more simple that way.

Alternatively, I guess we could add fwnode_graph_is_endpoint() or something
but I wonder if it'd be worth it just for this.

> +
> +	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