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Date:   Sun, 15 Mar 2020 12:29:56 +0200
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Lad Prabhakar <prabhakar.csengg@gmail.com>
Cc:     Niklas <niklas.soderlund@ragnatech.se>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        linux-media@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Subject: Re: [PATCH 2/2] media: rcar-csi2: Let the driver handle fwnode
 matching using match_custom callback
Message-ID: <20200315102956.GA4732@pendragon.ideasonboard.com>
References: <20200315102724.26850-1-prabhakar.mahadev-lad.rj@bp.renesas.com>
 <20200315102724.26850-3-prabhakar.mahadev-lad.rj@bp.renesas.com>
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Hi Prabhakar,

Thank you for the patch.

On Sun, Mar 15, 2020 at 10:27:24AM +0000, Lad Prabhakar wrote:
> The rcar-csi2 driver uses the v4l2-async framework to do endpoint matching
> instead of node matching. This is needed as it needs to work with the
> adv748x driver which register it self in v4l2-async using endpoints
> instead of nodes. The reason for this is that from a single DT node it
> creates multiple subdevices, one for each endpoint.
> 
> But when using subdevs which register itself in v4l2-async using nodes,
> the rcar-csi2 driver failed to find the matching endpoint because the
> match.fwnode was pointing to remote endpoint instead of remote parent
> port.
> 
> This commit adds support in rcar-csi2 driver to handle both the cases
> where subdev registers in v4l2-async using endpoints/nodes, by using
> match_type as V4L2_ASYNC_MATCH_CUSTOM and implementing the match()
> callback to compare the fwnode of either remote/parent.

This is not the way to go. The v4l2-async framework needs to be fixed
instead, so that fwnode match will do the right thing automatically
regardless of whether the node is a device node or and endpoint node.

> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> ---
>  drivers/media/platform/rcar-vin/rcar-csi2.c | 46 +++++++++++++++++++--
>  1 file changed, 43 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
> index faa9fb23a2e9..1bbf05e9f025 100644
> --- a/drivers/media/platform/rcar-vin/rcar-csi2.c
> +++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
> @@ -808,6 +808,46 @@ static int rcsi2_parse_v4l2(struct rcar_csi2 *priv,
>  	return 0;
>  }
>  
> +static bool rcsi2_asd_match(struct v4l2_subdev *sd,
> +			    struct v4l2_async_subdev *asd)
> +{
> +	struct rcar_csi2 *priv = (struct rcar_csi2 *)asd->match.custom.priv;
> +	struct fwnode_handle *remote_endpoint;
> +	struct fwnode_handle *subdev_endpoint;
> +	struct device_node *np;
> +	bool matched = false;
> +
> +	np = of_graph_get_endpoint_by_regs(priv->dev->of_node, 0, 0);
> +	if (!np) {
> +		dev_err(priv->dev, "Not connected to subdevice\n");
> +		return matched;
> +	}
> +
> +	remote_endpoint =
> +		fwnode_graph_get_remote_endpoint(of_fwnode_handle(np));
> +	if (!remote_endpoint) {
> +		dev_err(priv->dev, "Failed to get remote endpoint\n");
> +		of_node_put(np);
> +		return matched;
> +	}
> +	of_node_put(np);
> +
> +	if (sd->fwnode != dev_fwnode(sd->dev)) {
> +		if (remote_endpoint == sd->fwnode)
> +			matched = true;
> +	} else {
> +		subdev_endpoint =
> +		      fwnode_graph_get_next_endpoint(dev_fwnode(sd->dev), NULL);
> +		if (remote_endpoint == subdev_endpoint)
> +			matched = true;
> +		fwnode_handle_put(subdev_endpoint);
> +	}
> +
> +	fwnode_handle_put(remote_endpoint);
> +
> +	return matched;
> +}
> +
>  static int rcsi2_parse_dt(struct rcar_csi2 *priv)
>  {
>  	struct device_node *ep;
> @@ -833,9 +873,9 @@ static int rcsi2_parse_dt(struct rcar_csi2 *priv)
>  		return ret;
>  	}
>  
> -	priv->asd.match.fwnode =
> -		fwnode_graph_get_remote_endpoint(of_fwnode_handle(ep));
> -	priv->asd.match_type = V4L2_ASYNC_MATCH_FWNODE;
> +	priv->asd.match.custom.match = &rcsi2_asd_match;
> +	priv->asd.match.custom.priv = priv;
> +	priv->asd.match_type = V4L2_ASYNC_MATCH_CUSTOM;
>  
>  	of_node_put(ep);
>  

-- 
Regards,

Laurent Pinchart