linux-kernel - Re: [PATCH v1 3/3] v4l: async: Match parent devices

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Date:   Thu, 18 May 2017 17:01:48 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Kieran Bingham <kbingham@...nel.org>
Cc:     linux-renesas-soc@...r.kernel.org, linux-media@...r.kernel.org,
        sakari.ailus@....fi, niklas.soderlund@...natech.se,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Tuukka Toivonen <tuukka.toivonen@...el.com>,
        Javi Merino <javi.merino@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 3/3] v4l: async: Match parent devices

Hi Kieran,

Thank you for the patch.

On Wednesday 17 May 2017 16:03:39 Kieran Bingham wrote:
> From: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> 
> Devices supporting multiple endpoints on a single device node must set
> their subdevice fwnode to the endpoint to allow distinct comparisons.
> 
> Adapt the match_fwnode call to compare against the provided fwnodes
> first, but also to search for a comparison against the parent fwnode.
> 
> This allows notifiers to pass the endpoint for comparison and still
> support existing subdevices which store their default parent device
> node.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
> ---
>  drivers/media/v4l2-core/v4l2-async.c | 20 ++++++++++++++++----
>  1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c
> b/drivers/media/v4l2-core/v4l2-async.c index e1e181db90f7..65735a5c4350
> 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -41,14 +41,26 @@ static bool match_devname(struct v4l2_subdev *sd,
>  	return !strcmp(asd->match.device_name.name, dev_name(sd->dev));
>  }
> 
/*
 * Check whether the two device_node pointers refer to the same OF node. We
 * can't compare pointers directly as they can differ if overlays have been
 * applied.
 */

> +static bool match_of(struct device_node *a, struct device_node *b)
> +{
> +	return !of_node_cmp(of_node_full_name(a), of_node_full_name(b));
> +}
> +
>  static bool match_fwnode(struct v4l2_subdev *sd, struct v4l2_async_subdev
> *asd)
> {
> +	struct device_node *sdnode;
> +	struct fwnode_handle *async_device;

I would name this asd_fwnode, and to be consistent rename sdnode to sd_ofnode.

> +
> +	async_device = fwnode_graph_get_port_parent(asd->match.fwnode.fwnode);
> +
>  	if (!is_of_node(sd->fwnode) || !is_of_node(asd->match.fwnode.fwnode))
> -		return sd->fwnode == asd->match.fwnode.fwnode;
> +		return sd->fwnode == asd->match.fwnode.fwnode ||
> +		       sd->fwnode == async_device;

I wonder whether we could simplify this by changing the 
fwnode_graph_get_port_parent() API. At the moment the function walks two or 
three levels up depending on whether there's a ports name or not. If we turned 
in into a function that accepts an endpoint, port or device node, and returns 
the device node unconditionally (basically, returning the argument if its name 
is not "port(@[0-9]+)?" or "endpoint(@[0-9]+)?", and walking up until it 
reaches the device node otherwise), you could write the above

	asd_fwnode = fwnode_graph_get_port_parent(asd->match.fwnode.fwnode);

  	if (!is_of_node(sd->fwnode) || !is_of_node(asd_fwnode))
		       sd->fwnode == asd_fwnode;

	sdnode = to_of_node(sd->fwnode);
 
	return match_of(sdnode, to_of_node(asd_node));

> +
> +	sdnode = to_of_node(sd->fwnode);
> 
> -	return !of_node_cmp(of_node_full_name(to_of_node(sd->fwnode)),
> -			    of_node_full_name(
> -				    to_of_node(asd->match.fwnode.fwnode)));
> +	return match_of(sdnode, to_of_node(asd->match.fwnode.fwnode)) ||
> +	       match_of(sdnode, to_of_node(async_device));

This is getting a bit complex, could you document the function ?

>  }
> 
>  static bool match_custom(struct v4l2_subdev *sd, struct v4l2_async_subdev
> *asd)

-- 
Regards,

Laurent Pinchart