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Date:   Fri, 18 Dec 2020 18:22:22 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Daniel Scally <djrscally@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-media@...r.kernel.org, devel@...ica.org, rjw@...ysocki.net,
        lenb@...nel.org, gregkh@...uxfoundation.org, yong.zhi@...el.com,
        sakari.ailus@...ux.intel.com, bingbu.cao@...el.com,
        tian.shu.qiu@...el.com, mchehab@...nel.org, robert.moore@...el.com,
        erik.kaneda@...el.com, pmladek@...e.com, rostedt@...dmis.org,
        sergey.senozhatsky@...il.com, andriy.shevchenko@...ux.intel.com,
        linux@...musvillemoes.dk,
        laurent.pinchart+renesas@...asonboard.com,
        jacopo+renesas@...ndi.org, kieran.bingham+renesas@...asonboard.com,
        linus.walleij@...aro.org, heikki.krogerus@...ux.intel.com,
        kitakar@...il.com, jorhand@...ux.microsoft.com
Subject: Re: [PATCH v2 06/12] software_node: Add support for fwnode_graph*()
 family of functions

Hi Daniel,

Thank you for the patch.

On Thu, Dec 17, 2020 at 11:43:31PM +0000, Daniel Scally wrote:
> From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> 
> This implements the remaining .graph_* callbacks in the
> fwnode operations structure for the software nodes. That makes
> the fwnode_graph*() functions available in the drivers also
> when software nodes are used.
> 
> The implementation tries to mimic the "OF graph" as much as
> possible, but there is no support for the "reg" device
> property. The ports will need to have the index in their
> name which starts with "port@" (for example "port@0", "port@1",
> ...) and endpoints will use the index of the software node
> that is given to them during creation. The port nodes can
> also be grouped under a specially named "ports" subnode,
> just like in DT, if necessary.
> 
> The remote-endpoints are reference properties under the
> endpoint nodes that are named "remote-endpoint".
> 
> Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Co-developed-by: Daniel Scally <djrscally@...il.com>
> Signed-off-by: Daniel Scally <djrscally@...il.com>
> ---
> Changes in v2:
> 
> 	- Changed commit to specify port name prefix as port@
> 	- Accounted for that rename in *parse_endpoint()
> 
>  drivers/base/swnode.c | 110 +++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 109 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
> index 2b90d380039b..0d14d5ebe441 100644
> --- a/drivers/base/swnode.c
> +++ b/drivers/base/swnode.c
> @@ -540,6 +540,110 @@ software_node_get_reference_args(const struct fwnode_handle *fwnode,
>  	return 0;
>  }
>  
> +static struct fwnode_handle *
> +swnode_graph_find_next_port(const struct fwnode_handle *parent,
> +			    struct fwnode_handle *port)
> +{
> +	struct fwnode_handle *old = port;
> +
> +	while ((port = software_node_get_next_child(parent, old))) {
> +		if (!strncmp(to_swnode(port)->node->name, "port", 4))

Maybe we'll need to limit this to matching on "port" or "port@[0-9]+" to
avoid false positives, but that can be done later, if needed.

> +			return port;
> +		old = port;
> +	}
> +
> +	return NULL;
> +}
> +
> +static struct fwnode_handle *
> +software_node_graph_get_next_endpoint(const struct fwnode_handle *fwnode,
> +				      struct fwnode_handle *endpoint)
> +{
> +	struct swnode *swnode = to_swnode(fwnode);
> +	struct fwnode_handle *old = endpoint;
> +	struct fwnode_handle *parent;
> +	struct fwnode_handle *port;
> +
> +	if (!swnode)
> +		return NULL;
> +
> +	if (endpoint) {
> +		port = software_node_get_parent(endpoint);

Here the reference count to port is incremented.

> +		parent = software_node_get_parent(port);
> +	} else {
> +		parent = software_node_get_named_child_node(fwnode, "ports");
> +		if (!parent)
> +			parent = software_node_get(&swnode->fwnode);
> +
> +		port = swnode_graph_find_next_port(parent, NULL);

But here it isn't, software_node_get_next_child() doesn't deal with
reference counts.

> +	}
> +
> +	for (; port; port = swnode_graph_find_next_port(parent, port)) {

So if the loop terminates normally, the reference acquired in the first
branch of the if will be leaked.

> +		endpoint = software_node_get_next_child(port, old);
> +		if (endpoint) {
> +			fwnode_handle_put(port);

While in this case the reference not acquired in the second branch of
the if will be released incorrectly.

I think it's software_node_get_next_child() that needs to be fixed if
I'm not mistaken.

> +			break;
> +		}
> +
> +		/* No more endpoints for that port, so stop passing old */
> +		old = NULL;

I wonder if you could drop the 'old' variable and use 'enpoint' in the
call to software_node_get_next_child(). You could then drop these two
lines.

> +	}
> +
> +	fwnode_handle_put(parent);
> +
> +	return endpoint;
> +}
> +
> +static struct fwnode_handle *
> +software_node_graph_get_remote_endpoint(const struct fwnode_handle *fwnode)
> +{
> +	struct swnode *swnode = to_swnode(fwnode);
> +	const struct software_node_ref_args *ref;
> +	const struct property_entry *prop;
> +
> +	if (!swnode)
> +		return NULL;
> +
> +	prop = property_entry_get(swnode->node->properties, "remote-endpoint");
> +	if (!prop || prop->type != DEV_PROP_REF || prop->is_inline)
> +		return NULL;
> +
> +	ref = prop->pointer;
> +
> +	return software_node_get(software_node_fwnode(ref[0].node));
> +}
> +
> +static struct fwnode_handle *
> +software_node_graph_get_port_parent(struct fwnode_handle *fwnode)
> +{
> +	struct swnode *swnode = to_swnode(fwnode);
> +	struct fwnode_handle *parent;
> +
> +	if (!strcmp(swnode->parent->node->name, "ports"))
> +		parent = &swnode->parent->parent->fwnode;
> +	else
> +		parent = &swnode->parent->fwnode;
> +
> +	return software_node_get(parent);
> +}
> +
> +static int
> +software_node_graph_parse_endpoint(const struct fwnode_handle *fwnode,
> +				   struct fwnode_endpoint *endpoint)
> +{
> +	struct swnode *swnode = to_swnode(fwnode);
> +	int ret;
> +
> +	ret = kstrtou32(swnode->parent->node->name + 5, 10, &endpoint->port);
> +	if (ret)
> +		return ret;
> +
> +	endpoint->id = swnode->id;
> +	endpoint->local_fwnode = fwnode;
> +
> +	return 0;
> +}
> +
>  static const struct fwnode_operations software_node_ops = {
>  	.get = software_node_get,
>  	.put = software_node_put,
> @@ -551,7 +655,11 @@ static const struct fwnode_operations software_node_ops = {
>  	.get_parent = software_node_get_parent,
>  	.get_next_child_node = software_node_get_next_child,
>  	.get_named_child_node = software_node_get_named_child_node,
> -	.get_reference_args = software_node_get_reference_args
> +	.get_reference_args = software_node_get_reference_args,
> +	.graph_get_next_endpoint = software_node_graph_get_next_endpoint,
> +	.graph_get_remote_endpoint = software_node_graph_get_remote_endpoint,
> +	.graph_get_port_parent = software_node_graph_get_port_parent,
> +	.graph_parse_endpoint = software_node_graph_parse_endpoint,
>  };
>  
>  /* -------------------------------------------------------------------------- */

-- 
Regards,

Laurent Pinchart

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