linux-kernel - Re: [PATCH v7 1/6] of_graph: add of_graph_get_local

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Message-ID: <20200616012111.GE1629@pendragon.ideasonboard.com>
Date:   Tue, 16 Jun 2020 04:21:11 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/6] of_graph: add of_graph_get_local_port()

Hi Dmitry,

Thank you for the patch.

On Sun, Jun 14, 2020 at 08:22:29PM +0300, Dmitry Osipenko wrote:
> In some case, like a DRM display code for example, it's useful to silently
> check whether port node exists at all in a device-tree before proceeding
> with parsing the graph.
> 
> This patch adds of_graph_get_local_port() which returns pointer to a local
> port node, or NULL if graph isn't specified in a device-tree for a given
> device node.
> 
> Reviewed-by: Rob Herring <robh@...nel.org>
> Reviewed-by: Sam Ravnborg <sam@...nborg.org>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/of/property.c    | 32 +++++++++++++++++++++++---------
>  include/linux/of_graph.h |  7 +++++++
>  2 files changed, 30 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 1f2086f4e7ce..05c5f619b8bb 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -608,15 +608,7 @@ struct device_node *of_graph_get_next_endpoint(const struct device_node *parent,
>  	 * parent port node.
>  	 */
>  	if (!prev) {
> -		struct device_node *node;
> -
> -		node = of_get_child_by_name(parent, "ports");
> -		if (node)
> -			parent = node;
> -
> -		port = of_get_child_by_name(parent, "port");
> -		of_node_put(node);
> -
> +		port = of_graph_get_local_port(parent);
>  		if (!port) {
>  			pr_err("graph: no port node found in %pOF\n", parent);
>  			return NULL;
> @@ -765,6 +757,28 @@ struct device_node *of_graph_get_remote_port(const struct device_node *node)
>  }
>  EXPORT_SYMBOL(of_graph_get_remote_port);
>  
> +/**
> + * of_graph_get_local_port() - get local port node
> + * @node: pointer to a local endpoint device_node
> + *
> + * Return: First local port node associated with local endpoint node linked
> + *	   to @node. Use of_node_put() on it when done.
> + */
> +struct device_node *of_graph_get_local_port(const struct device_node *node)
> +{
> +	struct device_node *ports, *port;
> +
> +	ports = of_get_child_by_name(node, "ports");
> +	if (ports)
> +		node = ports;
> +
> +	port = of_get_child_by_name(node, "port");
> +	of_node_put(ports);
> +
> +	return port;

The implementation doesn't seem to match the documentation. If node is a
pointer to an endpoint, it should not have any ports child.

> +}
> +EXPORT_SYMBOL(of_graph_get_local_port);
> +
>  int of_graph_get_endpoint_count(const struct device_node *np)
>  {
>  	struct device_node *endpoint;
> diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
> index 01038a6aade0..1fdeb72c7765 100644
> --- a/include/linux/of_graph.h
> +++ b/include/linux/of_graph.h
> @@ -54,6 +54,7 @@ struct device_node *of_graph_get_remote_port_parent(
>  struct device_node *of_graph_get_remote_port(const struct device_node *node);
>  struct device_node *of_graph_get_remote_node(const struct device_node *node,
>  					     u32 port, u32 endpoint);
> +struct device_node *of_graph_get_local_port(const struct device_node *node);
>  #else
>  
>  static inline int of_graph_parse_endpoint(const struct device_node *node,
> @@ -116,6 +117,12 @@ static inline struct device_node *of_graph_get_remote_node(
>  	return NULL;
>  }
>  
> +static inline struct device_node *of_graph_get_local_port(
> +					const struct device_node *node)
> +{
> +	return NULL;
> +}
> +
>  #endif /* CONFIG_OF */
>  
>  #endif /* __LINUX_OF_GRAPH_H */
> -- 
> 2.26.0
> 

-- 
Regards,

Laurent Pinchart