linux-kernel - Re: [PATCH 5/8] of: Add of_graph_get_port_by

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Message-ID: <2335139.eKsPusnO4R@avalon>
Date:	Wed, 20 Aug 2014 22:13:34 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Philipp Zabel <p.zabel@...gutronix.de>
Cc:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	devel@...verdev.osuosl.org, Grant Likely <grant.likely@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Guennadi Liakhovetski <g.liakhovetski@....de>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Russell King <rmk+kernel@....linux.org.uk>,
	kernel@...gutronix.de
Subject: Re: [PATCH 5/8] of: Add of_graph_get_port_by_id function

Hi Philipp,

Thank you for the patch.

On Tuesday 19 August 2014 15:02:43 Philipp Zabel wrote:
> This patch adds a function to get a port device tree node by port id,
> or reg property value.
> 
> Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
> ---
>  drivers/of/base.c        | 30 ++++++++++++++++++++++++++++++
>  include/linux/of_graph.h |  7 +++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index a49b5628..6044c15 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -2053,6 +2053,36 @@ int of_graph_parse_endpoint(const struct device_node
> *node, EXPORT_SYMBOL(of_graph_parse_endpoint);
> 
>  /**
> + * of_graph_get_port_by_id() - get the port matching a given id
> + * @parent: pointer to the parent device node
> + * @id: id of the port
> + *
> + * Return: A 'port' node pointer with refcount incremented.The caller

Missing space before "The".

> + * has to use of_node_put() on it when done.
> + */
> +struct device_node *of_graph_get_port_by_id(struct device_node *node, int
> id)

How about making id and unsigned int, as it can't be negative ?

> +{
> +	struct device_node *port = NULL;
> +	int port_id;
> +
> +	while (true) {
> +		port = of_get_next_child(node, port);
> +		if (!port)
> +			return NULL;
> +		if (of_node_cmp(port->name, "port") != 0)
> +			continue;
> +		if (of_property_read_u32(port, "reg", &port_id)) {
> +			if (!id)
> +				return port;
> +		} else {
> +			if (id == port_id)
> +				return port;
> +		}

Nitpicking here, I would have written this

		int port_id = 0;

		port = of_get_next_child(node, port);
		if (!port)
			return NULL;
		if (of_node_cmp(port->name, "port") != 0)
			continue;
		of_property_read_u32(port, "reg", &port_id);
		if (id == port_id)
			return port;

That saves 8 bytes with my ARM cross-compiler (at the expense of using two 
extra local registers).

Please free to ignore this is you find your code layout easier to read.

> +	}
> +}
> +EXPORT_SYMBOL(of_graph_get_port_by_id);
> +
> +/**
>   * of_graph_get_next_endpoint() - get next endpoint node
>   * @parent: pointer to the parent device node
>   * @prev: previous endpoint node, or NULL to get first
> diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
> index 2890a4c..24ceb4b 100644
> --- a/include/linux/of_graph.h
> +++ b/include/linux/of_graph.h
> @@ -33,6 +33,7 @@ struct of_endpoint {
>  #ifdef CONFIG_OF
>  int of_graph_parse_endpoint(const struct device_node *node,
>  				struct of_endpoint *endpoint);
> +struct device_node *of_graph_get_port_by_id(struct device_node *node, int
> id); struct device_node *of_graph_get_next_endpoint(const struct
> device_node *parent, struct device_node *previous);
>  struct device_node *of_graph_get_remote_port_parent(
> @@ -46,6 +47,12 @@ static inline int of_graph_parse_endpoint(const struct
> device_node *node, return -ENOSYS;
>  }
> 
> +static inline struct device_node *of_graph_get_port_by_id(
> +					struct device_node *node, int id)
> +{
> +	return NULL;
> +}
> +
>  static inline struct device_node *of_graph_get_next_endpoint(
>  					const struct device_node *parent,
>  					struct device_node *previous)

-- 
Regards,

Laurent Pinchart

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