Re: [PATCH v4 1/9] of: property: add of_graph_get_next_port()

[Rob Herring <robh@kernel.org>]

On Wed, Aug 28, 2024 at 05:11:37AM +0000, Kuninori Morimoto wrote:
> We have endpoint base functions
> 	- of_graph_get_next_device_endpoint()
> 	- of_graph_get_device_endpoint_count()
> 	- for_each_of_graph_device_endpoint()
> 
> Here, for_each_of_graph_device_endpoint() loop finds each endpoints
> 
> 	ports {
> 		port@0 {
> (1)			endpoint {...};
> 		};
> 		port@1 {
> (2)			endpoint {...};
> 		};
> 		...
> 	};
> 
> In above case, it finds endpoint as (1) -> (2) -> ...
> 
> Basically, user/driver knows which port is used for what, but not in
> all cases. For example on flexible/generic driver case, how many ports
> are used is not fixed.
> 
> For example Sound Generic Card driver which is used from many venders
> can't know how many ports are used. Because the driver is very
> flexible/generic, it is impossible to know how many ports are used,
> it depends on each vender SoC and/or its used board.
> 
> And more, the port can have multi endpoints. For example Generic Sound
> Card case, it supports many type of connection between CPU / Codec, and
> some of them uses multi endpoint in one port.
> Then, Generic Sound Card want to handle each connection via "port"
> instead of "endpoint".
> But, it is very difficult to handle each "port" via existing
> for_each_of_graph_device_endpoint(). Getting "port" via of_get_parent()
> from "endpoint" doesn't work. see below.
> 
> 	ports {
> 		port@0 {
> (1)			endpoint@0 {...};
> (2)			endpoint@1 {...};
> 		};
> 		port@1 {
> (3)			endpoint {...};
> 		};
> 		...
> 	};
> 
> In other case, we want to handle "ports" same as "port" for some reasons.
> 
> 	node {
> =>		ports@0 {
> 			port@0 { ... };
> 			port@1 { ... };
> 			...
> 		};
> =>		ports@1 {
> 			...
> 		};
> 	};
> 
> Add "ports" / "port" base functions.
> 
> Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
> ---
>  drivers/of/property.c    | 108 +++++++++++++++++++++++++++++++++++++++
>  include/linux/of_graph.h |  49 ++++++++++++++++++
>  2 files changed, 157 insertions(+)
> 
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 164d77cb94458..d99b34dd2d5b4 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -625,6 +625,97 @@ struct device_node *of_graph_get_port_by_id(struct device_node *parent, u32 id)
>  }
>  EXPORT_SYMBOL(of_graph_get_port_by_id);
>  
> +/**
> + * of_graph_get_next_ports() - get next ports node.
> + * @parent: pointer to the parent device node
> + * @prev: previous ports node, or NULL to get first
> + *
> + * If "parent" node doesn't have "ports" node, it returns "parent" node itself as "ports" node.
> + *
> + * Return: A 'ports' node pointer with refcount incremented. Refcount
> + * of the passed @prev node is decremented.
> + */
> +struct device_node *of_graph_get_next_ports(struct device_node *parent,
> +					    struct device_node *prev)
> +{
> +	if (!parent)
> +		return NULL;
> +
> +	if (!prev) {
> +		/*
> +		 * Find "ports" node from parent
> +		 *
> +		 *	parent {
> +		 * =>		ports {
> +		 *			port {...};
> +		 *		};
> +		 *	};
> +		 */
> +		prev = of_get_child_by_name(parent, "ports");
> +
> +		/*
> +		 * Use parent as its ports if it not exist
> +		 *
> +		 * =>	parent {
> +		 *		port {...};
> +		 *	};
> +		 */
> +		if (!prev) {
> +			/* check whether "parent" has "port" node */
> +			struct device_node *port __free(device_node) = of_get_child_by_name(parent, "port");
> +
> +			if (port)
> +				prev = of_node_get(parent);
> +		}
> +
> +		return prev;
> +	}
> +
> +	/* Find next ports */
> +	do {
> +		prev = of_get_next_child(parent, prev);
> +		if (!prev)
> +			break;
> +	} while (!of_node_name_eq(prev, "ports"));
> +
> +	return prev;
> +}
> +EXPORT_SYMBOL(of_graph_get_next_ports);
> +
> +/**
> + * of_graph_get_next_port() - get next port node.
> + * @parent: pointer to the parent device node, or parent ports node
> + * @prev: previous port node, or NULL to get first
> + *
> + * Parent device node can be used as @parent whether device node has ports node or not.
> + * It will work same as ports@0 node.
> + *
> + * Return: A 'port' node pointer with refcount incremented. Refcount
> + * of the passed @prev node is decremented.
> + */
> +struct device_node *of_graph_get_next_port(struct device_node *parent,
> +					   struct device_node *prev)
> +{
> +	if (!parent)
> +		return NULL;
> +
> +	if (!prev) {
> +		struct device_node *ports __free(device_node) =
> +			of_graph_get_next_ports(parent, NULL);
> +
> +		return of_get_child_by_name(ports, "port");
> +	}
> +
> +	do {
> +		prev = of_get_next_child(parent, prev);
> +		if (!prev)
> +			break;
> +	} while (!of_node_name_eq(prev, "port"));
> +
> +	return prev;
> +}
> +EXPORT_SYMBOL(of_graph_get_next_port);

of_graph_is_present should be reimplemented using this function. So 
should part of of_graph_get_next_endpoint().

Rob