Re: [PATCH v2 01/13] of: property: add port base loop

[Rob Herring <robh@kernel.org>]

On Mon, Jan 29, 2024 at 12:54:44AM +0000, Kuninori Morimoto wrote:
> We have endpoint base functions
> 	- of_graph_get_next_endpoint()
> 	- of_graph_get_endpoint_count()
> 	- for_each_endpoint_of_node()
> 
> Here, for_each_endpoint_of_node() loop finds each endpoints
> 
> 	ports {
> 		port@0 {
> (1)			endpoint {...};
> 		};
> 		port@1 {
> (2)			endpoint {...};
> 		};
> 		...
> 	};
> 
> In above case, for_each_endpoint_of_node() loop 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" by
> for_each_endpoint_of_node(). Getting "port" by using of_get_parent()
> from "endpoint" doesn't work. see below.
> 
> 	ports {
> 		port@0 {
> (1)			endpoint@0 {...};
> (2)			endpoint@1 {...};
> 		};
> 		port@1 {
> (3)			endpoint {...};
> 		};
> 		...
> 	};
> 
> Add "port" base functions.
> 
> Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
> ---
>  drivers/of/property.c    | 48 ++++++++++++++++++++++++++++++++++++++++
>  include/linux/of_graph.h | 21 ++++++++++++++++++
>  2 files changed, 69 insertions(+)
> 
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index afdaefbd03f6..9e670e99dbbb 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -631,6 +631,42 @@ 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_port() - get next port node
> + * @parent: pointer to the parent device node
> + * @port: current port node, or NULL to get first
> + *
> + * Return: An 'port' node pointer with refcount incremented. Refcount
> + * of the passed @prev node is decremented.
> + */
> +struct device_node *of_graph_get_next_port(const struct device_node *parent,
> +					   struct device_node *port)
> +{
> +	if (!parent)
> +		return NULL;
> +
> +	if (!port) {
> +		struct device_node *node;
> +
> +		node = of_get_child_by_name(parent, "ports");
> +		if (node) {
> +			parent = node;
> +			of_node_put(node);

The original code had this right, but here you have it wrong.

You are releasing ports here, but then using it...

> +		}
> +
> +		return of_get_child_by_name(parent, "port");

...here. You have to get the child before you can put the parent.

> +	}
> +
> +	do {
> +		port = of_get_next_child(parent, port);
> +		if (!port)
> +			break;
> +	} while (!of_node_name_eq(port, "port"));
> +
> +	return port;
> +}
> +EXPORT_SYMBOL(of_graph_get_next_port);
> +