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@xxxxxxxxxxx>
> ---
> 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);
> +
