Re: [PATCH v4 1/7] device property: Helper to match multiple connections

Andy Shevchenko
2022-03-07T10:45:46Z

On Sun, Mar 06, 2022 at 07:40:34PM -0800, Bjorn Andersson wrote:
> In some cases multiple connections with the same connection id
> needs to be resolved from a fwnode graph.
>
> One such example is when separate hardware is used for performing muxing
> and/or orientation switching of the SuperSpeed and SBU lines in a USB
> Type-C connector. In this case the connector needs to belong to a graph
> with multiple matching remote endpoints, and the Type-C controller needs
> to be able to resolve them both.
>
> Add a new API that allows this kind of lookup.

Thanks for the update!

First of all, I have noticed that subject misses the verb, something like Add
or Introduce.

...

> +/**
> + * fwnode_connection_find_matches - Find connections from a device node
> + * @fwnode: Device node with the connection
> + * @con_id: Identifier for the connection
> + * @data: Data for the match function
> + * @match: Function to check and convert the connection description
> + * @matches: Array of pointers to fill with matches

(Optional) array...

> + * @matches_len: Length of @matches
> + *
> + * Find up to @matches_len connections with unique identifier @con_id between
> + * @fwnode and other device nodes. @match will be used to convert the
> + * connection description to data the caller is expecting to be returned
> + * through the @matches array.

> + * If @matches is NULL @matches_len is ignored and the total number of resolved
> + * matches is returned.

I would require matches_len to be 0, see below.

> + * Return: Number of matches resolved, or negative errno.
> + */
> +int fwnode_connection_find_matches(struct fwnode_handle *fwnode,
> + const char *con_id, void *data,
> + devcon_match_fn_t match,
> + void **matches, unsigned int matches_len)
> +{
> + unsigned int count_graph;
> + unsigned int count_ref;
> +
> + if (!fwnode || !match)
> + return -EINVAL;
> +
> + count_graph = fwnode_graph_devcon_matches(fwnode, con_id, data, match,
> + matches, matches_len);

> + if (matches) {
> + matches += count_graph;
> + matches_len -= count_graph;
> + }

So, the valid case is matches != NULL and matches_len == 0. For example, when
we have run something previously on the buffer and it becomes full.

In this case we have carefully handle this case.

if (matches) {
matches += count_graph;
if (matches_len)
matches_len -= count_graph;
}

Seems it can be also

if (matches)
matches += count_graph;

if (matches_len)
matches_len -= count_graph;

That said, do we have a test cases for this?

> + count_ref = fwnode_devcon_matches(fwnode, con_id, data, match,
> + matches, matches_len);
> +
> + return count_graph + count_ref;
> +}

--
With Best Regards,
Andy Shevchenko