[PATCH v2 1/6] device property: Helper to match multiple connections

[Bjorn Andersson <bjorn.andersson@linaro.org>]

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-C
connector. In this case the connector needs to belong to a graph with
multiple matching remote endpoints, and the TypeC controller needs to be
able to resolve them both.

Add a new API that allows this kind of lookup.

Given that the match() callback returns an opaque reference to something
provided by the client it's not possible for the implementation to
release the returned object and as such it's not possible to handle
errors, which in turn means that it's not possible to query the number
of elements or dynamically grow the results array. It's however expected
that the number of matches will be reasonably low and that the worst
case is known by the caller before hand.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---

Changes since v1:
- Iterator in fwnode_devcon_matches() is now unsigned.
- fwnode_handle_put() node for unavailable nodes.
- Extended commit message on the subject of supporting dynamically sized
  "matches" array.

 drivers/base/property.c  | 96 ++++++++++++++++++++++++++++++++++++++++
 include/linux/property.h |  5 +++
 2 files changed, 101 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index e6497f6877ee..5230ff5c8d48 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -1189,6 +1189,38 @@ fwnode_graph_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
 	return NULL;
 }
 
+static unsigned int fwnode_graph_devcon_matches(struct fwnode_handle *fwnode,
+						const char *con_id, void *data,
+						devcon_match_fn_t match,
+						void **matches,
+						unsigned int matches_len)
+{
+	struct fwnode_handle *node;
+	struct fwnode_handle *ep;
+	unsigned int count = 0;
+	void *ret;
+
+	fwnode_graph_for_each_endpoint(fwnode, ep) {
+		if (count >= matches_len) {
+			fwnode_handle_put(ep);
+			return count;
+		}
+
+		node = fwnode_graph_get_remote_port_parent(ep);
+		if (!fwnode_device_is_available(node)) {
+			fwnode_handle_put(node);
+			continue;
+		}
+
+		ret = match(node, con_id, data);
+		fwnode_handle_put(node);
+
+		if (ret)
+			matches[count++] = ret;
+	}
+	return count;
+}
+
 static void *
 fwnode_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
 		    void *data, devcon_match_fn_t match)
@@ -1211,6 +1243,35 @@ fwnode_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
 	return NULL;
 }
 
+static unsigned int fwnode_devcon_matches(struct fwnode_handle *fwnode,
+					  const char *con_id, void *data,
+					  devcon_match_fn_t match,
+					  void **matches,
+					  unsigned int matches_len)
+{
+	struct fwnode_handle *node;
+	unsigned int count = 0;
+	unsigned int i;
+	void *ret;
+
+	for (i = 0; ; i++) {
+		if (count >= matches_len)
+			return count;
+
+		node = fwnode_find_reference(fwnode, con_id, i);
+		if (IS_ERR(node))
+			break;
+
+		ret = match(node, NULL, data);
+		fwnode_handle_put(node);
+
+		if (ret)
+			matches[count++] = ret;
+	}
+
+	return count;
+}
+
 /**
  * fwnode_connection_find_match - Find connection from a device node
  * @fwnode: Device node with the connection
@@ -1238,3 +1299,38 @@ void *fwnode_connection_find_match(struct fwnode_handle *fwnode,
 	return fwnode_devcon_match(fwnode, con_id, data, match);
 }
 EXPORT_SYMBOL_GPL(fwnode_connection_find_match);
+
+/**
+ * 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
+ * @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.
+ *
+ * Return: Number of matches resolved, of 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;
+
+	if (!fwnode || !match || !matches)
+		return -EINVAL;
+
+	count = fwnode_graph_devcon_matches(fwnode, con_id, data, match,
+					    matches, matches_len);
+
+	return count + fwnode_devcon_matches(fwnode, con_id, data, match,
+					     matches + count,
+					     matches_len - count);
+}
+EXPORT_SYMBOL_GPL(fwnode_connection_find_matches);
diff --git a/include/linux/property.h b/include/linux/property.h
index 7399a0b45f98..aa7ef9d06ebe 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -446,6 +446,11 @@ static inline void *device_connection_find_match(struct device *dev,
 	return fwnode_connection_find_match(dev_fwnode(dev), con_id, data, match);
 }
 
+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);
+
 /* -------------------------------------------------------------------------- */
 /* Software fwnode support - when HW description is incomplete or missing */
 
-- 
2.33.1