[PATCH v8 01/16] device property: Add fwnode_graph_get_port_by_id()

[Chen-Yu Tsai <wenst@chromium.org>]

In some cases the driver needs a reference to the port firmware node.
Once such case is the upcoming USB power sequencing integration. The
USB hub port is tied to the corresponding port firmware node if it
exists.

Provide a helper for this.

Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
---
Changes since v7:
- Mention in kernel-doc that the function does not return ports that
  have no endpoints (Sakari)

Changes since v5:
- Dropped left-over declaration in header (Sashiko)

Changes since v4:
- Added flags parameter so users can specify whether incomplete ports
  are returned or not (Sashiko)

Changes since v2:
- Moved "Return:" kernel-doc section to the end. (Andy)

Changes since v1:
- New patch
---
 drivers/base/property.c  | 31 +++++++++++++++++++++++++++++++
 include/linux/property.h |  2 ++
 2 files changed, 33 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index b136c339ddae..68108805482d 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -1353,6 +1353,37 @@ int fwnode_graph_parse_endpoint(const struct fwnode_handle *fwnode,
 }
 EXPORT_SYMBOL(fwnode_graph_parse_endpoint);
 
+/**
+ * fwnode_graph_get_port_by_id - get the port matching a given id
+ * @fwnode: parent fwnode_handle containing the graph
+ * @id: id of the port
+ * @flags: fwnode lookup flags
+ *
+ * The caller is responsible for calling fwnode_handle_put() on the returned
+ * fwnode pointer.
+ *
+ * Does not return ports that belong to disabled devices or endpoints that
+ * are unconnected, unless FWNODE_GRAPH_DEVICE_DISABLED is passed in @flags.
+ *
+ * Does not return ports that have no endpoints.
+ *
+ * Return: A 'port' firmware node pointer with refcount incremented.
+ */
+struct fwnode_handle *fwnode_graph_get_port_by_id(struct fwnode_handle *fwnode,
+						  u32 id,
+						  unsigned long flags)
+{
+	struct fwnode_handle *ep;
+
+	ep = fwnode_graph_get_endpoint_by_id(fwnode, id, 0,
+					     flags | FWNODE_GRAPH_ENDPOINT_NEXT);
+	if (!ep)
+		return NULL;
+
+	return fwnode_get_next_parent(ep);
+}
+EXPORT_SYMBOL_GPL(fwnode_graph_get_port_by_id);
+
 const void *device_get_match_data(const struct device *dev)
 {
 	return fwnode_call_ptr_op(dev_fwnode(dev), device_get_match_data, dev);
diff --git a/include/linux/property.h b/include/linux/property.h
index 907c790a3f01..3dbbd01a52d0 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -507,6 +507,8 @@ int fwnode_get_phy_mode(const struct fwnode_handle *fwnode);
 
 void __iomem *fwnode_iomap(struct fwnode_handle *fwnode, int index);
 
+struct fwnode_handle *fwnode_graph_get_port_by_id(struct fwnode_handle *fwnode, u32 id,
+						  unsigned long flags);
 struct fwnode_handle *fwnode_graph_get_next_endpoint(
 	const struct fwnode_handle *fwnode, struct fwnode_handle *prev);
 struct fwnode_handle *
-- 
2.55.0.979.g7e5102b832-goog