From: Ahmad Fatoum <a.fatoum@pengutronix.de>
Date: Wed, 2 Mar 2022 18:09:45 +0100
Subject: [PATCH] of_path: support phandles in of_find_path

of_find_path currently handles properties taking string values, like

  device-path = &partition;

Teach it to handle

  backend = <&phandle>;

as well. As differentiating phandle and string is only possible
heuristically, we add a new OF_FIND_PATH_FLAGS_PHANDLE0 to decode first
property cell as phandle.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Upstream-Status: Submitted [https://lore.kernel.org/all/20250411074045.2019372-1-a.fatoum@pengutronix.de/]
---
 drivers/of/of_path.c | 49 ++++++++++++++++++++++++++++++++-----------------
 include/of.h         |  3 ++-
 2 files changed, 34 insertions(+), 18 deletions(-)

diff --git a/drivers/of/of_path.c b/drivers/of/of_path.c
index 42efb1ad1dbf..a1a47cad0c20 100644
--- a/drivers/of/of_path.c
+++ b/drivers/of/of_path.c
@@ -254,7 +254,11 @@ struct device_node *of_find_node_by_devpath(struct device_node *root, const char
  * @outpath: if this function returns 0 outpath will contain the path belonging
  *           to the input path description. Must be freed with free().
  * @flags: use OF_FIND_PATH_FLAGS_BB to return the .bb device if available
+ *         bitwise OR OF_FIND_PATH_FLAGS_PHANDLE0 to decode first cell as phandle
  *
+ * With OF_FIND_PATH_FLAGS_PHANDLE0, the first cell is a phandle to a physical
+ * device or to a partition contained within. Otherwise, the property contains
+ * a full path to a partition described by the OF partition binding
  * paths in the devicetree have the form of a multistring property. The first
  * string contains the full path to the physical device containing the path or
  * a full path to a partition described by the OF partition binding.
@@ -270,29 +274,40 @@ struct device_node *of_find_node_by_devpath(struct device_node *root, const char
  * device-path = &mmc0, "partname:0";
  * device-path = &norflash, "partname:barebox-environment";
  * device-path = &environment_nor;
+ * backend     = <&environment_nor>; // with OF_FIND_PATH_FLAGS_PHANDLE0
  */
 int of_find_path(struct device_node *node, const char *propname, char **outpath, unsigned flags)
 {
 	struct device_node *rnode;
-	const char *path;
 	const char *part = NULL;
-	const char partnamestr[] = "partname:";
-
-	path = of_get_property(node, propname, NULL);
-	if (!path)
-		return -EINVAL;
-
-	rnode = of_find_node_by_path(path);
-	if (!rnode)
-		return -ENODEV;
-
-	of_property_read_string_index(node, propname, 1, &part);
-	if (part) {
-		if (!strncmp(part, partnamestr, sizeof(partnamestr) - 1)) {
-			part += sizeof(partnamestr) - 1;
-		} else {
-			pr_err("Invalid device-path: %s\n", part);
+
+	if (flags & OF_FIND_PATH_FLAGS_PHANDLE0) {
+		rnode = of_parse_phandle(node, propname, 0);
+		if (!rnode) {
+			pr_err("%s: Cannot resolve \"%s\" phandle\n",
+			       node->full_name, propname);
+			return -ENOENT;
+		}
+	} else {
+		const char partnamestr[] = "partname:";
+		const char *path;
+
+		path = of_get_property(node, propname, NULL);
+		if (!path)
 			return -EINVAL;
+
+		rnode = of_find_node_by_path(path);
+		if (!rnode)
+			return -ENODEV;
+
+		of_property_read_string_index(node, propname, 1, &part);
+		if (part) {
+			if (!strncmp(part, partnamestr, sizeof(partnamestr) - 1)) {
+				part += sizeof(partnamestr) - 1;
+			} else {
+				pr_err("Invalid device-path: %s\n", part);
+				return -EINVAL;
+			}
 		}
 	}
 
diff --git a/include/of.h b/include/of.h
index 55f2c0cbdedf..187a55439a8a 100644
--- a/include/of.h
+++ b/include/of.h
@@ -350,7 +350,8 @@ int of_add_memory(struct device_node *node, bool dump);
 int of_add_memory_bank(struct device_node *node, bool dump, int r,
 		u64 base, u64 size);
 struct device *of_find_device_by_node_path(const char *path);
-#define OF_FIND_PATH_FLAGS_BB 1		/* return .bb device if available */
+#define OF_FIND_PATH_FLAGS_BB		0x01	/* return .bb device if available */
+#define OF_FIND_PATH_FLAGS_PHANDLE0	0x10	/* parse phandle instead of string */
 int of_find_path(struct device_node *node, const char *propname, char **outpath, unsigned flags);
 struct cdev *of_cdev_find(struct device_node *node);
 int of_find_path_by_node(struct device_node *node, char **outpath, unsigned flags);