linux-kernel - [PATCH v2] device property: Add scoped fwnode child node iterators

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Message-ID: <20250829130010.12959-1-jefflessard3@gmail.com>
Date: Fri, 29 Aug 2025 09:00:08 -0400
From: Jean-François Lessard <jefflessard3@...il.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Daniel Scally <djrscally@...il.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>
Cc: linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: [PATCH v2] device property: Add scoped fwnode child node iterators

Add scoped versions of fwnode child node iterators that automatically
handle reference counting cleanup using the __free() attribute:

- fwnode_for_each_child_node_scoped()
- fwnode_for_each_named_child_node_scoped()
- fwnode_for_each_available_child_node_scoped()

These macros follow the same pattern as existing scoped iterators in the
kernel, ensuring fwnode references are automatically released when the
iterator variable goes out of scope. This prevents resource leaks and
eliminates the need for manual cleanup in error paths.

The implementation mirrors the non-scoped variants but uses
__free(fwnode_handle) for automatic resource management, providing a safer
and more convenient interface for drivers iterating over firmware node
children.

Signed-off-by: Jean-François Lessard <jefflessard3@...il.com>
---

Notes:
    checkpatch reports false positives that are intentionally ignored:
    COMPLEX_MACRO, MACRO_ARG_REUSE, MACRO_ARG_PRECEDENCE
    This is a standard iterator pattern following kernel conventions.
    
v2 changelog:
- replace manual __free(fwnode_handle) of i2c-core-slave.c with
  fwnode_for_each_child_node_scoped

 drivers/i2c/i2c-core-slave.c |  3 +--
 include/linux/property.h     | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/i2c-core-slave.c b/drivers/i2c/i2c-core-slave.c
index 7ee6b992b..02ca55c22 100644
--- a/drivers/i2c/i2c-core-slave.c
+++ b/drivers/i2c/i2c-core-slave.c
@@ -112,10 +112,9 @@ bool i2c_detect_slave_mode(struct device *dev)
 	struct fwnode_handle *fwnode = dev_fwnode(dev);
 
 	if (is_of_node(fwnode)) {
-		struct fwnode_handle *child __free(fwnode_handle) = NULL;
 		u32 reg;
 
-		fwnode_for_each_child_node(fwnode, child) {
+		fwnode_for_each_child_node_scoped(fwnode, child) {
 			fwnode_property_read_u32(child, "reg", &reg);
 			if (reg & I2C_OWN_SLAVE_ADDRESS)
 				return true;
diff --git a/include/linux/property.h b/include/linux/property.h
index 82f0cb3ab..279c244db 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -176,6 +176,20 @@ struct fwnode_handle *fwnode_get_next_available_child_node(
 	for (child = fwnode_get_next_available_child_node(fwnode, NULL); child;\
 	     child = fwnode_get_next_available_child_node(fwnode, child))
 
+#define fwnode_for_each_child_node_scoped(fwnode, child)		\
+	for (struct fwnode_handle *child __free(fwnode_handle) =	\
+		fwnode_get_next_child_node(fwnode, NULL);		\
+	     child; child = fwnode_get_next_child_node(fwnode, child))
+
+#define fwnode_for_each_named_child_node_scoped(fwnode, child, name)	\
+	fwnode_for_each_child_node_scoped(fwnode, child)		\
+		for_each_if(fwnode_name_eq(child, name))
+
+#define fwnode_for_each_available_child_node_scoped(fwnode, child)	\
+	for (struct fwnode_handle *child __free(fwnode_handle) =	\
+		fwnode_get_next_available_child_node(fwnode, NULL);	\
+	     child; child = fwnode_get_next_available_child_node(fwnode, child))
+
 struct fwnode_handle *device_get_next_child_node(const struct device *dev,
 						 struct fwnode_handle *child);
 
-- 
2.43.0