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

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

[Jean-François Lessard]

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@gmail.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

Re: [PATCH v2] device property: Add scoped fwnode child node iterators

[Andy Shevchenko]

On Fri, Aug 29, 2025 at 09:00:08AM -0400, Jean-François Lessard wrote:
> 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.

The problem is that these two are not coupled, means there is no need to send
a single patch, so, please split to a series of two.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2] device property: Add scoped fwnode child node iterators

[Jean-François Lessard]

Le 1 septembre 2025 05 h 18 min 41 s HAE, Andy Shevchenko <andriy.shevchenko@linux.intel.com> a écrit :
>On Fri, Aug 29, 2025 at 09:00:08AM -0400, Jean-François Lessard wrote:
>> 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.
>
>The problem is that these two are not coupled, means there is no need to send
>a single patch, so, please split to a series of two.
>

Understood. I'll submit v3 splitted in a series of two.