Re: [PATCH v4 1/2] device property: Add scoped fwnode child node iterators

Sakari Ailus
2025-09-03T13:18:39Z

Hi Jean-François,

On Tue, Sep 02, 2025 at 03:04:39PM -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_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:
> MACRO_ARG_REUSE, MACRO_ARG_PRECEDENCE
> This is a standard iterator pattern following kernel conventions.
>
> include/linux/property.h | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/include/linux/property.h b/include/linux/property.h
> index 82f0cb3ab..862e20813 100644
> --- a/include/linux/property.h
> +++ b/include/linux/property.h
> @@ -176,6 +176,16 @@ 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_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))
> +

Do we really need the available variant?

Please see
<URL:https://lore.kernel.org/linux-acpi/Zwj12J5bTNUEnxA0@kekkonen.localdomain/>.

I'll post a patch to remove fwnode_get_next_available_child_node(), too.

> struct fwnode_handle *device_get_next_child_node(const struct device *dev,
> struct fwnode_handle *child);
>

--
Kind regards,

Sakari Ailus