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

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Message-ID: <2025082953-splendor-unsold-e4f2@gregkh>
Date: Fri, 29 Aug 2025 06:23:22 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Jean-François Lessard <jefflessard3@...il.com>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>,
	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>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] device property: Add scoped fwnode child node iterators

On Thu, Aug 28, 2025 at 10:17:59PM -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.
> 
> 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.
> 
>  include/linux/property.h | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> 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);
>  

We need a real user of this before we can add them, so please do that as
part of a patch series.

thanks

greg k-h