linux-kernel - Re: [PATCH v3 1/2] device property: Add scoped fwnode child node iterators

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Message-ID: <2025090203-epiphany-antsy-bf45@gregkh>
Date: Tue, 2 Sep 2025 06:50:08 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: Jean-François Lessard <jefflessard3@...il.com>
Cc: Danilo Krummrich <dakr@...nel.org>,
	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>,
	"Rafael J. Wysocki" <rafael@...nel.org>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v3 1/2] device property: Add scoped fwnode child node
 iterators

On Mon, Sep 01, 2025 at 02:16:35PM -0400, Jean-François Lessard wrote:
> Le 1 septembre 2025 13 h 48 min 14 s HAE, Danilo Krummrich <dakr@...nel.org> a écrit :
> >On 9/1/25 6:36 PM, 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>
> >
> >Thanks for adding a user and splitting it up (Andy was a bit faster than me :).
> >
> 
> Very welcome! Thanks for reviewing.
> 
> >> 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))
> >
> >IIRC, your first patch mentioned that your driver series would only use
> >fwnode_for_each_available_child_node_scoped().
> 
> You are correct. Next version of TM16XX driver patch series will use
> fwnode_for_each_available_child_node_scoped()
> 
> >
> >And this series adds a user for fwnode_for_each_child_node_scoped(); do you also have a user for fwnode_for_each_named_child_node_scoped()?
> 
> No, I haven't found an existing user that requires the scoped version. The only
> usage I found of the non-scoped fwnode_for_each_named_child_node() is in 
> drivers/base/property.c in fwnode_get_named_child_node_count(), which doesn't
> need to put the fwnode.
> 
> I included it for consistency since the header defines all three non-scoped
> variants, but I understand the "no dead code" policy concern.
> 
> Would you prefer I drop the fwnode_for_each_named_child_node_scoped() 
> variant and submit a v4 with only the two variants that have real users?

Yes please.