linux-kernel - [RFC PATCH 2/5] of: Introduce for_each_child_of_node_scoped() to automate of_node

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Date: Sun, 28 Jan 2024 16:05:39 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: linux-iio@...r.kernel.org,
	Rob Herring <robh@...nel.org>,
	Frank Rowand <frowand.list@...il.com>,
	linux-kernel@...r.kernel.org
Cc: Julia Lawall <Julia.Lawall@...ia.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Sumera Priyadarsini <sylphrenadin@...il.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nuno Sá <nuno.sa@...log.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [RFC PATCH 2/5] of: Introduce for_each_child_of_node_scoped() to automate of_node_put() handling

From: Jonathan Cameron <Jonathan.Cameron@...wei.com>

To avoid issues with out of order cleanup, or ambiguity about when the
auto freed data is first instantiated, do it within the for loop definition.

The disadvantage is that the struct device_node *child variable creation
is not immediately obvious where this is used.
However, in many cases, if there is another definition of
struct device_node *child; the compiler / static analysers will notify us
that it is unused, or uninitialized.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
---
 include/linux/of.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/of.h b/include/linux/of.h
index 50e882ee91da..f822226eac6d 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -1434,6 +1434,12 @@ static inline int of_property_read_s32(const struct device_node *np,
 	for (child = of_get_next_available_child(parent, NULL); child != NULL; \
 	     child = of_get_next_available_child(parent, child))
 
+#define for_each_child_of_node_scoped(parent, child) \
+	for (struct device_node *child __free(device_node) =		\
+	     of_get_next_child(parent, NULL);				\
+	     child != NULL;						\
+	     child = of_get_next_available_child(parent, child))
+
 #define for_each_of_cpu_node(cpu) \
 	for (cpu = of_get_next_cpu_node(NULL); cpu != NULL; \
 	     cpu = of_get_next_cpu_node(cpu))
-- 
2.43.0