4.9-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 36156f9241cb0f9e37d998052873ca7501ad4b36 ]
Add of_get_compatible_child() helper that can be used to lookup compatible child nodes.
Several drivers currently use of_find_compatible_node() to lookup child nodes while failing to notice that the of_find_ functions search the entire tree depth-first (from a given start node) and therefore can match unrelated nodes. The fact that these functions also drop a reference to the node they start searching from (e.g. the parent node) is typically also overlooked, something which can lead to use-after-free bugs.
Signed-off-by: Johan Hovold johan@kernel.org Signed-off-by: Rob Herring robh@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/of/base.c | 25 +++++++++++++++++++++++++ include/linux/of.h | 8 ++++++++ 2 files changed, 33 insertions(+)
diff --git a/drivers/of/base.c b/drivers/of/base.c index 466b285cef3e..f366af135d5b 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -738,6 +738,31 @@ struct device_node *of_get_next_available_child(const struct device_node *node, } EXPORT_SYMBOL(of_get_next_available_child);
+/** + * of_get_compatible_child - Find compatible child node + * @parent: parent node + * @compatible: compatible string + * + * Lookup child node whose compatible property contains the given compatible + * string. + * + * Returns a node pointer with refcount incremented, use of_node_put() on it + * when done; or NULL if not found. + */ +struct device_node *of_get_compatible_child(const struct device_node *parent, + const char *compatible) +{ + struct device_node *child; + + for_each_child_of_node(parent, child) { + if (of_device_is_compatible(child, compatible)) + break; + } + + return child; +} +EXPORT_SYMBOL(of_get_compatible_child); + /** * of_get_child_by_name - Find the child node by name for a given parent * @node: parent node diff --git a/include/linux/of.h b/include/linux/of.h index 299aeb192727..a19cc85b9373 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -275,6 +275,8 @@ extern struct device_node *of_get_next_child(const struct device_node *node, extern struct device_node *of_get_next_available_child( const struct device_node *node, struct device_node *prev);
+extern struct device_node *of_get_compatible_child(const struct device_node *parent, + const char *compatible); extern struct device_node *of_get_child_by_name(const struct device_node *node, const char *name);
@@ -606,6 +608,12 @@ static inline bool of_have_populated_dt(void) return false; }
+static inline struct device_node *of_get_compatible_child(const struct device_node *parent, + const char *compatible) +{ + return NULL; +} + static inline struct device_node *of_get_child_by_name( const struct device_node *node, const char *name)