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of: add helper to lookup compatible child node

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[ 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>
This commit is contained in:
Johan Hovold 2018-08-27 10:21:45 +02:00 committed by Greg Kroah-Hartman
parent c6a4b3c3b8
commit c1ede7043d
2 changed files with 33 additions and 0 deletions
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25
drivers/of/base.c
View File

@ -737,6 +737,31 @@ 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

8
include/linux/of.h
View File

@ -288,6 +288,8 @@ 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);
@ -625,6 +627,12 @@ 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)