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of: add helper to lookup compatible child node

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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>
This commit is contained in:
Johan Hovold
2018-08-27 10:21:45 +02:00
committed by Rob Herring
parent 5b394b2ddf
commit 36156f9241
2 changed files with 33 additions and 0 deletions
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8
include/linux/of.h
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@@ -290,6 +290,8 @@ 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);
@@ -632,6 +634,12 @@ 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)