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[POWERPC] Add of_get_next_parent()
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Iterating through a device node's parents is simple enough, but dealing
with the refcounts properly is a little ugly, and replicating that logic
is asking for someone to get it wrong or forget it all together, eg:

while (dn != NULL) {
	/* loop body */
	tmp = of_get_parent(dn);
	of_node_put(dn);
	dn = tmp;
}

So add of_get_next_parent(), inspired by of_get_next_child().  The
contract is that it returns the parent and drops the reference on the
current node, this makes the loop look like:

while (dn != NULL) {
	/* loop body */
	dn = of_get_next_parent(dn);
}

Signed-off-by: Michael Ellerman <[email protected]>
Acked-by: David S. Miller <[email protected]>
Signed-off-by: Paul Mackerras <[email protected]>
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mpe authored and paulusmack committed Feb 6, 2008
1 parent 5811906 commit f4eb010
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Showing 2 changed files with 26 additions and 0 deletions.
25 changes: 25 additions & 0 deletions drivers/of/base.c
Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,31 @@ struct device_node *of_get_parent(const struct device_node *node)
}
EXPORT_SYMBOL(of_get_parent);

/**
* of_get_next_parent - Iterate to a node's parent
* @node: Node to get parent of
*
* This is like of_get_parent() except that it drops the
* refcount on the passed node, making it suitable for iterating
* through a node's parents.
*
* Returns a node pointer with refcount incremented, use
* of_node_put() on it when done.
*/
struct device_node *of_get_next_parent(struct device_node *node)
{
struct device_node *parent;

if (!node)
return NULL;

read_lock(&devtree_lock);
parent = of_node_get(node->parent);
of_node_put(node);
read_unlock(&devtree_lock);
return parent;
}

/**
* of_get_next_child - Iterate a node childs
* @node: parent node
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1 change: 1 addition & 0 deletions include/linux/of.h
Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@ extern struct device_node *of_find_matching_node(struct device_node *from,
extern struct device_node *of_find_node_by_path(const char *path);
extern struct device_node *of_find_node_by_phandle(phandle handle);
extern struct device_node *of_get_parent(const struct device_node *node);
extern struct device_node *of_get_next_parent(struct device_node *node);
extern struct device_node *of_get_next_child(const struct device_node *node,
struct device_node *prev);
#define for_each_child_of_node(parent, child) \
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