[PATCH v2 1/6] libfdt: Add a subnodes iterator macro

[Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>]

From: Thierry Reding <treding@xxxxxxxxxx>

The fdt_for_each_subnode() iterator macro provided by this patch can be
used to iterate over a device tree node's subnodes. At each iteration a
loop variable will be set to the next subnode.

Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
---
 libfdt/libfdt.h         | 25 +++++++++++++++++++++++++
 tests/subnode_iterate.c |  8 ++------
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index 36222fd4a6f4..0cf46872b54e 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -168,6 +168,31 @@ int fdt_first_subnode(const void *fdt, int offset);
  */
 int fdt_next_subnode(const void *fdt, int offset);
 
+/**
+ * fdt_for_each_subnode - iterate over all subnodes of a parent
+ *
+ * This is actually a wrapper around a for loop and would be used like so:
+ *
+ *	fdt_for_each_subnode(fdt, node, parent) {
+ *		...
+ *		use node
+ *		...
+ *	}
+ *
+ * Note that this is implemented as a macro and node is used as iterator in
+ * the loop. It should therefore be a locally allocated variable. The parent
+ * variable on the other hand is never modified, so it can be constant or
+ * even a literal.
+ *
+ * @node:	child node (int)
+ * @fdt:	FDT blob (const void *)
+ * @parent:	parent node (int)
+ */
+#define fdt_for_each_subnode(node, fdt, parent)		\
+	for (node = fdt_first_subnode(fdt, parent);	\
+	     node >= 0;					\
+	     node = fdt_next_subnode(fdt, node))
+
 /**********************************************************************/
 /* General functions                                                  */
 /**********************************************************************/
diff --git a/tests/subnode_iterate.c b/tests/subnode_iterate.c
index b9f379d5963c..0fb5c901ebd7 100644
--- a/tests/subnode_iterate.c
+++ b/tests/subnode_iterate.c
@@ -48,9 +48,7 @@ static void test_node(void *fdt, int parent_offset)
 	subnodes = cpu_to_fdt32(*prop);
 
 	count = 0;
-	for (offset = fdt_first_subnode(fdt, parent_offset);
-	     offset >= 0;
-	     offset = fdt_next_subnode(fdt, offset))
+	fdt_for_each_subnode(offset, fdt, parent_offset)
 		count++;
 
 	if (count != subnodes) {
@@ -65,9 +63,7 @@ static void check_fdt_next_subnode(void *fdt)
 	int offset;
 	int count = 0;
 
-	for (offset = fdt_first_subnode(fdt, 0);
-	     offset >= 0;
-	     offset = fdt_next_subnode(fdt, offset)) {
+	fdt_for_each_subnode(offset, fdt, 0) {
 		test_node(fdt, offset);
 		count++;
 	}
-- 
2.9.0

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