[U-Boot] [RFC PATCH 04/44] libfdt: Add fdt_next_subnode() to permit easy subnode iteration

[Simon Glass]

This allows use to replace code like this:

for (ndepth = 0, count = 0,
	noffset = fdt_next_node(fit, images_noffset, &ndepth);
     (noffset >= 0) && (ndepth > 0);
     noffset = fdt_next_node(fit, noffset, &ndepth)) {
	if (ndepth == 1)
			...

with:

for (ndepth = 0,
		noffset = fdt_next_subnode(fit, image_noffset, &ndepth);
		noffset >= 0;
		noffset = fdt_next_subnode(fit, noffset, &ndepth)) {

which is slightly better, and doesn't require two levels of indentation for
code in the loop.

Signed-off-by: Simon Glass <sjg at chromium.org>
---
 include/libfdt.h |   17 +++++++++++++++++
 lib/libfdt/fdt.c |   12 ++++++++++++
 2 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/include/libfdt.h b/include/libfdt.h
index c93ae28..0dfb8a0 100644
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -136,6 +136,23 @@ uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset);
 
 int fdt_next_node(const void *fdt, int offset, int *depth);
 
+/**
+ * fdt_next_subnode() - get offset of next direct child
+ *
+ * Set depth to 0, offset to parent, then call this function repeatedly
+ * to get direct subnodes of a parent node.
+ *
+ * @fdt:	FDT blob
+ * @offset:	Set this to offset of parent for the first call. For
+ *		subsquent calls, pass in the value returns from the last
+ *		call.
+ * @depth:	Used internally to monitor depth - set this to 0 for the
+ *		first call.
+ * @return offset of next subnode, or -FDT_ERR_NOTFOUND if there are no more
+ * children
+ */
+int fdt_next_subnode(const void *fdt, int offset, int *depth);
+
 /**********************************************************************/
 /* General functions                                                  */
 /**********************************************************************/
diff --git a/lib/libfdt/fdt.c b/lib/libfdt/fdt.c
index 4157b21..8a0f323 100644
--- a/lib/libfdt/fdt.c
+++ b/lib/libfdt/fdt.c
@@ -202,6 +202,18 @@ int fdt_next_node(const void *fdt, int offset, int *depth)
 	return offset;
 }
 
+int fdt_next_subnode(const void *fdt, int offset, int *depth)
+{
+	/* Loop until we find a direct child of the parent (depth == 1) */
+	do {
+		offset = fdt_next_node(fdt, offset, depth);
+		if (offset < 0 || *depth < 1)
+			return -FDT_ERR_NOTFOUND;
+	} while (*depth > 1);
+
+	return offset;
+}
+
 const char *_fdt_find_string(const char *strtab, int tabsize, const char *s)
 {
 	int len = strlen(s) + 1;
-- 
1.7.7.3