libfdt: Add fdt_next_subnode() to permit easy subnode iteration

Iterating through subnodes with libfdt is a little painful to write as we
need something like this:

for (depth = 0, count = 0,
	offset = fdt_next_node(fdt, parent_offset, &depth);
     (offset >= 0) && (depth > 0);
     offset = fdt_next_node(fdt, offset, &depth)) {
	if (depth == 1) {
		/* code body */
	}
}

Using fdt_next_subnode() we can instead write this, which is shorter and
easier to get right:

for (offset = fdt_first_subnode(fdt, parent_offset);
     offset >= 0;
     offset = fdt_next_subnode(fdt, offset)) {
	/* code body */
}

Also, it doesn't require two levels of indentation for the loop body.

Signed-off-by: Simon Glass <sjg@chromium.org>
(Cherry-picked from dtc commit 4e76ec79)
Acked-by: Gerald Van Baren <vanbaren@cideas.com>

diff --git a/include/libfdt.h b/include/libfdt.h
index 7403d5a6dba41a67a0a9a527c0c381ac8e4fa80e..c5ec2acfd82927f070923e118766aad22986b3a9 100644 (file)
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -136,6 +136,28 @@ uint32_t fdt_next_tag(const void *fdt, int offset, int *nextoffset);
 
 int fdt_next_node(const void *fdt, int offset, int *depth);
 
+/**
+ * fdt_first_subnode() - get offset of first direct subnode
+ *
+ * @fdt:       FDT blob
+ * @offset:    Offset of node to check
+ * @return offset of first subnode, or -FDT_ERR_NOTFOUND if there is none
+ */
+int fdt_first_subnode(const void *fdt, int offset);
+
+/**
+ * fdt_next_subnode() - get offset of next direct subnode
+ *
+ * After first calling fdt_first_subnode(), call this function repeatedly to
+ * get direct subnodes of a parent node.
+ *
+ * @fdt:       FDT blob
+ * @offset:    Offset of previous subnode
+ * @return offset of next subnode, or -FDT_ERR_NOTFOUND if there are no more
+ * subnodes
+ */
+int fdt_next_subnode(const void *fdt, int offset);
+
 /**********************************************************************/
 /* General functions                                                  */
 /**********************************************************************/

diff --git a/lib/libfdt/fdt.c b/lib/libfdt/fdt.c
index 387e3544b7e578832eb4f27b443547b92d7e966a..154e9a4461794dc9ec7271e1b61cda38703626b9 100644 (file)
--- a/lib/libfdt/fdt.c
+++ b/lib/libfdt/fdt.c
@@ -202,6 +202,34 @@ int fdt_next_node(const void *fdt, int offset, int *depth)
        return offset;
 }
 
+int fdt_first_subnode(const void *fdt, int offset)
+{
+       int depth = 0;
+
+       offset = fdt_next_node(fdt, offset, &depth);
+       if (offset < 0 || depth != 1)
+               return -FDT_ERR_NOTFOUND;
+
+       return offset;
+}
+
+int fdt_next_subnode(const void *fdt, int offset)
+{
+       int depth = 1;
+
+       /*
+        * With respect to the parent, the depth of the next subnode will be
+        * the same as the last.
+        */
+       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;