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>
Acked-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 94 insertions, 0 deletions

diff --git a/tests/subnode_iterate.c b/tests/subnode_iterate.c
new file mode 100644
index 0000000..b9f379d
--- /dev/null
+++ b/tests/subnode_iterate.c
@@ -0,0 +1,94 @@
+/*
+ * libfdt - Flat Device Tree manipulation
+ *	Tests that fdt_next_subnode() works as expected
+ *
+ * Copyright (C) 2013 Google, Inc
+ *
+ * Copyright (C) 2007 David Gibson, IBM Corporation.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+
+#include <libfdt.h>
+
+#include "tests.h"
+#include "testdata.h"
+
+static void test_node(void *fdt, int parent_offset)
+{
+	fdt32_t subnodes;
+	const fdt32_t *prop;
+	int offset;
+	int count;
+	int len;
+
+	/* This property indicates the number of subnodes to expect */
+	prop = fdt_getprop(fdt, parent_offset, "subnodes", &len);
+	if (!prop || len != sizeof(fdt32_t)) {
+		FAIL("Missing/invalid subnodes property at '%s'",
+		     fdt_get_name(fdt, parent_offset, NULL));
+	}
+	subnodes = cpu_to_fdt32(*prop);
+
+	count = 0;
+	for (offset = fdt_first_subnode(fdt, parent_offset);
+	     offset >= 0;
+	     offset = fdt_next_subnode(fdt, offset))
+		count++;
+
+	if (count != subnodes) {
+		FAIL("Node '%s': Expected %d subnodes, got %d\n",
+		     fdt_get_name(fdt, parent_offset, NULL), subnodes,
+		     count);
+	}
+}
+
+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)) {
+		test_node(fdt, offset);
+		count++;
+	}
+
+	if (count != 2)
+		FAIL("Expected %d tests, got %d\n", 2, count);
+}
+
+int main(int argc, char *argv[])
+{
+	void *fdt;
+
+	test_init(argc, argv);
+	if (argc != 2)
+		CONFIG("Usage: %s <dtb file>", argv[0]);
+
+	fdt = load_blob(argv[1]);
+	if (!fdt)
+		FAIL("No device tree available");
+
+	check_fdt_next_subnode(fdt);
+
+	PASS();
+}