[PATCH v4 3/8] libfdt: Add max phandle retrieval function

[Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>]

Add a function to retrieve the highest phandle in a given device tree.

Acked-by: Simon Glass <sjg@xxxxxxxxxxxx>
Reviewed-by: Stefan Agner <stefan@xxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
---
 libfdt/fdt_ro.c     | 26 ++++++++++++++++++++++++++
 libfdt/libfdt.h     | 15 +++++++++++++++
 tests/get_phandle.c |  6 ++++++
 3 files changed, 47 insertions(+)

diff --git a/libfdt/fdt_ro.c b/libfdt/fdt_ro.c
index 50cce864283c..04590984bd51 100644
--- a/libfdt/fdt_ro.c
+++ b/libfdt/fdt_ro.c
@@ -88,6 +88,32 @@ static int _fdt_string_eq(const void *fdt, int stroffset,
 	return (strlen(p) == len) && (memcmp(p, s, len) == 0);
 }
 
+uint32_t fdt_get_max_phandle(const void *fdt)
+{
+	uint32_t max_phandle = 0;
+	int offset;
+
+	for (offset = fdt_next_node(fdt, -1, NULL);;
+	     offset = fdt_next_node(fdt, offset, NULL)) {
+		uint32_t phandle;
+
+		if (offset == -FDT_ERR_NOTFOUND)
+			return max_phandle;
+
+		if (offset < 0)
+			return (uint32_t)-1;
+
+		phandle = fdt_get_phandle(fdt, offset);
+		if (phandle == (uint32_t)-1)
+			continue;
+
+		if (phandle > max_phandle)
+			max_phandle = phandle;
+	}
+
+	return 0;
+}
+
 int fdt_get_mem_rsv(const void *fdt, int n, uint64_t *address, uint64_t *size)
 {
 	FDT_CHECK_HEADER(fdt);
diff --git a/libfdt/libfdt.h b/libfdt/libfdt.h
index be109a8aac84..06b84cc16bbf 100644
--- a/libfdt/libfdt.h
+++ b/libfdt/libfdt.h
@@ -286,6 +286,21 @@ int fdt_move(const void *fdt, void *buf, int bufsize);
  */
 const char *fdt_string(const void *fdt, int stroffset);
 
+/**
+ * fdt_get_max_phandle - retrieves the highest phandle in a tree
+ * @fdt: pointer to the device tree blob
+ *
+ * fdt_get_max_phandle retrieves the highest phandle in the given
+ * device tree. This will ignore badly formatted phandles, or phandles
+ * with a value of 0 or -1.
+ *
+ * returns:
+ *      the highest phandle on success
+ *      0, if no phandle was found in the device tree
+ *      -1, if an error occurred
+ */
+uint32_t fdt_get_max_phandle(const void *fdt);
+
 /**
  * fdt_num_mem_rsv - retrieve the number of memory reserve map entries
  * @fdt: pointer to the device tree blob
diff --git a/tests/get_phandle.c b/tests/get_phandle.c
index 2079591d4c49..22bd7b81b3f0 100644
--- a/tests/get_phandle.c
+++ b/tests/get_phandle.c
@@ -44,6 +44,7 @@ static void check_phandle(void *fdt, const char *path, uint32_t checkhandle)
 
 int main(int argc, char *argv[])
 {
+	uint32_t max;
 	void *fdt;
 
 	test_init(argc, argv);
@@ -53,5 +54,10 @@ int main(int argc, char *argv[])
 	check_phandle(fdt, "/subnode@2", PHANDLE_1);
 	check_phandle(fdt, "/subnode@2/subsubnode@0", PHANDLE_2);
 
+	max = fdt_get_max_phandle(fdt);
+	if (max != PHANDLE_2)
+		FAIL("fdt_get_max_phandle returned 0x%x instead of 0x%x\n",
+		     max, PHANDLE_2);
+
 	PASS();
 }
-- 
2.9.2

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