[U-Boot] [PATCH 3/6] libfdt: add fdtdec_lookup_phandle_index()

[Andre Przywara]

In some bindings a property points to multiple nodes, using a list of
phandles. A prominent example are UART pinctrl nodes, which use one node
to contain the RX/TX pins and another node to describe the lines used
for the hardware handshake.
The current fdtdec_lookup_phandle() helper function to chase a phandle
is quite convienent, but can only lookup the first of those handles.

Introduce an extra function fdtdec_lookup_phandle_index() to take an
index parameter and implement fdtdec_lookup_phandle() as a special case
of that.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
 include/fdtdec.h | 12 ++++++++++++
 lib/fdtdec.c     | 16 ++++++++++++----
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/include/fdtdec.h b/include/fdtdec.h
index eda2ffa..529e0fe 100644
--- a/include/fdtdec.h
+++ b/include/fdtdec.h
@@ -650,6 +650,18 @@ int fdtdec_get_chosen_node(const void *blob, const char *name);
  */
 const char *fdtdec_get_compatible(enum fdt_compat_id id);
 
+/* Look up a phandle with a given index and follow it to its node.
+ * Then return the offset of that node.
+ *
+ * @param blob		FDT blob
+ * @param node		node to examine
+ * @param prop_name	name of property to find
+ * @param index		index of the desired phandle in the list
+ * @return node offset if found, -ve error code on error
+ */
+int fdtdec_lookup_phandle_index(const void *blob, int node,
+				const char *prop_name, int index);
+
 /* Look up a phandle and follow it to its node. Then return the offset
  * of that node.
  *
diff --git a/lib/fdtdec.c b/lib/fdtdec.c
index 91503b8..e028a09 100644
--- a/lib/fdtdec.c
+++ b/lib/fdtdec.c
@@ -617,20 +617,28 @@ int fdtdec_prepare_fdt(void)
 	return 0;
 }
 
-int fdtdec_lookup_phandle(const void *blob, int node, const char *prop_name)
+int fdtdec_lookup_phandle_index(const void *blob, int node,
+				const char *prop_name, int index)
 {
 	const u32 *phandle;
 	int lookup;
+	int length;
 
 	debug("%s: %s\n", __func__, prop_name);
-	phandle = fdt_getprop(blob, node, prop_name, NULL);
-	if (!phandle)
+	phandle = fdt_getprop(blob, node, prop_name, &length);
+	if (!phandle || index * 4 >= length)
 		return -FDT_ERR_NOTFOUND;
 
-	lookup = fdt_node_offset_by_phandle(blob, fdt32_to_cpu(*phandle));
+	lookup = fdt_node_offset_by_phandle(blob,
+					    fdt32_to_cpu(phandle[index]));
 	return lookup;
 }
 
+int fdtdec_lookup_phandle(const void *blob, int node, const char *prop_name)
+{
+	return fdtdec_lookup_phandle_index(blob, node, prop_name, 0);
+}
+
 /**
  * Look up a property in a node and check that it has a minimum length.
  *
-- 
2.8.2