[PATCH 1/8] of: base: add of_parse_phandle_with_optional_args()

[Michael Walle]

Add a new variant of the of_parse_phandle_with_args() which treats the
cells name as optional. If it's missing, it is assumed that the phandle
has no arguments.

Up until now, a nvmem node didn't have any arguments, so all the device
trees haven't any '#*-cells' property. But there is a need for an
additional argument for the phandle, for which we need a '#*-cells'
property. Therefore, we need to support nvmem nodes with and without
this property.

Signed-off-by: Michael Walle <michael at walle.cc>
---
 drivers/of/base.c  | 23 +++++++++++++++++++++++
 include/linux/of.h | 12 ++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 5b907600f5b0..fb28bb26276e 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -1543,6 +1543,29 @@ int of_parse_phandle_with_args(const struct device_node *np, const char *list_na
 }
 EXPORT_SYMBOL(of_parse_phandle_with_args);
 
+/**
+ * of_parse_phandle_with_optional_args() - Find a node pointed by phandle in a list
+ *
+ * Same as of_parse_phandle_args() except that if the cells_name property is
+ * not found, cell_count of 0 is assumed.
+ *
+ * This is used to useful, if you have a phandle which didn't have arguments
+ * before and thus doesn't have a '#*-cells' property but is now migrated to
+ * having arguments while retaining backwards compatibility.
+ */
+int of_parse_phandle_with_optional_args(const struct device_node *np,
+					const char *list_name,
+					const char *cells_name, int index,
+					struct of_phandle_args *out_args)
+{
+	if (index < 0)
+		return -EINVAL;
+
+	return __of_parse_phandle_with_args(np, list_name, cells_name,
+					    0, index, out_args);
+}
+EXPORT_SYMBOL(of_parse_phandle_with_optional_args);
+
 /**
  * of_parse_phandle_with_args_map() - Find a node pointed by phandle in a list and remap it
  * @np:		pointer to a device tree node containing a list
diff --git a/include/linux/of.h b/include/linux/of.h
index ff143a027abc..ccace453d25f 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -376,6 +376,9 @@ extern int of_parse_phandle_with_args_map(const struct device_node *np,
 extern int of_parse_phandle_with_fixed_args(const struct device_node *np,
 	const char *list_name, int cells_count, int index,
 	struct of_phandle_args *out_args);
+extern int of_parse_phandle_with_optional_args(const struct device_node *np,
+	const char *list_name, const char *cells_name, int index,
+	struct of_phandle_args *out_args);
 extern int of_count_phandle_with_args(const struct device_node *np,
 	const char *list_name, const char *cells_name);
 
@@ -897,6 +900,15 @@ static inline int of_parse_phandle_with_fixed_args(const struct device_node *np,
 	return -ENOSYS;
 }
 
+static inline int of_parse_phandle_with_optional_args(const struct device_node *np,
+						      char *list_name,
+						      int cells_count,
+						      int index,
+						      struct of_phandle_args *out_args)
+{
+	return -ENOSYS;
+}
+
 static inline int of_count_phandle_with_args(const struct device_node *np,
 					     const char *list_name,
 					     const char *cells_name)
-- 
2.30.2