[PATCH v2 02/20] of: base: add of_parse_phandle_with_optional_args()

Michael Walle
2022-09-01T22:21:26Z

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@walle.cc>
Reviewed-by: Rob Herring <robh@kernel.org>
---
changes since v1:
- none

include/linux/of.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/include/linux/of.h b/include/linux/of.h
index 766d002bddb9..a0fe1a017452 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -1008,6 +1008,31 @@ static inline int of_parse_phandle_with_fixed_args(const struct device_node *np,
index, out_args);
}

+/**
+ * of_parse_phandle_with_optional_args() - Find a node pointed by phandle in a list
+ * @np: pointer to a device tree node containing a list
+ * @list_name: property name that contains a list
+ * @cells_name: property name that specifies phandles' arguments count
+ * @index: index of a phandle to parse out
+ * @out_args: optional pointer to output arguments structure (will be filled)
+ *
+ * Same as of_parse_phandle_with_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.
+ */
+static inline 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)
+{
+ return __of_parse_phandle_with_args(np, list_name, cells_name,
+ 0, index, out_args);
+}
+
/**
* of_property_count_u8_elems - Count the number of u8 elements in a property
*
--
2.30.2