[PATCH v2 02/15] of: base: add of_parse_phandle_with_optional_args()

[Marco Felsch <m.felsch@pengutronix.de>]

This ports Linux commit:

| commit c5d264d4b527c96ae8903376a4b195df47b05203
| Author: Michael Walle <michael@walle.cc>
| Date:   Mon Feb 6 13:43:43 2023 +0000
|
|     of: base: add of_parse_phandle_with_optional_args()
|
|     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>
|     Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
|     Link: https://lore.kernel.org/r/20230206134356.839737-10-srinivas.kandagatla@linaro.org
|     Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
 include/of.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/of.h b/include/of.h
index 0ffc09e079a8af097e77e855791439a7aba93f2a..f2cd33b0f6cc6c332512ea08fd9df17bd0660f9f 100644
--- a/include/of.h
+++ b/include/of.h
@@ -367,6 +367,31 @@ static inline int of_parse_phandle_with_args(const struct device_node *np,
 					    cell_count, 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);
+}
+
 extern int of_count_phandle_with_args(const struct device_node *np,
 	const char *list_name, const char *cells_name);
 

-- 
2.39.5