[PATCH 2/2] device property: Add fwnode_property_get_reference_optional_args

[Sean Anderson <sean.anderson@linux.dev>]

Add a fwnode variant of of_parse_phandle_with_optional_args to allow
nargs_prop to be absent from the referenced node. This improves
compatibility for references where the devicetree might not always have
nargs_prop.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

 drivers/base/property.c  | 46 ++++++++++++++++++++++++++++++++++++++++
 include/linux/property.h |  4 ++++
 2 files changed, 50 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index 049f8a6088a1..ef13ca32079b 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -618,6 +618,52 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
 }
 EXPORT_SYMBOL_GPL(fwnode_property_get_reference_args);
 
+/**
+ * fwnode_property_get_reference_optional_args() - Find a reference with optional arguments
+ * @fwnode:	Firmware node where to look for the reference
+ * @prop:	The name of the property
+ * @nargs_prop:	The name of the property telling the number of
+ *		arguments in the referred node.
+ * @index:	Index of the reference, from zero onwards.
+ * @args:	Result structure with reference and integer arguments.
+ *		May be NULL.
+ *
+ * Obtain a reference based on a named property in an fwnode, with
+ * integer arguments. If @nargs_prop is absent from the referenced node, then
+ * number of arguments is be assumed to be 0.
+ *
+ * The caller is responsible for calling fwnode_handle_put() on the returned
+ * @args->fwnode pointer.
+ *
+ * Return: %0 on success
+ *	    %-ENOENT when the index is out of bounds, the index has an empty
+ *		     reference or the property was not found
+ *	    %-EINVAL on parse error
+ */
+int fwnode_property_get_reference_optional_args(const struct fwnode_handle *fwnode,
+						const char *prop,
+						const char *nargs_prop,
+						unsigned int index,
+						struct fwnode_reference_args *args)
+{
+	int ret;
+
+	if (IS_ERR_OR_NULL(fwnode))
+		return -ENOENT;
+
+	ret = fwnode_call_int_op(fwnode, get_reference_args, prop, nargs_prop,
+				 0, index, args);
+	if (ret == 0)
+		return ret;
+
+	if (IS_ERR_OR_NULL(fwnode->secondary))
+		return ret;
+
+	return fwnode_call_int_op(fwnode->secondary, get_reference_args, prop, nargs_prop,
+				  0, index, args);
+}
+EXPORT_SYMBOL_GPL(fwnode_property_get_reference_optional_args);
+
 /**
  * fwnode_find_reference - Find named reference to a fwnode_handle
  * @fwnode: Firmware node where to look for the reference
diff --git a/include/linux/property.h b/include/linux/property.h
index e214ecd241eb..a1662b36d15f 100644
--- a/include/linux/property.h
+++ b/include/linux/property.h
@@ -139,6 +139,10 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
 				       const char *prop, const char *nargs_prop,
 				       unsigned int nargs, unsigned int index,
 				       struct fwnode_reference_args *args);
+int fwnode_property_get_reference_optional_args(const struct fwnode_handle *fwnode,
+						const char *prop, const char *nargs_prop,
+						unsigned int index,
+						struct fwnode_reference_args *args);
 
 struct fwnode_handle *fwnode_find_reference(const struct fwnode_handle *fwnode,
 					    const char *name,
-- 
2.35.1.1320.gc452695387.dirty