[v3,02/18] of: base: add of_parse_phandle_with_optional_args()

Commit Message

Michael Walle Nov. 18, 2022, 6:51 p.m. UTC

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 <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
---
changes since v2:
 - none

changes since v1:
 - none

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

Comments

Michael Walle Nov. 18, 2022, 9:31 p.m. UTC | #1

Am 2022-11-18 19:51, schrieb 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.

I've just noticed that this isn't enough. We also need to fix the 
parsing
in drivers/of/property.c, otherwise spurious device links will be 
created
because the phandle argument is treated as a phandle itself.

-michael

Patch

diff --git a/include/linux/of.h b/include/linux/of.h
index 8b9f94386dc3..98c252d2d851 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
  *