[PATCH 1/2] device property: Add optional nargs_prop for get_reference_args

Sean Anderson
2025-04-07T22:37:25Z

get_reference_args does not permit falling back to nargs when nargs_prop
is missing. This makes it difficult to support older devicetrees where
nargs_prop may not be present. Add support for this by converting nargs
to a signed value. Where before nargs was ignored if nargs_prop was
passed, now nargs is only ignored if it is strictly negative. When it is
positive, nargs represents the fallback cells to use if nargs_prop is
absent.

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

drivers/base/property.c | 4 ++--
drivers/base/swnode.c | 13 +++++++++----
drivers/of/property.c | 10 +++-------
include/linux/fwnode.h | 2 +-
4 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index c1392743df9c..049f8a6088a1 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -606,7 +606,7 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
return -ENOENT;

ret = fwnode_call_int_op(fwnode, get_reference_args, prop, nargs_prop,
- nargs, index, args);
+ nargs_prop ? -1 : nargs, index, args);
if (ret == 0)
return ret;

@@ -614,7 +614,7 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
return ret;

return fwnode_call_int_op(fwnode->secondary, get_reference_args, prop, nargs_prop,
- nargs, index, args);
+ nargs_prop ? -1 : nargs, index, args);
}
EXPORT_SYMBOL_GPL(fwnode_property_get_reference_args);

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index b1726a3515f6..11af2001478f 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -503,7 +503,7 @@ software_node_get_named_child_node(const struct fwnode_handle *fwnode,
static int
software_node_get_reference_args(const struct fwnode_handle *fwnode,
const char *propname, const char *nargs_prop,
- unsigned int nargs, unsigned int index,
+ int nargs, unsigned int index,
struct fwnode_reference_args *args)
{
struct swnode *swnode = to_swnode(fwnode);
@@ -543,10 +543,15 @@ software_node_get_reference_args(const struct fwnode_handle *fwnode,
error = property_entry_read_int_array(ref->node->properties,
nargs_prop, sizeof(u32),
&nargs_prop_val, 1);
- if (error)
+
+ if (error == -EINVAL) {
+ if (nargs < 0)
+ return error;
+ } else if (error) {
return error;
-
- nargs = nargs_prop_val;
+ } else {
+ nargs = nargs_prop_val;
+ }
}

if (nargs > NR_FWNODE_REFERENCE_ARGS)
diff --git a/drivers/of/property.c b/drivers/of/property.c
index c1feb631e383..c41190e47111 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1116,19 +1116,15 @@ of_fwnode_get_named_child_node(const struct fwnode_handle *fwnode,
static int
of_fwnode_get_reference_args(const struct fwnode_handle *fwnode,
const char *prop, const char *nargs_prop,
- unsigned int nargs, unsigned int index,
+ int nargs, unsigned int index,
struct fwnode_reference_args *args)
{
struct of_phandle_args of_args;
unsigned int i;
int ret;

- if (nargs_prop)
- ret = of_parse_phandle_with_args(to_of_node(fwnode), prop,
- nargs_prop, index, &of_args);
- else
- ret = of_parse_phandle_with_fixed_args(to_of_node(fwnode), prop,
- nargs, index, &of_args);
+ ret = __of_parse_phandle_with_args(to_of_node(fwnode), prop, nargs_prop,
+ nargs, index, &of_args);
if (ret < 0)
return ret;
if (!args) {
diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index 6fa0a268d538..69fe44c68f8c 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h
@@ -163,7 +163,7 @@ struct fwnode_operations {
const char *name);
int (*get_reference_args)(const struct fwnode_handle *fwnode,
const char *prop, const char *nargs_prop,
- unsigned int nargs, unsigned int index,
+ int nargs, unsigned int index,
struct fwnode_reference_args *args);
struct fwnode_handle *
(*graph_get_next_endpoint)(const struct fwnode_handle *fwnode,
--
2.35.1.1320.gc452695387.dirty