[PATCH v8 15/24] ACPI: Add support for nargs_prop in acpi_fwnode_get_reference_args()
From: Anup Patel
Date: Fri Jul 04 2025 - 03:10:10 EST
From: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
Currently, ACPI does not support the use of a nargs_prop (e.g.,
associated with a reference in fwnode_property_get_reference_args().
Instead, ACPI expects the number of arguments (nargs) to be explicitly
passed or known.
This behavior diverges from Open Firmware (OF), which allows the use of
a #*-cells property in the referenced node to determine the number of
arguments. Since fwnode_property_get_reference_args() is a common
interface used across both OF and ACPI firmware paradigms, it is
desirable to have a unified calling convention that works seamlessly for
both.
Add the support for ACPI to parse a nargs_prop from the referenced
fwnode, aligning its behavior with the OF backend. This allows drivers
and subsystems using fwnode_property_get_reference_args() to work in a
firmware-agnostic way without having to hardcode or special-case
argument counts for ACPI.
Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
---
drivers/acpi/property.c | 29 +++++++++++++++++++++++++----
drivers/base/property.c | 2 +-
2 files changed, 26 insertions(+), 5 deletions(-)
diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
index d4863746fb11..e92402deee77 100644
--- a/drivers/acpi/property.c
+++ b/drivers/acpi/property.c
@@ -804,13 +804,35 @@ acpi_fwnode_get_named_child_node(const struct fwnode_handle *fwnode,
return NULL;
}
+static unsigned int acpi_fwnode_get_args_count(struct fwnode_handle *fwnode,
+ const char *nargs_prop)
+{
+ const struct acpi_device_data *data;
+ const union acpi_object *obj;
+ int ret;
+
+ data = acpi_device_data_of_node(fwnode);
+ if (!data)
+ return 0;
+
+ ret = acpi_data_get_property(data, nargs_prop, ACPI_TYPE_INTEGER, &obj);
+ if (ret)
+ return 0;
+
+ return obj->integer.value;
+}
+
static int acpi_get_ref_args(struct fwnode_reference_args *args,
struct fwnode_handle *ref_fwnode,
+ const char *nargs_prop,
const union acpi_object **element,
const union acpi_object *end, size_t num_args)
{
u32 nargs = 0, i;
+ if (nargs_prop)
+ num_args = acpi_fwnode_get_args_count(ref_fwnode, nargs_prop);
+
/*
* Assume the following integer elements are all args. Stop counting on
* the first reference (possibly represented as a string) or end of the
@@ -961,10 +983,10 @@ static int acpi_fwnode_get_reference_args(const struct fwnode_handle *fwnode,
return -EINVAL;
element++;
-
ret = acpi_get_ref_args(idx == index ? args : NULL,
acpi_fwnode_handle(device),
- &element, end, args_count);
+ nargs_prop, &element, end,
+ args_count);
if (ret < 0)
return ret;
@@ -979,9 +1001,8 @@ static int acpi_fwnode_get_reference_args(const struct fwnode_handle *fwnode,
return -EINVAL;
element++;
-
ret = acpi_get_ref_args(idx == index ? args : NULL,
- ref_fwnode, &element, end,
+ ref_fwnode, nargs_prop, &element, end,
args_count);
if (ret < 0)
return ret;
diff --git a/drivers/base/property.c b/drivers/base/property.c
index f626d5bbe806..6a63860579dd 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c
@@ -578,7 +578,7 @@ EXPORT_SYMBOL_GPL(fwnode_property_match_property_string);
* @prop: The name of the property
* @nargs_prop: The name of the property telling the number of
* arguments in the referred node. NULL if @nargs is known,
- * otherwise @nargs is ignored. Only relevant on OF.
+ * otherwise @nargs is ignored.
* @nargs: Number of arguments. Ignored if @nargs_prop is non-NULL.
* @index: Index of the reference, from zero onwards.
* @args: Result structure with reference and integer arguments.
--
2.43.0