ACPI: Add support for nargs_prop in acpi_fwnode_get_reference_args()

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.

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Link: https://lore.kernel.org/r/20250818040920.272664-16-apatel@ventanamicro.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>

diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
index d4863746fb11eeee188eb976e22ac3c0b7a567df..e92402deee7749acc295dc68c18346e5397b597e 100644 (file)
--- 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 f626d5bbe8067d042b81a65d52daf342eae2891e..6a63860579dd3198bdb6fde03b5f1dc17ee214bf 100644 (file)
--- 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.