linux-kernel - [PATCH v8 15/24] ACPI: Add support for nargs_prop in acpi_fwnode_get_reference

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Message-ID: <20250704070356.1683992-16-apatel@ventanamicro.com>
Date: Fri,  4 Jul 2025 12:33:47 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Jassi Brar <jassisinghbrar@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Uwe Kleine-König <ukleinek@...nel.org>
Cc: Palmer Dabbelt <palmer@...belt.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Alexandre Ghiti <alex@...ti.fr>,
	Len Brown <lenb@...nel.org>,
	Sunil V L <sunilvl@...tanamicro.com>,
	Rahul Pathak <rpathak@...tanamicro.com>,
	Leyfoon Tan <leyfoon.tan@...rfivetech.com>,
	Atish Patra <atish.patra@...ux.dev>,
	Andrew Jones <ajones@...tanamicro.com>,
	Samuel Holland <samuel.holland@...ive.com>,
	Anup Patel <anup@...infault.org>,
	linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Anup Patel <apatel@...tanamicro.com>
Subject: [PATCH v8 15/24] ACPI: Add support for nargs_prop in acpi_fwnode_get_reference_args()

From: Sunil V L <sunilvl@...tanamicro.com>

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@...tanamicro.com>
Signed-off-by: Anup Patel <apatel@...tanamicro.com>
---
 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