platform/wmi: Add kunit test for the marshalling code

The marshalling code used by the WMI driver core is implemented as
a separate component, suitable for unit tests.

Implmented such a unit test using KUnit. Those unit tests verify that
ACPI objects are correctly converted into WMI buffers and that WMI
strings are correctly converted into ACPI strings. They also verify
that invalid ACPI data (like nested packages) is rejected.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://patch.msgid.link/20260116204116.4030-3-W_Armin@gmx.de
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: Wer-Wolf

drivers/platform/wmi/Kconfig

@@ -31,4 +31,6 @@ config ACPI_WMI_LEGACY_DEVICE_NAMES
 	  userspace applications but will cause the registration of WMI devices with
 	  the same GUID to fail in some corner cases.
 
+source "drivers/platform/wmi/tests/Kconfig"
+
 endif # ACPI_WMI

drivers/platform/wmi/Makefile

@@ -6,3 +6,6 @@
 
 wmi-y			:= core.o marshalling.o
 obj-$(CONFIG_ACPI_WMI)	+= wmi.o
+
+# Unit tests
+obj-y			+= tests/

drivers/platform/wmi/tests/Kconfig

@@ -0,0 +1,16 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# ACPI WMI KUnit tests
+#
+
+config ACPI_WMI_MARSHALLING_KUNIT_TEST
+	tristate "KUnit Test for ACPI-WMI marshalling" if !KUNIT_ALL_TESTS
+	depends on KUNIT
+	default KUNIT_ALL_TESTS
+	help
+	  This builds unit tests for the ACPI-WMI marshalling code.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit/.
+
+	  If unsure, say N.

drivers/platform/wmi/tests/Makefile

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Makefile for linux/drivers/platform/x86/wmi/tests
+# ACPI WMI KUnit tests
+#
+
+wmi_marshalling_kunit-y				:= marshalling_kunit.o
+obj-$(CONFIG_ACPI_WMI_MARSHALLING_KUNIT_TEST)	+= wmi_marshalling_kunit.o