[v4,2/4] HID: uclogic: Add KUnit tests for uclogic_rdesc_template_apply()

diff --git a/drivers/hid/.kunitconfig b/drivers/hid/.kunitconfig
new file mode 100644
index 000000000000..04daeff5c970
--- /dev/null
+++ b/drivers/hid/.kunitconfig
@@ -0,0 +1,5 @@ 
+CONFIG_KUNIT=y
+CONFIG_USB=y
+CONFIG_USB_HID=y
+CONFIG_HID_UCLOGIC=y
+CONFIG_HID_KUNIT_TEST=y
diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 70da5931082f..6ce92830b5d1 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -1306,6 +1306,22 @@  config HID_MCP2221
 	To compile this driver as a module, choose M here: the module
 	will be called hid-mcp2221.ko.
 
+config HID_KUNIT_TEST
+	bool "KUnit tests for HID" if !KUNIT_ALL_TESTS
+	depends on KUNIT=y
+	depends on HID_UCLOGIC
+	default KUNIT_ALL_TESTS
+	help
+	  This builds unit tests for HID. This option is not useful for
+	  distributions or general kernels, but only for kernel
+	  developers working on HID and associated drivers.
+
+	  For more information on KUnit and unit tests in general,
+	  please refer to the KUnit documentation in
+	  Documentation/dev-tools/kunit/.
+
+	  If in doubt, say "N".
+
 endmenu
 
 endif # HID
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index cac2cbe26d11..b0bef8098139 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -144,6 +144,9 @@  obj-$(CONFIG_HID_WIIMOTE)	+= hid-wiimote.o
 obj-$(CONFIG_HID_SENSOR_HUB)	+= hid-sensor-hub.o
 obj-$(CONFIG_HID_SENSOR_CUSTOM_SENSOR)	+= hid-sensor-custom.o
 
+obj-$(CONFIG_HID_KUNIT_TEST)	+= hid-uclogic-rdesc.o \
+				   hid-uclogic-rdesc-test.o
+
 obj-$(CONFIG_USB_HID)		+= usbhid/
 obj-$(CONFIG_USB_MOUSE)		+= usbhid/
 obj-$(CONFIG_USB_KBD)		+= usbhid/
diff --git a/drivers/hid/hid-uclogic-rdesc-test.c b/drivers/hid/hid-uclogic-rdesc-test.c
new file mode 100644
index 000000000000..ded59e226230
--- /dev/null
+++ b/drivers/hid/hid-uclogic-rdesc-test.c
@@ -0,0 +1,183 @@ 
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ *  HID driver for UC-Logic devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2022 José Expósito <jose.exposito89@gmail.com>
+ */
+
+#include <kunit/test.h>
+#include "./hid-uclogic-rdesc.h"
+
+struct uclogic_template_case {
+	const char *name;
+	const __u8 *template;
+	size_t template_size;
+	const s32 *param_list;
+	size_t param_num;
+	const __u8 *expected;
+};
+
+static const s32 params_pen_all[UCLOGIC_RDESC_PH_ID_NUM] = {
+	[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xAA,
+	[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0xBB,
+	[UCLOGIC_RDESC_PEN_PH_ID_Y_LM] = 0xCC,
+	[UCLOGIC_RDESC_PEN_PH_ID_Y_PM] = 0xDD,
+	[UCLOGIC_RDESC_PEN_PH_ID_PRESSURE_LM] = 0xEE,
+};
+
+static const s32 params_pen_some[] = {
+	[UCLOGIC_RDESC_PEN_PH_ID_X_LM] = 0xAA,
+	[UCLOGIC_RDESC_PEN_PH_ID_X_PM] = 0xBB,
+};
+
+static const __u8 template_empty[] = { };
+static const __u8 template_small[] = { 0x00 };
+static const __u8 template_no_ph[] = { 0xAA, 0xFE, 0xAA, 0xED, 0x1D };
+
+static const __u8 template_pen_ph_end[] = {
+	0xAA, 0xBB, UCLOGIC_RDESC_PEN_PH_HEAD
+};
+
+static const __u8 template_pen_all_params[] = {
+	UCLOGIC_RDESC_PEN_PH(X_LM),
+	0x47, UCLOGIC_RDESC_PEN_PH(X_PM),
+	0x27, UCLOGIC_RDESC_PEN_PH(Y_LM),
+	UCLOGIC_RDESC_PEN_PH(Y_PM),
+	0x00, UCLOGIC_RDESC_PEN_PH(PRESSURE_LM),
+};
+
+static const __u8 expected_pen_all_params[] = {
+	0xAA, 0x00, 0x00, 0x00,
+	0x47, 0xBB, 0x00, 0x00, 0x00,
+	0x27, 0xCC, 0x00, 0x00, 0x00,
+	0xDD, 0x00, 0x00, 0x00,
+	0x00, 0xEE, 0x00, 0x00, 0x00,
+};
+
+static const __u8 template_pen_some_params[] = {
+	0x01, 0x02,
+	UCLOGIC_RDESC_PEN_PH(X_LM),
+	0x03, UCLOGIC_RDESC_PEN_PH(X_PM),
+	0x04, 0x05,
+};
+
+static const __u8 expected_pen_some_params[] = {
+	0x01, 0x02,
+	0xAA, 0x00, 0x00, 0x00,
+	0x03, 0xBB, 0x00, 0x00, 0x00,
+	0x04, 0x05,
+};
+
+static const __u8 template_params_none[] = {
+	0x27, UCLOGIC_RDESC_PEN_PH(Y_LM),
+	UCLOGIC_RDESC_PEN_PH(Y_PM),
+	0x00, UCLOGIC_RDESC_PEN_PH(PRESSURE_LM),
+};
+
+static struct uclogic_template_case uclogic_template_cases[] = {
+	{
+		.name = "Empty template",
+		.template = template_empty,
+		.template_size = sizeof(template_empty),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_empty,
+	},
+	{
+		.name = "Template smaller than the placeholder",
+		.template = template_small,
+		.template_size = sizeof(template_small),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_small,
+	},
+	{
+		.name = "No placeholder",
+		.template = template_no_ph,
+		.template_size = sizeof(template_no_ph),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_no_ph,
+	},
+	{
+		.name = "Pen placeholder at the end, without ID",
+		.template = template_pen_ph_end,
+		.template_size = sizeof(template_pen_ph_end),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = template_pen_ph_end,
+	},
+	{
+		.name = "All params present in the pen template",
+		.template = template_pen_all_params,
+		.template_size = sizeof(template_pen_all_params),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = expected_pen_all_params,
+	},
+	{
+		.name = "Some params present in the pen template (complete param list)",
+		.template = template_pen_some_params,
+		.template_size = sizeof(template_pen_some_params),
+		.param_list = params_pen_all,
+		.param_num = ARRAY_SIZE(params_pen_all),
+		.expected = expected_pen_some_params,
+	},
+	{
+		.name = "Some params present in the pen template (incomplete param list)",
+		.template = template_pen_some_params,
+		.template_size = sizeof(template_pen_some_params),
+		.param_list = params_pen_some,
+		.param_num = ARRAY_SIZE(params_pen_some),
+		.expected = expected_pen_some_params,
+	},
+	{
+		.name = "No params present in the template",
+		.template = template_params_none,
+		.template_size = sizeof(template_params_none),
+		.param_list = params_pen_some,
+		.param_num = ARRAY_SIZE(params_pen_some),
+		.expected = template_params_none,
+	},
+};
+
+static void uclogic_template_case_desc(struct uclogic_template_case *t,
+				       char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(uclogic_template, uclogic_template_cases,
+		  uclogic_template_case_desc);
+
+static void uclogic_template_test(struct kunit *test)
+{
+	__u8 *res;
+	const struct uclogic_template_case *params = test->param_value;
+
+	res = uclogic_rdesc_template_apply(params->template,
+					   params->template_size,
+					   params->param_list,
+					   params->param_num);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, res);
+	KUNIT_EXPECT_EQ(test, 0,
+			memcmp(res, params->expected, params->template_size));
+	kfree(res);
+}
+
+static struct kunit_case hid_uclogic_rdesc_test_cases[] = {
+	KUNIT_CASE_PARAM(uclogic_template_test, uclogic_template_gen_params),
+	{}
+};
+
+static struct kunit_suite hid_uclogic_rdesc_test_suite = {
+	.name = "hid-uclogic-rdesc-test",
+	.test_cases = hid_uclogic_rdesc_test_cases,
+};
+
+kunit_test_suite(hid_uclogic_rdesc_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for the UC-Logic driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("José Expósito <jose.exposito89@gmail.com>");