HID: uclogic: Add KUnit tests for uclogic_rdesc_template_apply()

The uclogic_rdesc_template_apply() function is used by the driver to
generate HID descriptors from templates.

In order to avoid regressions in future patches, add KUnit tests to
test the function.

To run the tests:

$ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/hid \
--kconfig_add CONFIG_VIRTIO_UML=y \
--kconfig_add CONFIG_UML_PCI_OVER_VIRTIO=y

Signed-off-by: José Expósito <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

drivers/hid/.kunitconfig

···
+CONFIG_KUNIT=y
+CONFIG_USB=y
+CONFIG_USB_HID=y
+CONFIG_HID_UCLOGIC=y
+CONFIG_HID_KUNIT_TEST=y

drivers/hid/Kconfig

···
 	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

drivers/hid/Makefile

···
 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/

drivers/hid/hid-uclogic-rdesc-test.c

···
+// SPDX-License-Identifier: GPL-2.0+
+
+/*
+ *  HID driver for UC-Logic devices not fully compliant with HID standard
+ *
+ *  Copyright (c) 2022 José Expósito <[e-mail]>
+ */
+
+#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 <[e-mail]>");