Input: Add KUnit tests for some of the input core helper functions

The input subsystem doesn't currently have any unit tests, let's add a
CONFIG_INPUT_KUNIT_TEST option that builds a test suite to be executed
with the KUnit test infrastructure.

For now, only three tests were added for some of the input core helper
functions that are trivial to test:

* input_test_polling: set/get poll interval and set-up a poll handler.

* input_test_timestamp: set/get input event timestamps.

* input_test_match_device_id: match a device by bus, vendor, product,
version and events capable of handling.

But having the minimal KUnit support allows to add more tests and suites
as follow-up changes. The tests can be run with the following command:

$ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/input/tests/

Signed-off-by: Javier Martinez Canillas <[e-mail]>
Tested-by: Enric Balletbo i Serra <[e-mail]>
config: powerpc-allnoconfig (https://download.01.org/0day-ci/archive/20230330/[e-mail]/config)
Link: https://lore.kernel.org/r/[e-mail]

Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/Kconfig

···
 	  To compile this driver as a module, choose M here: the
 	  module will be called evbug.
 
+config INPUT_KUNIT_TEST
+	tristate "KUnit tests for Input" if !KUNIT_ALL_TESTS
+	depends on INPUT && KUNIT=y
+	default KUNIT_ALL_TESTS
+	help
+	  Say Y here if you want to build the KUnit tests for the input
+	  subsystem.
+
+	  If in doubt, say "N".
+
 config INPUT_APMPOWER
 	tristate "Input Power Event -> APM Bridge" if EXPERT
 	depends on INPUT && APM_EMULATION

drivers/input/Makefile

···
 obj-$(CONFIG_INPUT_TABLET)	+= tablet/
 obj-$(CONFIG_INPUT_TOUCHSCREEN)	+= touchscreen/
 obj-$(CONFIG_INPUT_MISC)	+= misc/
+obj-$(CONFIG_INPUT_KUNIT_TEST)	+= tests/
 
 obj-$(CONFIG_INPUT_APMPOWER)	+= apm-power.o
 

drivers/input/tests/.kunitconfig

···
+CONFIG_KUNIT=y
+CONFIG_INPUT=y
+CONFIG_INPUT_KUNIT_TEST=y

drivers/input/tests/Makefile

···
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_INPUT_KUNIT_TEST) += input_test.o

drivers/input/tests/input_test.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test for the input core.
+ *
+ * Copyright (c) 2023 Red Hat Inc
+ */
+
+#include <linux/delay.h>
+#include <linux/input.h>
+
+#include <kunit/test.h>
+
+#define POLL_INTERVAL 100
+
+static int input_test_init(struct kunit *test)
+{
+	struct input_dev *input_dev;
+	int ret;
+
+	input_dev = input_allocate_device();
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, input_dev);
+
+	input_dev->name = "Test input device";
+	input_dev->id.bustype = BUS_VIRTUAL;
+	input_dev->id.vendor = 1;
+	input_dev->id.product = 1;
+	input_dev->id.version = 1;
+	input_set_capability(input_dev, EV_KEY, BTN_LEFT);
+	input_set_capability(input_dev, EV_KEY, BTN_RIGHT);
+
+	ret = input_register_device(input_dev);
+	if (ret) {
+		input_free_device(input_dev);
+		KUNIT_ASSERT_FAILURE(test, "Register device failed: %d", ret);
+	}
+
+	test->priv = input_dev;
+
+	return 0;
+}
+
+static void input_test_exit(struct kunit *test)
+{
+	struct input_dev *input_dev = test->priv;
+
+	input_unregister_device(input_dev);
+	input_free_device(input_dev);
+}
+
+static void input_test_poll(struct input_dev *input) { }
+
+static void input_test_polling(struct kunit *test)
+{
+	struct input_dev *input_dev = test->priv;
+
+	/* Must fail because a poll handler has not been set-up yet */
+	KUNIT_ASSERT_EQ(test, input_get_poll_interval(input_dev), -EINVAL);
+
+	KUNIT_ASSERT_EQ(test, input_setup_polling(input_dev, input_test_poll), 0);
+
+	input_set_poll_interval(input_dev, POLL_INTERVAL);
+
+	/* Must succeed because poll handler was set-up and poll interval set */
+	KUNIT_ASSERT_EQ(test, input_get_poll_interval(input_dev), POLL_INTERVAL);
+}
+
+static void input_test_timestamp(struct kunit *test)
+{
+	const ktime_t invalid_timestamp = ktime_set(0, 0);
+	struct input_dev *input_dev = test->priv;
+	ktime_t *timestamp, time;
+
+	timestamp = input_get_timestamp(input_dev);
+	time = timestamp[INPUT_CLK_MONO];
+
+	/* The returned timestamp must always be valid */
+	KUNIT_ASSERT_EQ(test, ktime_compare(time, invalid_timestamp), 1);
+
+	time = ktime_get();
+	input_set_timestamp(input_dev, time);
+
+	timestamp = input_get_timestamp(input_dev);
+	/* The timestamp must be the same than set before */
+	KUNIT_ASSERT_EQ(test, ktime_compare(timestamp[INPUT_CLK_MONO], time), 0);
+}
+
+static void input_test_match_device_id(struct kunit *test)
+{
+	struct input_dev *input_dev = test->priv;
+	struct input_device_id id;
+
+	/*
+	 * Must match when the input device bus, vendor, product, version
+	 * and events capable of handling are the same and fail to match
+	 * otherwise.
+	 */
+	id.flags = INPUT_DEVICE_ID_MATCH_BUS;
+	id.bustype = BUS_VIRTUAL;
+	KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id));
+
+	id.bustype = BUS_I2C;
+	KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id));
+
+	id.flags = INPUT_DEVICE_ID_MATCH_VENDOR;
+	id.vendor = 1;
+	KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id));
+
+	id.vendor = 2;
+	KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id));
+
+	id.flags = INPUT_DEVICE_ID_MATCH_PRODUCT;
+	id.product = 1;
+	KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id));
+
+	id.product = 2;
+	KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id));
+
+	id.flags = INPUT_DEVICE_ID_MATCH_VERSION;
+	id.version = 1;
+	KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id));
+
+	id.version = 2;
+	KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id));
+
+	id.flags = INPUT_DEVICE_ID_MATCH_EVBIT;
+	__set_bit(EV_KEY, id.evbit);
+	KUNIT_ASSERT_TRUE(test, input_match_device_id(input_dev, &id));
+
+	__set_bit(EV_ABS, id.evbit);
+	KUNIT_ASSERT_FALSE(test, input_match_device_id(input_dev, &id));
+}
+
+static struct kunit_case input_tests[] = {
+	KUNIT_CASE(input_test_polling),
+	KUNIT_CASE(input_test_timestamp),
+	KUNIT_CASE(input_test_match_device_id),
+	{ /* sentinel */ }
+};
+
+static struct kunit_suite input_test_suite = {
+	.name = "input_core",
+	.init = input_test_init,
+	.exit = input_test_exit,
+	.test_cases = input_tests,
+};
+
+kunit_test_suite(input_test_suite);
+
+MODULE_AUTHOR("Javier Martinez Canillas <[e-mail]>");
+MODULE_LICENSE("GPL");