kunit: add ability to specify suite-level init and exit functions

KUnit has support for setup/cleanup logic for each test case in a suite.
But it lacks the ability to specify setup/cleanup for the entire suite
itself.

This can be used to do setup that is too expensive or cumbersome to do
for each test.
Or it can be used to do simpler things like log debug information after
the suite completes.
It's a fairly common feature, so the lack of it is noticeable.

Some examples in other frameworks and languages:
* https://docs.python.org/3/library/unittest.html#setupclass-and-teardownclass
* https://google.github.io/googletest/reference/testing.html#Test::SetUpTestSuite

Meta:
This is very similar to this patch here: https://lore.kernel.org/linux-kselftest/[e-mail]/
The changes from that patch:
* pass in `struct kunit *` so users can do stuff like
`kunit_info(suite, "debug message")`
* makes sure the init failure is bubbled up as a failure
* updates kunit-example-test.c to use a suite init
* Updates kunit/usage.rst to mention the new support
* some minor cosmetic things
* use `suite_{init,exit}` instead of `{init/exit}_suite`
* make suite init error message more consistent w/ test init
* etc.

Signed-off-by: Daniel Latypov <[e-mail]>
Reviewed-by: David Gow <[e-mail]>
Reviewed-by: Brendan Higgins <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

Documentation/dev-tools/kunit/usage.rst

···
 many similar tests. In order to reduce duplication in these closely related
 tests, most unit testing frameworks (including KUnit) provide the concept of a
 *test suite*. A test suite is a collection of test cases for a unit of code
-with a setup function that gets invoked before every test case and then a tear
-down function that gets invoked after every test case completes. For example:
+with optional setup and teardown functions that run before/after the whole
+suite and/or every test case. For example:
 
 .. code-block:: c
 
···
 		.name = "example",
 		.init = example_test_init,
 		.exit = example_test_exit,
+		.suite_init = example_suite_init,
+		.suite_exit = example_suite_exit,
 		.test_cases = example_test_cases,
 	};
 	kunit_test_suite(example_test_suite);
 
-In the above example, the test suite ``example_test_suite`` would run the test
-cases ``example_test_foo``, ``example_test_bar``, and ``example_test_baz``. Each
-would have ``example_test_init`` called immediately before it and
-``example_test_exit`` called immediately after it.
-``kunit_test_suite(example_test_suite)`` registers the test suite with the
-KUnit test framework.
+In the above example, the test suite ``example_test_suite`` would first run
+``example_suite_init``, then run the test cases ``example_test_foo``,
+``example_test_bar``, and ``example_test_baz``. Each would have
+``example_test_init`` called immediately before it and ``example_test_exit``
+called immediately after it. Finally, ``example_suite_exit`` would be called
+after everything else. ``kunit_test_suite(example_test_suite)`` registers the
+test suite with the KUnit test framework.
 
 .. note::
    A test case will only run if it is associated with a test suite.

include/kunit/test.h

···
  * struct kunit_suite - describes a related collection of &struct kunit_case
  *
  * @name:	the name of the test. Purely informational.
+ * @suite_init:	called once per test suite before the test cases.
+ * @suite_exit:	called once per test suite after all test cases.
  * @init:	called before every test case.
  * @exit:	called after every test case.
  * @test_cases:	a null terminated array of test cases.
···
  */
 struct kunit_suite {
 	const char name[256];
+	int (*suite_init)(struct kunit_suite *suite);
+	void (*suite_exit)(struct kunit_suite *suite);
 	int (*init)(struct kunit *test);
 	void (*exit)(struct kunit *test);
 	struct kunit_case *test_cases;
···
 	char status_comment[KUNIT_STATUS_COMMENT_SIZE];
 	struct dentry *debugfs;
 	char *log;
+	int suite_init_err;
 };
 
 /**

lib/kunit/kunit-example-test.c

···
 }
 
 /*
+ * This is run once before all test cases in the suite.
+ * See the comment on example_test_suite for more information.
+ */
+static int example_test_init_suite(struct kunit_suite *suite)
+{
+	kunit_info(suite, "initializing suite\n");
+
+	return 0;
+}
+
+/*
  * This test should always be skipped.
  */
 static void example_skip_test(struct kunit *test)
···
  * may be specified which runs after every test case and can be used to for
  * cleanup. For clarity, running tests in a test suite would behave as follows:
  *
+ * suite.suite_init(suite);
  * suite.init(test);
  * suite.test_case[0](test);
  * suite.exit(test);
  * suite.init(test);
  * suite.test_case[1](test);
  * suite.exit(test);
+ * suite.suite_exit(suite);
  * ...;
  */
 static struct kunit_suite example_test_suite = {
 	.name = "example",
 	.init = example_test_init,
+	.suite_init = example_test_init_suite,
 	.test_cases = example_test_cases,
 };
 

lib/kunit/test.c

···
 	const struct kunit_case *test_case;
 	enum kunit_status status = KUNIT_SKIPPED;
 
+	if (suite->suite_init_err)
+		return KUNIT_FAILURE;
+
 	kunit_suite_for_each_test_case(suite, test_case) {
 		if (test_case->status == KUNIT_FAILURE)
 			return KUNIT_FAILURE;
···
 	struct kunit_result_stats suite_stats = { 0 };
 	struct kunit_result_stats total_stats = { 0 };
 
+	if (suite->suite_init) {
+		suite->suite_init_err = suite->suite_init(suite);
+		if (suite->suite_init_err) {
+			kunit_err(suite, KUNIT_SUBTEST_INDENT
+				  "# failed to initialize (%d)", suite->suite_init_err);
+			goto suite_end;
+		}
+	}
+
 	kunit_print_suite_start(suite);
 
 	kunit_suite_for_each_test_case(suite, test_case) {
···
 		kunit_accumulate_stats(&total_stats, param_stats);
 	}
 
+	if (suite->suite_exit)
+		suite->suite_exit(suite);
+
 	kunit_print_suite_stats(suite, suite_stats, total_stats);
+suite_end:
 	kunit_print_suite_end(suite);
 
 	return 0;
···
 {
 	kunit_debugfs_create_suite(suite);
 	suite->status_comment[0] = '\0';
+	suite->suite_init_err = 0;
 }
 
 int __kunit_test_suites_init(struct kunit_suite * const * const suites)