thunderbolt: test: get running under UML, add kunitconfig

These tests didn't work under the normal `kunit.py run` command since
they require CONFIG_PCI=y, which could not be set on ARCH=um.

Commit 68f5d3f ("um: add PCI over virtio emulation driver") lets us
do so. To make it so people don't have to figure out how to do so, we
add a drivers/thunderbolt/.kunitconfig.

Can now run these tests using
$ ./tools/testing/kunit/kunit.py run --kunitconfig=drivers/thunderbolt

Potentially controversial bits:
1. this .kunitconfig is UML-specific, can't do this for example
$ ./tools/testing/kunit/kunit.py run --arch=x86_64 --kunitconfig=drivers/thunderbolt
2. this removes the manual call to __kunit_test_suites_init(), which
   allowed us to control exactly when the tests got run.

The main motivation for both is convenience.

For #1, we could drop the UML specific options, but then users would
always have to set --arch. Since UML is a bit faster and there's less to
type when running it with kunit.py, let's make it work by default.
Users can manually edit the .kunitconfig to run under x86_64.

For #2, running our suite separately prevents kunit.py from picking up
results properly as it only parses one set of KUnit results. I.e.
there's an assumption that __kunit_test_suites_init() only gets called
once. Since the tests seem to run fine when kunit runs them, giving up
this control seems fine.

Signed-off-by: Daniel Latypov <dlatypov@google.com>

drivers/thunderbolt/.kunitconfig

@@ -0,0 +1,7 @@
+CONFIG_PCI=y
+CONFIG_VIRTIO_UML=y
+CONFIG_UML_PCI_OVER_VIRTIO=y
+
+CONFIG_KUNIT=y
+CONFIG_USB4=y
+CONFIG_USB4_KUNIT_TEST=y

drivers/thunderbolt/domain.c

@@ -878,7 +878,6 @@ int tb_domain_init(void)
 {
 	int ret;
 
-	tb_test_init();
 	tb_debugfs_init();
 	tb_acpi_init();
 
@@ -896,7 +895,6 @@ int tb_domain_init(void)
 err_acpi:
 	tb_acpi_exit();
 	tb_debugfs_exit();
-	tb_test_exit();
 
 	return ret;
 }
@@ -909,5 +907,4 @@ void tb_domain_exit(void)
 	tb_xdomain_exit();
 	tb_acpi_exit();
 	tb_debugfs_exit();
-	tb_test_exit();
 }

drivers/thunderbolt/tb.h

@@ -1261,12 +1261,4 @@ static inline void tb_service_debugfs_init(struct tb_service *svc) { }
 static inline void tb_service_debugfs_remove(struct tb_service *svc) { }
 #endif
 
-#ifdef CONFIG_USB4_KUNIT_TEST
-int tb_test_init(void);
-void tb_test_exit(void);
-#else
-static inline int tb_test_init(void) { return 0; }
-static inline void tb_test_exit(void) { }
-#endif
-
 #endif

drivers/thunderbolt/test.c

@@ -2725,14 +2725,4 @@ static struct kunit_suite tb_test_suite = {
 	.test_cases = tb_test_cases,
 };
 
-static struct kunit_suite *tb_test_suites[] = { &tb_test_suite, NULL };
-
-int tb_test_init(void)
-{
-	return __kunit_test_suites_init(tb_test_suites);
-}
-
-void tb_test_exit(void)
-{
-	return __kunit_test_suites_exit(tb_test_suites);
-}
+kunit_test_suites(&tb_test_suite);