kunit: Add APIs for managing devices

Tests for drivers often require a struct device to pass to other
functions. While it's possible to create these with
root_device_register(), or to use something like a platform device, this
is both a misuse of those APIs, and can be difficult to clean up after,
for example, a failed assertion.

Add some KUnit-specific functions for registering and unregistering a
struct device:
- kunit_device_register()
- kunit_device_register_with_driver()
- kunit_device_unregister()

These helpers allocate a on a 'kunit' bus which will either probe the
driver passed in (kunit_device_register_with_driver), or will create a
stub driver (kunit_device_register) which is cleaned up on test shutdown.

Devices are automatically unregistered on test shutdown, but can be
manually unregistered earlier with kunit_device_unregister() in order
to, for example, test device release code.

Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/kunit/device-impl.h b/lib/kunit/device-impl.h
new file mode 100644
index 000000000000..54bd55836405
--- /dev/null
+++ b/lib/kunit/device-impl.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KUnit internal header for device helpers
+ *
+ * Header for KUnit-internal driver / bus management.
+ *
+ * Copyright (C) 2023, Google LLC.
+ * Author: David Gow <davidgow@google.com>
+ */
+
+#ifndef _KUNIT_DEVICE_IMPL_H
+#define _KUNIT_DEVICE_IMPL_H
+
+// For internal use only -- registers the kunit_bus.
+int kunit_bus_init(void);
+
+#endif //_KUNIT_DEVICE_IMPL_H