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>

5 files changed, 336 insertions, 2 deletions

diff --git a/lib/kunit/Makefile b/lib/kunit/Makefile
index 46f75f23dfe4..309659a32a78 100644
--- a/lib/kunit/Makefile
+++ b/lib/kunit/Makefile
@@ -7,7 +7,8 @@ kunit-objs +=				test.o \
 					assert.o \
 					try-catch.o \
 					executor.o \
-					attributes.o
+					attributes.o \
+					device.o
 
 ifeq ($(CONFIG_KUNIT_DEBUGFS),y)
 kunit-objs +=				debugfs.o
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
diff --git a/lib/kunit/device.c b/lib/kunit/device.c
new file mode 100644
index 000000000000..1db4305b615a
--- /dev/null
+++ b/lib/kunit/device.c
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit-managed device implementation
+ *
+ * Implementation of struct kunit_device helpers for fake devices whose
+ * lifecycle is managed by KUnit.
+ *
+ * Copyright (C) 2023, Google LLC.
+ * Author: David Gow <davidgow@google.com>
+ */
+
+#include <linux/device.h>
+
+#include <kunit/test.h>
+#include <kunit/device.h>
+#include <kunit/resource.h>
+
+#include "device-impl.h"
+
+/* Wrappers for use with kunit_add_action() */
+KUNIT_DEFINE_ACTION_WRAPPER(device_unregister_wrapper, device_unregister, struct device *);
+KUNIT_DEFINE_ACTION_WRAPPER(driver_unregister_wrapper, driver_unregister, struct device_driver *);
+
+/* The root device for the KUnit bus, parent of all kunit_devices. */
+static struct device *kunit_bus_device;
+
+/* A device owned by a KUnit test. */
+struct kunit_device {
+	struct device dev;
+	/* The KUnit test which owns this device. */
+	struct kunit *owner;
+	/* If the driver is managed by KUnit and unique to this device. */
+	const struct device_driver *driver;
+};
+
+#define to_kunit_device(d) container_of_const(d, struct kunit_device, dev)
+
+static struct bus_type kunit_bus_type = {
+	.name		= "kunit",
+};
+
+/* Register the 'kunit_bus' used for fake devices. */
+int kunit_bus_init(void)
+{
+	int error;
+
+	kunit_bus_device = root_device_register("kunit");
+	if (!kunit_bus_device)
+		return -ENOMEM;
+
+	error = bus_register(&kunit_bus_type);
+	if (error)
+		bus_unregister(&kunit_bus_type);
+	return error;
+}
+
+/* Release a 'fake' KUnit device. */
+static void kunit_device_release(struct device *d)
+{
+	kfree(to_kunit_device(d));
+}
+
+/**
+ * Create and register a KUnit-managed struct device_driver on the kunit_bus.
+ * Returns an error pointer on failure.
+ */
+struct device_driver *kunit_driver_create(struct kunit *test, const char *name)
+{
+	struct device_driver *driver;
+	int err = -ENOMEM;
+
+	driver = kunit_kzalloc(test, sizeof(*driver), GFP_KERNEL);
+
+	if (!driver)
+		return ERR_PTR(err);
+
+	driver->name = name;
+	driver->bus = &kunit_bus_type;
+	driver->owner = THIS_MODULE;
+
+	err = driver_register(driver);
+	if (err) {
+		kunit_kfree(test, driver);
+		return ERR_PTR(err);
+	}
+
+	kunit_add_action(test, driver_unregister_wrapper, driver);
+	return driver;
+}
+EXPORT_SYMBOL_GPL(kunit_driver_create);
+
+/* Helper which creates a kunit_device, attaches it to the kunit_bus*/
+static struct kunit_device *kunit_device_register_internal(struct kunit *test,
+							   const char *name,
+							   const struct device_driver *drv)
+{
+	struct kunit_device *kunit_dev;
+	int err = -ENOMEM;
+
+	kunit_dev = kzalloc(sizeof(*kunit_dev), GFP_KERNEL);
+	if (!kunit_dev)
+		return ERR_PTR(err);
+
+	kunit_dev->owner = test;
+
+	err = dev_set_name(&kunit_dev->dev, "%s.%s", test->name, name);
+	if (err) {
+		kfree(kunit_dev);
+		return ERR_PTR(err);
+	}
+
+	kunit_dev->dev.release = kunit_device_release;
+	kunit_dev->dev.bus = &kunit_bus_type;
+	kunit_dev->dev.parent = kunit_bus_device;
+
+	err = device_register(&kunit_dev->dev);
+	if (err) {
+		put_device(&kunit_dev->dev);
+		return ERR_PTR(err);
+	}
+
+	kunit_add_action(test, device_unregister_wrapper, &kunit_dev->dev);
+
+	return kunit_dev;
+}
+
+/**
+ * Create and register a new KUnit-managed device, using the user-supplied device_driver.
+ * On failure, returns an error pointer.
+ */
+struct device *kunit_device_register_with_driver(struct kunit *test,
+						 const char *name,
+						 const struct device_driver *drv)
+{
+	struct kunit_device *kunit_dev = kunit_device_register_internal(test, name, drv);
+
+	if (IS_ERR_OR_NULL(kunit_dev))
+		return ERR_CAST(kunit_dev);
+
+	return &kunit_dev->dev;
+}
+EXPORT_SYMBOL_GPL(kunit_device_register_with_driver);
+
+/**
+ * Create and register a new KUnit-managed device, including a matching device_driver.
+ * On failure, returns an error pointer.
+ */
+struct device *kunit_device_register(struct kunit *test, const char *name)
+{
+	struct device_driver *drv;
+	struct kunit_device *dev;
+
+	drv = kunit_driver_create(test, name);
+	if (IS_ERR(drv))
+		return ERR_CAST(drv);
+
+	dev = kunit_device_register_internal(test, name, drv);
+	if (IS_ERR(dev)) {
+		kunit_release_action(test, driver_unregister_wrapper, (void *)drv);
+		return ERR_CAST(dev);
+	}
+
+	/* Request the driver be freed. */
+	dev->driver = drv;
+
+
+	return &dev->dev;
+}
+EXPORT_SYMBOL_GPL(kunit_device_register);
+
+/* Unregisters a KUnit-managed device early (including the driver, if automatically created). */
+void kunit_device_unregister(struct kunit *test, struct device *dev)
+{
+	const struct device_driver *driver = to_kunit_device(dev)->driver;
+
+	kunit_release_action(test, device_unregister_wrapper, dev);
+	if (driver)
+		kunit_release_action(test, driver_unregister_wrapper, (void *)driver);
+}
+EXPORT_SYMBOL_GPL(kunit_device_unregister);
+
diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c
index ee6927c60979..c4259d910356 100644
--- a/lib/kunit/kunit-test.c
+++ b/lib/kunit/kunit-test.c
@@ -5,9 +5,13 @@
  * Copyright (C) 2019, Google LLC.
  * Author: Brendan Higgins <brendanhiggins@google.com>
  */
+#include "linux/gfp_types.h"
 #include <kunit/test.h>
 #include <kunit/test-bug.h>
 
+#include <linux/device.h>
+#include <kunit/device.h>
+
 #include "string-stream.h"
 #include "try-catch-impl.h"
 
@@ -687,6 +691,134 @@ static struct kunit_case kunit_current_test_cases[] = {
 	{}
 };
 
+static void test_dev_action(void *priv)
+{
+	*(void **)priv = (void *)1;
+}
+
+static void kunit_device_test(struct kunit *test)
+{
+	struct device *test_device;
+	long action_was_run = 0;
+
+	test_device = kunit_device_register(test, "my_device");
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, test_device);
+
+	// Add an action to verify cleanup.
+	devm_add_action(test_device, test_dev_action, &action_was_run);
+
+	KUNIT_EXPECT_EQ(test, action_was_run, 0);
+
+	kunit_device_unregister(test, test_device);
+
+	KUNIT_EXPECT_EQ(test, action_was_run, 1);
+}
+
+static void kunit_device_cleanup_test(struct kunit *test)
+{
+	struct device *test_device;
+	long action_was_run = 0;
+
+	test_device = kunit_device_register(test, "my_device");
+	KUNIT_ASSERT_NOT_NULL(test, test_device);
+
+	/* Add an action to verify cleanup. */
+	devm_add_action(test_device, test_dev_action, &action_was_run);
+
+	KUNIT_EXPECT_EQ(test, action_was_run, 0);
+
+	/* Force KUnit to run cleanup early. */
+	kunit_cleanup(test);
+
+	KUNIT_EXPECT_EQ(test, action_was_run, 1);
+}
+
+struct driver_test_state {
+	bool driver_device_probed;
+	bool driver_device_removed;
+	long action_was_run;
+};
+
+static int driver_probe_hook(struct device *dev)
+{
+	struct kunit *test = kunit_get_current_test();
+	struct driver_test_state *state = (struct driver_test_state *)test->priv;
+
+	state->driver_device_probed = true;
+	return 0;
+}
+
+static int driver_remove_hook(struct device *dev)
+{
+	struct kunit *test = kunit_get_current_test();
+	struct driver_test_state *state = (struct driver_test_state *)test->priv;
+
+	state->driver_device_removed = true;
+	return 0;
+}
+
+static void kunit_device_driver_test(struct kunit *test)
+{
+	struct device_driver *test_driver;
+	struct device *test_device;
+	struct driver_test_state *test_state = kunit_kzalloc(test, sizeof(*test_state), GFP_KERNEL);
+
+	test->priv = test_state;
+	test_driver = kunit_driver_create(test, "my_driver");
+
+	// This can fail with an error pointer.
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, test_driver);
+
+	test_driver->probe = driver_probe_hook;
+	test_driver->remove = driver_remove_hook;
+
+	test_device = kunit_device_register_with_driver(test, "my_device", test_driver);
+
+	// This can fail with an error pointer.
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, test_device);
+
+	// Make sure the probe function was called.
+	KUNIT_ASSERT_TRUE(test, test_state->driver_device_probed);
+
+	// Add an action to verify cleanup.
+	devm_add_action(test_device, test_dev_action, &test_state->action_was_run);
+
+	KUNIT_EXPECT_EQ(test, test_state->action_was_run, 0);
+
+	kunit_device_unregister(test, test_device);
+	test_device = NULL;
+
+	// Make sure the remove hook was called.
+	KUNIT_ASSERT_TRUE(test, test_state->driver_device_removed);
+
+	// We're going to test this again.
+	test_state->driver_device_probed = false;
+
+	// The driver should not automatically be destroyed by
+	// kunit_device_unregister, so we can re-use it.
+	test_device = kunit_device_register_with_driver(test, "my_device", test_driver);
+
+	// This can fail with an error pointer.
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, test_device);
+
+	// Probe was called again.
+	KUNIT_ASSERT_TRUE(test, test_state->driver_device_probed);
+
+	// Everything is automatically freed here.
+}
+
+static struct kunit_case kunit_device_test_cases[] = {
+	KUNIT_CASE(kunit_device_test),
+	KUNIT_CASE(kunit_device_cleanup_test),
+	KUNIT_CASE(kunit_device_driver_test),
+	{}
+};
+
+static struct kunit_suite kunit_device_test_suite = {
+	.name = "kunit_device",
+	.test_cases = kunit_device_test_cases,
+};
+
 static struct kunit_suite kunit_current_test_suite = {
 	.name = "kunit_current",
 	.test_cases = kunit_current_test_cases,
@@ -694,6 +826,6 @@ static struct kunit_suite kunit_current_test_suite = {
 
 kunit_test_suites(&kunit_try_catch_test_suite, &kunit_resource_test_suite,
 		  &kunit_log_test_suite, &kunit_status_test_suite,
-		  &kunit_current_test_suite);
+		  &kunit_current_test_suite, &kunit_device_test_suite);
 
 MODULE_LICENSE("GPL v2");
diff --git a/lib/kunit/test.c b/lib/kunit/test.c
index 088489856db8..14a77b2d702a 100644
--- a/lib/kunit/test.c
+++ b/lib/kunit/test.c
@@ -19,6 +19,7 @@
 #include <linux/sched.h>
 
 #include "debugfs.h"
+#include "device-impl.h"
 #include "hooks-impl.h"
 #include "string-stream.h"
 #include "try-catch-impl.h"
@@ -900,6 +901,8 @@ static int __init kunit_init(void)
 	kunit_install_hooks();
 
 	kunit_debugfs_init();
+
+	kunit_bus_init();
 #ifdef CONFIG_MODULES
 	return register_module_notifier(&kunit_mod_nb);
 #else