Re: [PATCH 1/4] kunit: Add APIs for managing devices

Hi David,

Thanks a lot for working on this.

On Tue, Dec 05, 2023 at 03:31:33PM +0800, davidgow@google.com wrote:

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.

Signed-off-by: David Gow davidgow@google.com

Documentation/dev-tools/kunit/usage.rst | 49 +++++++++ include/kunit/device.h | 76 ++++++++++++++ lib/kunit/Makefile | 3 +- lib/kunit/device.c | 176 ++++++++++++++++++++++++++++++++ lib/kunit/kunit-test.c | 68 +++++++++++- lib/kunit/test.c | 3 + 6 files changed, 373 insertions(+), 2 deletions(-)

diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst index 9db12e91668e..a222a98edceb 100644 --- a/Documentation/dev-tools/kunit/usage.rst +++ b/Documentation/dev-tools/kunit/usage.rst @@ -797,3 +797,52 @@ structures as shown below: KUnit is not enabled, or if no test is running in the current task, it will do nothing. This compiles down to either a no-op or a static key check, so will have a negligible performance impact when no test is running.

+Managing Fake Devcices and Drivers

^ Devices

+----------------------------------

+When testing drivers or code which interacts with drivers, many functions will +require a ``struct device`` or ``struct device_driver``. In many cases, setting +up a real device is not required to test any given function, so a fake device +can be used instead.

+KUnit provides helper functions to create and manage these fake devices, which +are internally of type ``struct kunit_device``, and are attached to a special +``kunit_bus``. These devices support managed device resources (devres), as +described in Documentation/driver-api/driver-model/devres.rst

+To create a KUnit-managed ``struct device_driver``, use ``kunit_driver_create()``, +which will create a driver with the given name, on the ``kunit_bus``. This driver +will automatically be destroyed when the corresponding test finishes, but can also +be manually destroyed with ``driver_unregister()``.

+To create a fake device, use the ``kunit_device_register()``, which will create +and register a device, using a new KUnit-managed driver created with ``kunit_driver_create()``. +To provide a specific, non-KUnit-managed driver, use ``kunit_device_register_with_driver()`` +instead. Like with managed drivers, KUnit-managed fake devices are automatically +cleaned up when the test finishes, but can be manually cleaned up early with +``kunit_device_unregister()``.

I think we should add a test for that, just like we did for root and platform devices. We've been bitten by that before :)

+The KUnit devices should be used in preference to ``root_device_register()``, and +instead of ``platform_device_register()`` in cases where the device is not otherwise +a platform device.

+For example:

+.. code-block:: c

• #include <kunit/device.h>
• static void test_my_device(struct kunit *test)
• {

• struct device *fake_device;
  

• const char *dev_managed_string;
  

• // Create a fake device.
  

• fake_device = kunit_device_register(test, "my_device");
  

• // Pass it to functions which need a device.
  

• dev_managed_string = devm_kstrdup(fake_device, "Hello, World!");
  

• // Everything is cleaned up automatically when the test ends.
  

• }

\ No newline at end of file diff --git a/include/kunit/device.h b/include/kunit/device.h new file mode 100644 index 000000000000..fd2193bc55f1 --- /dev/null +++ b/include/kunit/device.h @@ -0,0 +1,76 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/*

• • KUnit basic device implementation
• • Helpers for creating and managing fake devices for KUnit tests.
• • Copyright (C) 2023, Google LLC.
• • Author: David Gow davidgow@google.com
• */

+#ifndef _KUNIT_DEVICE_H +#define _KUNIT_DEVICE_H

+#if IS_ENABLED(CONFIG_KUNIT)

+#include <kunit/test.h>

+struct kunit_device; +struct device; +struct device_driver;

+// For internal use only -- registers the kunit_bus. +int kunit_bus_init(void);

+/**

• • kunit_driver_create() - Create a struct device_driver attached to the kunit_bus
• • @test: The test context object.
• • @name: The name to give the created driver.
• • Creates a struct device_driver attached to the kunit_bus, with the name @name.
• • This driver will automatically be cleaned up on test exit.
• */

+struct device_driver *kunit_driver_create(struct kunit *test, const char *name);

+/**

• • kunit_device_register() - Create a struct device for use in KUnit tests
• • @test: The test context object.
• • @name: The name to give the created device.
• • Creates a struct kunit_device (which is a struct device) with the given name,
• • and a corresponding driver. The device and driver will be cleaned up on test
• • exit, or when kunit_device_unregister is called. See also
• • kunit_device_register_with_driver, if you wish to provide your own
• • struct device_driver.
• */

+struct device *kunit_device_register(struct kunit *test, const char *name);

+/**

• • kunit_device_register_with_driver() - Create a struct device for use in KUnit tests
• • @test: The test context object.
• • @name: The name to give the created device.
• • @drv: The struct device_driver to associate with the device.
• • Creates a struct kunit_device (which is a struct device) with the given
• • name, and driver. The device will be cleaned up on test exit, or when
• • kunit_device_unregister is called. See also kunit_device_register, if you
• • wish KUnit to create and manage a driver for you
• */

+struct device *kunit_device_register_with_driver(struct kunit *test,

• 				 const char *name,
  

• 				 struct device_driver *drv);
  

+/**

• • kunit_device_unregister() - Unregister a KUnit-managed device
• • @test: The test context object which created the device
• • @dev: The device.
• • Unregisters and destroys a struct device which was created with
• • kunit_device_register or kunit_device_register_with_driver. If KUnit created
• • a driver, cleans it up as well.
• */

+void kunit_device_unregister(struct kunit *test, struct device *dev);

+#endif

+#endif 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.c b/lib/kunit/device.c new file mode 100644 index 000000000000..93ace1a2297d --- /dev/null +++ b/lib/kunit/device.c @@ -0,0 +1,176 @@ +// SPDX-License-Identifier: GPL-2.0 +/*

• • KUnit basic device implementation
• • Implementation of struct kunit_device helpers.
• • 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>

+/* 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 *);

+static struct device kunit_bus = {

• .init_name = "kunit"

+};

+/* A device owned by a KUnit test. */ +struct kunit_device {

• struct device dev;
• struct kunit *owner;
• /* Force binding to a specific driver. */
• struct device_driver *driver;
• /* The driver is managed by KUnit and unique to this device. */
• bool cleanup_driver;

+};

+static inline struct kunit_device *to_kunit_device(struct device *d) +{

• return container_of(d, struct kunit_device, dev);

+}

+static int kunit_bus_match(struct device *dev, struct device_driver *driver) +{

• struct kunit_device *kunit_dev = to_kunit_device(dev);
• if (kunit_dev->driver == driver)

• return 1;
  

• return 0;

+}

+static struct bus_type kunit_bus_type = {

• .name = "kunit",
• .match = kunit_bus_match

+};

+int kunit_bus_init(void) +{

• int error;
• error = bus_register(&kunit_bus_type);
• if (!error) {

• error = device_register(&kunit_bus);
  

• if (error)
  

• 	bus_unregister(&kunit_bus_type);
  

• }
• return error;

+} +late_initcall(kunit_bus_init);

+static void kunit_device_release(struct device *d) +{

• kfree(to_kunit_device(d));

+}

+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);

+struct kunit_device *__kunit_device_register_internal(struct kunit *test,

• 				      const char *name,
  

• 				      struct device_driver *drv)
  

+{

• struct kunit_device *kunit_dev;
• int err = -ENOMEM;
• kunit_dev = kzalloc(sizeof(struct kunit_device), GFP_KERNEL);

The preferred syntax is sizeof(*kunit_dev) here

• 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);
  

• }
• /* Set the expected driver pointer, so we match. */
• kunit_dev->driver = drv;
• kunit_dev->dev.release = kunit_device_release;
• kunit_dev->dev.bus = &kunit_bus_type;
• kunit_dev->dev.parent = &kunit_bus;
• 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;

+}

+struct device *kunit_device_register_with_driver(struct kunit *test,

• 				 const char *name,
  

• 				 struct device_driver *drv)
  

+{

• struct kunit_device *kunit_dev = __kunit_device_register_internal(test, name, drv);
• if (IS_ERR_OR_NULL(kunit_dev))

• return (struct device *)kunit_dev; /* This is an error or NULL, so is compatible */
  

• return &kunit_dev->dev;

+} +EXPORT_SYMBOL_GPL(kunit_device_register_with_driver);

+struct device *kunit_device_register(struct kunit *test, const char *name) +{

• struct device_driver *drv = kunit_driver_create(test, name);
• struct kunit_device *dev;
• KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drv);
• dev = __kunit_device_register_internal(test, name, drv);
• KUNIT_ASSERT_NOT_ERR_OR_NULL(test, dev);
• dev->cleanup_driver = true;
• return (struct device *)dev;

+} +EXPORT_SYMBOL_GPL(kunit_device_register);

+void kunit_device_unregister(struct kunit *test, struct device *dev) +{

• bool cleanup_driver = ((struct kunit_device *)dev)->cleanup_driver;
• struct device_driver *driver = ((struct kunit_device *)dev)->driver;
• kunit_release_action(test, device_unregister_wrapper, dev);
• if (cleanup_driver)

• kunit_release_action(test, driver_unregister_wrapper, driver);
  

+} +EXPORT_SYMBOL_GPL(kunit_device_unregister);

diff --git a/lib/kunit/kunit-test.c b/lib/kunit/kunit-test.c index 3e9c5192d095..a4007158bf36 100644 --- a/lib/kunit/kunit-test.c +++ b/lib/kunit/kunit-test.c @@ -8,6 +8,9 @@ #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 +690,69 @@ 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;
• 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, &test->priv);
• KUNIT_EXPECT_PTR_EQ(test, test->priv, (void *)0);
• kunit_device_unregister(test, test_device);
• KUNIT_EXPECT_PTR_EQ(test, test->priv, (void *)1);

+}

Oh, it looks like you do check there, sorry.

I guess I would have expected an explicit test for that, but that works :)

+static void kunit_device_driver_test(struct kunit *test) +{

• struct device_driver *test_driver;
• struct device *test_device;
• test_driver = kunit_driver_create(test, "my_driver");
• KUNIT_ASSERT_NOT_NULL(test, test_driver);
• test_device = kunit_device_register_with_driver(test, "my_device", test_driver);
• KUNIT_ASSERT_NOT_NULL(test, test_device);

Should we test that the probe (and remove) hooks has been called too?

Maxime