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

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.

At first glance, nice work. But looks like 0-day doesn't like it that much, so I'll wait for the next version to review it properly.

One nit I did notice:

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

Put stuff like this in a local .h file, don't pollute the include/linux/ files for things that you do not want any other part of the kernel to call.

+/**

• • 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);
  

Shouldn't "struct device_driver *" be a constant pointer?

But really, why is this a "raw" device_driver pointer and not a pointer to the driver type for your bus?

Oh heck, let's point out the other issues as I'm already here...

@@ -7,7 +7,8 @@ kunit-objs += test.o \ assert.o \ try-catch.o \ executor.o \

• 			attributes.o
  

• 			attributes.o \
  

• 			device.o
  

Shouldn't this file be "bus.c" as you are creating a kunit bus?

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

"basic bus/driver implementation", not device, right?

• • 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 static device as a bus? This feels wrong, what is it for? And where does this live? If you _REALLY_ want a single device for the root of your bus (which is a good idea), then make it a dynamic variable (as it is reference counted), NOT a static struct device which should not be done if at all possible.

+/* 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;

+};

Wait, why isn't your "kunit" device above a struct kunit_device structure? Why is it ok to be a "raw" struct device (hint, that's almost never a good idea.)

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

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

container_of_const()? And to use that properly, why not make this a #define?

+}

+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;

I don't understand, what are you trying to match here?

+}

+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);
• 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;

Ah, so this is the match function to pass above? If so, why do you need it at all?

• 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))

This is almost always a sign that something is wrong with the api.

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

Ick, the cast is odd, are you sure you need it? Why would you return a struct device and not a kunit_device() anyway?

• return &kunit_dev->dev;

Again, why this type, why not use the real type you have?

thanks,

greg k-h