Message-ID: <CABVgOSk=jGzj55v+YWzOBCsG7Wdk68pyZr0VdAYftybv+5X67A@mail.gmail.com>
Date: Wed, 1 May 2024 15:55:46 +0800
From: David Gow <davidgow@...gle.com>
To: Stephen Boyd <sboyd@...nel.org>
Cc: Michael Turquette <mturquette@...libre.com>, linux-kernel@...r.kernel.org, 
	linux-clk@...r.kernel.org, patches@...ts.linux.dev, 
	kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org, 
	devicetree@...r.kernel.org, Brendan Higgins <brendan.higgins@...ux.dev>, 
	Rae Moar <rmoar@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J . Wysocki" <rafael@...nel.org>, Rob Herring <robh@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, Daniel Latypov <dlatypov@...gle.com>, 
	Christian Marangi <ansuelsmth@...il.com>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley <conor+dt@...nel.org>, 
	Maxime Ripard <maxime@...no.tech>
Subject: Re: [PATCH v4 05/10] platform: Add test managed platform_device/driver
 APIs

On Tue, 23 Apr 2024 at 07:24, Stephen Boyd <sboyd@...nel.org> wrote:
>
> Introduce KUnit resource wrappers around platform_driver_register(),
> platform_device_alloc(), and platform_device_add() so that test authors
> can register platform drivers/devices from their tests and have the
> drivers/devices automatically be unregistered when the test is done.
>
> This makes test setup code simpler when a platform driver or platform
> device is needed. Add a few test cases at the same time to make sure the
> APIs work as intended.
>
> Cc: Brendan Higgins <brendan.higgins@...ux.dev>
> Cc: David Gow <davidgow@...gle.com>
> Cc: Rae Moar <rmoar@...gle.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@...nel.org>
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>
> ---

I really like this: I think it'll definitely help make platform
devices easier to use in tests. (And the handling of the unregistering
is particularly much nicer than trying to do it by hand, IMO.)

I've got a few suggestions below, mostly around naming and that it's
probably best to put this in lib/kunit/, given that the header is in
include/kunit, and there's already the generic kunit_device
functionality there. There's also a control-flow-integrity issue or
two, as casting function pointers will trigger that.

Otherwise, this looks good.

-- David

>  Documentation/dev-tools/kunit/api/index.rst   |   5 +
>  .../dev-tools/kunit/api/platformdevice.rst    |  10 +
>  drivers/base/test/Makefile                    |   3 +
>  drivers/base/test/platform_kunit-test.c       | 140 ++++++++++++++
>  drivers/base/test/platform_kunit.c            | 174 ++++++++++++++++++
>  include/kunit/platform_device.h               |  15 ++
>  6 files changed, 347 insertions(+)
>  create mode 100644 Documentation/dev-tools/kunit/api/platformdevice.rst
>  create mode 100644 drivers/base/test/platform_kunit-test.c
>  create mode 100644 drivers/base/test/platform_kunit.c
>  create mode 100644 include/kunit/platform_device.h
>
> diff --git a/Documentation/dev-tools/kunit/api/index.rst b/Documentation/dev-tools/kunit/api/index.rst
> index 282befa17edf..02b26f5e8750 100644
> --- a/Documentation/dev-tools/kunit/api/index.rst
> +++ b/Documentation/dev-tools/kunit/api/index.rst
> @@ -10,6 +10,7 @@ API Reference
>         resource
>         functionredirection
>         of
> +       platformdevice

A note (to myself, as much as anything): for the other device
wrappers, we considered them 'resources' and so bundled the
documentation in with the 'resource' documentation.
Maybe it'd make sense to split it out into its own device.rst file. We
could optionally include the platformdevice stuff in the same file if
we wanted to consolidate documentation for "device helpers", though
I'm not sure if it's worthwhile.

>
>
>  This page documents the KUnit kernel testing API. It is divided into the
> @@ -36,3 +37,7 @@ Driver KUnit API
>  Documentation/dev-tools/kunit/api/of.rst
>
>   - Documents the KUnit device tree (OF) API
> +
> +Documentation/dev-tools/kunit/api/platformdevice.rst
> +
> + - Documents the KUnit platform device API
> diff --git a/Documentation/dev-tools/kunit/api/platformdevice.rst b/Documentation/dev-tools/kunit/api/platformdevice.rst
> new file mode 100644
> index 000000000000..b228fb6558c2
> --- /dev/null
> +++ b/Documentation/dev-tools/kunit/api/platformdevice.rst
> @@ -0,0 +1,10 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===================
> +Platform Device API
> +===================
> +
> +The KUnit platform device API is used to test platform devices.
> +
> +.. kernel-doc:: drivers/base/test/platform_kunit.c
> +   :export:
> diff --git a/drivers/base/test/Makefile b/drivers/base/test/Makefile
> index e321dfc7e922..740aef267fbe 100644
> --- a/drivers/base/test/Makefile
> +++ b/drivers/base/test/Makefile
> @@ -1,8 +1,11 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_TEST_ASYNC_DRIVER_PROBE)  += test_async_driver_probe.o
>
> +obj-$(CONFIG_KUNIT) += platform_kunit.o
> +

Do we want this to be part of the kunit.ko module (and hence,
probably, under lib/kunit), or to keep this as a separate module.
I'm tempted, personally, to treat this as a part of KUnit, and have it
be part of the same module. There are a couple of reasons for this:
- It's nice to have CONFIG_KUNIT produce only one module. If we want
this to be separate, I'd be tempted to put it behind its own kconfig
entry.
- The name platform_kunit.ko suggests (to me, at least) that this is
the test for platform devices, not the implementation of the helper.

I probably can be persuaded otherwise if you've got a strong
preference for it to stay as-is, though.

>  obj-$(CONFIG_DM_KUNIT_TEST)    += root-device-test.o
>  obj-$(CONFIG_DM_KUNIT_TEST)    += platform-device-test.o
> +obj-$(CONFIG_DM_KUNIT_TEST)    += platform_kunit-test.o
>
>  obj-$(CONFIG_DRIVER_PE_KUNIT_TEST) += property-entry-test.o
>  CFLAGS_property-entry-test.o += $(DISABLE_STRUCTLEAK_PLUGIN)
> diff --git a/drivers/base/test/platform_kunit-test.c b/drivers/base/test/platform_kunit-test.c
> new file mode 100644
> index 000000000000..ce545532d209
> --- /dev/null
> +++ b/drivers/base/test/platform_kunit-test.c
> @@ -0,0 +1,140 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * KUnit test for platform driver infrastructure.
> + */
> +
> +#include <linux/platform_device.h>
> +
> +#include <kunit/platform_device.h>
> +#include <kunit/test.h>
> +
> +static const char * const kunit_devname = "kunit-platform";
> +
> +/*
> + * Test that platform_device_alloc_kunit() creates a platform device.
> + */
> +static void platform_device_alloc_kunit_test(struct kunit *test)
> +{
> +       KUNIT_EXPECT_NOT_ERR_OR_NULL(test,
> +                       platform_device_alloc_kunit(test, kunit_devname, 1));
> +}
> +
> +/*
> + * Test that platform_device_add_kunit() registers a platform device on the
> + * platform bus with the proper name and id.
> + */
> +static void platform_device_add_kunit_test(struct kunit *test)
> +{
> +       struct platform_device *pdev;
> +       const char *name = kunit_devname;
> +       const int id = -1;
> +
> +       pdev = platform_device_alloc_kunit(test, name, id);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
> +
> +       KUNIT_EXPECT_EQ(test, 0, platform_device_add_kunit(test, pdev));
> +       KUNIT_EXPECT_TRUE(test, dev_is_platform(&pdev->dev));
> +       KUNIT_EXPECT_STREQ(test, pdev->name, name);
> +       KUNIT_EXPECT_EQ(test, pdev->id, id);
> +}
> +
> +/*
> + * Test that platform_device_add_kunit() called twice with the same device name
> + * and id fails the second time and properly cleans up.
> + */
> +static void platform_device_add_kunit_twice_fails_test(struct kunit *test)
> +{
> +       struct platform_device *pdev;
> +       const char *name = kunit_devname;
> +       const int id = -1;
> +
> +       pdev = platform_device_alloc_kunit(test, name, id);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
> +       KUNIT_ASSERT_EQ(test, 0, platform_device_add_kunit(test, pdev));
> +
> +       pdev = platform_device_alloc_kunit(test, name, id);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
> +
> +       KUNIT_EXPECT_NE(test, 0, platform_device_add_kunit(test, pdev));
> +}
> +
> +/*
> + * Test suite for struct platform_device kunit APIs
> + */
> +static struct kunit_case platform_device_kunit_test_cases[] = {
> +       KUNIT_CASE(platform_device_alloc_kunit_test),
> +       KUNIT_CASE(platform_device_add_kunit_test),
> +       KUNIT_CASE(platform_device_add_kunit_twice_fails_test),
> +       {}
> +};
> +
> +static struct kunit_suite platform_device_kunit_suite = {
> +       .name = "platform_device_kunit",
> +       .test_cases = platform_device_kunit_test_cases,
> +};
> +
> +struct kunit_platform_driver_test_context {
> +       struct platform_driver pdrv;
> +       const char *data;
> +};
> +
> +static const char * const test_data = "test data";
> +
> +static inline struct kunit_platform_driver_test_context *
> +to_test_context(struct platform_device *pdev)
> +{
> +       return container_of(to_platform_driver(pdev->dev.driver),
> +                           struct kunit_platform_driver_test_context,
> +                           pdrv);
> +}
> +
> +static int kunit_platform_driver_probe(struct platform_device *pdev)
> +{
> +       struct kunit_platform_driver_test_context *ctx;
> +
> +       ctx = to_test_context(pdev);
> +       ctx->data = test_data;
> +
> +       return 0;
> +}
> +
> +/* Test that platform_driver_register_kunit() registers a driver that probes. */
> +static void platform_driver_register_kunit_test(struct kunit *test)
> +{
> +       struct platform_device *pdev;
> +       struct kunit_platform_driver_test_context *ctx;
> +
> +       ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);
> +
> +       pdev = platform_device_alloc_kunit(test, kunit_devname, -1);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, pdev);
> +       KUNIT_ASSERT_EQ(test, 0, platform_device_add_kunit(test, pdev));
> +
> +       ctx->pdrv.probe = kunit_platform_driver_probe;
> +       ctx->pdrv.driver.name = kunit_devname;
> +       ctx->pdrv.driver.owner = THIS_MODULE;
> +
> +       KUNIT_EXPECT_EQ(test, 0, platform_driver_register_kunit(test, &ctx->pdrv));
> +       KUNIT_EXPECT_STREQ(test, ctx->data, test_data);
> +}
> +
> +static struct kunit_case platform_driver_kunit_test_cases[] = {
> +       KUNIT_CASE(platform_driver_register_kunit_test),
> +       {}
> +};
> +
> +/*
> + * Test suite for struct platform_driver kunit APIs
> + */
> +static struct kunit_suite platform_driver_kunit_suite = {
> +       .name = "platform_driver_kunit",
> +       .test_cases = platform_driver_kunit_test_cases,
> +};
> +
> +kunit_test_suites(
> +       &platform_device_kunit_suite,
> +       &platform_driver_kunit_suite,
> +);
> +
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/base/test/platform_kunit.c b/drivers/base/test/platform_kunit.c
> new file mode 100644
> index 000000000000..54af6db2a6d8
> --- /dev/null
> +++ b/drivers/base/test/platform_kunit.c
> @@ -0,0 +1,174 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Test managed platform driver
> + */
> +
> +#include <linux/device/driver.h>
> +#include <linux/platform_device.h>
> +
> +#include <kunit/platform_device.h>
> +#include <kunit/resource.h>
> +
> +/**
> + * platform_device_alloc_kunit() - Allocate a KUnit test managed platform device
> + * @test: test context
> + * @name: device name of platform device to alloc
> + * @id: identifier of platform device to alloc.
> + *
> + * Allocate a test managed platform device. The device is put when the test completes.
> + *
> + * Return: Allocated platform device on success, NULL on failure.
> + */
> +struct platform_device *
> +platform_device_alloc_kunit(struct kunit *test, const char *name, int id)

I'd prefer, personally, this be named something like
kunit_platform_device_alloc(), to match the existing
kunit_device_register() functions.


> +{
> +       struct platform_device *pdev;
> +
> +       pdev = platform_device_alloc(name, id);
> +       if (!pdev)
> +               return NULL;
> +
> +       if (kunit_add_action_or_reset(test, (kunit_action_t *)&platform_device_put, pdev))

Alas, casting function pointers to kunit_action_t* breaks CFI. It's
worth using a wrapper, which can be created with the
KUNIT_DEFINE_ACTION_WRAPPER() macro, e.g.

KUNIT_DEFINE_ACTION_WRAPPER(platform_device_put_wrapper,
platform_device_put, struct platform_device *);

> +               return NULL;
> +
> +       return pdev;
> +}
> +EXPORT_SYMBOL_GPL(platform_device_alloc_kunit);
> +
> +static void platform_device_add_kunit_exit(struct kunit_resource *res)
> +{
> +       struct platform_device *pdev = res->data;
> +
> +       platform_device_unregister(pdev);
> +}
> +
> +static bool
> +platform_device_alloc_kunit_match(struct kunit *test,
> +                                 struct kunit_resource *res, void *match_data)
> +{
> +       struct platform_device *pdev = match_data;
> +
> +       return res->data == pdev;
> +}
> +
> +/**
> + * platform_device_add_kunit() - Register a KUnit test managed platform device
> + * @test: test context
> + * @pdev: platform device to add
> + *
> + * Register a test managed platform device. The device is unregistered when the
> + * test completes.
> + *
> + * Return: 0 on success, negative errno on failure.
> + */
> +int platform_device_add_kunit(struct kunit *test, struct platform_device *pdev)

As above, I'd lean towards naming this kunit_platform_device_add() for
consistency with the other KUnit device helpers.

> +{
> +       struct kunit_resource *res;
> +       int ret;
> +
> +       ret = platform_device_add(pdev);
> +       if (ret)
> +               return ret;
> +
> +       res = kunit_find_resource(test, platform_device_alloc_kunit_match, pdev);
> +       if (res) {
> +               /*
> +                * Transfer the reference count of the platform device if it was
> +                * allocated with platform_device_alloc_kunit(). In that case,
> +                * calling platform_device_put() leads to reference count
> +                * underflow because platform_device_unregister() does it for
> +                * us and we call platform_device_unregister() from
> +                * platform_device_add_kunit_exit().
> +                *
> +                * Usually callers transfer the refcount from
> +                * platform_device_alloc() to platform_device_add() and simply
> +                * call platform_device_unregister() when done, but with kunit
> +                * we have to keep this straight by redirecting the free
> +                * routine for the resource.
> +                */
> +               res->free = platform_device_add_kunit_exit;
> +               kunit_put_resource(res);
> +       } else if (kunit_add_action_or_reset(test,
> +                                            (kunit_action_t *)&platform_device_unregister,
> +                                            pdev)) {

Nit: We don't want to cast directly to kunit_action_t *, as that
breaks CFI. Can we use KUNIT_DEFINE_ACTION_WRAPPER()?

> +               return -ENOMEM;

Nit: This is fine, as kunit_add_action_or_reset() only returns 0 or
-ENOMEM at the moment, but it could cause problems down the line if we
ever want to return a different error. I don't think that's
particularly likely, but it might be nicer to properly propagate the
error.

> +       }
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(platform_device_add_kunit);
> +
> +/**
> + * platform_driver_register_kunit() - Register a KUnit test managed platform driver
> + * @test: test context
> + * @drv: platform driver to register
> + *
> + * Register a test managed platform driver. This allows callers to embed the
> + * @drv in a container structure and use container_of() in the probe function
> + * to pass information to KUnit tests. It can be assumed that the driver has
> + * probed when this function returns.
> + *
> + * Example
> + *
> + * .. code-block:: c
> + *
> + *     struct kunit_test_context {
> + *             struct platform_driver pdrv;
> + *             const char *data;
> + *     };
> + *
> + *     static inline struct kunit_test_context *
> + *     to_test_context(struct platform_device *pdev)
> + *     {
> + *             return container_of(to_platform_driver(pdev->dev.driver),
> + *                                 struct kunit_test_context,
> + *                                 pdrv);
> + *     }
> + *
> + *     static int kunit_platform_driver_probe(struct platform_device *pdev)
> + *     {
> + *             struct kunit_test_context *ctx;
> + *
> + *             ctx = to_test_context(pdev);
> + *             ctx->data = "test data";
> + *
> + *             return 0;
> + *     }
> + *
> + *     static void kunit_platform_driver_test(struct kunit *test)
> + *     {
> + *             struct kunit_test_context *ctx;
> + *
> + *             ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL);
> + *             KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx);
> + *
> + *             ctx->pdrv.probe = kunit_platform_driver_probe;
> + *             ctx->pdrv.driver.name = "kunit-platform";
> + *             ctx->pdrv.driver.owner = THIS_MODULE;
> + *
> + *             KUNIT_EXPECT_EQ(test, 0, platform_driver_register_kunit(test, &ctx->pdrv));
> + *             KUNIT_EXPECT_STREQ(test, ctx->data, "test data");
> + *     }
> + *
> + * Return: 0 on success, negative errno on failure.
> + */
> +int platform_driver_register_kunit(struct kunit *test,
> +                                  struct platform_driver *drv)

As above, I'd prefer kunit_platform_driver_register()

> +{
> +       int ret;
> +
> +       ret = platform_driver_register(drv);
> +       if (ret)
> +               return ret;
> +
> +       /*
> +        * Wait for the driver to probe (or at least flush out of the deferred
> +        * workqueue)
> +        */
> +       wait_for_device_probe();

Personally, I don't mind if this wrapper waits here (even if it makes
it less of a 'pure' wrapper), so long as we document it. Can you think
of any cases where we explicitly want _not_ to wait in a test?


> +
> +       return kunit_add_action_or_reset(test,
> +                                        (kunit_action_t *)&platform_driver_unregister,
> +                                        drv);
> +}
> +EXPORT_SYMBOL_GPL(platform_driver_register_kunit);
> diff --git a/include/kunit/platform_device.h b/include/kunit/platform_device.h
> new file mode 100644
> index 000000000000..28d28abf15a4
> --- /dev/null
> +++ b/include/kunit/platform_device.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _KUNIT_PLATFORM_DRIVER_H
> +#define _KUNIT_PLATFORM_DRIVER_H
> +
> +struct kunit;
> +struct platform_device;
> +struct platform_driver;
> +
> +struct platform_device *
> +platform_device_alloc_kunit(struct kunit *test, const char *name, int id);
> +int platform_device_add_kunit(struct kunit *test, struct platform_device *pdev);
> +
> +int platform_driver_register_kunit(struct kunit *test, struct platform_driver *drv);
> +
> +#endif
> --
> https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git/
> https://git.kernel.org/pub/scm/linux/kernel/git/sboyd/spmi.git
>
> --
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