Message-ID: <CABVgOSmBssmMz3qQi+TdEoaGQJNXaSVBrsO8RSW0MjLUUHPakg@mail.gmail.com>
Date: Sat, 2 Aug 2025 17:44:52 +0800
From: David Gow <davidgow@...gle.com>
To: Marie Zhussupova <marievic@...gle.com>
Cc: rmoar@...gle.com, shuah@...nel.org, brendan.higgins@...ux.dev, 
	elver@...gle.com, dvyukov@...gle.com, lucas.demarchi@...el.com, 
	thomas.hellstrom@...ux.intel.com, rodrigo.vivi@...el.com, 
	linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com, 
	kasan-dev@...glegroups.com, intel-xe@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/9] kunit: Add example parameterized test with shared
 resources and direct static parameter array setup

On Wed, 30 Jul 2025 at 03:37, Marie Zhussupova <marievic@...gle.com> wrote:
>
> Add `example_params_test_with_init` to illustrate how to manage
> shared resources across parameterized KUnit tests. This example
> showcases the use of the new `param_init` function and its registration
> to a test using the `KUNIT_CASE_PARAM_WITH_INIT` macro.
>
> Additionally, the test demonstrates:
> - How to directly assign a static parameter array to a test via
>   `kunit_register_params_array`.
> - Leveraging the Resource API for test resource management.
>
> Signed-off-by: Marie Zhussupova <marievic@...gle.com>
> ---

Thanks for writing some examples! This is great, and makes the rest of
the series much easier to understand.

(It also reminds me how much I hate the verbose parts of the resource
API, but it's definitely out of scope to refactor that here. :-))

It does seem like this is a lot of effort to go through for one shared
integer, though. In the real world, I'd suggest using
kunit->parent->priv here. As an example, though, it's fine (though
maybe using a named resource or even kunit_kzalloc() or similar would
give a better example of how convenient this could be.

It's also not entirely clear why we're using
kunit_register_params_array() for a static array, when
KUNIT_ARRAY_PARAM() exists. (This is clearly because the latter
doesn't support init functions; and I see why we don't necessarily
want to make the number of macros explode through adding
KUNIT_ARRAY_PARAM_WITH_INIT() et al, but maybe we should note that in
the commit description, either here or before.)

Actual test looks fine, though:

Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David


>  lib/kunit/kunit-example-test.c | 112 +++++++++++++++++++++++++++++++++
>  1 file changed, 112 insertions(+)
>
> diff --git a/lib/kunit/kunit-example-test.c b/lib/kunit/kunit-example-test.c
> index 3056d6bc705d..5bf559e243f6 100644
> --- a/lib/kunit/kunit-example-test.c
> +++ b/lib/kunit/kunit-example-test.c
> @@ -277,6 +277,116 @@ static void example_slow_test(struct kunit *test)
>         KUNIT_EXPECT_EQ(test, 1 + 1, 2);
>  }
>
> +/*
> + * This custom function allocates memory for the kunit_resource data field.
> + * The function is passed to kunit_alloc_resource() and executed once
> + * by the internal helper __kunit_add_resource().
> + */
> +static int example_resource_init(struct kunit_resource *res, void *context)
> +{
> +       int *info = kmalloc(sizeof(*info), GFP_KERNEL);
> +
> +       if (!info)
> +               return -ENOMEM;
> +       *info = *(int *)context;
> +       res->data = info;
> +       return 0;
> +}
> +
> +/*
> + * This function deallocates memory for the 'kunit_resource' data field.
> + * The function is passed to kunit_alloc_resource() and automatically
> + * executes within kunit_release_resource() when the resource's reference
> + * count, via kunit_put_resource(), drops to zero. KUnit uses reference
> + * counting to ensure that resources are not freed prematurely.
> + */
> +static void example_resource_free(struct kunit_resource *res)
> +{
> +       kfree(res->data);
> +}
> +
> +/*
> + * This match function is invoked by kunit_find_resource() to locate
> + * a test resource based on defined criteria. The current example
> + * uniquely identifies the resource by its free function; however,
> + * alternative custom criteria can be implemented. Refer to
> + * lib/kunit/platform.c and lib/kunit/static_stub.c for further examples.
> + */
> +static bool example_resource_alloc_match(struct kunit *test,
> +                                        struct kunit_resource *res,
> +                                        void *match_data)
> +{
> +       return res->data && res->free == example_resource_free;
> +}
> +
> +/*
> + * This is an example of a function that provides a description for each of the
> + * parameters.
> + */
> +static void example_param_array_get_desc(const void *p, char *desc)
> +{
> +       const struct example_param *param = p;
> +
> +       snprintf(desc, KUNIT_PARAM_DESC_SIZE,
> +                "example check if %d is less than or equal to 3", param->value);
> +}
> +
> +/*
> + * Initializes the parent kunit struct for parameterized KUnit tests.
> + * This function enables sharing resources across all parameterized
> + * tests by adding them to the `parent` kunit test struct. It also supports
> + * registering either static or dynamic arrays of test parameters.
> + */
> +static int example_param_init(struct kunit *test)
> +{
> +       int ctx = 3; /* Data to be stored. */
> +       int arr_size = ARRAY_SIZE(example_params_array);
> +
> +       /*
> +        * This allocates a struct kunit_resource, sets its data field to
> +        * ctx, and adds it to the kunit struct's resources list. Note that
> +        * this is test managed so we don't need to have a custom exit function
> +        * to free it.
> +        */
> +       void *data = kunit_alloc_resource(test, example_resource_init, example_resource_free,
> +                                         GFP_KERNEL, &ctx);
> +
> +       if (!data)
> +               return -ENOMEM;
> +       /* Pass the static param array information to the parent struct kunit. */
> +       kunit_register_params_array(test, example_params_array, arr_size,
> +                                   example_param_array_get_desc);
> +       return 0;
> +}
> +
> +/*
> + * This is an example of a parameterized test that uses shared resources
> + * available from the struct kunit parent field of the kunit struct.
> + */
> +static void example_params_test_with_init(struct kunit *test)
> +{
> +       int threshold;
> +       struct kunit_resource *res;
> +       const struct example_param *param = test->param_value;
> +
> +       /* By design, param pointer will not be NULL. */
> +       KUNIT_ASSERT_NOT_NULL(test, param);
> +
> +       /* Here we access the parent pointer of the test to find the shared resource. */
> +       res = kunit_find_resource(test->parent, example_resource_alloc_match, NULL);
> +
> +       KUNIT_ASSERT_NOT_NULL(test, res);
> +
> +       /* Since the data field in kunit_resource is a void pointer we need to typecast it. */
> +       threshold = *((int *)res->data);
> +
> +       /* Assert that the parameter is less than or equal to a certain threshold. */
> +       KUNIT_ASSERT_LE(test, param->value, threshold);
> +
> +       /* This decreases the reference count after calling kunit_find_resource(). */
> +       kunit_put_resource(res);
> +}
> +
>  /*
>   * Here we make a list of all the test cases we want to add to the test suite
>   * below.
> @@ -296,6 +406,8 @@ static struct kunit_case example_test_cases[] = {
>         KUNIT_CASE(example_static_stub_using_fn_ptr_test),
>         KUNIT_CASE(example_priv_test),
>         KUNIT_CASE_PARAM(example_params_test, example_gen_params),
> +       KUNIT_CASE_PARAM_WITH_INIT(example_params_test_with_init, NULL,
> +                                  example_param_init, NULL),
>         KUNIT_CASE_SLOW(example_slow_test),
>         {}
>  };
> --
> 2.50.1.552.g942d659e1b-goog
>

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