On Wed, 30 Jul 2025 at 03:37, Marie Zhussupova <marie...@google.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 <marie...@google.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 <david...@google.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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