Add Kunit test case to verify DEFINE_REVOCABLE() can successfully access
the resource and drop the reference count.

A way to run the test:
$ ./tools/testing/kunit/kunit.py run \
        --kconfig_add CONFIG_REVOCABLE_KUNIT_TEST=y \
        revocable_test

Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
 drivers/base/revocable_test.c | 54 +++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/drivers/base/revocable_test.c b/drivers/base/revocable_test.c
index 28d46ce1ba0c..e0efffe6e04f 100644
--- a/drivers/base/revocable_test.c
+++ b/drivers/base/revocable_test.c
@@ -14,10 +14,15 @@
  *
  * - Try Access Macro: Same as "Revocation" but uses the
  *   REVOCABLE_TRY_ACCESS_WITH() and REVOCABLE_TRY_ACCESS_SCOPED().
+ *
+ * - Define Macro: Verifies DEFINE_REVOCABLE() can successfully access the
+ *   resource and drop the reference count.
  */
 
 #include <kunit/test.h>
+#include <linux/kref.h>
 #include <linux/revocable.h>
+#include <linux/srcu.h>
 
 static void revocable_test_basic(struct kunit *test)
 {
@@ -123,11 +128,60 @@ static void revocable_test_try_access_macro2(struct kunit *test)
 	revocable_free(rev);
 }
 
+static void revocable_test_define_macro(struct kunit *test)
+{
+	/* To access the opaque struct */
+	struct {
+		struct srcu_struct srcu;
+		void *res;
+		struct kref kref;
+	} *_rp;
+	struct revocable_provider *rp;
+	void *real_res = (void *)0x12345678, *res;
+
+	rp = revocable_provider_alloc(real_res);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rp);
+
+	_rp = (void *)rp;
+	KUNIT_EXPECT_EQ(test, kref_read(&_rp->kref), 1);
+
+	{
+		DEFINE_REVOCABLE(rev, rp);
+		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rev);
+		KUNIT_EXPECT_EQ(test, kref_read(&_rp->kref), 2);
+
+		REVOCABLE_TRY_ACCESS_WITH(rev, res);
+		KUNIT_EXPECT_PTR_EQ(test, res, real_res);
+	}
+	KUNIT_EXPECT_EQ(test, kref_read(&_rp->kref), 1);
+
+	{
+		bool accessed = false;
+
+		DEFINE_REVOCABLE(rev, rp);
+		KUNIT_ASSERT_NOT_ERR_OR_NULL(test, rev);
+		KUNIT_EXPECT_EQ(test, kref_read(&_rp->kref), 2);
+
+		REVOCABLE_TRY_ACCESS_SCOPED(rev, res) {
+			KUNIT_EXPECT_PTR_EQ(test, res, real_res);
+			accessed = true;
+		}
+		KUNIT_EXPECT_TRUE(test, accessed);
+
+		revocable_provider_revoke(rp);
+		KUNIT_EXPECT_EQ(test, kref_read(&_rp->kref), 1);
+
+		REVOCABLE_TRY_ACCESS_WITH(rev, res);
+		KUNIT_EXPECT_PTR_EQ(test, res, NULL);
+	}
+}
+
 static struct kunit_case revocable_test_cases[] = {
 	KUNIT_CASE(revocable_test_basic),
 	KUNIT_CASE(revocable_test_revocation),
 	KUNIT_CASE(revocable_test_try_access_macro),
 	KUNIT_CASE(revocable_test_try_access_macro2),
+	KUNIT_CASE(revocable_test_define_macro),
 	{}
 };
 
-- 
2.52.0.457.g6b5491de43-goog