kunit: add parameter generation macro using description from array

The existing KUNIT_ARRAY_PARAM macro requires a separate function to
get the description. However, in a lot of cases the description can
just be copied directly from the array. Add a second macro that
avoids having to write a static function just for a single strscpy.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Reviewed-by: David Gow <davidgow@google.com>
Link: https://msgid.link/20231220151952.415232-2-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Documentation/dev-tools/kunit/usage.rst

@@ -566,13 +566,9 @@ By reusing the same ``cases`` array from above, we can write the test as a
 		},
 	};
 
-	// Need a helper function to generate a name for each test case.
-	static void case_to_desc(const struct sha1_test_case *t, char *desc)
-	{
-		strcpy(desc, t->str);
-	}
-	// Creates `sha1_gen_params()` to iterate over `cases`.
-	KUNIT_ARRAY_PARAM(sha1, cases, case_to_desc);
+	// Creates `sha1_gen_params()` to iterate over `cases` while using
+	// the struct member `str` for the case description.
+	KUNIT_ARRAY_PARAM_DESC(sha1, cases, str);
 
 	// Looks no different from a normal test.
 	static void sha1_test(struct kunit *test)
@@ -588,7 +584,7 @@ By reusing the same ``cases`` array from above, we can write the test as a
 	}
 
 	// Instead of KUNIT_CASE, we use KUNIT_CASE_PARAM and pass in the
-	// function declared by KUNIT_ARRAY_PARAM.
+	// function declared by KUNIT_ARRAY_PARAM or KUNIT_ARRAY_PARAM_DESC.
 	static struct kunit_case sha1_test_cases[] = {
 		KUNIT_CASE_PARAM(sha1_test, sha1_gen_params),
 		{}

include/kunit/test.h

@@ -1514,6 +1514,25 @@ do {									       \
 		return NULL;									\
 	}
 
+/**
+ * KUNIT_ARRAY_PARAM_DESC() - Define test parameter generator from an array.
+ * @name:  prefix for the test parameter generator function.
+ * @array: array of test parameters.
+ * @desc_member: structure member from array element to use as description
+ *
+ * Define function @name_gen_params which uses @array to generate parameters.
+ */
+#define KUNIT_ARRAY_PARAM_DESC(name, array, desc_member)					\
+	static const void *name##_gen_params(const void *prev, char *desc)			\
+	{											\
+		typeof((array)[0]) *__next = prev ? ((typeof(__next)) prev) + 1 : (array);	\
+		if (__next - (array) < ARRAY_SIZE((array))) {					\
+			strscpy(desc, __next->desc_member, KUNIT_PARAM_DESC_SIZE);		\
+			return __next;								\
+		}										\
+		return NULL;									\
+	}
+
 // TODO(dlatypov@google.com): consider eventually migrating users to explicitly
 // include resource.h themselves if they need it.
 #include <kunit/resource.h>