refactor: use an enum for FF-A errors

Change-Id: Id30f36840e0668daa152ab90a2559fade7883c5f
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/include/runtime_services/ffa_svc.h b/include/runtime_services/ffa_svc.h
index ddf4559..4c82507 100644
--- a/include/runtime_services/ffa_svc.h
+++ b/include/runtime_services/ffa_svc.h
@@ -15,18 +15,22 @@
  * FFA error codes.
  * Don't forget to update `ffa_error_name` if you add a new one.
  */
-#define FFA_ERROR_NOT_SUPPORTED		-1
-#define FFA_ERROR_INVALID_PARAMETER	-2
-#define FFA_ERROR_NO_MEMORY		-3
-#define FFA_ERROR_BUSY			-4
-#define FFA_ERROR_INTERRUPTED		-5
-#define FFA_ERROR_DENIED		-6
-#define FFA_ERROR_RETRY			-7
-#define FFA_ERROR_ABORTED		-8
-#define FFA_ERROR_NO_DATA		-9
+/* clang-format off */
+enum ffa_error {
+	FFA_ERROR_NOT_SUPPORTED 	= -1,
+	FFA_ERROR_INVALID_PARAMETER 	= -2,
+	FFA_ERROR_NO_MEMORY 		= -3,
+	FFA_ERROR_BUSY 			= -4,
+	FFA_ERROR_INTERRUPTED 		= -5,
+	FFA_ERROR_DENIED 		= -6,
+	FFA_ERROR_RETRY 		= -7,
+	FFA_ERROR_ABORTED 		= -8,
+	FFA_ERROR_NO_DATA 		= -9,
+};
+/* clang-format on */
 
 /* Return the name of the error code. */
-static inline const char *ffa_error_name(int32_t error)
+static inline const char *ffa_error_name(enum ffa_error error)
 {
 	switch (error) {
 	case FFA_ERROR_NOT_SUPPORTED:
@@ -47,9 +51,8 @@
 		return "FFA_ERROR_ABORTED";
 	case FFA_ERROR_NO_DATA:
 		return "FFA_ERROR_NO_DATA";
-	default:
-		return "UNKNOWN";
 	}
+	return "UNKNOWN";
 }
 
 /* The macros below are used to identify FFA calls from the SMC function ID */
diff --git a/include/runtime_services/spm_test_helpers.h b/include/runtime_services/spm_test_helpers.h
index 14b2fb5..93675ce 100644
--- a/include/runtime_services/spm_test_helpers.h
+++ b/include/runtime_services/spm_test_helpers.h
@@ -15,14 +15,16 @@
 #define SKIP_TEST_IF_FFA_VERSION_LESS_THAN(major, minor)			\
 	do {									\
 		struct ffa_value ret = ffa_version(FFA_VERSION_COMPILED);	\
-		enum ffa_version version = ret.fid;				\
+		enum ffa_version version;					\
 										\
-		if (version == FFA_ERROR_NOT_SUPPORTED) {			\
+		if (ret.fid == FFA_ERROR_NOT_SUPPORTED) {			\
 			tftf_testcase_printf("FFA_VERSION not supported.\n");	\
 			return TEST_RESULT_SKIPPED;				\
 		}								\
 										\
-		if (!ffa_version_is_valid(version)) {			\
+		version = ret.fid;						\
+										\
+		if (!ffa_version_is_valid(version)) {				\
 			tftf_testcase_printf("FFA_VERSION bad response: %x\n",	\
 					version);				\
 			return TEST_RESULT_FAIL;				\