diff --git a/services/std_svc/drtm/drtm_main.h b/services/std_svc/drtm/drtm_main.h
index b60d954..59e5608 100644
--- a/services/std_svc/drtm/drtm_main.h
+++ b/services/std_svc/drtm/drtm_main.h
@@ -9,10 +9,28 @@
 
 #include <stdint.h>
 
+#include <assert.h>
 #include <lib/smccc.h>
 
 #include "drtm_dma_prot.h"
 
+#define ALIGNED_UP(x, a) __extension__ ({ \
+	__typeof__(a) _a = (a); \
+	__typeof__(a) _one = 1; \
+	assert(IS_POWER_OF_TWO(_a)); \
+	((x) + (_a - _one)) & ~(_a - _one); \
+})
+
+#define ALIGNED_DOWN(x, a) __extension__ ({ \
+	__typeof__(a) _a = (a); \
+	__typeof__(a) _one = 1; \
+	assert(IS_POWER_OF_TWO(_a)); \
+	(x) & ~(_a - _one); \
+})
+
+#define DRTM_PAGE_SIZE		(4 * (1 << 10))
+#define DRTM_PAGE_SIZE_STR	"4-KiB"
+
 enum drtm_retc {
 	SUCCESS = SMC_OK,
 	NOT_SUPPORTED = SMC_UNK,
@@ -31,7 +49,28 @@
 	uint64_t tcb_hash_features;
 } drtm_features_t;
 
+struct __packed drtm_dl_args_v1 {
+	uint16_t version;        /* Must be 1. */
+	uint8_t __res[2];
+	uint32_t features;
+	uint64_t dlme_paddr;
+	uint64_t dlme_size;
+	uint64_t dlme_img_off;
+	uint64_t dlme_img_ep_off;
+	uint64_t dlme_img_size;
+	uint64_t dlme_data_off;
+	uint64_t dce_nwd_paddr;
+	uint64_t dce_nwd_size;
+	drtm_dl_dma_prot_args_v1_t dma_prot_args;
+} __aligned(__alignof(uint16_t /* First member's type, `uint16_t version' */));
+
 drtm_memory_region_descriptor_table_t *drtm_build_address_map(void);
 uint64_t drtm_get_address_map_size(void);
 
+/*
+ * Version-independent type.  May be used to avoid excessive line of code
+ * changes when migrating to new struct versions.
+ */
+typedef struct drtm_dl_args_v1 struct_drtm_dl_args;
+
 #endif /* DRTM_MAIN_H */