diff --git a/trusty/storage/interface/include/trusty/interface/storage.h b/trusty/storage/interface/include/trusty/interface/storage.h
index 255ade127..32916074b 100644
--- a/trusty/storage/interface/include/trusty/interface/storage.h
+++ b/trusty/storage/interface/include/trusty/interface/storage.h
@@ -53,6 +53,8 @@ enum storage_cmd {
 
 	/* transaction support */
 	STORAGE_END_TRANSACTION = 9 << STORAGE_REQ_SHIFT,
+
+	STORAGE_FILE_GET_MAX_SIZE = 12 << STORAGE_REQ_SHIFT,
 };
 
 /**
@@ -183,6 +185,24 @@ struct storage_file_close_req {
 	uint32_t handle;
 };
 
+/**
+ * struct storage_file_get_max_size_req - request format for
+ *                                        STORAGE_FILE_GET_MAX_SIZE
+ * @handle: the handle for the file whose max size is requested
+ */
+struct storage_file_get_max_size_req {
+	uint32_t handle;
+};
+
+/**
+ * struct storage_file_get_max_size_resp - response format for
+ *                                         STORAGE_FILE_GET_MAX_SIZE
+ * @max_size:   the maximum size of the file
+ */
+struct storage_file_get_max_size_resp {
+	uint64_t max_size;
+};
+
 /**
  * struct storage_file_read_req - request format for STORAGE_FILE_READ
  * @handle: the handle for the file from which to read