Index: uspace/lib/c/include/async.h
===================================================================
--- uspace/lib/c/include/async.h	(revision 76b5a95cdf127e6bca3c36046fa6af8e0e443f48)
+++ uspace/lib/c/include/async.h	(revision f6bffeebe3a4e9f347a03931d2c463a8718cd991)
@@ -340,5 +340,8 @@
 	    (arg4), (answer))
 
-extern int async_data_read_start(int, void *, size_t);
+#define async_data_read_start(p, buf, len) \
+	async_data_read_start_flexible((p), (buf), (len), IPC_XF_NONE)
+
+extern int async_data_read_start_flexible(int, void *, size_t, int);
 extern bool async_data_read_receive(ipc_callid_t *, size_t *);
 extern int async_data_read_finalize(ipc_callid_t, const void *, size_t);
@@ -379,5 +382,8 @@
 	    (arg4), (answer))
 
-extern int async_data_write_start(int, const void *, size_t);
+#define async_data_write_start(p, buf, len) \
+	async_data_write_start_flexible((p), (buf), (len), IPC_XF_NONE)
+
+extern int async_data_write_start_flexible(int, const void *, size_t, int);
 extern bool async_data_write_receive(ipc_callid_t *, size_t *);
 extern int async_data_write_finalize(ipc_callid_t, void *, size_t);