Index: uspace/lib/c/include/ipc/dev_iface.h
===================================================================
--- uspace/lib/c/include/ipc/dev_iface.h	(revision 228e490270cec3d6a6de666f61839f0d9ed5f193)
+++ uspace/lib/c/include/ipc/dev_iface.h	(revision 6e5dc07f868b16c838c79bc42117b6116010e91b)
@@ -38,4 +38,8 @@
 	HW_RES_DEV_IFACE = 0,	
 	CHAR_DEV_IFACE,
+
+	/** Interface provided by USB host controller. */
+	USBHC_DEV_IFACE,
+
 	// TODO add more interfaces
 	DEV_IFACE_MAX
@@ -50,4 +54,14 @@
 	DEV_IFACE_ID(DEV_FIRST_CUSTOM_METHOD_IDX)
 
+/*
+ * The first argument is actually method (as the "real" method is used
+ * for indexing into interfaces.
+ */
+
+#define DEV_IPC_GET_ARG1(call) IPC_GET_ARG2((call))
+#define DEV_IPC_GET_ARG2(call) IPC_GET_ARG3((call))
+#define DEV_IPC_GET_ARG3(call) IPC_GET_ARG4((call))
+#define DEV_IPC_GET_ARG4(call) IPC_GET_ARG5((call))
+
 
 #endif