#define BDOOR_MAGIC 0x564D5868
-/* Low-bandwidth backdoor port. */
+/* Low-bandwidth backdoor port number for the IN/OUT interface. */
-#define BDOOR_PORT 0x5658
+#define BDOOR_PORT 0x5658
+
+/* Flags used by the hypercall interface. */
+
+#define BDOOR_FLAGS_HB (1<<0)
+#define BDOOR_FLAGS_WRITE (1<<1)
+
+#define BDOOR_IS_LB(_flags) (((_flags) & BDOOR_FLAGS_HB) == 0)
+#define BDOOR_IS_HB(_flags) !BDOOR_IS_LB(_flags)
+#define BDOOR_IS_READ(_flags) (((_flags) & BDOOR_FLAGS_WRITE) == 0)
+#define BDOOR_IS_WRITE(_flags) !BDOOR_IS_READ(_flags)
#define BDOOR_CMD_GETMHZ 1
/*