+typedef u16 addr_t;
+
+/* addresses of these set at link time */
+/* to add more addresses, define them here with buffered_addr_h, in helpers.c
+ * with buffered_addr, and also in LDFLAGS in the Makefile
+ */
+#define buffered_addr_h(a) \
+ extern volatile u8* _##a; \
+ extern inline void set_##a(u8 b); \
+ extern inline void bset_##a(u8 m); \
+ extern inline void bclr_##a(u8 m); \
+
+buffered_addr_h(switch_input);
+buffered_addr_h(misc_input);
+buffered_addr_h(home_sensors);
+buffered_addr_h(changer_output);
+buffered_addr_h(misc_output);
+
+void spi_enable();
+void spi_disable();