diff --git a/include/hardware.h b/include/hardware.h
index f36bd8cb..69b638c6 100644
--- a/include/hardware.h
+++ b/include/hardware.h
@@ -4,6 +4,7 @@
 #define HW_REG(reg, type) *(volatile type *)(uintptr_t)((reg) | 0xa0000000)
 
 #define AI_STATUS_REG 0x0450000C
+#define AI_LEN_REG 0x04500004
 #define AI_STATUS_AI_FULL (1 << 31)
 
 #endif
\ No newline at end of file