diff --git a/include/linux/parport.h b/include/linux/parport.h
index f7ff0b0..f67f838 100644
--- a/include/linux/parport.h
+++ b/include/linux/parport.h
@@ -236,12 +236,14 @@
 
 /* IEEE1284 information */
 
-/* IEEE1284 phases */
+/* IEEE1284 phases. These are exposed to userland through ppdev IOCTL
+ * PP[GS]ETPHASE, so do not change existing values. */
 enum ieee1284_phase {
 	IEEE1284_PH_FWD_DATA,
 	IEEE1284_PH_FWD_IDLE,
 	IEEE1284_PH_TERMINATE,
 	IEEE1284_PH_NEGOTIATION,
+	IEEE1284_PH_HBUSY_DNA,
 	IEEE1284_PH_REV_IDLE,
 	IEEE1284_PH_HBUSY_DAVAIL,
 	IEEE1284_PH_REV_DATA,