diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index 6e2fd445688c..785aba11066b 100644
--- a/drivers/s390/block/dasd_eckd.c
+++ b/drivers/s390/block/dasd_eckd.c
@@ -199,8 +199,8 @@ recs_per_track(struct dasd_eckd_characteristics * rdc,
 static void set_ch_t(struct ch_t *geo, __u32 cyl, __u8 head)
 {
 	geo->cyl = (__u16) cyl;
-	geo->head = cyl >> 16;
-	geo->head <<= 4;
+	geo->head = cyl >> DASD_EAV_CYL_HI_SHIFT;
+	geo->head <<= DASD_EAV_HEAD_HI_SHIFT;
 	geo->head |= head;
 }
 
diff --git a/drivers/s390/block/dasd_eckd.h b/drivers/s390/block/dasd_eckd.h
index 763733bcc4d2..bad7ba666370 100644
--- a/drivers/s390/block/dasd_eckd.h
+++ b/drivers/s390/block/dasd_eckd.h
@@ -146,6 +146,14 @@ struct eckd_count {
 	__u16 dl;
 } __attribute__ ((packed));
 
+/*
+ * Extended Address Volume track address: the head field carries the actual
+ * head in its low-order 4 bits; the cylinder bits that do not fit the 16-bit
+ * cyl field are shifted in just above them.
+ */
+#define DASD_EAV_CYL_HI_SHIFT	16	/* cylinder bits beyond the 16-bit cyl field */
+#define DASD_EAV_HEAD_HI_SHIFT	4	/* head occupies the low-order 4 bits of head */
+
 struct ch_t {
 	__u16 cyl;
 	__u16 head;