+
+/* Define non-rotating (raid4) algorithms. These allow
+ * conversion of raid4 to raid5.
+ */
+#define ALGORITHM_PARITY_0 4 /* P or P,Q are initial devices */
+#define ALGORITHM_PARITY_N 5 /* P or P,Q are final devices. */
+
+/* DDF RAID6 layouts differ from md/raid6 layouts in two ways.
+ * Firstly, the exact positioning of the parity block is slightly
+ * different between the 'LEFT_*' modes of md and the "_N_*" modes
+ * of DDF.
+ * Secondly, or order of datablocks over which the Q syndrome is computed
+ * is different.
+ * Consequently we have different layouts for DDF/raid6 than md/raid6.
+ * These layouts are from the DDFv1.2 spec.
+ * Interestingly DDFv1.2-Errata-A does not specify N_CONTINUE but
+ * leaves RLQ=3 as 'Vendor Specific'
+ */
+
+#define ALGORITHM_ROTATING_ZERO_RESTART 8 /* DDF PRL=6 RLQ=1 */
+#define ALGORITHM_ROTATING_N_RESTART 9 /* DDF PRL=6 RLQ=2 */
+#define ALGORITHM_ROTATING_N_CONTINUE 10 /*DDF PRL=6 RLQ=3 */
+
+
+/* For every RAID5 algorithm we define a RAID6 algorithm
+ * with exactly the same layout for data and parity, and
+ * with the Q block always on the last device (N-1).
+ * This allows trivial conversion from RAID5 to RAID6
+ */
+#define ALGORITHM_LEFT_ASYMMETRIC_6 16
+#define ALGORITHM_RIGHT_ASYMMETRIC_6 17
+#define ALGORITHM_LEFT_SYMMETRIC_6 18
+#define ALGORITHM_RIGHT_SYMMETRIC_6 19
+#define ALGORITHM_PARITY_0_6 20
+#define ALGORITHM_PARITY_N_6 ALGORITHM_PARITY_N
+