1 files changed, 57 insertions, 4 deletions

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 0c7375ad12bd..633d79289616 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -394,9 +394,62 @@ typedef struct raid5_private_data raid5_conf_t;
 /*
  * Our supported algorithms
  */
-#define ALGORITHM_LEFT_ASYMMETRIC       0
-#define ALGORITHM_RIGHT_ASYMMETRIC      1
-#define ALGORITHM_LEFT_SYMMETRIC        2
-#define ALGORITHM_RIGHT_SYMMETRIC       3
+#define ALGORITHM_LEFT_ASYMMETRIC       0 /* Rotating Parity N with Data Restart */
+#define ALGORITHM_RIGHT_ASYMMETRIC      1 /* Rotating Parity 0 with Data Restart */
+#define ALGORITHM_LEFT_SYMMETRIC        2 /* Rotating Parity N with Data Continuation */
+#define ALGORITHM_RIGHT_SYMMETRIC       3 /* Rotating Parity 0 with Data Continuation */
 
+/* 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
+
+static inline int algorithm_valid_raid5(int layout)
+{
+        return (layout >= 0) &&
+                (layout <= 5);
+}
+static inline int algorithm_valid_raid6(int layout)
+{
+        return (layout >= 0 && layout <= 5)
+                ||
+                (layout == 8 || layout == 10)
+                ||
+                (layout >= 16 && layout <= 20);
+}
+
+static inline int algorithm_is_DDF(int layout)
+{
+        return layout >= 8 && layout <= 10;
+}
 #endif