st: raise device limit

The device limit of 128 tape drives was established in 2003 as a significant increase from the 8 tape drives allowed previously.

We're seeing customer sites that between a large number of drives and multipath are discovering more than 128 devices and running into problems.

Now that we're not stuck having to store a pointer in array and aren't limited by kmalloc failing on higher order allocs we can lift the limit to fill the entire minor range based on the number of modes.

Based on the current code, that's 2^17 devices.

---
 drivers/scsi/st.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 4456735..2092f93 100644
@@ -77,7 +77,7 @@ struct st_modedef {
 #define ST_MODE_SHIFT (7 - ST_NBR_MODE_BITS)
 #define ST_MODE_MASK ((ST_NBR_MODES - 1) << ST_MODE_SHIFT)
 
-#define ST_MAX_TAPES 128
+#define ST_MAX_TAPES (1 << (20 - (ST_NBR_MODE_BITS + 1)))
 #define ST_MAX_TAPE_ENTRIES  (ST_MAX_TAPES << (ST_NBR_MODE_BITS + 1))
 
 /* The status related to each partition */

1.7.9.2