[SCSI] st: add option to use SILI in variable block reads

Add new option MT_ST_SILI to enable setting the SILI bit in reads in variable
block mode. If SILI is set, reading a block shorter than the byte count does
not result in CHECK CONDITION. The length of the block is determined using the
residual count from the HBA. Avoiding the REQUEST SENSE command for every
block speeds up some real applications considerably.

Signed-off-by: Kai Makisara <kai.makisara@kolumbus.fi>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/Documentation/scsi/st.txt b/Documentation/scsi/st.txt
index b7be95b5bd2..38f81188def 100644
--- a/Documentation/scsi/st.txt
+++ b/Documentation/scsi/st.txt
@@ -2,7 +2,7 @@ This file contains brief information about the SCSI tape driver.
 The driver is currently maintained by Kai Mäkisara (email
 Kai.Makisara@kolumbus.fi)
 
-Last modified: Mon Mar  7 21:14:44 2005 by kai.makisara
+Last modified: Thu Feb 21 21:54:16 2008 by kai.makisara
 
 
 BASICS
@@ -372,6 +372,11 @@ MTSETDRVBUFFER
              MT_ST_SYSV sets the SYSV semantics (mode)
              MT_ST_NOWAIT enables immediate mode (i.e., don't wait for
                 the command to finish) for some commands (e.g., rewind)
+             MT_ST_SILI enables setting the SILI bit in SCSI commands when
+                reading in variable block mode to enhance performance when
+                reading blocks shorter than the byte count; set this only
+                if you are sure that the drive supports SILI and the HBA
+                correctly returns transfer residuals
              MT_ST_DEBUGGING debugging (global; debugging must be
                 compiled into the driver)
         MT_ST_SETBOOLEANS