cciss: auto engage SCSI mid layer at driver load time

A long time ago, probably in 2002, one of the distros, or maybe more than
one, loaded block drivers prior to loading the SCSI mid layer.  This meant
that the cciss driver, being a block driver, could not engage the SCSI mid
layer at init time without panicking, and relied on being poked by a
userland program after the system was up (and the SCSI mid layer was
therefore present) to engage the SCSI mid layer.

This is no longer the case, and cciss can safely rely on the SCSI mid
layer being present at init time and engage the SCSI mid layer straight
away.  This means that users will see their tape drives and medium
changers at driver load time without need for a script in /etc/rc.d that
does this:

for x in /proc/driver/cciss/cciss*
do
	echo "engage scsi" > $x
done

However, if no tape drives or medium changers are detected, the SCSI mid
layer will not be engaged.  If a tape drive or medium change is later
hot-added to the system it will then be necessary to use the above script
or similar for the device(s) to be acceesible.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 2 insertions, 0 deletions

diff --git a/drivers/block/cciss.c b/drivers/block/cciss.c
index 5b690194dd99..8004ac30a7a8 100644
--- a/drivers/block/cciss.c
+++ b/drivers/block/cciss.c
@@ -5163,6 +5163,7 @@ reinit_after_soft_reset:
         h->cciss_max_sectors = 8192;
 
         rebuild_lun_table(h, 1, 0);
+        cciss_engage_scsi(h);
         h->busy_initializing = 0;
         return 1;
 
diff --git a/drivers/block/cciss_scsi.c b/drivers/block/cciss_scsi.c
index 951a4e33b92b..e820b68d2f6c 100644
--- a/drivers/block/cciss_scsi.c
+++ b/drivers/block/cciss_scsi.c
@@ -1720,5 +1720,6 @@ static int  cciss_eh_abort_handler(struct scsi_cmnd *scsicmd)
 /* If no tape support, then these become defined out of existence */
 
 #define cciss_scsi_setup(cntl_num)
+#define cciss_engage_scsi(h)
 
 #endif /* CONFIG_CISS_SCSI_TAPE */