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Commit 0007a4c9 authored by Stephen M. Cameron's avatar Stephen M. Cameron Committed by Jens Axboe
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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: default avatarStephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 7035b5df

Documentation/blockdev/cciss.txt

+6 −8
Original line number Diff line number Diff line
@@ -98,14 +98,12 @@ You must enable "SCSI tape drive support for Smart Array 5xxx" and 
"SCSI support" in your kernel configuration to be able to use SCSI

tape drives with your Smart Array 5xxx controller.



Additionally, note that the driver will not engage the SCSI core at init 

time.  The driver must be directed to dynamically engage the SCSI core via 

the /proc filesystem entry which the "block" side of the driver creates as 

/proc/driver/cciss/cciss* at runtime.  This is because at driver init time, 

the SCSI core may not yet be initialized (because the driver is a block 

driver) and attempting to register it with the SCSI core in such a case 

would cause a hang.  This is best done via an initialization script 

(typically in /etc/init.d, but could vary depending on distribution). 

Additionally, note that the driver will engage the SCSI core at init

time if any tape drives or medium changers are detected.  The driver may

also be directed to dynamically engage the SCSI core via the /proc filesystem

entry which the "block" side of the driver creates as

/proc/driver/cciss/cciss* at runtime.  This is best done via a script.



For example:



	for x in /proc/driver/cciss/cciss[0-9]*

drivers/block/cciss.c

+1 −0
Original line number Diff line number Diff line
@@ -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;

drivers/block/cciss_scsi.c

+1 −0
Original line number Diff line number Diff line
@@ -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 */