It seems, upon reading the 2.2.16 and 2.4.0-test1 source, that the 
peripheral qualifier field of a SCSI inquiry isn't really used (except to 
skip LUNs where a physical device is 
not supported).  To refresh, the peripheral qualifier field is the top 3 
bits of byte 0 of the inquiry data, particularly the two values:
	000b - physical device is connected to this LUN
	001b - physical device *can* be connected to this LUN, but is not 
presently

We have a device, part of a storage area network (SAN), that returns 000b 
in this field if there is a disk attached that can be directly accessed by 
this system, or 001b if the LUN would be supported, but is actually being 
handled by a different controller.  This would seem to be the proper use 
of this field.

Since the scsi layer does not read/use these bits, when the LUN shows up 
as TYPE_DISK, a READ_CAPACITY command is issued to the disk.  In the 000b 
case, this is proper.  In the 001b, this is not, as the device isn't 
really there, it's merely a placeholder, and the command returns with a 
check condition, and no further I/Os are performed.  The outcome is 
proper, but there's an error printed that could be avoided by making use 
of the peripheral qualifier bits, which could lead to a customer 
satisfaction issue, tech support calls about SCSI errors, and the like.

I'd like sd.c to be able to ignore 001b devices, so it looks like the 
right thing to do is to set SDp->online = FALSE in scan_scsis_single() in 
this case.  Patches to 2.2.16 and 2.4.0-test1 below.

Thoughts?


Thanks,
Matt Domsch
Dell Enterprise Systems Group
Linux Development Team

--- linux-2.4.0-test1/drivers/scsi/scsi_scan.c.orig	Tue Jul 11 
11:41:56 2000
+++ linux/drivers/scsi/scsi_scan.c	Tue Jul 11 11:44:33 2000
@@ -552,7 +552,8 @@
 	memcpy(SDpnt->rev, scsi_result + 32, 4);
 
 	SDpnt->removable = (0x80 & scsi_result[1]) >> 7;
-	SDpnt->online = TRUE;
+	if (((scsi_result[0] >> 5) & 7) == 1) 	SDpnt->online = FALSE;
+	else SDpnt->online = TRUE;
 	SDpnt->lockable = SDpnt->removable;
 	SDpnt->changed = 0;
 	SDpnt->access_count = 0;

--- linux-2.2.16/drivers/scsi/scsi.c.orig	Tue Jul  4 04:20:59 2000
+++ linux/drivers/scsi/scsi.c scsi.c	Tue Jul 11 06:45:46 2000
@@ -796,7 +796,8 @@
   memcpy (SDpnt->rev, scsi_result + 32, 4);
 
   SDpnt->removable = (0x80 & scsi_result[1]) >> 7;
-  SDpnt->online = TRUE;
+  if (((scsi_result[0] >> 5) & 7) == 1)  SDpnt->online = FALSE;
+  else SDpnt->online = TRUE;
   SDpnt->lockable = SDpnt->removable;
   SDpnt->changed = 0;
   SDpnt->access_count = 0;