cciss: add support for multi lun tape devices

This patch adds support for multi-lun devices in a SAS environment. It's
required for the support of media changers.

Signed-off-by: Stephen M. Cameron <[e-mail]>
Signed-off-by: Mike Miller <[e-mail]>
Signed-off-by: Jens Axboe <[e-mail]>

drivers/block/cciss_scsi.c

···
 	/* assumes hba[ctlr]->scsi_ctlr->lock is held */ 
 	int n = ccissscsi[ctlr].ndevices;
 	struct cciss_scsi_dev_t *sd;
+	int i, bus, target, lun;
+	unsigned char addr1[8], addr2[8];
 
 	if (n >= CCISS_MAX_SCSI_DEVS_PER_HBA) {
 		printk("cciss%d: Too many devices, "
 			"some will be inaccessible.\n", ctlr);
 		return -1;
 	}
-	sd = &ccissscsi[ctlr].dev[n];
-	if (find_bus_target_lun(ctlr, &sd->bus, &sd->target, &sd->lun) != 0)
-		return -1;
 
+	bus = target = -1;
+	lun = 0;
+	/* Is this device a non-zero lun of a multi-lun device */
+	/* byte 4 of the 8-byte LUN addr will contain the logical unit no. */
+	if (scsi3addr[4] != 0) {
+		/* Search through our list and find the device which */
+		/* has the same 8 byte LUN address, excepting byte 4. */
+		/* Assign the same bus and target for this new LUN. */
+		/* Use the logical unit number from the firmware. */
+		memcpy(addr1, scsi3addr, 8);
+		addr1[4] = 0;
+		for (i = 0; i < n; i++) {
+			sd = &ccissscsi[ctlr].dev[i];
+			memcpy(addr2, sd->scsi3addr, 8);
+			addr2[4] = 0;
+			/* differ only in byte 4? */
+			if (memcmp(addr1, addr2, 8) == 0) {
+				bus = sd->bus;
+				target = sd->target;
+				lun = scsi3addr[4];
+				break;
+			}
+		}
+	}
+
+	sd = &ccissscsi[ctlr].dev[n];
+	if (lun == 0) {
+		if (find_bus_target_lun(ctlr,
+			&sd->bus, &sd->target, &sd->lun) != 0)
+			return -1;
+	} else {
+		sd->bus = bus;
+		sd->target = target;
+		sd->lun = lun;
+	}
 	added[*nadded].bus = sd->bus;
 	added[*nadded].target = sd->target;
 	added[*nadded].lun = sd->lun;