scsi: scsi_debug: Make the READ CAPACITY response compliant with ZBC

From ZBC-1:

 - RC BASIS = 0: The RETURNED LOGICAL BLOCK ADDRESS field indicates the
   highest LBA of a contiguous range of zones that are not sequential write
   required zones starting with the first zone.

 - RC BASIS = 1: The RETURNED LOGICAL BLOCK ADDRESS field indicates the LBA
   of the last logical block on the logical unit.

The current scsi_debug READ CAPACITY response does not comply with the
above if there are one or more sequential write required zones. SCSI
initiators need a way to retrieve the largest valid LBA from SCSI
devices. Reporting the largest valid LBA if there are one or more
sequential zones requires to set the RC BASIS field in the READ CAPACITY
response to one. Hence this patch.

Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Suggested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20221102193248.3177608-1-bvanassche@acm.orgReviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_debug.c

@@ -1899,6 +1899,13 @@ static int resp_readcap16(struct scsi_cmnd *scp,
 			arr[14] |= 0x40;
 	}
 
+	/*
+	 * Since the scsi_debug READ CAPACITY implementation always reports the
+	 * total disk capacity, set RC BASIS = 1 for host-managed ZBC devices.
+	 */
+	if (devip->zmodel == BLK_ZONED_HM)
+		arr[12] |= 1 << 4;
+
 	arr[15] = sdebug_lowest_aligned & 0xff;
 
 	if (have_dif_prot) {