scsi: core: map PQ=1, PDT=other values to SCSI_SCAN_TARGET_PRESENT

commit 84961f28 ("[SCSI] Don't add scsi_device for devices that return
PQ=1, PDT=0x1f") returns SCSI_SCAN_TARGET_PRESENT if inquiry returns PQ=1,
and PDT = 0x1f. However, from the scsi spec, it seemed setting PQ=1, and
PDT to the type it is capable to support, can also mean the device is not
connected. E.g. we see an IBM/2145 returns PQ=1 and PDT=0 for a non-mapped
lun (details attached at the end).

This patch changes the check condition a bit, so the check don't require
PTD to be 0x1f when PQ=1.

$ echo 0 0 1 > /sys/class/scsi_host/host1/scan
[ 2483.722186] scsi 1:0:0:1: scsi scan: INQUIRY pass 1 length 36
[ 2483.725687] scsi 1:0:0:1: scsi scan: INQUIRY successful with code 0x0
[ 2483.729171] scsi 1:0:0:1: scsi scan: INQUIRY pass 2 length 109
[ 2483.732481] scsi 1:0:0:1: scsi scan: INQUIRY successful with code 0x0
[ 2483.735911] scsi 1:0:0:1: Direct-Access     IBM      2145             0000 PQ: 1 ANSI: 6
[ 2483.741282] scsi 1:0:0:1: Attached scsi generic sg2 type 0

$ tail /proc/scsi/scsi
Attached devices:
Host: scsi1 Channel: 00 Id: 00 Lun: 00
  Vendor: IBM      Model: 2145             Rev: 0000
  Type:   Direct-Access                    ANSI  SCSI revision: 06
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: IBM      Model: 2145             Rev: 0000
  Type:   Direct-Access                    ANSI  SCSI revision: 06
Host: scsi1 Channel: 00 Id: 00 Lun: 01
  Vendor: IBM      Model: 2145             Rev: 0000
  Type:   Direct-Access                    ANSI  SCSI revision: 06

$ lsscsi
[0:0:0:0]    disk    IBM      2145             0000  /dev/sdb
[1:0:0:0]    disk    IBM      2145             0000  /dev/sda
[1:0:0:1]    disk    IBM      2145             0000  -
Signed-off-by: Li Zhong <lizhongfs@gmail.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_scan.c

@@ -1129,7 +1129,8 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget,
 	 * that no LUN is present, so don't add sdev in these cases.
 	 * Two specific examples are:
 	 * 1) NetApp targets: return PQ=1, PDT=0x1f
-	 * 2) USB UFI: returns PDT=0x1f, with the PQ bits being "reserved"
+	 * 2) IBM/2145 targets: return PQ=1, PDT=0
+	 * 3) USB UFI: returns PDT=0x1f, with the PQ bits being "reserved"
 	 *    in the UFI 1.0 spec (we cannot rely on reserved bits).
 	 *
 	 * References:
@@ -1143,8 +1144,8 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget,
 	 * PDT=00h Direct-access device (floppy)
 	 * PDT=1Fh none (no FDD connected to the requested logical unit)
 	 */
-	if (((result[0] >> 5) == 1 || starget->pdt_1f_for_no_lun) &&
-	    (result[0] & 0x1f) == 0x1f &&
+	if (((result[0] >> 5) == 1 ||
+	    (starget->pdt_1f_for_no_lun && (result[0] & 0x1f) == 0x1f)) &&
 	    !scsi_is_wlun(lun)) {
 		SCSI_LOG_SCAN_BUS(3, sdev_printk(KERN_INFO, sdev,
 					"scsi scan: peripheral device type"