[SCSI] Don't add scsi_device for devices that return PQ=1, PDT=0x1f

Some targets may return slight variations of PQ and PDT to indicate
no LUN mapped.  USB UFI setting PDT=0x1f but having reserved bits for
PQ is one example, and NetApp targets returning PQ=1 and PDT=0x1f is
another.  Both instances seem like reasonable responses according to
SPC-3 and UFI specs.

The current scsi_probe_and_add_lun() code adds a scsi_device
for targets that return PQ=1 and PDT=0x1f.  This causes LUNs of type
"UNKNOWN" to show up in /proc/scsi/scsi when no LUNs are mapped.
In addition, subsequent rescans fail to recognize LUNs that may be
added on the target, unless preceded by a write to the delete attribute
of the "UNKNOWN" LUN.

This patch addresses this problem by skipping over the scsi_add_lun()
when PQ=1,PDT=0x1f is encountered, and just returns
SCSI_SCAN_TARGET_PRESENT.

Signed-off-by: Dave Wysochanski <davidw@netapp.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 114e2067dce57df165bc47e0e580fe2cbd7310bb..a24d3461fc788b797f492cfff333fa419e9f3bc3 100644 (file)
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -893,11 +893,26 @@ static int scsi_probe_and_add_lun(struct scsi_target *starget,
        }
 
        /*
-        * Non-standard SCSI targets may set the PDT to 0x1f (unknown or
-        * no device type) instead of using the Peripheral Qualifier to
-        * indicate that no LUN is present.  For example, USB UFI does this.
+        * Some targets may set slight variations of PQ and PDT to signal
+        * 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"
+        *    in the UFI 1.0 spec (we cannot rely on reserved bits).
+        *
+        * References:
+        * 1) SCSI SPC-3, pp. 145-146
+        * PQ=1: "A peripheral device having the specified peripheral
+        * device type is not connected to this logical unit. However, the
+        * device server is capable of supporting the specified peripheral
+        * device type on this logical unit."
+        * PDT=0x1f: "Unknown or no device type"
+        * 2) USB UFI 1.0, p. 20
+        * PDT=00h Direct-access device (floppy)
+        * PDT=1Fh none (no FDD connected to the requested logical unit)
         */
-       if (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_LOG_SCAN_BUS(3, printk(KERN_INFO
                                        "scsi scan: peripheral device type"
                                        " of 31, no device added\n"));