Don't add scsi_device for devices that return PQ=1, PDT=0x1f
PATCH 1/1 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.
drivers/scsi/scsi_scan.c +19 -4
@@ -943,11 +943,26 @@ static int scsi_probe_and_add_lun(struct }/* -* 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" ));