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Commit 84961f28 authored by dave wysochanski's avatar dave wysochanski Committed by James Bottomley
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[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: default avatarDave Wysochanski <davidw@netapp.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@SteelEye.com>
parent 8c867b25

drivers/scsi/scsi_scan.c

+19 −4
Original line number Diff line number Diff line
@@ -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"));