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I'm developing a USB-based mass storage device. Control is via SCSI commands.

One of the LUNs of this device is "hidden", all commands (except INQUIRY and REQUEST SENSE) return COMMAND FAILED (1). REQUEST SENSE returns NOT READY (MEDIUM NOT PRESENT).

Despite this, Windows repeatedly sends READ CAPACITY. In addition to returning COMMAND FAILED, I've tried returning COMMAND PASSED (0) with all zero data. But that causes Windows to stop sending any further commands at all, and the device enumeration stalls.

What is the proper response to these requests?

Michael Young
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1 Answers1

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I suspect you will have to dig through some of the following:

http://www.t10.org/drafts.htm#SCSI3_UAS
http://msdn.microsoft.com/en-us/library/ff567427%28v=vs.85%29.aspx

from MSDN SCSI compliance tests:

9.1 READ CAPACITY (10) Basic Verification Test Test Assertion GUID: 6bfd177d-c6a7-11da-94f5-00123f3a6b601 Windows Logo Program: STORAGE-0003 SCSI based devices meet SCSI protocol requirements Additional Information: Test: The TD-28.25 SCSI Compliance test checks that the READ CAPACITY (10) command returns correct disk capacity information. Info: The test sends the command to request for the number of logical block addresses and block length of the disk. Apply: The test sends a READ CAPACITY (10) command (0x25) to the device to request the number of logical block addresses and block length of the disk. Expect: The value of ScsiStatus should be 0x0.

9.2 READ CAPACITY (10) PMI Test Test Assertion GUID: 6bfd177e-c6a7-11da-94f5-00123f3a6b601 Windows Logo Program: STORAGE-0003 SCSI based devices meet SCSI protocol requirements

9.3 READ CAPACITY (10) Negative Test Test Assertion GUID: 6bfd177f-c6a7-11da-94f5-00123f3a6b601 Windows Logo Program: STORAGE-0003 SCSI based devices meet SCSI protocol requirements

Yahia
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  • Thanks for your help. I did have a look at the SCSI compliance tests, but didn't think it was intended for a situation where the medium is not present. I guess there must be some other way to indicate to the OS that the "hidden" LUN is not ready. A similar scenario is an empty DVD drive. – Michael Young Aug 02 '11 at 04:23
  • did your try "The value of ScsiStatus should be 0x0" ? – Yahia Aug 02 '11 at 04:27