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7.2

SPTI corrupts CDB (Windows 2000 only)

Asked by skris in Windows Programming

Tags: ioctl_scsi_pass_through, spti

While writing a tool for ATAPI CD-RW drives I encountered following problem :

Using SPTI (both IOCTL_SCSI_PASS_THROUGH_DIRECT & IOCTL_SCSI_PASS_THROUGH) in Windows 2000 will cause my CDB (command descriptor block) to be corrupted.

I'll illustrate this with following (fictional) 12-byte CDB:
FF FF FF FF FF FF FF FF FF FF FF FF
When you send this CDB it will appear on the bus (checked with hardware bus analyzer) as :
FF 1F FF FF FF FF FF FF FF FF FF FF

So, the 3 upper bits of the most significant nibble of byte 1 (=2nd byte) will be reset.
Normally this is not a problem since apparently no MMC commands use these bits.
Unless you are using vendor specific commands that do use byte 1... If this is the case you have a major problem !

- This problem will not occur in Windows NT 4 (only checked with IOCTL_SCSI_PASS_THROUGH)
- This problem will not occur when you use Adaptec's ASPI layer
- The problem has been verified on other SPTI implementations (so it's doubtful that this is caused by my code)
- Happens also with Windows 2000 service pack 1

So :

- Is this a known problem ?
- Are there any work-arounds ?
- Would writing a lower/upper filter driver to reconstruct the I/O request packet do the trick ? Only if there really isn't an alternative, since I don't look forward to doing this.

Thanks,
[+][-]10/05/00 02:53 PM, ID: 4600920Accepted Solution

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About this solution

Zone: Windows Programming
Tags: ioctl_scsi_pass_through, spti
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Solution Provided By: aa571
Participating Experts: 3
Solution Grade: B
 
[+][-]05/16/01 10:25 AM, ID: 6087461Expert Comment

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[+][-]06/10/01 05:32 PM, ID: 6174892Expert Comment

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