Re: PATCH: scsi_scan.c: emulate windows behavior

Riley Williams (rhw@MemAlpha.cx)
Wed, 14 Nov 2001 00:45:19 +0000 (GMT)


Hi Rob.

> Getting more than 36 bytes should not be a problem for any device.
> The root problem seems to be that 255 is an odd number. On
> Wide-SCSI, a lot of devices have difficulty handling odd byte counts
> as they have to use additional messaging to flag the residue in the
> last 16-bit transfer. Also, the IDE-SCSI layer has trouble, as the
> IDE spec doesn't allow odd byte transfers at all. I've experienced
> issues with IDE devices that had to have their firmware patched just
> to deal with the Linux odd-byte request.

> Maybe a better change would be to use 64 or 128 byte requests. Your
> thoughts?

Probably the best option would be to tweak this to 256 if that is
available, or 252 if not - I seem to remember there's at least one
SCSI drive that can't handle other than multiples of 4 bytes.

Best wishes from Riley.

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