On Wed, Dec 21, 2011 at 2:19 PM, Nicholas A. Bellinger
<nab@xxxxxxxxxxxxxxx> wrote:
> So we know that SBC says zero-length READs is allowed, but AFAICT there
> is no requirement for allowing any zero-length control CDBs, aside from
> the CDBs already designated as SCF_SCSI_NON_DATA_CDB..
Actually I think that's wrong -- my draft of SPC4 says:
4.3.5.6 Allocation length
...
An allocation length of zero specifies that no data shall be
transferred. This
condition shall not be considered as an error.
and eg on a real SCSI disk I have:
# sg_raw -v /dev/sdas 3 0 0 0 0 0
cdb to send: 03 00 00 00 00 00
SCSI Status: Good
Sense Information:
sense buffer empty
But I don't think we can just silently succeed control CDBs with allocation
length 0, eg REQUEST SENSE will allocation length 0 still needs to clear
unit attention conditions. So we probably need to push the handling down
into the emulation for each command.
And also I think the code that fails INQUIRY with allocation length < 6
is wrong too -- eg if the initiator sense us an allocation length of
1, we should
return good status and just send back the first byte of the inquiry data.
But that's a secondary issue -- at least we don't crash in that case.
- R.
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