On Wed, 2011-12-21 at 14:37 -0800, Roland Dreier wrote: > 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 > Sorry yes, you are indeed correct here. > 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. > I'd really like to avoid pushing down the handling of this into the emulation for each command.. So that said, I'm thinking to silently succeed on allocate length zero, and add a special case call to core_scsi3_ua_clear_for_request_sense() for the unit attention case.. I need to think about this a bit more and do some testing, and will look at posting a patch soon. > 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. I'm not sure if supporting this type of scenario makes sense, as I've never actually seen it in practice. --nab -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
