Date: Tue, 7 Mar 2000 14:46:42 +0000 (GMT) From: Nick Hibma <n_hibma@calcaphon.com> To: Matthew Jacob <mjacob@feral.com> Cc: FreeBSD SCSI Mailing List <scsi@FreeBSD.ORG> Subject: Re: first INQUIRY goes round in circles (fwd) Message-ID: <Pine.BSF.4.20.0003071438580.1418-100000@localhost> In-Reply-To: <Pine.BSF.4.10.10003070601300.26781-100000@beppo.feral.com>
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> > The solution to all this Jim pointed out was to not request sense after > > INQUIRY. This I can live with as it is a valid solution. If INQUIRY > > fails, the data stage of the USB transfer will fail and you have another > > indicator that things went wrong. > > Note that might be a case in which it's possible for an unadorned INQUIRY* to > generate a CHECK CONDITION- that's when there's a parity error on the IDENTIFY > message at the start of the command or a parity error sending the CDB. I > haven't done this level of SCSI for 10 years and don't have the spec in front > of me, but IIRC it's up to the target as to how it decides it wants to cope > with received bytes with parity errors so the mechanisms that cope with parity > errors while the command is active may not be used and a CHECK CONDITION with > the ASC/ASCQ may be latched up. Transport problems (so-called wire errors) are handled in the USB part and are signalled differently. They are reported as CAM_REQ_CMP_ERR. > *The second INQUIRY that FreeBSD's xpt_probe always sends that asks for the > VPD info will generally always get a CHECK CONDITION for devices that don't > support VDP info, so blindly saying "don't request sense after an INQUIRY" is > a Bad Thing To Do (tm) as it will leave the latched up Illegal Bit in CDB for > the next command to have to cope with- which will be the poor old Test Unit > Ready. In that case the command or data transport will fail. This means that SENSE will be requested. Nick -- n_hibma@webweaving.org n_hibma@freebsd.org USB project http://www.etla.net/~n_hibma/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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