Date: Wed, 20 Feb 2002 13:57:32 -0800 (PST) From: Kelly Yancey <kbyanc@posi.net> To: Joerg Wunsch <joerg_wunsch@uriah.heep.sax.de> Cc: freebsd-scsi@FreeBSD.ORG Subject: Re: RBC support patch Message-ID: <20020220134946.X86372-100000@gateway.posi.net> In-Reply-To: <20020220223124.A9579@uriah.heep.sax.de>
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On Wed, 20 Feb 2002, Joerg Wunsch wrote:
> As Kelly Yancey wrote:
>
> > > They are not broken. READ(6)/WRITE(6) are not mandatory for direct
> > > access devices by the standard, but READ(10)/WRITE(10) are.
>
> > Unfortunately, my copy of the SCSI-2 draft lists READ(10) and
> > WRITE(10) as optional for direct-access devices. Otherwise, this
> > would be an easy fix to a
> > long standing annoyance. :|
>
> Hmm, after reading the docs again, i have to correct myself: both
> are mandatory, either by my SCSI-2 copy as well as by the SCSI-3
> drafts i've got. The latter contain a footnote explaining that the
> 6-byte commands have been kept as `mandatory' since some boot
> environments require it, while applications are requested to migrate to
> the 10-byte commands.
>
> So perhaps we should simply reverse the logic, use the 10-byte opcodes
> as default, and collect the list of (too old) devices that require the
> 6-byte CDBs. How does that sound?
>
> --
> cheers, J"org .-.-. --... ...-- -.. . DL8DTL
You are right, SCSI 3 lists both 6 and 10-byte READ/WRITE commands are
mandatory. However, SCSI 2 lists both as optional. So we could just key off
the INQUIRY results and if the device reports itself as SCSI3 or newer force
10 byte commands, otherwise keep using 6 byte commands. Sounds reasonable to
me.
What will be interesting is seeing if this would fix all the SCSI->USB
quirks along the way (i.e. do they report themselves as SCSI3 conforming?).
I'll make up a quick patch and post it for review shortly.
Kelly
kbyanc@{posi.net,FreeBSD.org}
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