[5155] in linux-scsi channel archive
Re: Linux as a SCSI _Target_ device?
daemon@ATHENA.MIT.EDU (Gerard Roudier)
Tue Nov 17 03:24:35 1998
Date: Mon, 16 Nov 1998 22:01:15 +0100 (MET)
From: Gerard Roudier <groudier@club-internet.fr>
To: Jeff Noxon <jeff@planetfall.com>
cc: linux-scsi@vger.rutgers.edu
In-Reply-To: <19981115230640.C4383@planetfall.com>
On Sun, 15 Nov 1998, Jeff Noxon wrote:
> On Sat, Nov 14, 1998 at 09:27:21PM +0100, Gerard Roudier wrote:
> > YES!
> > I read you have been told about some SCSI project for Linux that
> > implements SCSI target mode. It seems guys wanted to implement kind of
> > network or cluster link. For that, just implementing the PROCESSOR device
> > should have been enough. You should have a look at this code, I think.
>
> Are you talking about IP over SCSI? They did not use target mode.
Should be that one, but I didn't follow this project.
I donnot know what mode they use, but you must consider that SCSI cores
donnot allow you to do everything you want with SCSI signals. You have
at least to perform some minimal SCSI protocol otherwise they will
just refuse to work by triggerring error conditions.
You must at least perform arbitration and some minimal selection.
BTW, in fact all that is performed by the SCSI core, just have to
ask it to do the work. Anyway one side must act as an initiator and
the other side as a target, otherwise no data transfer will occur.
> If I recall correctly they used a SEND MESSAGE command or similar. I
> need to look back at that project and find a copy of the SCSI spec.
They probably implements some kind of PROCESSOR device.
Read the SCSI SPI specs and your SYMBIOS manuals and things will get
more clear for you, I think.
> > > I want to try to write a module that can export any Linux block device
> > > as a SCSI target emulating a direct-access device. I have a spare Alpha
> > > machine with an onboard 53c810 for the development.
> >
> > You probably need at least a second controller for testing.
>
> My Alpha also has a 3940W, and I have a few other (BusLogic, Advansys)
> in other machines.
This will work at the moment your block device will behave well. :-)
> > Data manuals have everythings needed to write your driver but lack of the
> > full SCRIPTS symbolic language syntax documentation. The ncr53c8xx driver
> > does not use the SYMBIOS SCRIPTS language but just some tricky C macros
> > for SCRIPTS programming, but Drew Eckward had written years ago a SCRIPTS
> > assembler in perl for his 53c7,8xx driver development. You should ask Drew
> > for his perl program, or perhaps the source is still available at some ftp
> > site.
>
> I thought that it was still part of the kernel source tree. I have a vague
> memory of using that driver at one time, probably with Linux 1.0. I think
> It seems like your macros were not such a bad idea, though.
The macros are from the FreeBSD ncr driver I have initially ported to
Linux, and not from me. I also think the authors have had a good idea,
but the macros are slightly different from SYMBIOS official memnonics.
Regards,
Gerard.
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