Date: Thu, 30 Apr 1998 06:06:38 -0400 (EDT) From: Peter Dufault <dufault@hda.com> To: julian@whistle.com (Julian Elischer) Cc: schofiel@xs4all.nl, freebsd-hardware@FreeBSD.ORG Subject: Re: [Target Mode] Was: Ooops - sorry Message-ID: <199804301006.GAA14359@hda.hda.com> In-Reply-To: <354785AB.63DECDAD@whistle.com> from Julian Elischer at "Apr 29, 98 12:55:23 pm"
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> The 1740 was supposed to support target mode too, but we > eventually gave up on them ever getting it to work correctly. > (talk to peter dufault on this). They documented the 1740 interface in the manuals, sold it through pre-sales, it was buggy as could be (dropped a mailbox slot each time it received something and so hung up after 16 transfers, etc), they flailed trying to fix it and finally wrote a letter saying "Adaptec does not support target mode on any of their host adapters". It "worked" enough that it took several weeks of wasting time, finding and proving firmware bugs, getting fixes, finding firmware bugs, ... before finally giving up. Grrr. I switched to a Vesalogic board with an NCR chip for that project. The scripting was done using NCR SCSI SCRIPTS for an embedded system and never went into FreeBSD. As Julian says later on, I decided you had to go to the "chip merchants" and not the PC board merchants for target mode - at a cold hearted level you can't blame them for not spending engineering resources on such a small market. > It was like the 1540 in that it had a coprocessor, but they > never got the target mode reliable during the time that we > tried to use it. They eventually told us that they were going to > stop saying that they supported target mode on that and that we > should stop asking them to fix it. > > Rumour was that there was one release of the firmware that > worked, but they quickly corrected that oversight and we could never > get one. Once again since you couldn't bypass the coprocessor > you were dependent on it doing it correctly. They never had it working. The 1542B was sold to some OEM and so they made it work. They probably had similar nibbles for the 174x and so planned it but never put the resources into making it work. > Peter had changes to the SCSI system to make allowances for target > mode operation of adapters, but as we couldn't get any adapters > that could actually do it at that time (1993?) we never checked them > in. No, they are in there for the 1542B If you boot verbose with a 1542B with the correct firmware rev it will say ", target ops". Last time I tried it it worked but it could be rotted by now. Even if it is rotted it is simple enough that someone who needed it and had a 1542B could get it working quickly. Basically, you configure a target device wiring down the ID and LUN, open it, and then "dd" from it. It will disconnect and you'll get an interrupt with the transfer request direction and size when an initiator tries to access it. It doesn't support scatter gather so you need contiguous memory, etc, etc. Even with these restrictions it worked fine developing a big system. > I guess that there will eventually be someone who wants to patch > target mode into the CAM based version and I'm sure that Justin will > have made allowances for that. (CAM supports it, so his > implimentation should at least have the hooks in the right places > for it) I've had three calls about this in the last six months including one this month, so interest is picking up. I've given them Justin's and Stefan's e-mail addresses and told them "have PO will work" (in the July time frame though). We'll see if anything comes out of it. Peter -- Peter Dufault (dufault@hda.com) Realtime development, Machine control, HD Associates, Inc. Safety critical systems, Agency approval To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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