From owner-freebsd-scsi Wed Aug 11 20:31:29 1999 Delivered-To: freebsd-scsi@freebsd.org Received: from weenix.guru.org (weenix.guru.org [209.241.220.18]) by hub.freebsd.org (Postfix) with ESMTP id 5C25A15631 for ; Wed, 11 Aug 1999 20:31:25 -0700 (PDT) (envelope-from kmitch@weenix.guru.org) Received: (from kmitch@localhost) by weenix.guru.org (8.9.3/8.9.3) id XAA96110 for scsi@freebsd.org; Wed, 11 Aug 1999 23:31:11 -0400 (EDT) (envelope-from kmitch) Date: Wed, 11 Aug 1999 22:33:15 -0400 From: Keith Mitchell To: "Kenneth D. Merry" Subject: Re: CAM (driver devel) question Message-ID: <19990811223315.A93634@weenix.guru.org> References: <19990811201425.A89846@weenix.guru.org> <199908120100.TAA51068@panzer.kdm.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.95.6i In-Reply-To: <199908120100.TAA51068@panzer.kdm.org>; from Kenneth D. Merry on Wed, Aug 11, 1999 at 07:00:44PM -0600 Sender: owner-freebsd-scsi@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Wed, Aug 11, 1999 at 07:00:44PM -0600, Kenneth D. Merry wrote: > Not all of the drivers support S/G. And you're right, it isn't used in any > of the upper level code at the moment. All of the drivers I looked at (aic7xxx, dpt, buslogic) all supported scatter/gather. But it looked like they only supported scatter/gather if they were passed a scatter/gather buffer from the upper layer (and since it doesn't look like the upper layer sends down a scatter gather list then I am guessing that scatter/gather never occurs). It looks like from the drivers they take whatever buffer they get passed from the upper layer and pass it down to the card (if its a physical address or maps it into DMAable memory via bus_dmamap_load() if its a virtual address). So my initial conclusion was the drivers were architected so that when the upper layer supported S/G they would too without modification. but I wanted to be sure before I coded everything. > You can probably get away with not supporting it, but it would probably be > a good idea to do so if you can. Yeah its a very good thing to have (especially for large transfers). > Just out of curiosity, what card are you writing a driver for? It would be > nice to know, to make sure you aren't duplicating any effort... I'm working on a driver for the IBM ServeRAID card but unfortunately I don't have the necessary approval to distribute any of it when I'm done. I need to convince management that its worthwhile to support FreeBSD -- right now most of them have never heard of it let alone feel the need to support it. Thats something I plan on trying to fix but its uncertain if I'll succeed (especially if very few people request it). If lots of people buying the ServeRAID card / Netfinity servers were to call IBM and request BSD that might help... That seemed to work for Linux ;-> -- Keith Mitchell Email: kmitch@guru.org PGP key available upon request To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message