Date: 11 Oct 1999 16:38:55 +0000 From: Randell Jesup <rjesup@wgate.com> To: Gerard Roudier <groudier@club-internet.fr> Cc: "Matthew N. Dodd" <winter@jurai.net>, scsi@FreeBSD.ORG Subject: Re: Driver for GDT6517RD RAID controller Message-ID: <ybu7lkt26ow.fsf@jesup.eng.tvol.net.jesup.eng.tvol.net> In-Reply-To: Gerard Roudier's message of "Mon, 11 Oct 1999 22:22:03 %2B0200 (MET DST)" References: <Pine.LNX.3.95.991011211622.403A-100000@localhost>
index | next in thread | previous in thread | raw e-mail
Gerard Roudier <groudier@club-internet.fr> writes:
>> The other possible thing I'm considering doing (since a couple of
>> the SIM's do have support for target-mode) is to build an IP transport
>
>You must distinguish between phase cognizant target mode and host target
>mode. What I intend to implement in the future is something that avoids
>stalling the phase engine as possible, thus host target mode. Note that if
>you just read the messages after selection, accept the command and
>disconnect prior to signaling the upper layer, then this host target mode
>will never stall the phase engine in normal situations when implemented
>with 53c8xx chips. This will allow to use both initiator and target mode
>on an HBA without wasting uselessly SCSI BUS bandwitch for the target mode
>part.
The original design of target mode in CAM had efficient operation
in both initiator and target mode (as you described) as a primary goal,
as well as a reasonably low level of complexity in the SIM (though
obviously it must be more complex).
>As seen from SIM the handling of the target mode is in fact much simpler
>tham initiator mode, since the part that acts as a target has the baton in
>SCSI. So, a SIM that will only implement target mode should be
>significantly simpler than common ones that only implement initiator mode
>(given appropriate hardware).
True, though that isn't the goal I'd have. In any case, I'd be
writing code (for the CAM IP transport) to talk to the CAM interface, and
probably not writing SIMs unless they don't exist or have problems handling
both initiation and target-mode at the same time.
--
Randell Jesup, Worldgate Communications, ex-Scala, ex-Amiga OS team ('88-94)
rjesup@wgate.com
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-scsi" in the body of the message
help
Want to link to this message? Use this
URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?ybu7lkt26ow.fsf>