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Date:      Sat, 29 Jun 1996 05:54:13 -0400 (EDT)
From:      Peter Dufault <dufault@hda.com>
To:        cau@cc.gatech.edu (Carlos Ugarte)
Cc:        freebsd-scsi@FreeBSD.org, cau@cc.gatech.edu
Subject:   Re: help writing a new SCSI device driver
Message-ID:  <199606290954.FAA03755@hda.com>
In-Reply-To: <199606290407.AAA11695@oscar.cc.gatech.edu> from "Carlos Ugarte" at Jun 29, 96 00:07:34 am

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> 
> Also, I noticed that not all drivers seem to support
> disconnection/reselection.  Is this because it is difficult to
> implement, or because it provides little improvement?  All docs
> I've seen imply that you gain some, but never quantify how
> much...  Is it worth the trouble, if it can be done?

All drivers should support disconnection/reselection to permit
adequate bus utilization.  The gains are great - you will tie up
the bus during disk seeks, etc. if you don't support it.

The drivers that don't explicitly support it probably rely on the
adapter firmware to do the right thing.  The drivers that you see
it in are probably the ones we write the firmware for.

-- 
Peter Dufault               Real-Time Machine Control and Simulation
HD Associates, Inc.         Voice: 508 433 6936
dufault@hda.com             Fax:   508 433 5267



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