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Date:      Tue, 27 Aug 2002 13:20:10 +0100
From:      Bruce M Simpson <bms@spc.org>
To:        Bob Johnson <bob88@garbonzo.hos.ufl.edu>
Cc:        Kevin Oberman <oberman@es.net>, mobile@FreeBSD.ORG, imp@freebsd.org, n_hibma@freebsd.org, joe@freebsd.org
Subject:   USB->ATA devices
Message-ID:  <20020827122010.GA5438@spc.org>
In-Reply-To: <3D68095B.3000106@garbonzo.hos.ufl.edu>
References:  <20020811235053.2E7935D04@ptavv.es.net> <20020813100445.GJ23205@spc.org> <3D68095B.3000106@garbonzo.hos.ufl.edu>

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On Sat, Aug 24, 2002 at 06:31:55PM -0400, Bob Johnson wrote:
> Assuming it is similar to the two USB flash drives I've played with,
> you need to hack /src/sys/cam/scsi/scsi_da.c to tell the scsi driver
> about the capabilities of your device.

The exception to the rule would seem to be devices behind USB->ATA bridges;
some of the bridge chips on the market (OnSpec for example) implement a
protocol which is nonstandard and is composed of the ATA task register file
writes one would normally make in the ISA or PCI i/o address space.

The devices which use this are generally SmartMedia or downmarket
CompactFlash/multi-I/O devices.

I discussed this with Joe Karthausen earlier this month, and it seems that
in order to support these devices, some architectural changes would be
needed in order to allow the ATA driver to operate on top of the USB bus.

BMS

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