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Date: Mon, 28 Jun 2010 12:16:58 +0200
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [Qemu-devel] Re: [PATCH 08/12] block: Catch attempt to attach
	multiple devices to a blockdev
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To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org, kraxel@redhat.com, Christoph Hellwig <hch@lst.de>, Markus Armbruster <armbru@redhat.com>

On Mon, Jun 28, 2010 at 10:24:49AM +0200, Kevin Wolf wrote:
> How would breaking compatibility help us? For the user a USB MSD is only
> one device, so requiring two -device parameters sounds wrong.

But it is separate devices.  At least the standards compliant usb
storage devices just are a bride of scsi commands over usb and fit into
the SAM device model, which makes a difference between initiator, target
and LUN.  So having a different device for the specific target vs the
initiator port makes a difference. (and yes, we're still totally missing
support for multiple luns, which would require another level of
devices).  Trying to hide this is not all that useful - not anymore
useful than hiding it on a "normal" scsi host controller anyway.