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Date: Fri, 18 Jun 2010 16:22:11 +0100
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Re: [PATCH 09/10] pci: set PCI multi-function bit
	appropriately.
Message-ID: <20100618152210.GA10919@shareable.org>
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To: Isaku Yamahata <yamahata@valinux.co.jp>
Cc: stefano.stabellini@eu.citrix.com, jan.kiszka@siemens.com, "Michael S. Tsirkin" <mst@redhat.com>, allen.m.kay@intel.com, qemu-devel@nongnu.org, blauwirbel@gmail.com, kraxel@redhat.com, jean.guyader@gmail.com

Isaku Yamahata wrote:
> On Fri, Jun 18, 2010 at 03:44:04PM +0300, Michael S. Tsirkin wrote:
> > If we really want the ability to put unrelated devices
> > as functions in a single one, let's just add
> > a 'multifunction' qdev property, and validate that
> > it is set appropriately.
> 
> I think "unrelated" is policy. There is no obvious way to determine
> which functions can be in a same device.
> For example, popular chipset contains isa bridge, ide controller,
> usb controller, sound and modem in a single device as functions.
> It's up to hardware designer policy which functions are grouped into
> a device.

In hardware terms, quad-port ethernet controllers often present
themselves as a PCI bridge with four independent PCI ethernet
controllers, so they work with standard drivers.  Even though all four
are in a single chip.  Some USB devices do the same, presenting a
small bulk storage device to ship windows drivers [:roll-eyes: ;-)]
alongside the actual device.

-- Jamie