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Date: Wed, 22 Dec 2010 14:03:55 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH 2/3] pci: introduce a parser for fw device
 path to pci device
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To: Isaku Yamahata <yamahata@valinux.co.jp>
Cc: qemu-devel@nongnu.org

On Wed, Dec 22, 2010 at 08:36:40PM +0900, Isaku Yamahata wrote:
> On Wed, Dec 22, 2010 at 01:04:43PM +0200, Michael S. Tsirkin wrote:
> > On Wed, Dec 22, 2010 at 07:54:49PM +0900, Isaku Yamahata wrote:
> > > Introduce a function to parse fw device path to pci device.
> > > the format is
> > > /pci@{<ioport>, <mmio>}/[<fw_name>]@<slot>,<func>/.../[<fw_name>]@<slot>,<func>
> > > 
> > > <ioport> = "i"<ioport addr in hex>
> > > <mmio> = <mmio addr in hex>
> > > <slot> = slot number in hex
> > > <func> = func number in hex
> > > 
> > > Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
> > 
> > What concerns me the most here is the use of io addresses,
> > not sure it's the right thing for the command interface.
> >
> > Why do we need to support full path at all?  Can we use the id of the
> > parent bus for this?  Supplying a bus id for the device seems like a
> > natural way to describe a tree, with minimal need for parsing.
> 
> The ids of most devices are set NULL currently. So the id is useless
> right now unfortunately.

It's up to the user to assign ids. If one doesn't one won't be able
to activate hotplug/aer, which does not seem like a serious limitation.

> Maybe how to assign ids to all of qdevs
> systematically would be difficult.

I don't think it's urgent. No id -> can't use some of the
functionality. No big deal IMO.

> To be honest, I don't have strong opinion for format of pci topology.
> So far we discussed the following candidates.
> what format do you prefer?
> 
> - domain:<bus>:<slot>.<func>
>   guest assigns bus number, so this can't be used for qemu internal use.
> - domain:00:<slot>.<func>:...:<slot>.<func>
> - fw device path
> - id
>   Unfortunately id is NULL for most devices right now. So id doesn't work.
> - any other?
> 
> thanks,
> -- 
> yamahata