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Date: Wed, 22 Dec 2010 20:36:40 +0900
From: Isaku Yamahata <yamahata@valinux.co.jp>
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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: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org

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

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