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Date: Wed, 02 Jun 2010 23:03:35 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] Name the default PCI bus "pci.0" on all
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To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org

   Hi,

> I disagree.  Anything that depends on device creation order is fundamentally
> broken. If you want to create globally unique user-friendly tags for devices
> or busses then that is a completely different problem, and should be done via
> explicit aliases.

For anything created via -device the id does the job.  The device gets 
tagged with the supplied id, and any child busses of that device carry 
the id too, i.e.

   -device lsi,id=foo

creates a lsi scsi hostadapter with id 'foo' and a scsi bus with the 
name 'foo.0'.  A (theoretical) scsi hba with two scsi busses would have 
'foo.0' and 'foo.1' child busses.  If you don't specify a id you'll get 
'scsi.$nr'.  Numbers are per device, not global.  So if you add two lsi 
adapters without id you'll get two 'scsi.0' busses, so better don't do 
that if you want be able to address them via bus= ...

For devices created by machine->init() the names are more or less 
hard-coded in qemu though (and hopefully some day in some machine 
description file).  'pci.0' is the default name for a pci bus and IMHO a 
good choice for the primary pci bus.  secondary busses created by 
machine->init() (sparc64 does this I think) should get some other name.

cheers,
   Gerd