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Date: Mon, 13 Apr 2009 10:30:21 -0300
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [Qemu-devel] [patch 2/2] qemu: switch pci device init
	functions to accept devfn
Message-ID: <20090413133021.GA1065@amt.cnet>
References: <20090413035311.009617911@amt.cnet>
	<20090413035340.296329700@amt.cnet>
	<200904131327.35201.paul@codesourcery.com>
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To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>

On Mon, Apr 13, 2009 at 01:27:34PM +0100, Paul Brook wrote:
> On Monday 13 April 2009, Marcelo Tosatti wrote:
> > Some pci device initialization functions do not accept a devfn parameter,
> > but instead use "-1", which caused pci_register_device to find the first
> > free slot on the given bus.
> >
> > Have them accept a "devfn" parameter, and use the newly introduced
> > pci_bus_assign_dev_addr function on platform init code to perform
> > the "first free" enumeration.
> 
> I don't see how this is better. If anything we want the platform code to get 
> smaller, not larger.

Paul,

This is a intermediate step. Later you'd get rid of
pci_bus_assign_dev_addr in platform code.

Ideally you'd have (I think):

- generic machine initialization code fills in details of pci device
  address in pci device structure (or a temporary placeholder) taken from
  machine description (optionally auto assigns from a free slot).

- pci driver init functions take generic device pointer as an
  argument (either containing the pre allocated pci device or temporary
  placeholder), and pass that to pci_register_device, which does
  actual registration of pci device on particular bus.

Does that make sense?

A benefit of the proposed patch is that it moves assumptions about pci  
device address assignment from drivers up to platform code. Later you'd
remove that from platform code to devtree data.