Re: [Qemu-devel] [PATCH v6 7/7] hw/pci-bridge: format SeaBIOS-compliant OFW device node for PXB

[Kevin O'Connor]

On Wed, Jun 17, 2015 at 09:15:24PM +0200, Laszlo Ersek wrote:
> On 06/17/15 20:54, Michael S. Tsirkin wrote:
> > Right. But what I was discussing is a different issue.  The point is
> > that it does not make sense to have /address@hidden under two hierarchies:
> > it's the same register.  What happens is that you access /address@hidden and
> > then *through that* you access another pci root.  Not the other way
> > around.  The proposal thus is to switch to /address@hidden/address@hidden in
> > seabios,
> 
> For me this is still Question 1 -- 'everything in that pattern that is
> not "N"'.
> 
> You seem to care about the *semantics* of that OFW device path fragment.
> I don't. First, the relevant IEEE spec is prohibitively hard for me to
> interpret semantically. Second, there is no known firmware that actually
> looks at the "i0cf8" unit-address term and decides *based on that term*
> that it has to talk PCI via 0xCF8 and 0xCFC. In other words, the current
> second node is entirely opaque in my interpretation.
> 
> > unconditionally - not if (QEMU).
> 
> This might qualify as some kind of semantic cleanup, but it will
> nonetheless break the SeaBIOS boot options expressed in OFW notation
> that are already persistently stored in cbfs, on physical machines. (As
> far as I understood.) It might not break the Coreboot-SeaBIOS interface,
> but it might invalidate preexistent entries that exist in the prior form
> (wherever they exist on physical hardware).
> 
> > And I thought Kevin agreed
> > it's a good idea.
> > 
> > Kevin - is this a good summary of your opinion?
> 
> Kevin, please do answer.

It is true that it would "invalidate preexistent entries" for
coreboot/seabios users that upgrade, but I think that is manageable.
So I defer the syntax discussion and decisions to the QEMU developers
that are doing the bulk of the work.

-Kevin