Re: Going beyond 256 PCI buses

[Jeff Garzik <jgarzik@mandrakesoft.com>]

"David S. Miller" wrote:
> Jeff Garzik writes:
>  > Why do you want to make the bus number larger than the PCI bus number
>  > register?
> 
> This isn't it.  What I'm trying to provoke thought on is
> "is there a way to make mindless apps using these syscalls
> work transparently"
> 
> I think the answer is no.  Apps should really fetch info out
> of /proc/bus/pci and use the controller ioctl.
> 
> But someone could surprise me :-)

yeah, those syscalls weren't built with much eye towards the future. 
And I don't think they are present in other OS's either...


>  > It seems like adding 'unsigned int domain_num' makes more sense, and is
>  > more correct.  Maybe that implies fixing up other code to use a
>  > (domain,bus) pair, but that's IMHO a much better change than totally
>  > changing the interpretation of pci_bus::bus_number...
> 
> Correct, I agree.  But I don't even believe we should be sticking
> the domain thing into struct pci_bus.
> 
> It's a platform thing.  Most platforms have a single domain, so why
> clutter up struct pci_bus with this value?  By this reasoning we could
> say that since it's arch-specific, this stuff belongs in sysdata or
> wherever.

Pretty much any arch with a PCI slot can have multiple domains, now that
hotplug controllers are out and about.  So it seems a generic enough
concept to me...


> And this is what is happening right now.  So in essence, the work is
> done :-)  The only "limiting factor" is that x86 doesn't support
> multiple domains as some other platforms do.  So all these hot-plug
> patches just need to use domains properly, and perhaps add domain
> support to X86 when one of these hot-plug capable controllers are
> being used.

point.

Regards,

	Jeff


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