Re: RFC: Changes for PCI

[Jeff Garzik <jgarzik@mandrakesoft.com>]

Gérard Roudier wrote:
> The driver checks against PCI bus+dev+func in 2 situations:
> 
> 1) To apply the boot order that user can set up in the controller NVRAMs.
> 2) To detect buggy double reporting of the same device by the kernel PCI
>    code (this made lot of troubles at some time).

Cool.  The premise of the thread was that you merely were checking for
uniqueness, not order.  That changes our answer...


> The great bug is to invent useless abstractions that don't match reality.
> Such brain masturbation leads to confusion (hence subtle bugs)  and
> useless software bloatage (thus _real_ resource wastage).
> 
> If we want to handle _real_ PCI bus domains, we just have to add a domain
> number to identify a _real_ PCI device. Anything that wants to hide such
> reality in some opaque data looks like brain masturbation to me.

I think all of us agree on this:  in 2.5, our solution is to have a
system domain number, which increases from zero each time you add sbus,
pci bus, isa bus, etc.

For 2.4, non-x86 arches first had to deal with PCI domains, so the
solution was to stick "arch-specific data" into pci_dev->sysdata, which
in some cases was the PCI domain number.

So, you have an ugly solution in drivers for 2.4 if you need to know PCI
domain for what reason, and a clean solution in 2.5.

	Jeff


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