On Mon, 2014-09-29 at 15:33 -0600, Bjorn Helgaas wrote:

quoted

Right and on powerpc and others as well. We need to survey existing
resources. We also have a number of platform things that might need
to happen before we do the final re-assignment pass.

That's true today.  But I don't know whether it *has* to be this way
forever.  On x86, pcibios_resource_survey() throws in E820 information
(which we know long before we do any PCI enumeration) and some IO-APIC
resources (it looks like we also know these before PCI enumeration).
Powerpc has pcibios_reserve_legacy_regions(), but that looks like
mostly stuff that could be done when we find the host bridge, before
we enumerate PCI devices below it.

Oh we can probably change that but it's going to be much more work than
just moving the assignment into pci_scan_root_bus(). There are also a
number of subtle and not-so-subtle bits of code that rely on side
effects of the current code such as anything that tests for bus->added
or dev->added. Again, nothing we can't sort out eventually but the
transition might be a bit painful.

We might need to introduce a new flag for platforms converted to the
"new style" generalized resource assignment which we can deprecate once
everybody has moved over.

Cheers,
Ben.