Re: [RFC] ARM/ARM64 PCI_PROBE_ONLY platforms

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Jan 20, 2016 at 06:10:03PM +0000, Lorenzo Pieralisi wrote:

> To do that, we must claim resources on PCI_PROBE_ONLY systems, but
> I know for certain Bjorn does not like the idea (I let you trawl
> the archives - at least he does not accept the idea of claiming
> resources ONLY on PCI_PROBE_ONLY systems, he thinks we should
> always claim resources regardless of that flag and fall-back to
> reassigning them in case claiming fails. That's perfectly reasonable,
> at least on systems with FW initializing PCI). The problem is dealing
> with legacy, so switching to resources claiming by default is a tad
> complicated, at least for testing (code is easy to implement).

I'd like to think of PCI_PROBE_ONLY basically as "setting
IORESOURCE_PCI_FIXED for every BAR", i.e., we can do everything we
normally do *except* write to the BAR (of course we have to write to
it to size the BAR during enumeration, but we have to restore the
original value).

I don't think PCI_PROBE_ONLY should have anything to do with the
iomem_resource and ioport_resource trees.  /proc/iomem and
/proc/ioports should still contain every resource we know about,
regardless of whether PCI_PROBE_ONLY is set or not.

Bjorn