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    SubjectRe: [PATCH 4/4] ACPI PCI slot detection driver
    * Greg KH <>:
    > On Sat, Mar 01, 2008 at 07:43:07AM -0700, Matthew Wilcox wrote:
    > > On Fri, Feb 29, 2008 at 09:25:42PM -0800, Greg KH wrote:
    > > > What is the guarantee that the names of these slots are correct

    No guarantee there. We report whatever firmware tells us.

    > > > and do not happen to be the same as the hotpluggable ones?

    Stronger guarantee here, since both pci_slot and <foo>hp driver
    will be getting the name of the slot from the same place.

    > > That would be a bug -- and yes, bugs happen, and we have to deal with
    > > them.
    > My main concern is that BIOS vendors will not fix these bugs, as no
    > other OS cares/does this kind of thing today. The ammount of bad
    > information out there might be quite large, and I think this was
    > confirmed by some initial testing of IBM systems, right?

    We saw problems on Fujitsu machines, where they return an error
    code when the _SUN method is called on a slot that exists in the
    namespace but isn't actually present.

    After discussing with Kenji-san about specs, we came to the
    agreement that he was ok with this behavior because he had the
    option to not load pci_slot on his machines.

    I agree that there might be lots of buggy firmwares out there,
    but we won't know for certain until we get some exposure. And I
    think the upside is worth it.

    Kristen suggested the linux-next tree. That sounds viable to

    > > > Why show this information on machines that can not do
    > > > anything with these slots at all? Will that not just
    > > > confuse people?
    > >
    > > Only for people who think that /sys/bus/pci/slots/ is for
    > > hotpluggable slots only. There is plenty of useful
    > > information available for slots that aren't hotpluggable (eg
    > > bus address, speed, width, error status).
    > Can the userspace tools that are using the existing directories
    > thinking that only hotplug slots are there, handle
    > "non-hotplug" slots showing up in this location?

    Of course we shouldn't break userspace, no one wants that. But
    nothing about that name (/sys/bus/pci/slots/) implies "hotplug
    only", and we have no idea how big the problem might be.

    Again, I'm thinking more exposure in linux-next might be a
    reasonable way for us to figure out how bad (or good) the
    situation might really be out there.



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