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    SubjectRe: [PATCH 2/12] pci: add pci_bridge_release_unused_res and pci_bus_release_unused_bridge_res -v2
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    On Fri, 2009-12-18 at 13:24 -0800, Linus Torvalds wrote:
    >
    > On Fri, 18 Dec 2009, Yinghai Lu wrote:
    > >
    > > so later we could use it to release small resource before pci assign unassign res
    >
    > However, I think this one is wrong.
    >
    > > +static void release_child_resources(struct resource *r)
    > > +{
    > > + struct resource *p;
    > > + resource_size_t size;
    > > +
    > > + p = r->child;
    > > + while (p) {
    > > + release_child_resources(p);
    > > + release_resource(p);
    >
    > So not only is this releasing resources that aren't necessarily PCI
    > devices, it's releasing the whole tree - regardless of how they were
    > allocated and initialized. ...

    Help me fill in my mental picture of these resources ... This function
    just takes a struct resource, so it doesn't know whether it's a PCI,
    ACPI, or other resource. But in Yinghai's usage, I think we do know
    that we're starting with a PCI resource. In that case, is it possible
    that some child is a non-PCI resource?

    The picture in my mind is that once we are downstream of a PCI host
    bridge, all child resources must be PCI, and they must all conform to
    the forwarding rules for PCI bridges and so on. I know there are PCI
    devices with BARs at non-standard places, so Linux wouldn't know about
    those resources (and that worries me a bit when we're talking about
    reprogramming a bridge window that might be upstream of such a device).
    But if Linux *did* learn about those non-standard resources via a quirk
    or something, I would still think of those as PCI resources, not ACPI or
    something else.

    Anyway, I'd like to correct my mental picture if it's mistaken.

    Bjorn




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