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    SubjectRe: [PATCH 08/13] PCI: Add pci_bus_extend/shrink_top()
    On Fri, Jan 27, 2012 at 6:49 PM, Yinghai Lu <yinghai@kernel.org> wrote:
    > extend or shrink bus and parent buses top (subordinate)
    >
    > extended range is verified safe range, and stop at recorded parent_res.
    >
    > Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    > ---
    >  drivers/pci/probe.c |   50 ++++++++++++++++++++++++++++++++++++++++++++++++++
    >  1 files changed, 50 insertions(+), 0 deletions(-)
    >
    > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
    > index 55404c3..3e62f45 100644
    > --- a/drivers/pci/probe.c
    > +++ b/drivers/pci/probe.c
    > @@ -624,6 +624,56 @@ static void pci_fixup_parent_subordinate_busnr(struct pci_bus *child, int max)
    >        }
    >  }
    >
    > +static void __devinit pci_bus_extend_top(struct pci_bus *parent,
    > +                resource_size_t size, struct resource *parent_res)
    > +{
    > +       struct resource *res;
    > +
    > +       if (!size)
    > +               return;
    > +
    > +       while (parent) {
    > +               res = &parent->busn_res;
    > +               if (res == parent_res)
    > +                       break;
    > +               res->end += size;
    > +               parent->subordinate += size;

    This makes me nervous for the same reason as
    pci_bus_update_busn_res_end() -- we're changing res->end for resources
    already in a tree. How do we know the tree remains consistent?

    > +               pci_write_config_byte(parent->self, PCI_SUBORDINATE_BUS,
    > +                                        parent->subordinate);
    > +               dev_printk(KERN_DEBUG, &parent->dev,
    > +                               "busn_res: extended %02llx to %06llx-%06llx\n",
    > +                               (unsigned long long)size,
    > +                               (unsigned long long)res->start,
    > +                               (unsigned long long)res->end);
    > +               parent = parent->parent;
    > +       }
    > +}
    > +
    > +static void __devinit pci_bus_shrink_top(struct pci_bus *parent,
    > +                resource_size_t size, struct resource *parent_res)
    > +{
    > +       struct resource *res;
    > +
    > +       if (!size)
    > +               return;
    > +
    > +       while (parent) {
    > +               res = &parent->busn_res;
    > +               if (res == parent_res)
    > +                       break;
    > +               res->end -= size;
    > +               parent->subordinate -= size;
    > +               pci_write_config_byte(parent->self, PCI_SUBORDINATE_BUS,
    > +                                        parent->subordinate);
    > +               dev_printk(KERN_DEBUG, &parent->dev,
    > +                               "busn_res: shrunk %02llx to %06llx-%06llx\n",
    > +                               (unsigned long long)size,
    > +                               (unsigned long long)res->start,
    > +                               (unsigned long long)res->end);
    > +               parent = parent->parent;
    > +       }
    > +}
    > +
    >  /*
    >  * If it's a bridge, configure it and scan the bus behind it.
    >  * For CardBus bridges, we don't scan behind as the devices will
    > --
    > 1.7.7
    >
    --
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