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    SubjectRe: [PATCH v2 35/37] PCI: Make /sys/bus/pci/rescan rescan root
    On Tue, Mar 13, 2012 at 12:26 AM, Yinghai Lu <yinghai@kernel.org> wrote:
    > On Mon, Mar 12, 2012 at 8:44 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
    >> On Sat, Mar 10, 2012 at 12:00 AM, Yinghai Lu <yinghai@kernel.org> wrote:
    >>> It will rediscover removed pci root buses.
    >>>
    >>> Signed-off-by: Yinghai Lu <yinghai@kernel.org>
    >>> ---
    >>>  drivers/pci/pci-sysfs.c |    2 ++
    >>>  1 files changed, 2 insertions(+), 0 deletions(-)
    >>>
    >>> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
    >>> index 4d122cb..fc0a7de 100644
    >>> --- a/drivers/pci/pci-sysfs.c
    >>> +++ b/drivers/pci/pci-sysfs.c
    >>> @@ -284,6 +284,7 @@ msi_bus_store(struct device *dev, struct device_attribute *attr,
    >>>
    >>>  #ifdef CONFIG_HOTPLUG
    >>>  static DEFINE_MUTEX(pci_remove_rescan_mutex);
    >>> +void __weak arch_pci_root_rescan(void) { }
    >>>  static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,
    >>>                                size_t count)
    >>>  {
    >>> @@ -295,6 +296,7 @@ static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,
    >>>
    >>>        if (val) {
    >>>                mutex_lock(&pci_remove_rescan_mutex);
    >>> +               arch_pci_root_rescan();
    >>>                while ((b = pci_find_next_bus(b)) != NULL)
    >>>                        pci_rescan_bus(b);
    >>>                mutex_unlock(&pci_remove_rescan_mutex);
    >>
    >> This is gross.  We used to rescan every previously-discovered PCI root bus.
    >>
    >> Now, we do the same, plus:
    >> 1) Scan the ACPI namespace for PCI host bridges, adding and scanning
    >> any we haven't seen before, and
    >> 2) scan domain 0, buses 0 - pcibios_last_bus, looking for any we
    >> haven't seen before.
    >
    > to have /sys/bus/pci/scan_root again?

    Host bridges are not PCI devices, so scanning for them is not a PCI
    operation. It should not be in the /sys/bus/pci hierarchy.
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