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    SubjectRe: [PATCH v2 23/37] PCI, ACPI: Add pci_root_hp hot add hotplug notification
    On Tue, Mar 13, 2012 at 12:03 AM, Yinghai Lu <yinghai@kernel.org> wrote:
    > On Mon, Mar 12, 2012 at 8:22 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
    >> On Sat, Mar 10, 2012 at 12:00 AM, Yinghai Lu <yinghai@kernel.org> wrote:
    >>> It is from acpiphp_glue.c
    >>>
    >>> How to use it?
    >>> Find out root bus number to acpi root name mapping from dmesg or /sys
    >>>
    >>>  echo "\_SB.PCIB 0" > /proc/acpi/sci/notify
    >>> to add it back
    >>
    >> Nope.  That might be a way to exercise this for debug purposes (and it
    >> only works when /proc/acpi/sci/notify is compiled in), but we
    >> definitely don't want normal users to deal with ACPI pathnames like
    >> this.
    >
    > before this patch set, only way is: Users really put one root bus in
    > and press buton etc to trigger notification
    > to get it work.
    >
    >>
    >> Most of this functionality belongs in the ACPI core, not here.  The
    >> core should be handling these notify events and turning them into
    >> .add() and .remove() calls to the driver.
    >>
    >> But since the ACPI core doesn't do that yet, we have to do it in the
    >> driver, like we do for CPU, memory, etc.  That part is fine.  But I
    >> think it at least belongs *in* the driver, i.e., in pci_root.c, not in
    >> a new pci_root_hp.c file.
    >
    > don't want to pollute pci_root.c.
    >
    > in separated file, we can use CONFIG_HOTPLUG in Makefile instead of pci_root.c

    I don't buy this argument. Most of this functionality should someday
    be in the ACPI core. Until then, it is intimately connected to the
    stuff in pci_root.c. It is not "pollution."

    >> There definitely should not be another acpi_walk_namespace() and
    >> another list of ACPI host bridges.  The core *does* already walk the
    >> namespace and call acpi_pci_root_add() for us.  And the driver already
    >> has a list of host bridges (acpi_pci_roots).
    >
    > no, we may not have acpi_pci_root there.

    I don't understand what you're saying here. I think you should be
    basically implementing the "turn notify events into add/remove calls"
    functionality. This is what *should* be in the ACPI core, but isn't
    yet. If you put this in the driver, and hopefully follow the style
    already used by the processor/memory/etc. drivers, it will be easier
    to someday move it into the ACPI core.

    Bjorn
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