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    SubjectRe: [PATCH v2 0/7] ACPI: Add _OST support for ACPI hotplug
    On Wed, 2012-05-09 at 11:36 -0600, Shuah Khan wrote:
    > On Tue, 2012-05-08 at 14:12 -0600, Toshi Kani wrote:
    > > This patchset supports ACPI OSPM Status Indication (_OST) method for
    > > ACPI CPU/memory/container hotplug operations and sysfs eject. After
    > > ACPI hotplug operation has completed, OSPM calls _OST to indicate the
    > > status of the operation to the platform. If _OST is not present, this
    > > patchset has no effect on the platform.
    > >
    > > This _OST support can be enabled or disabled with a new config option
    > > CONFIG_ACPI_HOTPLUG_OST. This option is disabled by default. When
    > > this option is disabled, this patchset has no effect on the platform.
    > >
    > > The _OST definition can be found in section 6.3.5 of ACPI 5.0 spec.
    > > The HPPF spec below also describes hotplug flows with _OST.
    > >
    > > DIG64 Hot-Plug & Partitioning Flow (HPPF) Specification R1.0
    > >
    > >
    > > The changes have been tested with simulated _OST methods.
    > >
    > > v2:
    > > - Added CONFIG_ACPI_HOTPLUG_OST option.
    > > - Added _OST support for container hotplug and sysfs eject.
    > > - Reordered patchset to enable _OST support bit of _OSC in the
    > > last patch.
    > >
    > > ---
    > > Toshi Kani (7):
    > > ACPI: Add CONFIG_HOTPLUG_OST option
    > > ACPI: Add an interface to evaluate _OST
    > > ACPI: Add _OST support for sysfs eject
    > > ACPI: Add _OST support for ACPI CPU hotplug
    > > ACPI: Add _OST support for ACPI memory hotplug
    > > ACPI: Add _OST support for ACPI container hotplug
    > > ACPI: Set hotplug _OST support bit to _OSC
    > >
    > Did you look into implementing this maybe in a generic way by adding a
    > new device_ops that adds the ability to return status back to firmware?
    > It can be left null on systems that don't implement _OST. This way it
    > might be cleaner and can extend to other means of returning status back
    > to firmware if any.

    As Bjorn pointed out in his review comments, if the OS indicates hotplug
    _OST support to _OSC, it needs to evaluate _OST for any devices.
    Therefore, we should not provide a way for each device to have different
    ways of supporting _OST. This patchset is designed to provide
    consistent behavior among multiple devices.

    > Adding _OST support the way it is done in this patch set is rather
    > invasive and CONFIG_HOTPLUG_OST only helps disable just the evaluation
    > of _OST method. Other code changes do get executed on all platforms.

    This _OST config option, as it is defined, enables or disables _OST
    support. The _OST code changes are limited to the scope of hotplug
    operation code paths, which can also be enabled / disabled with their
    HOTPLUG config options.


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