Re: [PATCH v2 0/7] ACPI: Add _OST support for ACPI hotplug

From: Toshi Kani
Date: Wed May 09 2012 - 14:46:31 EST

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 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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