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SubjectRe: [PATCH] ACPI: PM: Export the function acpi_sleep_state_supported()
Hi,

On Fri, Jun 14, 2019 at 10:19:02PM +0000, Dexuan Cui wrote:
> > -----Original Message-----
> > From: Michael Kelley <mikelley@microsoft.com>
> > Sent: Friday, June 14, 2019 1:48 PM
> > To: Dexuan Cui <decui@microsoft.com>; linux-acpi@vger.kernel.org;
> > rjw@rjwysocki.net; lenb@kernel.org; robert.moore@intel.com;
> > erik.schmauss@intel.com
> > Cc: linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org; KY Srinivasan
> > <kys@microsoft.com>; Stephen Hemminger <sthemmin@microsoft.com>;
> > Haiyang Zhang <haiyangz@microsoft.com>; Sasha Levin
> > <Alexander.Levin@microsoft.com>; olaf@aepfle.de; apw@canonical.com;
> > jasowang@redhat.com; vkuznets <vkuznets@redhat.com>;
> > marcelo.cerri@canonical.com
> > Subject: RE: [PATCH] ACPI: PM: Export the function
> > acpi_sleep_state_supported()
> >
> > It seems that sleep.c isn't built when on the ARM64 architecture. Using
> > acpi_sleep_state_supported() directly in hv_balloon.c will be problematic
> > since hv_balloon.c needs to be architecture independent when the
> > Hyper-V ARM64 support is added. If that doesn't change, a per-architecture
> > wrapper will be needed to give hv_balloon.c the correct information. This
> > may affect whether acpi_sleep_state_supported() needs to be exported vs.
> > just removing the "static". I'm not sure what the best approach is.
> >
> > Michael
>
> + some ARM experts who worked on arch/arm/kernel/hibernate.c.
>
> drivers/acpi/sleep.c is only built if ACPI_SYSTEM_POWER_STATES_SUPPORT
> is defined, but it looks this option is not defined on ARM.
>
> It looks ARM does not support the ACPI S4 state, then how do we know
> if an ARM host supports hibernation or not?

Don't forget that Linux does not support ACPI on 32-bit ARM, which is
quite different from the situation on 64-bit ARM.

arch/arm/kernel/hibernate.c is only for 32-bit ARM, and is written with
the assumption that there is no interaction required with any firmware
to save state, and later restore state upon resuming.

Or am I missing something?

--
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