linux-kernel - RE: [PATCH v2 2/6] Drivers: hv: allow non ACPI compilation for hv_is_hibernation

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Date:   Thu, 2 Feb 2023 15:33:13 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Saurabh Singh Sengar <ssengar@...ux.microsoft.com>
CC:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        Saurabh Singh Sengar <ssengar@...rosoft.com>
Subject: RE: [PATCH v2 2/6] Drivers: hv: allow non ACPI compilation for
 hv_is_hibernation_supported

From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com> Sent: Thursday, February 2, 2023 6:49 AM
> 
> On Wed, Feb 01, 2023 at 05:47:44PM +0000, Michael Kelley (LINUX) wrote:
> > From: Saurabh Sengar <ssengar@...ux.microsoft.com> Sent: Tuesday, January 31,
> 2023 10:10 AM
> > >
> > > acpi_sleep_state_supported API is only define for CONFIG_ACPI flag and
> > > thus it can't be used for non-ACPI builds. Initaly there won't be
> >
> > s/Initaly/Initially/
> 
> OK
> 
> >
> > > hibernate support for non ACPI builds.
> >
> > s/hibernate/hibernation/
> 
> OK
> 
> >
> > >
> > > This change will help adding device tree support in subsequent commits.
> > >
> > > Signed-off-by: Saurabh Sengar <ssengar@...ux.microsoft.com>
> > > ---
> > >  drivers/hv/hv_common.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> > > index 52a6f89ccdbd..370ec20d1993 100644
> > > --- a/drivers/hv/hv_common.c
> > > +++ b/drivers/hv/hv_common.c
> > > @@ -234,7 +234,11 @@ EXPORT_SYMBOL_GPL(hv_setup_dma_ops);
> > >
> > >  bool hv_is_hibernation_supported(void)
> > >  {
> > > +#ifdef CONFIG_ACPI
> > >  	return !hv_root_partition && acpi_sleep_state_supported(ACPI_STATE_S4);
> > > +#else
> > > +	return false;
> > > +#endif
> >
> > Is this patch needed?  If CONFIG_ACPI is not set, then per
> > arch/x86/Kconfig, CONFIG_ACPI_SYSTEM_POWER_STATES_SUPPORT
> > is not selected.  In that case, the #ifdef in include/acpi/acpi_bus.h
> > provides a stub for acpi_sleep_state_supported() that returns "false".
> > So it seems like the existing code should compile and correctly return
> > "false" when CONFIG_ACPI is not set.
> 
> You are right, if CONFIG_ACPI_SYSTEM_POWER_STATES_SUPPORT is not set
> acpi_sleep_state_supported will return false, but this is applicable only
> when CONFIG_ACPI is enable. If CONFIG_ACPI is not enable both these
> functions are not defined.
> 

Indeed, you are right.  Most of include/acpi/acpi_bus.h is bracketed with
#ifdef CONFIG_ACPI, including the stub acpi_sleep_state_supported().
Oh well. :-(

Michael