RE: [PATCH] ACPI: PM: Export the function acpi_sleep_state_supported()

From: Michael Kelley <mikelley@microsoft.com>
To: Dexuan Cui <decui@microsoft.com>,
	"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
	"rjw@rjwysocki.net" <rjw@rjwysocki.net>,
	"lenb@kernel.org" <lenb@kernel.org>,
	"robert.moore@intel.com" <robert.moore@intel.com>,
	"erik.schmauss@intel.com" <erik.schmauss@intel.com>
Cc: "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-kernel@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" <olaf@aepfle.de>,
	"apw@canonical.com" <apw@canonical.com>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	vkuznets <vkuznets@redhat.com>,
	"marcelo.cerri@canonical.com" <marcelo.cerri@canonical.com>
Subject: RE: [PATCH] ACPI: PM: Export the function acpi_sleep_state_supported()
Date: Fri, 14 Jun 2019 20:48:06 +0000	[thread overview]
Message-ID: <BL0PR2101MB134895BADA1D8E0FA631D532D7EE0@BL0PR2101MB1348.namprd21.prod.outlook.com> (raw)
In-Reply-To: <1560536224-35338-1-git-send-email-decui@microsoft.com>

From: Dexuan Cui <decui@microsoft.com>  Sent: Friday, June 14, 2019 11:19 AM
> 
> In a Linux VM running on Hyper-V, when ACPI S4 is enabled, the balloon
> driver (drivers/hv/hv_balloon.c) needs to ask the host not to do memory
> hot-add/remove.
> 
> So let's export acpi_sleep_state_supported() for the hv_balloon driver.
> This might also be useful to the other drivers in the future.
> 
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ---
>  drivers/acpi/sleep.c    | 3 ++-
>  include/acpi/acpi_bus.h | 2 ++
>  2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/sleep.c b/drivers/acpi/sleep.c
> index a34deccd7317..69755411e008 100644
> --- a/drivers/acpi/sleep.c
> +++ b/drivers/acpi/sleep.c
> @@ -79,7 +79,7 @@ static int acpi_sleep_prepare(u32 acpi_state)
>  	return 0;
>  }
> 
> -static bool acpi_sleep_state_supported(u8 sleep_state)
> +bool acpi_sleep_state_supported(u8 sleep_state)
>  {
>  	acpi_status status;
>  	u8 type_a, type_b;
> @@ -89,6 +89,7 @@ static bool acpi_sleep_state_supported(u8 sleep_state)
>  		|| (acpi_gbl_FADT.sleep_control.address
>  			&& acpi_gbl_FADT.sleep_status.address));
>  }
> +EXPORT_SYMBOL_GPL(acpi_sleep_state_supported);
> 
>  #ifdef CONFIG_ACPI_SLEEP
>  static u32 acpi_target_sleep_state = ACPI_STATE_S0;
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 31b6c87d6240..5b102e7bbf25 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -651,6 +651,8 @@ static inline int acpi_pm_set_bridge_wakeup(struct device *dev,
> bool enable)
>  }
>  #endif
> 
> +bool acpi_sleep_state_supported(u8 sleep_state);
> +
>  #ifdef CONFIG_ACPI_SLEEP
>  u32 acpi_target_system_state(void);
>  #else
> --
> 2.19.1

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