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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Fri, 20 Sep 2019 09:33:13 +0200
Message-ID: <CAK8P3a0EvdR0SZdPhRV2o3PrxHo4BpJdWzAjExmKHhwrOsL54Q@mail.gmail.com>
Subject: Re: [PATCH] Drivers: hv: vmbus: Fix harmless building warnings
 without CONFIG_PM
To:     Dexuan Cui <decui@microsoft.com>
Cc:     KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "sashal@kernel.org" <sashal@kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Michael Kelley <mikelley@microsoft.com>
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On Thu, Sep 19, 2019 at 11:38 PM Dexuan Cui <decui@microsoft.com> wrote:
> > Sent: Thursday, September 19, 2019 5:11 AM
> > On Thu, Sep 19, 2019 at 7:19 AM Dexuan Cui <decui@microsoft.com> wrote:

> > I think this will still produce a warning if CONFIG_PM is set but
> > CONFIG_PM_SLEEP is not, possibly in other configurations as
> > well.
>
> You're correct. Thanks!
>
> I'll use " #ifdef CONFIG_PM_SLEEP ... #endif" instead.
>
> The mentioned functions are only used in the micros
> SET_NOIRQ_SYSTEM_SLEEP_PM_OPS, which is empty if CONFIG_PM_SLEEP
> is not defined. So it looks to me using "#ifdef CONFIG_PM_SLEEP ..." should
> resolve the issue.

Probably, yes. There are sometimes surprising effects, such as when one of the
functions inside of the #ifdef call another function that is otherwise unused.

I would normally try to build a few hundred randconfig builds to be fairly sure
of a change like this, or use __maybe_unused like most other drivers do here.

       Arnd