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From: Arnd Bergmann <arnd@arndb.de>
Date: Mon, 20 Mar 2017 13:27:32 +0100
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Subject: Re: [PATCH] tpm/tpm_crb: mark PM functions as __maybe_unused
To: "Winkler, Tomas" <tomas.winkler@intel.com>
Cc: Peter Huewe <peterhuewe@gmx.de>, Marcel Selhorst <tpmdd@selhorst.net>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Jason Gunthorpe <jgunthorpe@obsidianresearch.com>,
        Jerry Snitselaar <jsnitsel@redhat.com>,
        "tpmdd-devel@lists.sourceforge.net" 
        <tpmdd-devel@lists.sourceforge.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Mon, Mar 20, 2017 at 1:11 PM, Winkler, Tomas <tomas.winkler@intel.com> wrote:
>>
>> When CONFIG_PM_SLEEP is disabled, we get a warning about unused
>> functions:
>>
>> drivers/char/tpm/tpm_crb.c:551:12: error: 'crb_pm_resume' defined but not
>> used [-Werror=unused-function]
>> drivers/char/tpm/tpm_crb.c:540:12: error: 'crb_pm_suspend' defined but not
>> used [-Werror=unused-function]
>>
> Note that the runtime_pm functions are not affected by this issue the macro
> SET_RUNTIME_PM_OPS is under CONFIG_PM. This patch does more than described.

Well, the problem is that there is an #ifdef that is wrong here as I
tried to indicate:

>> We could solve this with more sophistated #ifdefs, but a simpler and safer way
>> is to just mark them as __maybe_unused.

>> @@ -547,7 +546,7 @@ static int crb_pm_suspend(struct device *dev)
>>       return crb_pm_runtime_suspend(dev);
>>  }
>
> It's enough to
> #endif /* CONFIG_PM */
> #ifdef CONFIG_PM_SLEEP
>> -static int crb_pm_resume(struct device *dev)
>> +static __maybe_unused int crb_pm_resume(struct device *dev)
>>  {
>>       int ret;
>>
>> @@ -558,8 +557,6 @@ static int crb_pm_resume(struct device *dev)
>>       return tpm_pm_resume(dev);
>>  }
>>
>> -#endif /* CONFIG_PM */
> And
> #endif CONFIG_PM_SLEEP

This tends to cause other warnings half of the time, when both the
runtime-pm and pm-sleep variants call into another function that
becomes unused when both are disabled.

       Arnd