linux-kernel - Re: [PATCH] coresight: etm4x: fix unused function warning

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Date:   Thu, 12 Dec 2019 10:19:01 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andrew Murray <andrew.murray@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mike Leach <mike.leach@...aro.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] coresight: etm4x: fix unused function warning

On Tue, 10 Dec 2019 at 13:33, Arnd Bergmann <arnd@...db.de> wrote:
>
> Some of the newly added code in the etm4x driver is inside of an #ifdef,
> and some other code is outside of it, leading to a harmless warning when
> CONFIG_CPU_PM is disabled:
>
> drivers/hwtracing/coresight/coresight-etm4x.c:68:13: error: 'etm4_os_lock' defined but not used [-Werror=unused-function]
>  static void etm4_os_lock(struct etmv4_drvdata *drvdata)
>              ^~~~~~~~~~~~
>
> To avoid the warning and simplify the the #ifdef checks, use
> IS_ENABLED() instead, so the compiler can drop the unused functions
> without complaining.
>
> Fixes: f188b5e76aae ("coresight: etm4x: Save/restore state across CPU low power states")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index dc3f507e7562..a90d757f7043 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -1132,7 +1132,6 @@ static void etm4_init_trace_id(struct etmv4_drvdata *drvdata)
>         drvdata->trcid = coresight_get_trace_id(drvdata->cpu);
>  }
>
> -#ifdef CONFIG_CPU_PM
>  static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
>  {
>         int i, ret = 0;
> @@ -1402,17 +1401,17 @@ static struct notifier_block etm4_cpu_pm_nb = {
>
>  static int etm4_cpu_pm_register(void)
>  {
> -       return cpu_pm_register_notifier(&etm4_cpu_pm_nb);
> +       if (IS_ENABLED(CONFIG_CPU_PM))
> +               return cpu_pm_register_notifier(&etm4_cpu_pm_nb);
> +
> +       return 0;
>  }
>
>  static void etm4_cpu_pm_unregister(void)
>  {
> -       cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
> +       if (IS_ENABLED(CONFIG_CPU_PM))
> +               cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
>  }
> -#else
> -static int etm4_cpu_pm_register(void) { return 0; }
> -static void etm4_cpu_pm_unregister(void) { }
> -#endif

I have applied this.

Thanks,
Mathieu

>
>  static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
>  {
> --
> 2.20.0
>