linux-kernel - Re: [PATCH] drm/msm/gpu: Avoid -Wunused-function with !CONFIG_PM

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Message-ID: <4deb0930-b244-677a-9f97-3730686eff5a@linaro.org>
Date:   Mon, 11 Apr 2022 03:53:01 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Nathan Chancellor <nathan@...nel.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>
Cc:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev
Subject: Re: [PATCH] drm/msm/gpu: Avoid -Wunused-function with
 !CONFIG_PM_SLEEP

On 30/03/2022 21:05, Nathan Chancellor wrote:
> When building with CONFIG_PM=y and CONFIG_PM_SLEEP=n (such as ARCH=riscv
> allmodconfig), the following warnings/errors occur:
> 
>    drivers/gpu/drm/msm/adreno/adreno_device.c:679:12: error: 'adreno_system_resume' defined but not used [-Werror=unused-function]
>      679 | static int adreno_system_resume(struct device *dev)
>          |            ^~~~~~~~~~~~~~~~~~~~
>    drivers/gpu/drm/msm/adreno/adreno_device.c:655:12: error: 'adreno_system_suspend' defined but not used [-Werror=unused-function]
>      655 | static int adreno_system_suspend(struct device *dev)
>          |            ^~~~~~~~~~~~~~~~~~~~~
>    cc1: all warnings being treated as errors
> 
> These functions are only used in SET_SYSTEM_SLEEP_PM_OPS(), which
> evaluates to empty when CONFIG_PM_SLEEP is not set, making these
> functions unused.
> 
> Traditionally, these functions are marked as __maybe_unused but in this
> case, there is already an '#ifdef CONFIG_PM' in the code, so just do the
> same thing with CONFIG_PM_SLEEP to resolve the warning.
> 
> Fixes: 7e4167c9e021 ("drm/msm/gpu: Park scheduler threads for system suspend")
> Signed-off-by: Nathan Chancellor <nathan@...nel.org>

I'd suggest using __maybe_unused instead (and maybe even sending the 
followup patch changing the #ifdef CONFIG_PM to __maybe_unused too):

If the code is included into the compilation, it means it's more widely 
compile tested. Which tends to reveal obscure bugs, dependencies, etc.


> ---
>   drivers/gpu/drm/msm/adreno/adreno_device.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
> index 661dfa7681fb..b25915230bab 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
> +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
> @@ -621,6 +621,7 @@ static int adreno_runtime_suspend(struct device *dev)
>   	return gpu->funcs->pm_suspend(gpu);
>   }
>   
> +#ifdef CONFIG_PM_SLEEP
>   static void suspend_scheduler(struct msm_gpu *gpu)
>   {
>   	int i;
> @@ -681,8 +682,8 @@ static int adreno_system_resume(struct device *dev)
>   	resume_scheduler(dev_to_gpu(dev));
>   	return pm_runtime_force_resume(dev);
>   }
> -
> -#endif
> +#endif /* CONFIG_PM_SLEEP */
> +#endif /* CONFIG_PM */
>   
>   static const struct dev_pm_ops adreno_pm_ops = {
>   	SET_SYSTEM_SLEEP_PM_OPS(adreno_system_suspend, adreno_system_resume)
> 
> base-commit: 05241de1f69eb7f56b0a5e0bec96a7752fad1b2f


-- 
With best wishes
Dmitry