linux-kernel - Re: [PATCH] pwm: stm32: fix build warning with CONFIG_DMA

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Message-ID: <CAMuHMdXJg0mYbs=e0QJMDb=A+bRbPsNF=TJzSumSjjOK3yJw2Q@mail.gmail.com>
Date:   Tue, 12 Jun 2018 09:25:05 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Linux PWM List <linux-pwm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        fabrice.gasnier@...com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] pwm: stm32: fix build warning with CONFIG_DMA_ENGINE disabled

Hi Arnd,

On Fri, May 25, 2018 at 11:09 PM Arnd Bergmann <arnd@...db.de> wrote:
> Without dmaengine support, we get a harmless warning about an
> unused function:
>
> drivers/pwm/pwm-stm32.c:166:12: error: 'stm32_pwm_capture' defined but not used [-Werror=unused-function]
>
> Changing the #ifdef to an IS_ENABLED() check shuts up that warning
> and is slightly nicer to read.
>
> Fixes: 53e38fe73f94 ("pwm: stm32: Add capture support")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks!

Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>

> --- a/drivers/pwm/pwm-stm32.c
> +++ b/drivers/pwm/pwm-stm32.c
> @@ -484,9 +484,7 @@ static int stm32_pwm_apply_locked(struct pwm_chip *chip, struct pwm_device *pwm,
>  static const struct pwm_ops stm32pwm_ops = {
>         .owner = THIS_MODULE,
>         .apply = stm32_pwm_apply_locked,
> -#if IS_ENABLED(CONFIG_DMA_ENGINE)
> -       .capture = stm32_pwm_capture,
> -#endif
> +       .capture = IS_ENABLED(CONFIG_DMA_ENGINE) ? stm32_pwm_capture : NULL,

Cool, I didn't know IS_ENABLED() can be used in static initializers.
I guess it's too late/much work to use this trick in e.g. SET_*_PM_OPS(),
as there are lots of places protecting the functions by #ifdefs?

>  };

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds