linux-kernel - Re: [PATCH 55/57] staging: comedi: drivers: ni_mio_common: Move 'range_ni_E_ao

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Date:   Thu, 15 Apr 2021 08:55:35 +0200
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     linux-kernel@...r.kernel.org, Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thierry Reding <thierry.reding@...il.com>,
        "David A. Schleef" <ds@...leef.org>,
        Mori Hess <fmhess@...rs.sourceforge.net>,
        Truxton Fulton <trux@...xton.com>,
        linux-staging@...ts.linux.dev, linux-pwm@...r.kernel.org
Subject: Re: [PATCH 55/57] staging: comedi: drivers: ni_mio_common: Move
 'range_ni_E_ao_ext' to where it is used

Hello Lee,

nitpick: You move range_ni_E_ao_ext to the header. However that header
doesn't use range_ni_E_ao_ext, so the subject is technically wrong.

On Wed, Apr 14, 2021 at 07:11:27PM +0100, Lee Jones wrote:
> ... and mark it as __maybe_unused since not all users of the
> header file reference it.
> 
> Fixes the following W=1 kernel build warning(s):
> 
>  drivers/staging/comedi/drivers/ni_mio_common.c:163:35: warning: ‘range_ni_E_ao_ext’ defined but not used [-Wunused-const-variable=]
> 
> Cc: Ian Abbott <abbotti@....co.uk>
> Cc: H Hartley Sweeten <hsweeten@...ionengravers.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Thierry Reding <thierry.reding@...il.com>
> Cc: "Uwe Kleine-König" <u.kleine-koenig@...gutronix.de>
> Cc: Lee Jones <lee.jones@...aro.org>
> Cc: "David A. Schleef" <ds@...leef.org>
> Cc: Mori Hess <fmhess@...rs.sourceforge.net>
> Cc: Truxton Fulton <trux@...xton.com>
> Cc: linux-staging@...ts.linux.dev
> Cc: linux-pwm@...r.kernel.org
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>  drivers/staging/comedi/drivers/ni_mio_common.c | 9 ---------
>  drivers/staging/comedi/drivers/ni_stc.h        | 9 ++++++++-
>  2 files changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/staging/comedi/drivers/ni_mio_common.c b/drivers/staging/comedi/drivers/ni_mio_common.c
> index 4f80a4991f953..37615b4e2c10d 100644
> --- a/drivers/staging/comedi/drivers/ni_mio_common.c
> +++ b/drivers/staging/comedi/drivers/ni_mio_common.c
> @@ -160,15 +160,6 @@ static const struct comedi_lrange range_ni_M_ai_628x = {
>  	}
>  };
>  
> -static const struct comedi_lrange range_ni_E_ao_ext = {
> -	4, {
> -		BIP_RANGE(10),
> -		UNI_RANGE(10),
> -		RANGE_ext(-1, 1),
> -		RANGE_ext(0, 1)
> -	}
> -};
> -
>  static const struct comedi_lrange *const ni_range_lkup[] = {
>  	[ai_gain_16] = &range_ni_E_ai,
>  	[ai_gain_8] = &range_ni_E_ai_limited,
> diff --git a/drivers/staging/comedi/drivers/ni_stc.h b/drivers/staging/comedi/drivers/ni_stc.h
> index fbc0b753a0f59..0822e65f709dd 100644
> --- a/drivers/staging/comedi/drivers/ni_stc.h
> +++ b/drivers/staging/comedi/drivers/ni_stc.h
> @@ -1137,6 +1137,13 @@ struct ni_private {
>  	u8 rgout0_usage;
>  };
>  
> -static const struct comedi_lrange range_ni_E_ao_ext;
> +static const struct comedi_lrange __maybe_unused range_ni_E_ao_ext = {
> +	4, {
> +		BIP_RANGE(10),
> +		UNI_RANGE(10),
> +		RANGE_ext(-1, 1),
> +		RANGE_ext(0, 1)
> +	}
> +};

I think a downside of this solution is that range_ni_E_ao_ext might be
duplicated in the object files. (Ditto for the status quo BTW.)

I think the right approach to fix the compiler warning and the
duplication is to declare range_ni_E_ao_ext external in the header and
keep the definition in ni_mio_common.c.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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