linux-kernel - Re: [PATCH 3/3] media: atomisp: Use max() macros

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Message-ID: <c88f736f-6845-414b-aeff-fcf76fa83cda@xs4all.nl>
Date: Fri, 27 Sep 2024 12:00:27 +0200
From: Hans Verkuil <hverkuil-cisco@...all.nl>
To: Ricardo Ribalda <ribalda@...omium.org>, Benoit Parrot <bparrot@...com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Sakari Ailus <sakari.ailus@...ux.intel.com>,
 Bingbu Cao <bingbu.cao@...el.com>, Tianshu Qiu <tian.shu.qiu@...el.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Hans de Goede <hdegoede@...hat.com>, Andy Shevchenko <andy@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-staging@...ts.linux.dev
Subject: Re: [PATCH 3/3] media: atomisp: Use max() macros

On 27/09/2024 11:42, Ricardo Ribalda wrote:
> The max() macro produce nicer code and also fixes the following cocci
> errors:
> 
> drivers/staging/media/atomisp/pci/sh_css_frac.h:40:17-18: WARNING opportunity for max()
> drivers/staging/media/atomisp/pci/sh_css_frac.h:50:17-18: WARNING opportunity for max()
> 
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> ---
>  drivers/staging/media/atomisp/pci/sh_css_frac.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/media/atomisp/pci/sh_css_frac.h b/drivers/staging/media/atomisp/pci/sh_css_frac.h
> index 8ba65161f7a9..9642506d2388 100644
> --- a/drivers/staging/media/atomisp/pci/sh_css_frac.h
> +++ b/drivers/staging/media/atomisp/pci/sh_css_frac.h
> @@ -37,7 +37,7 @@ static inline int sDIGIT_FITTING(int v, int a, int b)
>  	int fit_shift = sFRACTION_BITS_FITTING(a) - b;
>  
>  	v >>= sSHIFT;
> -	v >>= fit_shift > 0 ? fit_shift : 0;
> +	v >>= max(fit_shift, 0);

Does the warning go away if you change this to:

	if (fit_shift > 0)
		v >>= fit_shift;

Using 'max' for a shift is a bit weird in my opinion.
Also this change was done to reduce the min/max calls, so introducing
a new max call feels odd (although it should be fine).

Note that I think those cocci warnings should perhaps be ignored or
dropped. In part because of the huge macro expansion of min and max, but
also I often find the code that is not using min or max at least as readable,
if not more.

Regards,

	Hans

>  
>  	return clamp_t(int, v, sISP_VAL_MIN, sISP_VAL_MAX);
>  }
> @@ -47,7 +47,7 @@ static inline unsigned int uDIGIT_FITTING(unsigned int v, int a, int b)
>  	int fit_shift = uFRACTION_BITS_FITTING(a) - b;
>  
>  	v >>= uSHIFT;
> -	v >>= fit_shift > 0 ? fit_shift : 0;
> +	v >>= max(fit_shift, 0);
>  
>  	return clamp_t(unsigned int, v, uISP_VAL_MIN, uISP_VAL_MAX);
>  }
>