linux-kernel - Re: [PATCH v4 1/4] math.h: Introduce data types for fractional numbers

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Date:   Sun, 30 Jan 2022 12:30:47 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Andreas Kemnade <andreas@...nade.info>,
        linux-arm-msm@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v4 1/4] math.h: Introduce data types for fractional
 numbers

On Wed, 26 Jan 2022 15:53:50 +0200
Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> Introduce a macro to produce data types like
> 
> 	struct TYPE_fract {
> 		__TYPE numerator;
> 		__TYPE denominator;
> 	};
> 
> to be used in the code wherever it's needed.
> 
> In the following changes convert some users to it.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

I'm not 100% sold on this, but I'm going to give them the benefit
of the doubt as to long term usefulness and apply them.

Basically I'm taking the view Andy is often right :)

Applied to the togreg branch of iio.git and pushed out as testing
for 0-day to see if we missed anything.

Thanks,

Jonathan

> ---
> 
> May be pulled via IIO tree.
> 
> v4: no changes
> v3: no changes
> v2: no changes
> 
>  include/linux/math.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/include/linux/math.h b/include/linux/math.h
> index 53674a327e39..439b8f0b9ebd 100644
> --- a/include/linux/math.h
> +++ b/include/linux/math.h
> @@ -2,6 +2,7 @@
>  #ifndef _LINUX_MATH_H
>  #define _LINUX_MATH_H
>  
> +#include <linux/types.h>
>  #include <asm/div64.h>
>  #include <uapi/linux/kernel.h>
>  
> @@ -106,6 +107,17 @@
>  }							\
>  )
>  
> +#define __STRUCT_FRACT(type)				\
> +struct type##_fract {					\
> +	__##type numerator;				\
> +	__##type denominator;				\
> +};
> +__STRUCT_FRACT(s16)
> +__STRUCT_FRACT(u16)
> +__STRUCT_FRACT(s32)
> +__STRUCT_FRACT(u32)
> +#undef __STRUCT_FRACT
> +
>  /*
>   * Multiplies an integer by a fraction, while avoiding unnecessary
>   * overflow or loss of precision.