linux-kernel - Re: [PATCH 1/6] math.h: Add macros for rounding to closest value

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Message-ID: <4bf68f34-8a68-458f-9db2-c05b1b6bb711@suse.com>
Date: Tue, 9 Jul 2024 11:49:29 +0300
From: Nikolay Borisov <nik.borisov@...e.com>
To: Devarsh Thakkar <devarsht@...com>, mchehab@...nel.org,
 hverkuil-cisco@...all.nl, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org, sebastian.fricke@...labora.com,
 andriy.shevchenko@...ux.intel.com, jani.nikula@...el.com,
 jirislaby@...nel.org, corbet@....net, broonie@...nel.org,
 rdunlap@...radead.org, linux-doc@...r.kernel.org
Cc: laurent.pinchart@...asonboard.com, praneeth@...com, nm@...com,
 vigneshr@...com, a-bhatia1@...com, j-luthra@...com, b-brnich@...com,
 detheridge@...com, p-mantena@...com, vijayp@...com,
 andi.shyti@...ux.intel.com, nicolas@...fresne.ca, davidgow@...gle.com,
 dlatypov@...gle.com
Subject: Re: [PATCH 1/6] math.h: Add macros for rounding to closest value



On 8.07.24 г. 18:59 ч., Devarsh Thakkar wrote:
> Add below rounding related macros:
> 
> round_closest_up(x, y) : Rounds x to closest multiple of y where y is a
> power of 2, with a preference to round up in case two nearest values are
> possible.
> 
> round_closest_down(x, y) : Rounds x to closest multiple of y where y is a
> power of 2, with a preference to round down in case two nearest values are
> possible.
> 
> roundclosest(x, y) : Rounds x to closest multiple of y, this macro should
> generally be used only when y is not multiple of 2 as otherwise
> round_closest* macros should be used which are much faster.
> 
> Examples:
>   * round_closest_up(17, 4) = 16
>   * round_closest_up(15, 4) = 16
>   * round_closest_up(14, 4) = 16
>   * round_closest_down(17, 4) = 16
>   * round_closest_down(15, 4) = 16
>   * round_closest_down(14, 4) = 12
>   * roundclosest(21, 5) = 20
>   * roundclosest(19, 5) = 20
>   * roundclosest(17, 5) = 15
> 
> Signed-off-by: Devarsh Thakkar <devarsht@...com>
> Acked-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
> NOTE: This patch is inspired from the Mentor Graphics IPU driver [1]
> which uses similar macro locally and which is updated in further patch
> in the series to use this generic macro instead along with other drivers
> having similar requirements.
> 
> Link: https://elixir.bootlin.com/linux/v6.8.9/source/drivers/gpu/ipu-v3/ipu-image-convert.c#L480 [1]
> ---
>   include/linux/math.h | 63 ++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 63 insertions(+)
> 
> diff --git a/include/linux/math.h b/include/linux/math.h
> index dd4152711de7..79e3dfda77fc 100644
> --- a/include/linux/math.h
> +++ b/include/linux/math.h
> @@ -34,6 +34,52 @@
>    */
>   #define round_down(x, y) ((x) & ~__round_mask(x, y))
>   
> +/**
> + * round_closest_up - round closest to be multiple of specified value (which is
> + *                    power of 2) with preference to rounding up
> + * @x: the value to round
> + * @y: multiple to round closest to (must be a power of 2)
> + *
> + * Rounds @x to closest multiple of @y (which must be a power of 2).
> + * The value can be either rounded up or rounded down depending upon rounded
> + * value's closeness to the specified value. If there are two closest possible
> + * values, i.e. the difference between the specified value and it's rounded up
> + * and rounded down values is same then preference is given to rounded up
> + * value.
> + *
> + * To perform arbitrary rounding to closest value (not multiple of 2), use
> + * roundclosest().
> + *
> + * Examples:
> + * * round_closest_up(17, 4) = 16
> + * * round_closest_up(15, 4) = 16
> + * * round_closest_up(14, 4) = 16
> + */
> +#define round_closest_up(x, y) round_down((x) + (y) / 2, (y))
> +
> +/**
> + * round_closest_down - round closest to be multiple of specified value (which
> + *			is power of 2) with preference to rounding down
> + * @x: the value to round
> + * @y: multiple to round closest to (must be a power of 2)
> + *
> + * Rounds @x to closest multiple of @y (which must be a power of 2).
> + * The value can be either rounded up or rounded down depending upon rounded
> + * value's closeness to the specified value. If there are two closest possible
> + * values, i.e. the difference between the specified value and it's rounded up
> + * and rounded down values is same then preference is given to rounded up
> + * value.
> + *
> + * To perform arbitrary rounding to closest value (not multiple of 2), use
> + * roundclosest().
> + *
> + * Examples:
> + * * round_closest_down(17, 4) = 16
> + * * round_closest_down(15, 4) = 16
> + * * round_closest_down(14, 4) = 12
> + */
> +#define round_closest_down(x, y) round_up((x) - (y) / 2, (y))

This is already identical to the existing round_down, no ?

<snip>