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

Nikolay Borisov
2024-07-09T08:49:33Z

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@ti.com>
> Acked-by: Andy Shevchenko <andriy.shevchenko@linux.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>