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@xxxxxx> --- 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. [1]: https://elixir.bootlin.com/linux/v6.8.9/source/drivers/gpu/ipu-v3/ipu-image-convert.c#L480 V11: - Fix commenting style per review comments and remove extra whitespace V10: - Update example comment to fix formatting issues as observed with html docs V9: - No change V8: - Add new macro to round to nearest value for non-multiple of 2 - Update commit message as suggested: V1->V6 (No change, patch introduced in V7) --- 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)) + #define DIV_ROUND_UP __KERNEL_DIV_ROUND_UP #define DIV_ROUND_DOWN_ULL(ll, d) \ @@ -77,6 +123,23 @@ } \ ) +/** + * roundclosest - round to nearest multiple + * @x: the value to round + * @y: multiple to round nearest to + * + * Rounds @x to nearest multiple of @y. + * The rounded value can be greater than or less than @x depending + * upon it's nearness to @x. If @y will always be a power of 2, consider + * using the faster round_closest_up() or round_closest_down(). + * + * Examples: + * * roundclosest(21, 5) = 20 + * * roundclosest(19, 5) = 20 + * * roundclosest(17, 5) = 15 + */ +#define roundclosest(x, y) rounddown((x) + (y) / 2, (y)) + /* * Divide positive or negative dividend by positive or negative divisor * and round to closest integer. Result is undefined for negative -- 2.39.1
