Add below rounding related macros: round_closest_up(x, y) : Rounds x to the 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 the 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 the 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> Acked-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> --- 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] Past discussions and alignment on this: https://lore.kernel.org/all/7e3ad816-6a2a-4e02-9b41-03a8562812ad@xxxxxx/#r https://lore.kernel.org/all/ZkISG6p1tn9Do-xY@xxxxxxxxxxxxxxxxxx/#r https://lore.kernel.org/all/ZlTt-YWzyRyhmT9n@xxxxxxxxxxxxxxxxxx/ https://lore.kernel.org/all/ZmHDWeuezCEgj20m@xxxxxxxxxxxxxxxxxx/ https://lore.kernel.org/all/ZloMFfGKLry6EWNL@xxxxxxxxxxxxxxxxxx/ Changelog: V2: - Fix grammar in macro description - Update roundclosest macro to use roundup to avoid overflow scenario --- include/linux/math.h | 63 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/include/linux/math.h b/include/linux/math.h index f5f18dc3616b..b59a02a007d7 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 the 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 the closest multiple of @y (which must be a power of 2). + * The value can be rounded up or rounded down depending on the rounded + * value's closeness to the specified value. Also, there can be two closest + * values, i.e. the difference between the specified value and its rounded-up + * and rounded-down values could be the same. In that case, the rounded-up + * value is preferred. + * + * To perform arbitrary rounding to the 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 the 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 the closest multiple of @y (which must be a power of 2). + * The value can be rounded up or rounded down depending on the rounded + * value's closeness to the specified value. Also, there can be two closest + * values, i.e. the difference between the specified value and its rounded-up + * and rounded-down values could be the same. In that case, the rounded-down + * value is preferred. + * + * To perform arbitrary rounding to the 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 the nearest multiple + * @x: the value to round + * @y: multiple to round nearest to + * + * Rounds @x to the nearest multiple of @y. + * The rounded value can be greater or less than @x depending + * upon its nearness to @x. If @y is always 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) roundup((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
