Add macros to round to nearest specified power of 2. Two macros are added : round_closest_up and round_closest_down which round up to nearest multiple of 2 with a preference to round up or round down respectively if there are two possible nearest values to the given number. This patch is inspired from the Mentor Graphics IPU driver [1] which uses similar macro locally and which can be updated 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 Signed-off-by: Devarsh Thakkar <devarsht@xxxxxx> --- V1->V6 (No change, patch introduced in V7) --- include/linux/math.h | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/include/linux/math.h b/include/linux/math.h index dd4152711de7..82ee3265c910 100644 --- a/include/linux/math.h +++ b/include/linux/math.h @@ -34,6 +34,42 @@ */ #define round_down(x, y) ((x) & ~__round_mask(x, y)) +/** + * round_closest_up - round to nearest specified power of 2 with preference + * to rounding up + * @x: the value to round + * @y: multiple to round to (must be a power of 2) + * + * Rounds @x to nearest multiple of @y (which must be a power of 2). + * The rounded value can be greater than or less than @x depending + * upon it's nearness to @x. If there are two nearest possible values, + * then preference will be given to the greater value. + * + * 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 to nearest specified power of 2 with preference + * to rounding down + * @x: the value to round + * @y: multiple to round down to (must be a power of 2) + * + * Rounds @x to nearest multiple of @y (which must be a power of 2). + * The rounded value can be greater than or less than @x depending + * upon it's nearness to @x. If there are two nearest possible values, + * then preference will be given to the lesser value. + * + * 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) \ -- 2.39.1
