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@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]
---
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>
