include: kernel.h: port find_closest() from Linux

The find_closest() macro can be used to find an element in a sorted
array that is closest to an input value. Bring in this macro from
Linux v6.3-rc1-2-g8ca09d5fa354.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 3e71d61..5cd6c9d 100644 (file)
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -284,4 +284,28 @@
        offsetof(struct structure, member) == (offset), \
        "`struct " #structure "` offset for `" #member "` is not " #offset)
 
+#define __find_closest(x, a, as, op)                                   \
+({                                                                     \
+       typeof(as) __fc_i, __fc_as = (as) - 1;                          \
+       typeof(x) __fc_x = (x);                                         \
+       typeof(*a) const *__fc_a = (a);                                 \
+       for (__fc_i = 0; __fc_i < __fc_as; __fc_i++) {                  \
+               if (__fc_x op DIV_ROUND_CLOSEST(__fc_a[__fc_i] +        \
+                                               __fc_a[__fc_i + 1], 2)) \
+                       break;                                          \
+       }                                                               \
+       (__fc_i);                                                       \
+})
+
+/**
+ * find_closest - locate the closest element in a sorted array
+ * @x: The reference value.
+ * @a: The array in which to look for the closest element. Must be sorted
+ *  in ascending order.
+ * @as: Size of 'a'.
+ *
+ * Returns the index of the element closest to 'x'.
+ */
+#define find_closest(x, a, as) __find_closest(x, a, as, <=)
+
 #endif