lib/reciprocal_div.c

   1 #include <linux/kernel.h>
   2 #include <asm/div64.h>
   3 #include <linux/reciprocal_div.h>
   4 #include <linux/export.h>
   5
   6 /*
   7  * For a description of the algorithm please have a look at
   8  * include/linux/reciprocal_div.h
   9  */
  10
  11 struct reciprocal_value reciprocal_value(u32 d)
  12 {
  13         struct reciprocal_value R;
  14         u64 m;
  15         int l;
  16
  17         l = fls(d - 1);
  18         m = ((1ULL << 32) * ((1ULL << l) - d));
  19         do_div(m, d);
  20         ++m;
  21         R.m = (u32)m;
  22         R.sh1 = min(l, 1);
  23         R.sh2 = max(l - 1, 0);
  24
  25         return R;
  26 }
  27 EXPORT_SYMBOL(reciprocal_value);