lib/reciprocal_div.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/kernel.h>
   3 #include <asm/div64.h>
   4 #include <linux/reciprocal_div.h>
   5 #include <linux/export.h>
   6
   7 /*
   8  * For a description of the algorithm please have a look at
   9  * include/linux/reciprocal_div.h
  10  */
  11
  12 struct reciprocal_value reciprocal_value(u32 d)
  13 {
  14         struct reciprocal_value R;
  15         u64 m;
  16         int l;
  17
  18         l = fls(d - 1);
  19         m = ((1ULL << 32) * ((1ULL << l) - d));
  20         do_div(m, d);
  21         ++m;
  22         R.m = (u32)m;
  23         R.sh1 = min(l, 1);
  24         R.sh2 = max(l - 1, 0);
  25
  26         return R;
  27 }
  28 EXPORT_SYMBOL(reciprocal_value);