#ifndef _LINUX_RECIPROCAL_DIV_H
  #define _LINUX_RECIPROCAL_DIV_H
  
  #include <linux/types.h>
  
  /*
   * This file describes reciprocical division.
   *
   * This optimizes the (A/B) problem, when A and B are two u32
   * and B is a known value (but not known at compile time)
   *
   * The math principle used is :
   *   Let RECIPROCAL_VALUE(B) be (((1LL << 32) + (B - 1))/ B)
   *   Then A / B = (u32)(((u64)(A) * (R)) >> 32)
   *
   * This replaces a divide by a multiply (and a shift), and
   * is generally less expensive in CPU cycles.
   */
  
  /*
   * Computes the reciprocal value (R) for the value B of the divisor.
   * Should not be called before each reciprocal_divide(),
   * or else the performance is slower than a normal divide.
   */
  extern u32 reciprocal_value(u32 B);
  
  
  static inline u32 reciprocal_divide(u32 A, u32 R)
  {
  	return (u32)(((u64)A * R) >> 32);
  }
  #endif