/*
   * Copyright 2013 Broadcom Corporation.
   *
   * SPDX-License-Identifier:      GPL-2.0+
   */
  
  /*
   * Bitfield operations
   *
   * These are generic bitfield operations which allow manipulation of variable
   * width bitfields within a word. One use of this would be to use data tables
   * to determine how to reprogram fields within R/W hardware registers.
   *
   * Example:
   *
   *            old_reg_val
   * +--------+----+---+--+-----+----------+
   * |        |    |   |  | old |          |
   * +--------+----+---+--+-----+----------+
   *
   *            new_reg_val
   * +--------+----+---+--+-----+----------+
   * |        |    |   |  | new |          |
   * +--------+----+---+--+-----+----------+
   *
   * mask = bitfield_mask(10, 5);
   * old = bitfield_extract(old_reg_val, 10, 5);
   * new_reg_val = bitfield_replace(old_reg_val, 10, 5, new);
   *

   * or
   *
   * mask = bitfield_mask(10, 5);
   * old = bitfield_extract_by_mask(old_reg_val, mask);
   * new_reg_val = bitfield_replace_by_mask(old_reg_val, mask, new);
   *

   * The numbers 10 and 5 could for example come from data
   * tables which describe all bitfields in all registers.
   */
  
  #include <linux/types.h>
  
  /* Produces a mask of set bits covering a range of a uint value */
  static inline uint bitfield_mask(uint shift, uint width)
  {
  	return ((1 << width) - 1) << shift;
  }
  
  /* Extract the value of a bitfield found within a given register value */
  static inline uint bitfield_extract(uint reg_val, uint shift, uint width)
  {
  	return (reg_val & bitfield_mask(shift, width)) >> shift;
  }
  
  /*
   * Replace the value of a bitfield found within a given register value
   * Returns the newly modified uint value with the replaced field.
   */
  static inline uint bitfield_replace(uint reg_val, uint shift, uint width,
  				    uint bitfield_val)
  {
  	uint mask = bitfield_mask(shift, width);

  	return (reg_val & ~mask) | ((bitfield_val << shift) & mask);

  }

  
  /* Produces a shift of the bitfield given a mask */
  static inline uint bitfield_shift(uint mask)
  {
  	return mask ? ffs(mask) - 1 : 0;
  }
  
  /* Extract the value of a bitfield found within a given register value */
  static inline uint bitfield_extract_by_mask(uint reg_val, uint mask)
  {
  	uint shift = bitfield_shift(mask);
  
  	return (reg_val & mask) >> shift;
  }
  
  /*
   * Replace the value of a bitfield found within a given register value
   * Returns the newly modified uint value with the replaced field.
   */
  static inline uint bitfield_replace_by_mask(uint reg_val, uint mask,
  					    uint bitfield_val)
  {
  	uint shift = bitfield_shift(mask);
  
  	return (reg_val & ~mask) | ((bitfield_val << shift) & mask);
  }