text: /*
   * Copyright (c) 2004, 2005 David Young.  All rights reserved.
   *
   * Programmed for NetBSD by David Young.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in the
   *    documentation and/or other materials provided with the distribution.
   * 3. The name of David Young may not be used to endorse or promote
   *    products derived from this software without specific prior
   *    written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY David Young ``AS IS'' AND ANY
   * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
   * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL David
   * Young BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
   * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
   * OF SUCH DAMAGE.
   *
   * $DragonFly: src/sys/dev/netif/bwi/bitops.h,v 1.1 2007/09/08 06:15:54 sephe Exp $
   * $FreeBSD: releng/11.1/sys/dev/bwi/bitops.h 191762 2009-05-03 04:01:43Z imp $
   */
  
  #ifndef _BITOPS_H
  #define _BITOPS_H
  
  /*
   * __BIT(n): Return a bitmask with bit m set, where the least
   *           significant bit is bit 0.
   *
   * __BITS(m, n): Return a bitmask with bits m through n, inclusive,
   *               set.  It does not matter whether m>n or m<=n.  The
   *               least significant bit is bit 0.
   *
   * A "bitfield" is a span of consecutive bits defined by a bitmask,
   * where 1s select the bits in the bitfield.  __SHIFTIN, __SHIFTOUT,
   * and SHIFTOUT_MASK help read and write bitfields from device registers.
   *
   * __SHIFTIN(v, mask): Left-shift bits `v' into the bitfield
   *                     defined by `mask', and return them.  No
   *                     side-effects.
   *
   * __SHIFTOUT(v, mask): Extract and return the bitfield selected
   *                      by `mask' from `v', right-shifting the
   *                      bits so that the rightmost selected bit
   *                      is at bit 0.  No side-effects.
   *
   * __SHIFTOUT_MASK(mask): Right-shift the bits in `mask' so that
   *                        the rightmost non-zero bit is at bit
   *                        0.  This is useful for finding the
   *                        greatest unsigned value that a bitfield
   *                        can hold.  No side-effects.  Note that
   *                        SHIFTOUT_MASK(m) = SHIFTOUT(m, m).
   */
  
  /* __BIT(n): nth bit, where __BIT(0) == 0x1. */
  #define	__BIT(__n) (((__n) == 32) ? 0 : ((uint32_t)1 << (__n)))
  
  /* __BITS(m, n): bits m through n, m < n. */
  #define	__BITS(__m, __n)	\
  	((__BIT(MAX((__m), (__n)) + 1) - 1) ^ (__BIT(MIN((__m), (__n))) - 1))
  
  /* Find least significant bit that is set */
  #define	__LOWEST_SET_BIT(__mask) ((((__mask) - 1) & (__mask)) ^ (__mask))
  
  #define	__SHIFTOUT(__x, __mask) (((__x) & (__mask)) / __LOWEST_SET_BIT(__mask))
  #define	__SHIFTIN(__x, __mask) ((__x) * __LOWEST_SET_BIT(__mask))
  #define	__SHIFTOUT_MASK(__mask) __SHIFTOUT((__mask), (__mask))
  
  #endif	/* !_BITOPS_H */
  