/*
   * lib/bitmap.c
   * Helper functions for bitmap.h.
   *
   * This source code is licensed under the GNU General Public License,
   * Version 2.  See the file COPYING for more details.
   */
  #include <linux/module.h>
  #include <linux/ctype.h>
  #include <linux/errno.h>
  #include <linux/bitmap.h>
  #include <linux/bitops.h>
  #include <asm/uaccess.h>
  
  /*
   * bitmaps provide an array of bits, implemented using an an
   * array of unsigned longs.  The number of valid bits in a
   * given bitmap does _not_ need to be an exact multiple of
   * BITS_PER_LONG.
   *
   * The possible unused bits in the last, partially used word
   * of a bitmap are 'don't care'.  The implementation makes
   * no particular effort to keep them zero.  It ensures that
   * their value will not affect the results of any operation.
   * The bitmap operations that return Boolean (bitmap_empty,
   * for example) or scalar (bitmap_weight, for example) results
   * carefully filter out these unused bits from impacting their
   * results.
   *
   * These operations actually hold to a slightly stronger rule:
   * if you don't input any bitmaps to these ops that have some
   * unused bits set, then they won't output any set unused bits
   * in output bitmaps.
   *
   * The byte ordering of bitmaps is more natural on little
   * endian architectures.  See the big-endian headers
   * include/asm-ppc64/bitops.h and include/asm-s390/bitops.h
   * for the best explanations of this ordering.
   */
  
  int __bitmap_empty(const unsigned long *bitmap, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if (bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_empty);
  
  int __bitmap_full(const unsigned long *bitmap, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (~bitmap[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if (~bitmap[k] & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_full);
  
  int __bitmap_equal(const unsigned long *bitmap1,
  		const unsigned long *bitmap2, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] != bitmap2[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] ^ bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_equal);
  
  void __bitmap_complement(unsigned long *dst, const unsigned long *src, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		dst[k] = ~src[k];
  
  	if (bits % BITS_PER_LONG)
  		dst[k] = ~src[k] & BITMAP_LAST_WORD_MASK(bits);
  }
  EXPORT_SYMBOL(__bitmap_complement);
  
  /*
   * __bitmap_shift_right - logical right shift of the bits in a bitmap
   *   @dst - destination bitmap
   *   @src - source bitmap
   *   @nbits - shift by this many bits
   *   @bits - bitmap size, in bits
   *
   * Shifting right (dividing) means moving bits in the MS -> LS bit
   * direction.  Zeros are fed into the vacated MS positions and the
   * LS bits shifted off the bottom are lost.
   */
  void __bitmap_shift_right(unsigned long *dst,
  			const unsigned long *src, int shift, int bits)
  {
  	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
  	int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
  	unsigned long mask = (1UL << left) - 1;
  	for (k = 0; off + k < lim; ++k) {
  		unsigned long upper, lower;
  
  		/*
  		 * If shift is not word aligned, take lower rem bits of
  		 * word above and make them the top rem bits of result.
  		 */
  		if (!rem || off + k + 1 >= lim)
  			upper = 0;
  		else {
  			upper = src[off + k + 1];
  			if (off + k + 1 == lim - 1 && left)
  				upper &= mask;
  		}
  		lower = src[off + k];
  		if (left && off + k == lim - 1)
  			lower &= mask;
  		dst[k] = upper << (BITS_PER_LONG - rem) | lower >> rem;
  		if (left && k == lim - 1)
  			dst[k] &= mask;
  	}
  	if (off)
  		memset(&dst[lim - off], 0, off*sizeof(unsigned long));
  }
  EXPORT_SYMBOL(__bitmap_shift_right);
  
  
  /*
   * __bitmap_shift_left - logical left shift of the bits in a bitmap
   *   @dst - destination bitmap
   *   @src - source bitmap
   *   @nbits - shift by this many bits
   *   @bits - bitmap size, in bits
   *
   * Shifting left (multiplying) means moving bits in the LS -> MS
   * direction.  Zeros are fed into the vacated LS bit positions
   * and those MS bits shifted off the top are lost.
   */
  
  void __bitmap_shift_left(unsigned long *dst,
  			const unsigned long *src, int shift, int bits)
  {
  	int k, lim = BITS_TO_LONGS(bits), left = bits % BITS_PER_LONG;
  	int off = shift/BITS_PER_LONG, rem = shift % BITS_PER_LONG;
  	for (k = lim - off - 1; k >= 0; --k) {
  		unsigned long upper, lower;
  
  		/*
  		 * If shift is not word aligned, take upper rem bits of
  		 * word below and make them the bottom rem bits of result.
  		 */
  		if (rem && k > 0)
  			lower = src[k - 1];
  		else
  			lower = 0;
  		upper = src[k];
  		if (left && k == lim - 1)
  			upper &= (1UL << left) - 1;
  		dst[k + off] = lower  >> (BITS_PER_LONG - rem) | upper << rem;
  		if (left && k + off == lim - 1)
  			dst[k + off] &= (1UL << left) - 1;
  	}
  	if (off)
  		memset(dst, 0, off*sizeof(unsigned long));
  }
  EXPORT_SYMBOL(__bitmap_shift_left);
  
  void __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);
  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] & bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_and);
  
  void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);
  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] | bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_or);
  
  void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);
  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] ^ bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_xor);
  
  void __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k;
  	int nr = BITS_TO_LONGS(bits);
  
  	for (k = 0; k < nr; k++)
  		dst[k] = bitmap1[k] & ~bitmap2[k];
  }
  EXPORT_SYMBOL(__bitmap_andnot);
  
  int __bitmap_intersects(const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] & bitmap2[k])
  			return 1;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 1;
  	return 0;
  }
  EXPORT_SYMBOL(__bitmap_intersects);
  
  int __bitmap_subset(const unsigned long *bitmap1,
  				const unsigned long *bitmap2, int bits)
  {
  	int k, lim = bits/BITS_PER_LONG;
  	for (k = 0; k < lim; ++k)
  		if (bitmap1[k] & ~bitmap2[k])
  			return 0;
  
  	if (bits % BITS_PER_LONG)
  		if ((bitmap1[k] & ~bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
  			return 0;
  	return 1;
  }
  EXPORT_SYMBOL(__bitmap_subset);

  int __bitmap_weight(const unsigned long *bitmap, int bits)
  {
  	int k, w = 0, lim = bits/BITS_PER_LONG;
  
  	for (k = 0; k < lim; k++)

  		w += hweight_long(bitmap[k]);

  
  	if (bits % BITS_PER_LONG)

  		w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits));

  
  	return w;
  }

  EXPORT_SYMBOL(__bitmap_weight);
  
  /*
   * Bitmap printing & parsing functions: first version by Bill Irwin,
   * second version by Paul Jackson, third by Joe Korty.
   */
  
  #define CHUNKSZ				32
  #define nbits_to_hold_value(val)	fls(val)

  #define unhex(c)			(isdigit(c) ? (c - '0') : (toupper(c) - 'A' + 10))
  #define BASEDEC 10		/* fancier cpuset lists input in decimal */
  
  /**
   * bitmap_scnprintf - convert bitmap to an ASCII hex string.
   * @buf: byte buffer into which string is placed
   * @buflen: reserved size of @buf, in bytes
   * @maskp: pointer to bitmap to convert
   * @nmaskbits: size of bitmap, in bits
   *
   * Exactly @nmaskbits bits are displayed.  Hex digits are grouped into
   * comma-separated sets of eight digits per set.
   */
  int bitmap_scnprintf(char *buf, unsigned int buflen,
  	const unsigned long *maskp, int nmaskbits)
  {
  	int i, word, bit, len = 0;
  	unsigned long val;
  	const char *sep = "";
  	int chunksz;
  	u32 chunkmask;
  
  	chunksz = nmaskbits & (CHUNKSZ - 1);
  	if (chunksz == 0)
  		chunksz = CHUNKSZ;

  	i = ALIGN(nmaskbits, CHUNKSZ) - CHUNKSZ;

  	for (; i >= 0; i -= CHUNKSZ) {
  		chunkmask = ((1ULL << chunksz) - 1);
  		word = i / BITS_PER_LONG;
  		bit = i % BITS_PER_LONG;
  		val = (maskp[word] >> bit) & chunkmask;
  		len += scnprintf(buf+len, buflen-len, "%s%0*lx", sep,
  			(chunksz+3)/4, val);
  		chunksz = CHUNKSZ;
  		sep = ",";
  	}
  	return len;
  }
  EXPORT_SYMBOL(bitmap_scnprintf);
  
  /**
   * bitmap_parse - convert an ASCII hex string into a bitmap.
   * @buf: pointer to buffer in user space containing string.
   * @buflen: buffer size in bytes.  If string is smaller than this
   *    then it must be terminated with a \0.
   * @maskp: pointer to bitmap array that will contain result.
   * @nmaskbits: size of bitmap, in bits.
   *
   * Commas group hex digits into chunks.  Each chunk defines exactly 32
   * bits of the resultant bitmask.  No chunk may specify a value larger
   * than 32 bits (-EOVERFLOW), and if a chunk specifies a smaller value
   * then leading 0-bits are prepended.  -EINVAL is returned for illegal
   * characters and for grouping errors such as "1,,5", ",44", "," and "".
   * Leading and trailing whitespace accepted, but not embedded whitespace.
   */
  int bitmap_parse(const char __user *ubuf, unsigned int ubuflen,
          unsigned long *maskp, int nmaskbits)
  {
  	int c, old_c, totaldigits, ndigits, nchunks, nbits;
  	u32 chunk;
  
  	bitmap_zero(maskp, nmaskbits);
  
  	nchunks = nbits = totaldigits = c = 0;
  	do {
  		chunk = ndigits = 0;
  
  		/* Get the next chunk of the bitmap */
  		while (ubuflen) {
  			old_c = c;
  			if (get_user(c, ubuf++))
  				return -EFAULT;
  			ubuflen--;
  			if (isspace(c))
  				continue;
  
  			/*
  			 * If the last character was a space and the current
  			 * character isn't '\0', we've got embedded whitespace.
  			 * This is a no-no, so throw an error.
  			 */
  			if (totaldigits && c && isspace(old_c))
  				return -EINVAL;
  
  			/* A '\0' or a ',' signal the end of the chunk */
  			if (c == '\0' || c == ',')
  				break;
  
  			if (!isxdigit(c))
  				return -EINVAL;
  
  			/*
  			 * Make sure there are at least 4 free bits in 'chunk'.
  			 * If not, this hexdigit will overflow 'chunk', so
  			 * throw an error.
  			 */
  			if (chunk & ~((1UL << (CHUNKSZ - 4)) - 1))
  				return -EOVERFLOW;
  
  			chunk = (chunk << 4) | unhex(c);
  			ndigits++; totaldigits++;
  		}
  		if (ndigits == 0)
  			return -EINVAL;
  		if (nchunks == 0 && chunk == 0)
  			continue;
  
  		__bitmap_shift_left(maskp, maskp, CHUNKSZ, nmaskbits);
  		*maskp |= chunk;
  		nchunks++;
  		nbits += (nchunks == 1) ? nbits_to_hold_value(chunk) : CHUNKSZ;
  		if (nbits > nmaskbits)
  			return -EOVERFLOW;
  	} while (ubuflen && c == ',');
  
  	return 0;
  }
  EXPORT_SYMBOL(bitmap_parse);
  
  /*
   * bscnl_emit(buf, buflen, rbot, rtop, bp)
   *
   * Helper routine for bitmap_scnlistprintf().  Write decimal number
   * or range to buf, suppressing output past buf+buflen, with optional
   * comma-prefix.  Return len of what would be written to buf, if it
   * all fit.
   */
  static inline int bscnl_emit(char *buf, int buflen, int rbot, int rtop, int len)
  {
  	if (len > 0)
  		len += scnprintf(buf + len, buflen - len, ",");
  	if (rbot == rtop)
  		len += scnprintf(buf + len, buflen - len, "%d", rbot);
  	else
  		len += scnprintf(buf + len, buflen - len, "%d-%d", rbot, rtop);
  	return len;
  }
  
  /**
   * bitmap_scnlistprintf - convert bitmap to list format ASCII string
   * @buf: byte buffer into which string is placed
   * @buflen: reserved size of @buf, in bytes
   * @maskp: pointer to bitmap to convert
   * @nmaskbits: size of bitmap, in bits
   *
   * Output format is a comma-separated list of decimal numbers and
   * ranges.  Consecutively set bits are shown as two hyphen-separated
   * decimal numbers, the smallest and largest bit numbers set in
   * the range.  Output format is compatible with the format
   * accepted as input by bitmap_parselist().
   *
   * The return value is the number of characters which would be
   * generated for the given input, excluding the trailing '\0', as
   * per ISO C99.
   */
  int bitmap_scnlistprintf(char *buf, unsigned int buflen,
  	const unsigned long *maskp, int nmaskbits)
  {
  	int len = 0;
  	/* current bit is 'cur', most recently seen range is [rbot, rtop] */
  	int cur, rbot, rtop;
  
  	rbot = cur = find_first_bit(maskp, nmaskbits);
  	while (cur < nmaskbits) {
  		rtop = cur;
  		cur = find_next_bit(maskp, nmaskbits, cur+1);
  		if (cur >= nmaskbits || cur > rtop + 1) {
  			len = bscnl_emit(buf, buflen, rbot, rtop, len);
  			rbot = cur;
  		}
  	}
  	return len;
  }
  EXPORT_SYMBOL(bitmap_scnlistprintf);
  
  /**
   * bitmap_parselist - convert list format ASCII string to bitmap
   * @buf: read nul-terminated user string from this buffer
   * @mask: write resulting mask here
   * @nmaskbits: number of bits in mask to be written
   *
   * Input format is a comma-separated list of decimal numbers and
   * ranges.  Consecutively set bits are shown as two hyphen-separated
   * decimal numbers, the smallest and largest bit numbers set in
   * the range.
   *
   * Returns 0 on success, -errno on invalid input strings:
   *    -EINVAL:   second number in range smaller than first
   *    -EINVAL:   invalid character in string
   *    -ERANGE:   bit number specified too large for mask
   */
  int bitmap_parselist(const char *bp, unsigned long *maskp, int nmaskbits)
  {
  	unsigned a, b;
  
  	bitmap_zero(maskp, nmaskbits);
  	do {
  		if (!isdigit(*bp))
  			return -EINVAL;
  		b = a = simple_strtoul(bp, (char **)&bp, BASEDEC);
  		if (*bp == '-') {
  			bp++;
  			if (!isdigit(*bp))
  				return -EINVAL;
  			b = simple_strtoul(bp, (char **)&bp, BASEDEC);
  		}
  		if (!(a <= b))
  			return -EINVAL;
  		if (b >= nmaskbits)
  			return -ERANGE;
  		while (a <= b) {
  			set_bit(a, maskp);
  			a++;
  		}
  		if (*bp == ',')
  			bp++;
  	} while (*bp != '\0' && *bp != '
  ');
  	return 0;
  }
  EXPORT_SYMBOL(bitmap_parselist);

  /*
   * bitmap_pos_to_ord(buf, pos, bits)
   *	@buf: pointer to a bitmap
   *	@pos: a bit position in @buf (0 <= @pos < @bits)
   *	@bits: number of valid bit positions in @buf
   *
   * Map the bit at position @pos in @buf (of length @bits) to the
   * ordinal of which set bit it is.  If it is not set or if @pos

   * is not a valid bit position, map to -1.

   *
   * If for example, just bits 4 through 7 are set in @buf, then @pos
   * values 4 through 7 will get mapped to 0 through 3, respectively,
   * and other @pos values will get mapped to 0.  When @pos value 7
   * gets mapped to (returns) @ord value 3 in this example, that means
   * that bit 7 is the 3rd (starting with 0th) set bit in @buf.
   *
   * The bit positions 0 through @bits are valid positions in @buf.
   */
  static int bitmap_pos_to_ord(const unsigned long *buf, int pos, int bits)
  {

  	int i, ord;

  	if (pos < 0 || pos >= bits || !test_bit(pos, buf))
  		return -1;

  	i = find_first_bit(buf, bits);
  	ord = 0;
  	while (i < pos) {
  		i = find_next_bit(buf, bits, i + 1);
  	     	ord++;

  	}

  	BUG_ON(i != pos);

  	return ord;
  }
  
  /**
   * bitmap_ord_to_pos(buf, ord, bits)
   *	@buf: pointer to bitmap
   *	@ord: ordinal bit position (n-th set bit, n >= 0)
   *	@bits: number of valid bit positions in @buf
   *
   * Map the ordinal offset of bit @ord in @buf to its position in @buf.

   * Value of @ord should be in range 0 <= @ord < weight(buf), else
   * results are undefined.

   *
   * If for example, just bits 4 through 7 are set in @buf, then @ord
   * values 0 through 3 will get mapped to 4 through 7, respectively,

   * and all other @ord values return undefined values.  When @ord value 3

   * gets mapped to (returns) @pos value 7 in this example, that means
   * that the 3rd set bit (starting with 0th) is at position 7 in @buf.
   *
   * The bit positions 0 through @bits are valid positions in @buf.
   */
  static int bitmap_ord_to_pos(const unsigned long *buf, int ord, int bits)
  {
  	int pos = 0;
  
  	if (ord >= 0 && ord < bits) {
  		int i;
  
  		for (i = find_first_bit(buf, bits);
  		     i < bits && ord > 0;
  		     i = find_next_bit(buf, bits, i + 1))
  	     		ord--;
  		if (i < bits && ord == 0)
  			pos = i;
  	}
  
  	return pos;
  }
  
  /**
   * bitmap_remap - Apply map defined by a pair of bitmaps to another bitmap

   *	@dst: remapped result

   *	@src: subset to be remapped

   *	@old: defines domain of map
   *	@new: defines range of map
   *	@bits: number of bits in each of these bitmaps
   *
   * Let @old and @new define a mapping of bit positions, such that
   * whatever position is held by the n-th set bit in @old is mapped
   * to the n-th set bit in @new.  In the more general case, allowing
   * for the possibility that the weight 'w' of @new is less than the
   * weight of @old, map the position of the n-th set bit in @old to
   * the position of the m-th set bit in @new, where m == n % w.
   *

   * If either of the @old and @new bitmaps are empty, or if @src and
   * @dst point to the same location, then this routine copies @src
   * to @dst.

   *

   * The positions of unset bits in @old are mapped to themselves
   * (the identify map).

   *
   * Apply the above specified mapping to @src, placing the result in
   * @dst, clearing any bits previously set in @dst.
   *

   * For example, lets say that @old has bits 4 through 7 set, and
   * @new has bits 12 through 15 set.  This defines the mapping of bit
   * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other

   * bit positions unchanged.  So if say @src comes into this routine
   * with bits 1, 5 and 7 set, then @dst should leave with bits 1,
   * 13 and 15 set.

   */
  void bitmap_remap(unsigned long *dst, const unsigned long *src,
  		const unsigned long *old, const unsigned long *new,
  		int bits)
  {

  	int oldbit, w;

  	if (dst == src)		/* following doesn't handle inplace remaps */
  		return;

  	bitmap_zero(dst, bits);

  
  	w = bitmap_weight(new, bits);
  	for (oldbit = find_first_bit(src, bits);
  	     oldbit < bits;
  	     oldbit = find_next_bit(src, bits, oldbit + 1)) {
  	     	int n = bitmap_pos_to_ord(old, oldbit, bits);
  		if (n < 0 || w == 0)
  			set_bit(oldbit, dst);	/* identity map */
  		else
  			set_bit(bitmap_ord_to_pos(new, n % w, bits), dst);

  	}
  }
  EXPORT_SYMBOL(bitmap_remap);
  
  /**
   * bitmap_bitremap - Apply map defined by a pair of bitmaps to a single bit
   *	@oldbit - bit position to be mapped
   *      @old: defines domain of map
   *      @new: defines range of map
   *      @bits: number of bits in each of these bitmaps
   *
   * Let @old and @new define a mapping of bit positions, such that
   * whatever position is held by the n-th set bit in @old is mapped
   * to the n-th set bit in @new.  In the more general case, allowing
   * for the possibility that the weight 'w' of @new is less than the
   * weight of @old, map the position of the n-th set bit in @old to
   * the position of the m-th set bit in @new, where m == n % w.
   *

   * The positions of unset bits in @old are mapped to themselves
   * (the identify map).

   *
   * Apply the above specified mapping to bit position @oldbit, returning
   * the new bit position.
   *
   * For example, lets say that @old has bits 4 through 7 set, and
   * @new has bits 12 through 15 set.  This defines the mapping of bit
   * position 4 to 12, 5 to 13, 6 to 14 and 7 to 15, and of all other

   * bit positions unchanged.  So if say @oldbit is 5, then this routine
   * returns 13.

   */
  int bitmap_bitremap(int oldbit, const unsigned long *old,
  				const unsigned long *new, int bits)
  {

  	int w = bitmap_weight(new, bits);
  	int n = bitmap_pos_to_ord(old, oldbit, bits);
  	if (n < 0 || w == 0)
  		return oldbit;
  	else
  		return bitmap_ord_to_pos(new, n % w, bits);

  }
  EXPORT_SYMBOL(bitmap_bitremap);

  /*
   * Common code for bitmap_*_region() routines.
   *	bitmap: array of unsigned longs corresponding to the bitmap
   *	pos: the beginning of the region
   *	order: region size (log base 2 of number of bits)
   *	reg_op: operation(s) to perform on that region of bitmap

   *

   * Can set, verify and/or release a region of bits in a bitmap,
   * depending on which combination of REG_OP_* flag bits is set.

   *

   * A region of a bitmap is a sequence of bits in the bitmap, of
   * some size '1 << order' (a power of two), aligned to that same
   * '1 << order' power of two.
   *
   * Returns 1 if REG_OP_ISFREE succeeds (region is all zero bits).
   * Returns 0 in all other cases and reg_ops.

   */

  
  enum {
  	REG_OP_ISFREE,		/* true if region is all zero bits */
  	REG_OP_ALLOC,		/* set all bits in region */
  	REG_OP_RELEASE,		/* clear all bits in region */
  };
  
  static int __reg_op(unsigned long *bitmap, int pos, int order, int reg_op)

  {

  	int nbits_reg;		/* number of bits in region */
  	int index;		/* index first long of region in bitmap */
  	int offset;		/* bit offset region in bitmap[index] */
  	int nlongs_reg;		/* num longs spanned by region in bitmap */

  	int nbitsinlong;	/* num bits of region in each spanned long */

  	unsigned long mask;	/* bitmask for one long of region */

  	int i;			/* scans bitmap by longs */

  	int ret = 0;		/* return value */

  	/*
  	 * Either nlongs_reg == 1 (for small orders that fit in one long)
  	 * or (offset == 0 && mask == ~0UL) (for larger multiword orders.)
  	 */
  	nbits_reg = 1 << order;
  	index = pos / BITS_PER_LONG;
  	offset = pos - (index * BITS_PER_LONG);
  	nlongs_reg = BITS_TO_LONGS(nbits_reg);
  	nbitsinlong = min(nbits_reg,  BITS_PER_LONG);

  	/*
  	 * Can't do "mask = (1UL << nbitsinlong) - 1", as that
  	 * overflows if nbitsinlong == BITS_PER_LONG.
  	 */

  	mask = (1UL << (nbitsinlong - 1));

  	mask += mask - 1;

  	mask <<= offset;

  	switch (reg_op) {
  	case REG_OP_ISFREE:
  		for (i = 0; i < nlongs_reg; i++) {
  			if (bitmap[index + i] & mask)
  				goto done;
  		}
  		ret = 1;	/* all bits in region free (zero) */
  		break;
  
  	case REG_OP_ALLOC:
  		for (i = 0; i < nlongs_reg; i++)
  			bitmap[index + i] |= mask;
  		break;
  
  	case REG_OP_RELEASE:
  		for (i = 0; i < nlongs_reg; i++)
  			bitmap[index + i] &= ~mask;
  		break;

  	}

  done:
  	return ret;
  }
  
  /**
   * bitmap_find_free_region - find a contiguous aligned mem region
   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@bits: number of bits in the bitmap
   *	@order: region size (log base 2 of number of bits) to find
   *
   * Find a region of free (zero) bits in a @bitmap of @bits bits and
   * allocate them (set them to one).  Only consider regions of length
   * a power (@order) of two, aligned to that power of two, which
   * makes the search algorithm much faster.
   *
   * Return the bit offset in bitmap of the allocated region,
   * or -errno on failure.
   */
  int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)
  {
  	int pos;		/* scans bitmap by regions of size order */
  
  	for (pos = 0; pos < bits; pos += (1 << order))
  		if (__reg_op(bitmap, pos, order, REG_OP_ISFREE))
  			break;
  	if (pos == bits)
  		return -ENOMEM;
  	__reg_op(bitmap, pos, order, REG_OP_ALLOC);
  	return pos;

  }
  EXPORT_SYMBOL(bitmap_find_free_region);
  
  /**

   * bitmap_release_region - release allocated bitmap region

   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@pos: beginning of bit region to release
   *	@order: region size (log base 2 of number of bits) to release

   *
   * This is the complement to __bitmap_find_free_region and releases
   * the found region (by clearing it in the bitmap).

   *
   * No return value.

   */
  void bitmap_release_region(unsigned long *bitmap, int pos, int order)
  {

  	__reg_op(bitmap, pos, order, REG_OP_RELEASE);

  }
  EXPORT_SYMBOL(bitmap_release_region);

  /**
   * bitmap_allocate_region - allocate bitmap region

   *	@bitmap: array of unsigned longs corresponding to the bitmap
   *	@pos: beginning of bit region to allocate
   *	@order: region size (log base 2 of number of bits) to allocate

   *
   * Allocate (set bits in) a specified region of a bitmap.

   *

   * Return 0 on success, or -EBUSY if specified region wasn't
   * free (not all bits were zero).
   */

  int bitmap_allocate_region(unsigned long *bitmap, int pos, int order)
  {

  	if (!__reg_op(bitmap, pos, order, REG_OP_ISFREE))
  		return -EBUSY;
  	__reg_op(bitmap, pos, order, REG_OP_ALLOC);

  	return 0;
  }
  EXPORT_SYMBOL(bitmap_allocate_region);