root/include/linux/bitmap.h

INCLUDED FROM

DEFINITIONS

1. bitmap_find_next_zero_area
2. bitmap_zero
3. bitmap_fill
4. bitmap_copy
5. bitmap_copy_clear_tail
6. bitmap_and
7. bitmap_or
8. bitmap_xor
9. bitmap_andnot
10. bitmap_complement
11. bitmap_equal
12. bitmap_or_equal
13. bitmap_intersects
14. bitmap_subset
15. bitmap_empty
16. bitmap_full
17. bitmap_weight
18. bitmap_set
19. bitmap_clear
20. bitmap_shift_right
21. bitmap_shift_left
22. bitmap_parse
23. bitmap_from_u64

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_BITMAP_H
   3 #define __LINUX_BITMAP_H
   4 
   5 #ifndef __ASSEMBLY__
   6 
   7 #include <linux/types.h>
   8 #include <linux/bitops.h>
   9 #include <linux/string.h>
  10 #include <linux/kernel.h>
  11 
  12 /*
  13  * bitmaps provide bit arrays that consume one or more unsigned
  14  * longs.  The bitmap interface and available operations are listed
  15  * here, in bitmap.h
  16  *
  17  * Function implementations generic to all architectures are in
  18  * lib/bitmap.c.  Functions implementations that are architecture
  19  * specific are in various include/asm-<arch>/bitops.h headers
  20  * and other arch/<arch> specific files.
  21  *
  22  * See lib/bitmap.c for more details.
  23  */
  24 
  25 /**
  26  * DOC: bitmap overview
  27  *
  28  * The available bitmap operations and their rough meaning in the
  29  * case that the bitmap is a single unsigned long are thus:
  30  *
  31  * The generated code is more efficient when nbits is known at
  32  * compile-time and at most BITS_PER_LONG.
  33  *
  34  * ::
  35  *
  36  *  bitmap_zero(dst, nbits)                     *dst = 0UL
  37  *  bitmap_fill(dst, nbits)                     *dst = ~0UL
  38  *  bitmap_copy(dst, src, nbits)                *dst = *src
  39  *  bitmap_and(dst, src1, src2, nbits)          *dst = *src1 & *src2
  40  *  bitmap_or(dst, src1, src2, nbits)           *dst = *src1 | *src2
  41  *  bitmap_xor(dst, src1, src2, nbits)          *dst = *src1 ^ *src2
  42  *  bitmap_andnot(dst, src1, src2, nbits)       *dst = *src1 & ~(*src2)
  43  *  bitmap_complement(dst, src, nbits)          *dst = ~(*src)
  44  *  bitmap_equal(src1, src2, nbits)             Are *src1 and *src2 equal?
  45  *  bitmap_intersects(src1, src2, nbits)        Do *src1 and *src2 overlap?
  46  *  bitmap_subset(src1, src2, nbits)            Is *src1 a subset of *src2?
  47  *  bitmap_empty(src, nbits)                    Are all bits zero in *src?
  48  *  bitmap_full(src, nbits)                     Are all bits set in *src?
  49  *  bitmap_weight(src, nbits)                   Hamming Weight: number set bits
  50  *  bitmap_set(dst, pos, nbits)                 Set specified bit area
  51  *  bitmap_clear(dst, pos, nbits)               Clear specified bit area
  52  *  bitmap_find_next_zero_area(buf, len, pos, n, mask)  Find bit free area
  53  *  bitmap_find_next_zero_area_off(buf, len, pos, n, mask)  as above
  54  *  bitmap_shift_right(dst, src, n, nbits)      *dst = *src >> n
  55  *  bitmap_shift_left(dst, src, n, nbits)       *dst = *src << n
  56  *  bitmap_remap(dst, src, old, new, nbits)     *dst = map(old, new)(src)
  57  *  bitmap_bitremap(oldbit, old, new, nbits)    newbit = map(old, new)(oldbit)
  58  *  bitmap_onto(dst, orig, relmap, nbits)       *dst = orig relative to relmap
  59  *  bitmap_fold(dst, orig, sz, nbits)           dst bits = orig bits mod sz
  60  *  bitmap_parse(buf, buflen, dst, nbits)       Parse bitmap dst from kernel buf
  61  *  bitmap_parse_user(ubuf, ulen, dst, nbits)   Parse bitmap dst from user buf
  62  *  bitmap_parselist(buf, dst, nbits)           Parse bitmap dst from kernel buf
  63  *  bitmap_parselist_user(buf, dst, nbits)      Parse bitmap dst from user buf
  64  *  bitmap_find_free_region(bitmap, bits, order)  Find and allocate bit region
  65  *  bitmap_release_region(bitmap, pos, order)   Free specified bit region
  66  *  bitmap_allocate_region(bitmap, pos, order)  Allocate specified bit region
  67  *  bitmap_from_arr32(dst, buf, nbits)          Copy nbits from u32[] buf to dst
  68  *  bitmap_to_arr32(buf, src, nbits)            Copy nbits from buf to u32[] dst
  69  *
  70  * Note, bitmap_zero() and bitmap_fill() operate over the region of
  71  * unsigned longs, that is, bits behind bitmap till the unsigned long
  72  * boundary will be zeroed or filled as well. Consider to use
  73  * bitmap_clear() or bitmap_set() to make explicit zeroing or filling
  74  * respectively.
  75  */
  76 
  77 /**
  78  * DOC: bitmap bitops
  79  *
  80  * Also the following operations in asm/bitops.h apply to bitmaps.::
  81  *
  82  *  set_bit(bit, addr)                  *addr |= bit
  83  *  clear_bit(bit, addr)                *addr &= ~bit
  84  *  change_bit(bit, addr)               *addr ^= bit
  85  *  test_bit(bit, addr)                 Is bit set in *addr?
  86  *  test_and_set_bit(bit, addr)         Set bit and return old value
  87  *  test_and_clear_bit(bit, addr)       Clear bit and return old value
  88  *  test_and_change_bit(bit, addr)      Change bit and return old value
  89  *  find_first_zero_bit(addr, nbits)    Position first zero bit in *addr
  90  *  find_first_bit(addr, nbits)         Position first set bit in *addr
  91  *  find_next_zero_bit(addr, nbits, bit)
  92  *                                      Position next zero bit in *addr >= bit
  93  *  find_next_bit(addr, nbits, bit)     Position next set bit in *addr >= bit
  94  *  find_next_and_bit(addr1, addr2, nbits, bit)
  95  *                                      Same as find_next_bit, but in
  96  *                                      (*addr1 & *addr2)
  97  *
  98  */
  99 
 100 /**
 101  * DOC: declare bitmap
 102  * The DECLARE_BITMAP(name,bits) macro, in linux/types.h, can be used
 103  * to declare an array named 'name' of just enough unsigned longs to
 104  * contain all bit positions from 0 to 'bits' - 1.
 105  */
 106 
 107 /*
 108  * Allocation and deallocation of bitmap.
 109  * Provided in lib/bitmap.c to avoid circular dependency.
 110  */
 111 extern unsigned long *bitmap_alloc(unsigned int nbits, gfp_t flags);
 112 extern unsigned long *bitmap_zalloc(unsigned int nbits, gfp_t flags);
 113 extern void bitmap_free(const unsigned long *bitmap);
 114 
 115 /*
 116  * lib/bitmap.c provides these functions:
 117  */
 118 
 119 extern int __bitmap_empty(const unsigned long *bitmap, unsigned int nbits);
 120 extern int __bitmap_full(const unsigned long *bitmap, unsigned int nbits);
 121 extern int __bitmap_equal(const unsigned long *bitmap1,
 122                           const unsigned long *bitmap2, unsigned int nbits);
 123 extern bool __pure __bitmap_or_equal(const unsigned long *src1,
 124                                      const unsigned long *src2,
 125                                      const unsigned long *src3,
 126                                      unsigned int nbits);
 127 extern void __bitmap_complement(unsigned long *dst, const unsigned long *src,
 128                         unsigned int nbits);
 129 extern void __bitmap_shift_right(unsigned long *dst, const unsigned long *src,
 130                                 unsigned int shift, unsigned int nbits);
 131 extern void __bitmap_shift_left(unsigned long *dst, const unsigned long *src,
 132                                 unsigned int shift, unsigned int nbits);
 133 extern int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 134                         const unsigned long *bitmap2, unsigned int nbits);
 135 extern void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 136                         const unsigned long *bitmap2, unsigned int nbits);
 137 extern void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
 138                         const unsigned long *bitmap2, unsigned int nbits);
 139 extern int __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
 140                         const unsigned long *bitmap2, unsigned int nbits);
 141 extern int __bitmap_intersects(const unsigned long *bitmap1,
 142                         const unsigned long *bitmap2, unsigned int nbits);
 143 extern int __bitmap_subset(const unsigned long *bitmap1,
 144                         const unsigned long *bitmap2, unsigned int nbits);
 145 extern int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
 146 extern void __bitmap_set(unsigned long *map, unsigned int start, int len);
 147 extern void __bitmap_clear(unsigned long *map, unsigned int start, int len);
 148 
 149 extern unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
 150                                                     unsigned long size,
 151                                                     unsigned long start,
 152                                                     unsigned int nr,
 153                                                     unsigned long align_mask,
 154                                                     unsigned long align_offset);
 155 
 156 /**
 157  * bitmap_find_next_zero_area - find a contiguous aligned zero area
 158  * @map: The address to base the search on
 159  * @size: The bitmap size in bits
 160  * @start: The bitnumber to start searching at
 161  * @nr: The number of zeroed bits we're looking for
 162  * @align_mask: Alignment mask for zero area
 163  *
 164  * The @align_mask should be one less than a power of 2; the effect is that
 165  * the bit offset of all zero areas this function finds is multiples of that
 166  * power of 2. A @align_mask of 0 means no alignment is required.
 167  */
 168 static inline unsigned long
 169 bitmap_find_next_zero_area(unsigned long *map,
 170                            unsigned long size,
 171                            unsigned long start,
 172                            unsigned int nr,
 173                            unsigned long align_mask)
 174 {
 175         return bitmap_find_next_zero_area_off(map, size, start, nr,
 176                                               align_mask, 0);
 177 }
 178 
 179 extern int __bitmap_parse(const char *buf, unsigned int buflen, int is_user,
 180                         unsigned long *dst, int nbits);
 181 extern int bitmap_parse_user(const char __user *ubuf, unsigned int ulen,
 182                         unsigned long *dst, int nbits);
 183 extern int bitmap_parselist(const char *buf, unsigned long *maskp,
 184                         int nmaskbits);
 185 extern int bitmap_parselist_user(const char __user *ubuf, unsigned int ulen,
 186                         unsigned long *dst, int nbits);
 187 extern void bitmap_remap(unsigned long *dst, const unsigned long *src,
 188                 const unsigned long *old, const unsigned long *new, unsigned int nbits);
 189 extern int bitmap_bitremap(int oldbit,
 190                 const unsigned long *old, const unsigned long *new, int bits);
 191 extern void bitmap_onto(unsigned long *dst, const unsigned long *orig,
 192                 const unsigned long *relmap, unsigned int bits);
 193 extern void bitmap_fold(unsigned long *dst, const unsigned long *orig,
 194                 unsigned int sz, unsigned int nbits);
 195 extern int bitmap_find_free_region(unsigned long *bitmap, unsigned int bits, int order);
 196 extern void bitmap_release_region(unsigned long *bitmap, unsigned int pos, int order);
 197 extern int bitmap_allocate_region(unsigned long *bitmap, unsigned int pos, int order);
 198 
 199 #ifdef __BIG_ENDIAN
 200 extern void bitmap_copy_le(unsigned long *dst, const unsigned long *src, unsigned int nbits);
 201 #else
 202 #define bitmap_copy_le bitmap_copy
 203 #endif
 204 extern unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int ord, unsigned int nbits);
 205 extern int bitmap_print_to_pagebuf(bool list, char *buf,
 206                                    const unsigned long *maskp, int nmaskbits);
 207 
 208 #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
 209 #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
 210 
 211 /*
 212  * The static inlines below do not handle constant nbits==0 correctly,
 213  * so make such users (should any ever turn up) call the out-of-line
 214  * versions.
 215  */
 216 #define small_const_nbits(nbits) \
 217         (__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0)
 218 
 219 static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
 220 {
 221         unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
 222         memset(dst, 0, len);
 223 }
 224 
 225 static inline void bitmap_fill(unsigned long *dst, unsigned int nbits)
 226 {
 227         unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
 228         memset(dst, 0xff, len);
 229 }
 230 
 231 static inline void bitmap_copy(unsigned long *dst, const unsigned long *src,
 232                         unsigned int nbits)
 233 {
 234         unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
 235         memcpy(dst, src, len);
 236 }
 237 
 238 /*
 239  * Copy bitmap and clear tail bits in last word.
 240  */
 241 static inline void bitmap_copy_clear_tail(unsigned long *dst,
 242                 const unsigned long *src, unsigned int nbits)
 243 {
 244         bitmap_copy(dst, src, nbits);
 245         if (nbits % BITS_PER_LONG)
 246                 dst[nbits / BITS_PER_LONG] &= BITMAP_LAST_WORD_MASK(nbits);
 247 }
 248 
 249 /*
 250  * On 32-bit systems bitmaps are represented as u32 arrays internally, and
 251  * therefore conversion is not needed when copying data from/to arrays of u32.
 252  */
 253 #if BITS_PER_LONG == 64
 254 extern void bitmap_from_arr32(unsigned long *bitmap, const u32 *buf,
 255                                                         unsigned int nbits);
 256 extern void bitmap_to_arr32(u32 *buf, const unsigned long *bitmap,
 257                                                         unsigned int nbits);
 258 #else
 259 #define bitmap_from_arr32(bitmap, buf, nbits)                   \
 260         bitmap_copy_clear_tail((unsigned long *) (bitmap),      \
 261                         (const unsigned long *) (buf), (nbits))
 262 #define bitmap_to_arr32(buf, bitmap, nbits)                     \
 263         bitmap_copy_clear_tail((unsigned long *) (buf),         \
 264                         (const unsigned long *) (bitmap), (nbits))
 265 #endif
 266 
 267 static inline int bitmap_and(unsigned long *dst, const unsigned long *src1,
 268                         const unsigned long *src2, unsigned int nbits)
 269 {
 270         if (small_const_nbits(nbits))
 271                 return (*dst = *src1 & *src2 & BITMAP_LAST_WORD_MASK(nbits)) != 0;
 272         return __bitmap_and(dst, src1, src2, nbits);
 273 }
 274 
 275 static inline void bitmap_or(unsigned long *dst, const unsigned long *src1,
 276                         const unsigned long *src2, unsigned int nbits)
 277 {
 278         if (small_const_nbits(nbits))
 279                 *dst = *src1 | *src2;
 280         else
 281                 __bitmap_or(dst, src1, src2, nbits);
 282 }
 283 
 284 static inline void bitmap_xor(unsigned long *dst, const unsigned long *src1,
 285                         const unsigned long *src2, unsigned int nbits)
 286 {
 287         if (small_const_nbits(nbits))
 288                 *dst = *src1 ^ *src2;
 289         else
 290                 __bitmap_xor(dst, src1, src2, nbits);
 291 }
 292 
 293 static inline int bitmap_andnot(unsigned long *dst, const unsigned long *src1,
 294                         const unsigned long *src2, unsigned int nbits)
 295 {
 296         if (small_const_nbits(nbits))
 297                 return (*dst = *src1 & ~(*src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
 298         return __bitmap_andnot(dst, src1, src2, nbits);
 299 }
 300 
 301 static inline void bitmap_complement(unsigned long *dst, const unsigned long *src,
 302                         unsigned int nbits)
 303 {
 304         if (small_const_nbits(nbits))
 305                 *dst = ~(*src);
 306         else
 307                 __bitmap_complement(dst, src, nbits);
 308 }
 309 
 310 #ifdef __LITTLE_ENDIAN
 311 #define BITMAP_MEM_ALIGNMENT 8
 312 #else
 313 #define BITMAP_MEM_ALIGNMENT (8 * sizeof(unsigned long))
 314 #endif
 315 #define BITMAP_MEM_MASK (BITMAP_MEM_ALIGNMENT - 1)
 316 
 317 static inline int bitmap_equal(const unsigned long *src1,
 318                         const unsigned long *src2, unsigned int nbits)
 319 {
 320         if (small_const_nbits(nbits))
 321                 return !((*src1 ^ *src2) & BITMAP_LAST_WORD_MASK(nbits));
 322         if (__builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
 323             IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
 324                 return !memcmp(src1, src2, nbits / 8);
 325         return __bitmap_equal(src1, src2, nbits);
 326 }
 327 
 328 /**
 329  * bitmap_or_equal - Check whether the or of two bitmaps is equal to a third
 330  * @src1:       Pointer to bitmap 1
 331  * @src2:       Pointer to bitmap 2 will be or'ed with bitmap 1
 332  * @src3:       Pointer to bitmap 3. Compare to the result of *@src1 | *@src2
 333  * @nbits:      number of bits in each of these bitmaps
 334  *
 335  * Returns: True if (*@src1 | *@src2) == *@src3, false otherwise
 336  */
 337 static inline bool bitmap_or_equal(const unsigned long *src1,
 338                                    const unsigned long *src2,
 339                                    const unsigned long *src3,
 340                                    unsigned int nbits)
 341 {
 342         if (!small_const_nbits(nbits))
 343                 return __bitmap_or_equal(src1, src2, src3, nbits);
 344 
 345         return !(((*src1 | *src2) ^ *src3) & BITMAP_LAST_WORD_MASK(nbits));
 346 }
 347 
 348 static inline int bitmap_intersects(const unsigned long *src1,
 349                         const unsigned long *src2, unsigned int nbits)
 350 {
 351         if (small_const_nbits(nbits))
 352                 return ((*src1 & *src2) & BITMAP_LAST_WORD_MASK(nbits)) != 0;
 353         else
 354                 return __bitmap_intersects(src1, src2, nbits);
 355 }
 356 
 357 static inline int bitmap_subset(const unsigned long *src1,
 358                         const unsigned long *src2, unsigned int nbits)
 359 {
 360         if (small_const_nbits(nbits))
 361                 return ! ((*src1 & ~(*src2)) & BITMAP_LAST_WORD_MASK(nbits));
 362         else
 363                 return __bitmap_subset(src1, src2, nbits);
 364 }
 365 
 366 static inline int bitmap_empty(const unsigned long *src, unsigned nbits)
 367 {
 368         if (small_const_nbits(nbits))
 369                 return ! (*src & BITMAP_LAST_WORD_MASK(nbits));
 370 
 371         return find_first_bit(src, nbits) == nbits;
 372 }
 373 
 374 static inline int bitmap_full(const unsigned long *src, unsigned int nbits)
 375 {
 376         if (small_const_nbits(nbits))
 377                 return ! (~(*src) & BITMAP_LAST_WORD_MASK(nbits));
 378 
 379         return find_first_zero_bit(src, nbits) == nbits;
 380 }
 381 
 382 static __always_inline int bitmap_weight(const unsigned long *src, unsigned int nbits)
 383 {
 384         if (small_const_nbits(nbits))
 385                 return hweight_long(*src & BITMAP_LAST_WORD_MASK(nbits));
 386         return __bitmap_weight(src, nbits);
 387 }
 388 
 389 static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
 390                 unsigned int nbits)
 391 {
 392         if (__builtin_constant_p(nbits) && nbits == 1)
 393                 __set_bit(start, map);
 394         else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
 395                  IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
 396                  __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
 397                  IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
 398                 memset((char *)map + start / 8, 0xff, nbits / 8);
 399         else
 400                 __bitmap_set(map, start, nbits);
 401 }
 402 
 403 static __always_inline void bitmap_clear(unsigned long *map, unsigned int start,
 404                 unsigned int nbits)
 405 {
 406         if (__builtin_constant_p(nbits) && nbits == 1)
 407                 __clear_bit(start, map);
 408         else if (__builtin_constant_p(start & BITMAP_MEM_MASK) &&
 409                  IS_ALIGNED(start, BITMAP_MEM_ALIGNMENT) &&
 410                  __builtin_constant_p(nbits & BITMAP_MEM_MASK) &&
 411                  IS_ALIGNED(nbits, BITMAP_MEM_ALIGNMENT))
 412                 memset((char *)map + start / 8, 0, nbits / 8);
 413         else
 414                 __bitmap_clear(map, start, nbits);
 415 }
 416 
 417 static inline void bitmap_shift_right(unsigned long *dst, const unsigned long *src,
 418                                 unsigned int shift, unsigned int nbits)
 419 {
 420         if (small_const_nbits(nbits))
 421                 *dst = (*src & BITMAP_LAST_WORD_MASK(nbits)) >> shift;
 422         else
 423                 __bitmap_shift_right(dst, src, shift, nbits);
 424 }
 425 
 426 static inline void bitmap_shift_left(unsigned long *dst, const unsigned long *src,
 427                                 unsigned int shift, unsigned int nbits)
 428 {
 429         if (small_const_nbits(nbits))
 430                 *dst = (*src << shift) & BITMAP_LAST_WORD_MASK(nbits);
 431         else
 432                 __bitmap_shift_left(dst, src, shift, nbits);
 433 }
 434 
 435 static inline int bitmap_parse(const char *buf, unsigned int buflen,
 436                         unsigned long *maskp, int nmaskbits)
 437 {
 438         return __bitmap_parse(buf, buflen, 0, maskp, nmaskbits);
 439 }
 440 
 441 /**
 442  * BITMAP_FROM_U64() - Represent u64 value in the format suitable for bitmap.
 443  * @n: u64 value
 444  *
 445  * Linux bitmaps are internally arrays of unsigned longs, i.e. 32-bit
 446  * integers in 32-bit environment, and 64-bit integers in 64-bit one.
 447  *
 448  * There are four combinations of endianness and length of the word in linux
 449  * ABIs: LE64, BE64, LE32 and BE32.
 450  *
 451  * On 64-bit kernels 64-bit LE and BE numbers are naturally ordered in
 452  * bitmaps and therefore don't require any special handling.
 453  *
 454  * On 32-bit kernels 32-bit LE ABI orders lo word of 64-bit number in memory
 455  * prior to hi, and 32-bit BE orders hi word prior to lo. The bitmap on the
 456  * other hand is represented as an array of 32-bit words and the position of
 457  * bit N may therefore be calculated as: word #(N/32) and bit #(N%32) in that
 458  * word.  For example, bit #42 is located at 10th position of 2nd word.
 459  * It matches 32-bit LE ABI, and we can simply let the compiler store 64-bit
 460  * values in memory as it usually does. But for BE we need to swap hi and lo
 461  * words manually.
 462  *
 463  * With all that, the macro BITMAP_FROM_U64() does explicit reordering of hi and
 464  * lo parts of u64.  For LE32 it does nothing, and for BE environment it swaps
 465  * hi and lo words, as is expected by bitmap.
 466  */
 467 #if __BITS_PER_LONG == 64
 468 #define BITMAP_FROM_U64(n) (n)
 469 #else
 470 #define BITMAP_FROM_U64(n) ((unsigned long) ((u64)(n) & ULONG_MAX)), \
 471                                 ((unsigned long) ((u64)(n) >> 32))
 472 #endif
 473 
 474 /**
 475  * bitmap_from_u64 - Check and swap words within u64.
 476  *  @mask: source bitmap
 477  *  @dst:  destination bitmap
 478  *
 479  * In 32-bit Big Endian kernel, when using ``(u32 *)(&val)[*]``
 480  * to read u64 mask, we will get the wrong word.
 481  * That is ``(u32 *)(&val)[0]`` gets the upper 32 bits,
 482  * but we expect the lower 32-bits of u64.
 483  */
 484 static inline void bitmap_from_u64(unsigned long *dst, u64 mask)
 485 {
 486         dst[0] = mask & ULONG_MAX;
 487 
 488         if (sizeof(mask) > sizeof(unsigned long))
 489                 dst[1] = mask >> 32;
 490 }
 491 
 492 #endif /* __ASSEMBLY__ */
 493 
 494 #endif /* __LINUX_BITMAP_H */