arch/s390/lib/find.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * MSB0 numbered special bitops handling.
   4  *
   5  * The bits are numbered:
   6  *   |0..............63|64............127|128...........191|192...........255|
   7  *
   8  * The reason for this bit numbering is the fact that the hardware sets bits
   9  * in a bitmap starting at bit 0 (MSB) and we don't want to scan the bitmap
  10  * from the 'wrong end'.
  11  */
  12
  13 #include <linux/compiler.h>
  14 #include <linux/bitops.h>
  15 #include <linux/export.h>
  16
  17 unsigned long find_first_bit_inv(const unsigned long *addr, unsigned long size)
  18 {
  19         const unsigned long *p = addr;
  20         unsigned long result = 0;
  21         unsigned long tmp;
  22
  23         while (size & ~(BITS_PER_LONG - 1)) {
  24                 if ((tmp = *(p++)))
  25                         goto found;
  26                 result += BITS_PER_LONG;
  27                 size -= BITS_PER_LONG;
  28         }
  29         if (!size)
  30                 return result;
  31         tmp = (*p) & (~0UL << (BITS_PER_LONG - size));
  32         if (!tmp)               /* Are any bits set? */
  33                 return result + size;   /* Nope. */
  34 found:
  35         return result + (__fls(tmp) ^ (BITS_PER_LONG - 1));
  36 }
  37 EXPORT_SYMBOL(find_first_bit_inv);
  38
  39 unsigned long find_next_bit_inv(const unsigned long *addr, unsigned long size,
  40                                 unsigned long offset)
  41 {
  42         const unsigned long *p = addr + (offset / BITS_PER_LONG);
  43         unsigned long result = offset & ~(BITS_PER_LONG - 1);
  44         unsigned long tmp;
  45
  46         if (offset >= size)
  47                 return size;
  48         size -= result;
  49         offset %= BITS_PER_LONG;
  50         if (offset) {
  51                 tmp = *(p++);
  52                 tmp &= (~0UL >> offset);
  53                 if (size < BITS_PER_LONG)
  54                         goto found_first;
  55                 if (tmp)
  56                         goto found_middle;
  57                 size -= BITS_PER_LONG;
  58                 result += BITS_PER_LONG;
  59         }
  60         while (size & ~(BITS_PER_LONG-1)) {
  61                 if ((tmp = *(p++)))
  62                         goto found_middle;
  63                 result += BITS_PER_LONG;
  64                 size -= BITS_PER_LONG;
  65         }
  66         if (!size)
  67                 return result;
  68         tmp = *p;
  69 found_first:
  70         tmp &= (~0UL << (BITS_PER_LONG - size));
  71         if (!tmp)               /* Are any bits set? */
  72                 return result + size;   /* Nope. */
  73 found_middle:
  74         return result + (__fls(tmp) ^ (BITS_PER_LONG - 1));
  75 }
  76 EXPORT_SYMBOL(find_next_bit_inv);