arch/s390/lib/find.c

   1 /*
   2  * MSB0 numbered special bitops handling.
   3  *
   4  * On s390x the bits are numbered:
   5  *   |0..............63|64............127|128...........191|192...........255|
   6  * and on s390:
   7  *   |0.....31|32....63|64....95|96...127|128..159|160..191|192..223|224..255|
   8  *
   9  * The reason for this bit numbering is the fact that the hardware sets bits
  10  * in a bitmap starting at bit 0 (MSB) and we don't want to scan the bitmap
  11  * from the 'wrong end'.
  12  */
  13
  14 #include <linux/compiler.h>
  15 #include <linux/bitops.h>
  16 #include <linux/export.h>
  17
  18 unsigned long find_first_bit_inv(const unsigned long *addr, unsigned long size)
  19 {
  20         const unsigned long *p = addr;
  21         unsigned long result = 0;
  22         unsigned long tmp;
  23
  24         while (size & ~(BITS_PER_LONG - 1)) {
  25                 if ((tmp = *(p++)))
  26                         goto found;
  27                 result += BITS_PER_LONG;
  28                 size -= BITS_PER_LONG;
  29         }
  30         if (!size)
  31                 return result;
  32         tmp = (*p) & (~0UL << (BITS_PER_LONG - size));
  33         if (!tmp)               /* Are any bits set? */
  34                 return result + size;   /* Nope. */
  35 found:
  36         return result + (__fls(tmp) ^ (BITS_PER_LONG - 1));
  37 }
  38 EXPORT_SYMBOL(find_first_bit_inv);
  39
  40 unsigned long find_next_bit_inv(const unsigned long *addr, unsigned long size,
  41                                 unsigned long offset)
  42 {
  43         const unsigned long *p = addr + (offset / BITS_PER_LONG);
  44         unsigned long result = offset & ~(BITS_PER_LONG - 1);
  45         unsigned long tmp;
  46
  47         if (offset >= size)
  48                 return size;
  49         size -= result;
  50         offset %= BITS_PER_LONG;
  51         if (offset) {
  52                 tmp = *(p++);
  53                 tmp &= (~0UL >> offset);
  54                 if (size < BITS_PER_LONG)
  55                         goto found_first;
  56                 if (tmp)
  57                         goto found_middle;
  58                 size -= BITS_PER_LONG;
  59                 result += BITS_PER_LONG;
  60         }
  61         while (size & ~(BITS_PER_LONG-1)) {
  62                 if ((tmp = *(p++)))
  63                         goto found_middle;
  64                 result += BITS_PER_LONG;
  65                 size -= BITS_PER_LONG;
  66         }
  67         if (!size)
  68                 return result;
  69         tmp = *p;
  70 found_first:
  71         tmp &= (~0UL << (BITS_PER_LONG - size));
  72         if (!tmp)               /* Are any bits set? */
  73                 return result + size;   /* Nope. */
  74 found_middle:
  75         return result + (__fls(tmp) ^ (BITS_PER_LONG - 1));
  76 }
  77 EXPORT_SYMBOL(find_next_bit_inv);