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Commit c7f612cdf091def01454e7e132c7d7a3f419fbc4

Authored by Akinobu Mita
Committed by Linus Torvalds
1 parent 2dfc383ad5
Exists in master and in 7 other branches imx_3.0.35_4.1.0, imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga, smarc-l5.0.0_1.0.0-ga

[PATCH] bitops: generic find_{next,first}{,_zero}_bit() 

This patch introduces the C-language equivalents of the functions below:

unsigned logn find_next_bit(const unsigned long *addr, unsigned long size,
                            unsigned long offset);
unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
                                 unsigned long offset);
unsigned long find_first_zero_bit(const unsigned long *addr,
                                  unsigned long size);
unsigned long find_first_bit(const unsigned long *addr, unsigned long size);

In include/asm-generic/bitops/find.h

This code largely copied from: arch/powerpc/lib/bitops.c

Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Showing 2 changed files with 94 additions and 31 deletions Side-by-side Diff

include/asm-generic/bitops/find.h
Diff comments   View file @ c7f612c
  1 +#ifndef _ASM_GENERIC_BITOPS_FIND_H_
  2 +#define _ASM_GENERIC_BITOPS_FIND_H_
  3 +
  4 +extern unsigned long find_next_bit(const unsigned long *addr, unsigned long
  5 + size, unsigned long offset);
  6 +
  7 +extern unsigned long find_next_zero_bit(const unsigned long *addr, unsigned
  8 + long size, unsigned long offset);
  9 +
  10 +#define find_first_bit(addr, size) find_next_bit((addr), (size), 0)
  11 +#define find_first_zero_bit(addr, size) find_next_zero_bit((addr), (size), 0)
  12 +
  13 +#endif /*_ASM_GENERIC_BITOPS_FIND_H_ */
... ... @@ -11,49 +11,99 @@
11 11  
12 12 #include <linux/bitops.h>
13 13 #include <linux/module.h>
  14 +#include <asm/types.h>
14 15  
15   -int find_next_bit(const unsigned long *addr, int size, int offset)
  16 +#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG)
  17 +
  18 +/**
  19 + * find_next_bit - find the next set bit in a memory region
  20 + * @addr: The address to base the search on
  21 + * @offset: The bitnumber to start searching at
  22 + * @size: The maximum size to search
  23 + */
  24 +unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
  25 + unsigned long offset)
16 26 {
17   - const unsigned long *base;
18   - const int NBITS = sizeof(*addr) * 8;
  27 + const unsigned long *p = addr + BITOP_WORD(offset);
  28 + unsigned long result = offset & ~(BITS_PER_LONG-1);
19 29 unsigned long tmp;
20 30  
21   - base = addr;
  31 + if (offset >= size)
  32 + return size;
  33 + size -= result;
  34 + offset %= BITS_PER_LONG;
22 35 if (offset) {
23   - int suboffset;
24   -
25   - addr += offset / NBITS;
26   -
27   - suboffset = offset % NBITS;
28   - if (suboffset) {
29   - tmp = *addr;
30   - tmp >>= suboffset;
31   - if (tmp)
32   - goto finish;
33   - }
34   -
35   - addr++;
  36 + tmp = *(p++);
  37 + tmp &= (~0UL << offset);
  38 + if (size < BITS_PER_LONG)
  39 + goto found_first;
  40 + if (tmp)
  41 + goto found_middle;
  42 + size -= BITS_PER_LONG;
  43 + result += BITS_PER_LONG;
36 44 }
  45 + while (size & ~(BITS_PER_LONG-1)) {
  46 + if ((tmp = *(p++)))
  47 + goto found_middle;
  48 + result += BITS_PER_LONG;
  49 + size -= BITS_PER_LONG;
  50 + }
  51 + if (!size)
  52 + return result;
  53 + tmp = *p;
37 54  
38   - while ((tmp = *addr) == 0)
39   - addr++;
  55 +found_first:
  56 + tmp &= (~0UL >> (BITS_PER_LONG - size));
  57 + if (tmp == 0UL) /* Are any bits set? */
  58 + return result + size; /* Nope. */
  59 +found_middle:
  60 + return result + __ffs(tmp);
  61 +}
40 62  
41   - offset = (addr - base) * NBITS;
  63 +EXPORT_SYMBOL(find_next_bit);
42 64  
43   - finish:
44   - /* count the remaining bits without using __ffs() since that takes a 32-bit arg */
45   - while (!(tmp & 0xff)) {
46   - offset += 8;
47   - tmp >>= 8;
48   - }
  65 +/*
  66 + * This implementation of find_{first,next}_zero_bit was stolen from
  67 + * Linus' asm-alpha/bitops.h.
  68 + */
  69 +unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
  70 + unsigned long offset)
  71 +{
  72 + const unsigned long *p = addr + BITOP_WORD(offset);
  73 + unsigned long result = offset & ~(BITS_PER_LONG-1);
  74 + unsigned long tmp;
49 75  
50   - while (!(tmp & 1)) {
51   - offset++;
52   - tmp >>= 1;
  76 + if (offset >= size)
  77 + return size;
  78 + size -= result;
  79 + offset %= BITS_PER_LONG;
  80 + if (offset) {
  81 + tmp = *(p++);
  82 + tmp |= ~0UL >> (BITS_PER_LONG - offset);
  83 + if (size < BITS_PER_LONG)
  84 + goto found_first;
  85 + if (~tmp)
  86 + goto found_middle;
  87 + size -= BITS_PER_LONG;
  88 + result += BITS_PER_LONG;
53 89 }
  90 + while (size & ~(BITS_PER_LONG-1)) {
  91 + if (~(tmp = *(p++)))
  92 + goto found_middle;
  93 + result += BITS_PER_LONG;
  94 + size -= BITS_PER_LONG;
  95 + }
  96 + if (!size)
  97 + return result;
  98 + tmp = *p;
54 99  
55   - return offset;
  100 +found_first:
  101 + tmp |= ~0UL << size;
  102 + if (tmp == ~0UL) /* Are any bits zero? */
  103 + return result + size; /* Nope. */
  104 +found_middle:
  105 + return result + ffz(tmp);
56 106 }
57 107  
58   -EXPORT_SYMBOL(find_next_bit);
  108 +EXPORT_SYMBOL(find_next_zero_bit);