root/include/asm/bitops.h

/* */

INCLUDED FROM

DEFINITIONS

1. set_bit
2. clear_bit
3. test_bit
4. set_bit
5. clear_bit
6. test_bit

   1 #ifndef _ASM_BITOPS_H
   2 /*
   3  * Copyright 1992, Linus Torvalds.
   4  */
   5 
   6 #ifdef i386
   7 /*
   8  * These have to be done with inline assembly: that way the bit-setting
   9  * is guaranteed to be atomic. Both set_bit and clear_bit return 0
  10  * if the bit-setting went ok, != 0 if the bit already was set/cleared.
  11  *
  12  * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  13  */
  14 extern inline int set_bit(int nr,int * addr)
     /*  */
  15 {
  16         char ok;
  17 
  18         __asm__ __volatile__("btsl %1,%2\n\tsetb %0":
  19                 "=q" (ok):"r" (nr),"m" (*(addr)));
  20         return ok;
  21 }
  22 
  23 extern inline int clear_bit(int nr, int * addr)
     /*  */
  24 {
  25         char ok;
  26 
  27         __asm__ __volatile__("btrl %1,%2\n\tsetnb %0":
  28                 "=q" (ok):"r" (nr),"m" (*(addr)));
  29         return ok;
  30 }
  31 
  32 /*
  33  * This routine doesn't need to be atomic, but it's faster to code it
  34  * this way.
  35  */
  36 extern inline int test_bit(int nr, int * addr)
     /*  */
  37 {
  38         char ok;
  39 
  40         __asm__ __volatile__("btl %1,%2\n\tsetb %0":
  41                 "=q" (ok):"r" (nr),"m" (*(addr)));
  42         return ok;
  43 }
  44 
  45 #else
  46 /*
  47  * For the benefit of those who are trying to port Linux to another
  48  * architecture, here are some C-language equivalents.  You should
  49  * recode these in the native assmebly language, if at all possible.
  50  * To guarantee atomicity, these routines call cli() and sti() to
  51  * disable interrupts while they operate.  (You have to provide inline
  52  * routines to cli() and sti().)
  53  *
  54  * Also note, these routines assume that you have 32 bit integers.
  55  * You will have to change this if you are trying to port Linux to the
  56  * Alpha architecture or to a Cray.  :-)
  57  * 
  58  * C language equivalents written by Theodore Ts'o, 9/26/92
  59  */
  60 
  61 extern inline int set_bit(int nr,int * addr)
     /*  */
  62 {
  63         int     mask, retval;
  64 
  65         addr += nr >> 5;
  66         mask = 1 << (nr & 0x1f);
  67         cli();
  68         retval = (mask & *addr) != 0;
  69         *addr |= mask;
  70         sti();
  71         return retval;
  72 }
  73 
  74 extern inline int clear_bit(int nr, int * addr)
     /*  */
  75 {
  76         int     mask, retval;
  77 
  78         addr += nr >> 5;
  79         mask = 1 << (nr & 0x1f);
  80         cli();
  81         retval = (mask & *addr) == 0;
  82         *addr &= ~mask;
  83         sti();
  84         return retval;
  85 }
  86 
  87 extern inline int test_bit(int nr, int * addr)
     /*  */
  88 {
  89         int     mask;
  90 
  91         addr += nr >> 5;
  92         mask = 1 << (nr & 0x1f);
  93         return ((mask & *addr) != 0);
  94 }
  95 #endif  /* i386 */
  96 #endif /* _ASM_BITOPS_H */

/* */