root/include/asm-i386/bitops.h

/* */

INCLUDED FROM

DEFINITIONS

1. set_bit
2. clear_bit
3. change_bit
4. test_bit

   1 #ifndef _I386_BITOPS_H
   2 #define _I386_BITOPS_H
   3 
   4 /*
   5  * Copyright 1992, Linus Torvalds.
   6  */
   7 
   8 /*
   9  * These have to be done with inline assembly: that way the bit-setting
  10  * is guaranteed to be atomic. All bit operations return 0 if the bit
  11  * was cleared before the operation and != 0 if it was not.
  12  *
  13  * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  14  */
  15 
  16 /*
  17  * Some hacks to defeat gcc over-optimizations..
  18  */
  19 struct __dummy { unsigned long a[100]; };
  20 #define ADDR (*(struct __dummy *) addr)
  21 
  22 extern __inline__ int set_bit(int nr, void * addr)
     /*  */
  23 {
  24         int oldbit;
  25 
  26         __asm__ __volatile__("btsl %2,%1\n\tsbbl %0,%0"
  27                 :"=r" (oldbit),"=m" (ADDR)
  28                 :"r" (nr));
  29         return oldbit;
  30 }
  31 
  32 extern __inline__ int clear_bit(int nr, void * addr)
     /*  */
  33 {
  34         int oldbit;
  35 
  36         __asm__ __volatile__("btrl %2,%1\n\tsbbl %0,%0"
  37                 :"=r" (oldbit),"=m" (ADDR)
  38                 :"r" (nr));
  39         return oldbit;
  40 }
  41 
  42 extern __inline__ int change_bit(int nr, void * addr)
     /*  */
  43 {
  44         int oldbit;
  45 
  46         __asm__ __volatile__("btcl %2,%1\n\tsbbl %0,%0"
  47                 :"=r" (oldbit),"=m" (ADDR)
  48                 :"r" (nr));
  49         return oldbit;
  50 }
  51 
  52 /*
  53  * This routine doesn't need to be atomic, but it's faster to code it
  54  * this way.
  55  */
  56 extern __inline__ int test_bit(int nr, void * addr)
     /*  */
  57 {
  58         int oldbit;
  59 
  60         __asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
  61                 :"=r" (oldbit)
  62                 :"m" (ADDR),"r" (nr));
  63         return oldbit;
  64 }
  65 
  66 #endif /* _I386_BITOPS_H */

/* */