root/include/asm/bitops.h

/* [previous][next][first][last][top][bottom][index][help] */

INCLUDED FROM


DEFINITIONS

This source file includes following definitions.
  1. set_bit
  2. clear_bit
  3. change_bit
  4. test_bit
  5. set_bit
  6. clear_bit
  7. test_bit

   1 #ifndef _ASM_BITOPS_H
   2 #define _ASM_BITOPS_H
   3 /*
   4  * Copyright 1992, Linus Torvalds.
   5  */
   6 
   7 #ifdef i386
   8 /*
   9  * These have to be done with inline assembly: that way the bit-setting
  10  * is guaranteed to be atomic. All bitoperations 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)
     /* [previous][next][first][last][top][bottom][index][help] */
  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)
     /* [previous][next][first][last][top][bottom][index][help] */
  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)
     /* [previous][next][first][last][top][bottom][index][help] */
  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)
     /* [previous][next][first][last][top][bottom][index][help] */
  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 #else
  67 /*
  68  * For the benefit of those who are trying to port Linux to another
  69  * architecture, here are some C-language equivalents.  You should
  70  * recode these in the native assmebly language, if at all possible.
  71  * To guarantee atomicity, these routines call cli() and sti() to
  72  * disable interrupts while they operate.  (You have to provide inline
  73  * routines to cli() and sti().)
  74  *
  75  * Also note, these routines assume that you have 32 bit integers.
  76  * You will have to change this if you are trying to port Linux to the
  77  * Alpha architecture or to a Cray.  :-)
  78  * 
  79  * C language equivalents written by Theodore Ts'o, 9/26/92
  80  */
  81 
  82 extern __inline__ int set_bit(int nr,int * addr)
     /* [previous][next][first][last][top][bottom][index][help] */
  83 {
  84         int     mask, retval;
  85 
  86         addr += nr >> 5;
  87         mask = 1 << (nr & 0x1f);
  88         cli();
  89         retval = (mask & *addr) != 0;
  90         *addr |= mask;
  91         sti();
  92         return retval;
  93 }
  94 
  95 extern __inline__ int clear_bit(int nr, int * addr)
     /* [previous][next][first][last][top][bottom][index][help] */
  96 {
  97         int     mask, retval;
  98 
  99         addr += nr >> 5;
 100         mask = 1 << (nr & 0x1f);
 101         cli();
 102         retval = (mask & *addr) != 0;
 103         *addr &= ~mask;
 104         sti();
 105         return retval;
 106 }
 107 
 108 extern __inline__ int test_bit(int nr, int * addr)
     /* [previous][next][first][last][top][bottom][index][help] */
 109 {
 110         int     mask;
 111 
 112         addr += nr >> 5;
 113         mask = 1 << (nr & 0x1f);
 114         return ((mask & *addr) != 0);
 115 }
 116 #endif  /* i386 */
 117 #endif /* _ASM_BITOPS_H */

/* [previous][next][first][last][top][bottom][index][help] */