位操作相关宏与函数

static inline int test_bit(int nr , const volatile void *addr) //测试位，测试addr的第nr位为0还是为1
{
    return 1 & (((const volatile unsigned int *)addr)[nr >> 5 ] >> (nr & 31)) ;    
}

//设置位，把addr的第nr位置1
#define set_bit(nr,addr) ({\
        register int res;\
        __asm__ __volatile__("btsl %2,%3\n\t setb %%al"\
            :"=a"(res) :"0" (0),"r"(nr),"m"(*(addr)));\
        res;})
//清位，把addr的第nr位清0
#define clear_bit(nr,addr) ({\
        register int res;\
        __asm__ __volatile__("btrl %2,%3\n\t setnb %%al"\
            :"=a"(res):"0"(0),"r"(nr),"m"(*(addr)));\
            res;})

后面这几个是我模仿内核来写的两个以C实现的程序，比较容易理解:

static inline int __set_bit(int nr, const volatile void *addr)
{  
    unsigned long *add = (unsigned long *)addr ;
    return add[nr/32] |= (1UL << (nr % 32)); 
}

static inline int __clr_bit(int nr , const volatile void *addr)
{
    unsigned long *add = (unsigned long *)addr ;
    return add[nr/32] &= ~(1UL << (nr %32));       
}