Linux在应用层读写寄存器的方法

可以通过操作/dev/mem设备文件，以及mmap函数，将寄存器的地址映射到用户空间，直接在应用层对寄存器进行操作，示例如下：

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#define AUDIO_REG_BASE   (0xB800E000)
#define MAP_SIZE        0xFF

static int dev_fd;
int main(int argc, char **argv)
{

    dev_fd = open("/dev/mem", O_RDWR | O_NDELAY);

    if (dev_fd < 0)
    {
        printf("open(/dev/mem) failed.");
        return 0;
    }

    unsigned char *map_base=(unsigned char * )mmap(NULL, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, dev_fd, AUDIO_REG_BASE );

    printf("%x 
", *(volatile unsigned int *)(map_base+0x38)); //打印该寄存器地址的value

#if 1 // LINE IN
    printf("%x 
", *(volatile unsigned int *)(map_base+0x30));

    *(volatile unsigned int *)(map_base + 0x30) = 0x208121bc; //修改该寄存器地址的value
    usleep(1000000);
    *(volatile unsigned int *)(map_base + 0x30) &= ~(0x1<<16); //修改该寄存器地址的value
    usleep(1000000);

    printf("%x 
", *(volatile unsigned int *)(map_base+0x30));
#endif

    if(dev_fd)
        close(dev_fd);

    munmap(map_base,MAP_SIZE);//解除映射关系

    return 0;
}