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 \n", *(volatile unsigned int *)(map_base+0x38)); //打印该寄存器地址的value
- #if 1 // LINE IN
- printf("%x \n", *(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 \n", *(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;
- }
