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：
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#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;
}
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