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 
#include 
#include 
#include 
#include 
#include  
#include 
#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;
}