Linux用户态程序读写IO端口方法总结

http://blog.csdn.net/deep_pro/archive/2010/02/22/5315655.aspx

 

1、使用ioperm() and iopl()来获得权限，然后To write data to an I/O port, use outb(), outw(), outl(), or their cousins. To read data from a port, use inb(), inw(), inl(), or their relatives.这种方法只在x86上有效
附带一个例子，读取pc兼容机上的rtc时钟（属于cmos的一部分）的秒

#include <sys/io.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>

void dump_port(unsigned char addr_port, unsigned char data_port,
          unsigned short offset, unsigned short length)
{
unsigned char i, *data;

if (!(data = (unsigned char *)malloc(length)))
    {
      perror("Bad Malloc/n");
      exit(1);
    }

/* Write the offset to the index port
     and read data from the data port */
for (i=offset; i<offset+length; i++)
    {
      outb(i, addr_port );
      data[i-offset] = inb(data_port);
    }

/* Dump */
for (i=0; i<length; i++)
    printf("%02X/n", data[i]);

free(data);
}

int main(int argc, char *argv[])
{

/* Get access permissions */
if ( iopl(3) < 0)
    {
      perror("iopl access error/n");
      exit(1);
    }
while (1)
    {
      dump_port(0x70, 0x71, 0x0, 1);
      sleep(1);
    }
}

 

2、使用/dev/port 这个由内核提供的驱动，这比前一种方式会损失一些性能，好处是比ioperm() and iopl()得到更加有效的权限管理

#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>


int main(int argc, char *argv[])
{
char seconds=0;
char data = 0;
int fd = open("/dev/port", O_RDWR);

while (1)
    {
      lseek(fd, 0x70, SEEK_SET);
      write(fd, &data, 1);

      lseek(fd, 0x71, SEEK_SET);
      read(fd, &seconds, 1);
      printf("%02X/n", seconds);
      sleep(1);
    }
}