Linux用户态程序读写IO端口方法总结

从ELDD上看到的，人家总结的很全很好很强大，这里拿来用了
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); }}