（3）编写用户态的测试程序如下：
/*
*=======================================================================
* Filename: usr_test.c
*
* Description:
*
* Version: 1.0 (02/26/2013)
* Created: xhzuoxin(xiahouzuoxin@163.com)
* Compiler: gcc
*=======================================================================
*/
#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdlib.h>
intmain(void)
{
int testdev;
int n, i, ret;
char write_buf[] = "xiahouzuoxin";
char buf[12];
testdev =open("/dev/mycdev", O_RDWR);
if (testdev == -1) {
printf("cannot open file.\n");
exit(1);
}
n = sizeof(write_buf)/sizeof(char);
if (ret = write(testdev, write_buf, n) < n) {
printf("write error!\n");
exit(1);
}
// close(testdev);
// testdev =open("/dev/mycdev", O_RDWR);
lseek(testdev,0, SEEK_SET);
if (testdev == -1) {
printf("cannot open file.\n");
exit(1);
}
if (ret = read(testdev, buf, n) < n) {
printf("read error!\n");
exit(1);
}
for (i=0; i<n; i++) {
printf("%c", buf[i]);
}
printf("\n");
close(testdev);
return 0;
}
在PC机上使用arm-linux-gcc usr_test.c –ousr_test编译，通过NFS共享或ftp下载到Tiny6410开发板上执行./usr_test（超级终端输入）。