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

#define MEM_CLEAR 0x01
#define CHAR_DEV_NAME "/dev/chr_dev"

int main()
{
        int ret;
        int fd;
        int index;
        char buf[32];

  /* open device */
        fd = open(CHAR_DEV_NAME, O_RDWR | O_NONBLOCK);
        if(fd < 0)
        {
                printf("open failed!\n");
                return -1;
        }

  /* set buffer data, which will be stored into device */
        for(index = 0; index < 32; index ++)
        {
                buf[index] = index;
        }

  /* write data */
        write(fd, buf, 32);
        memset(buf, 0, 32);

  /* read data */
        lseek(fd, 0, SEEK_SET);
        read(fd, buf, 32);
        for(index = 0; index < 32; index ++)
        {
                printf("data[%d] = %d\n", index, buf[index]);
        }

  /* reset all data to zero, read it and check whether it is ok */
  ioctl(fd, MEM_CLEAR, NULL);
  lseek(fd, 0, SEEK_SET);
        read(fd, buf, 32);
        for(index = 0; index < 32; index ++)
        {
                printf("data[%d] = %d\n", index, buf[index]);
        }

        close(fd);
        return 0;
}