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

#define DEVICE_FILE "/dev/gpio_led"

int main()
{
    int fd;
    char write_buf[100] = "Hello from user space!";
    char read_buf[100] = "\0";

    // 打开设备文件
    fd = open(DEVICE_FILE, O_RDWR);
    if (fd < 0) {
        perror("open");
        return -1;
    }

    // 从设备读取数据
    ssize_t read_bytes = read(fd, read_buf, sizeof(read_buf)); // 尝试读取更多数据
    if (read_bytes < 0) {
        perror("read");
        close(fd);
        return -1;
    } else if (read_bytes == 0) {
        printf("No data read from the device.\n");
    } else {
        read_buf[read_bytes] = '\0';
        printf("Read from the device: %s\n", read_buf);
        memset(read_buf, 0, sizeof(read_buf));  // 将 read_buf 数组的所有元素设置为 0
    }

    // 向设备写入数据
    ssize_t written = write(fd, write_buf, sizeof(write_buf));
    if (written < 0) {
        perror("write");
        close(fd);
        return -1;
    } else {
        printf("Wrote %zd bytes to the device.\n", written);
    }

    // 从设备读取数据
    ssize_t read_bytes1 = read(fd, read_buf, 40);  // 继续读取更多数据
    if (read_bytes1 < 0) {
        perror("read");
        close(fd);
        return -1;
    } else if (read_bytes1 == 0) {
        printf("No data read from the device.\n");
    } else {
        printf("Read from the device: %s\n", read_buf);
    }

    // 关闭设备文件
    close(fd);

    return 0;
}