基于gpio子系统编写LED灯的驱动，编写应用程序测试

mychrdev.c

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
 
// 构建LED开关的功能码，添加ioctl第三个参数int
#define LED_ON _IOW('l', 1, int)
#define LED_OFF _IOW('l', 0, int)
 
struct device_node *dnode;
struct gpio_desc *gpiono1, *gpiono2, *gpiono3;
int major;
char kbuf[128] = {0};
struct class *cls;
struct device *dev;
int mycdev_open(struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    return 0;
}
 
long mycdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    int which;
    // 获取arg对应的用户空间中的值
    copy_from_user(&which, (void *)arg, 4);
    switch (cmd)
    {
    case LED_ON: // 开灯
        gpiod_set_value(gpiono1, 1);
        gpiod_set_value(gpiono2, 1);
        gpiod_set_value(gpiono3, 1);
        break;
    case LED_OFF: // 关灯
        gpiod_set_value(gpiono1, 0);
        gpiod_set_value(gpiono2, 0);
        gpiod_set_value(gpiono3, 0);
        break;
    }
    return 0;
}
 
int mycdev_close(struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    return 0;
}
 
// 定义操作方法结构体变量并赋值
struct file_operations fops = {
    .open = mycdev_open,
    .unlocked_ioctl = mycdev_ioctl,
    .release = mycdev_close,
};
 
static int __init mycdev_init(void)
{
    // 字符设备驱动注册
    major = register_chrdev(0, "mychrdev", &fops);
    if (major < 0)
    {
        printk("字符设备驱动注册失败\n");
        return major;
    }
    printk("字符设备驱动注册成功:major=%d\n", major);
 
    // 向上提交目录
    cls = class_create(THIS_MODULE, "mychrdev");
    if (IS_ERR(cls))
    {
        printk("向上提交目录失败\n");
        return -PTR_ERR(cls);
    }
    printk("向上提交目录成功\n");
    // 向上提交设备节点信息
    int i;
    for (i = 0; i < 3; i++)
    {
        dev = device_create(cls, NULL, MKDEV(major, i), NULL, "mychrdev%d", i);
        if (IS_ERR(dev))
        {
            printk("向上提交设备节点信息失败\n");
            return -PTR_ERR(dev);
        }
    }
    printk("向上提交设备节点信息成功\n");
 
    // 解析LED的设备树节点
    dnode = of_find_node_by_path("/myled");
    if (dnode == NULL)
    {
        printk("解析设备树节点失败\n");
        return -ENXIO;
    }
    printk("解析GPIO信息成功\n");
 
    // 申请gpio对象
    gpiono1 = gpiod_get_from_of_node(dnode, "led1-gpio", 0, GPIOD_OUT_LOW, NULL);
    gpiono2 = gpiod_get_from_of_node(dnode, "led2-gpio", 0, GPIOD_OUT_LOW, NULL);
    gpiono3 = gpiod_get_from_of_node(dnode, "led3-gpio", 0, GPIOD_OUT_LOW, NULL);
    if (IS_ERR(gpiono1) || IS_ERR(gpiono2) || IS_ERR(gpiono3))
    {
        printk("申请gpio对象失败\n");
        return PTR_ERR(gpiono2);
    }
    printk("申请gpio信息对象成功\n");
 
    return 0;
}
static void __exit mycdev_exit(void)
{
    /*销毁设备节点信息*/
    int i;
    for (i = 0; i < 3; i++)
    {
        device_destroy(cls, MKDEV(major, i));
    }
    // 销毁目录信息
    class_destroy(cls);
 
    // 在卸载驱动时熄灭LED
    gpiod_set_value(gpiono1, 0);
    gpiod_set_value(gpiono2, 0);
    gpiod_set_value(gpiono3, 0);
 
    // 释放gpio编号
    gpiod_put(gpiono1);
    gpiod_put(gpiono2);
    gpiod_put(gpiono3);
 
    // 注销字符设备驱动
    unregister_chrdev(major, "mychrdev");
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

test.c

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include "head.h"
 
int main(int argc, char const *argv[])
{
    int a;
    char buf[128] = {0};
    int fd = open("/dev/mychrdev0", O_RDWR);
    if (fd < 0)
    {
        printf("打开设备文件失败\n");
        exit(-1);
    }
    while (1)
    {
        // 从终端读取
        printf("请输入对LED灯的控制：1(开灯)0(关灯)>");
        scanf("%d", &a);
        switch (a)
        {
        case 1:
            ioctl(fd, LED_ON); // 开灯
            break;
        case 0:
            ioctl(fd, LED_OFF); // 关灯
        }
    }
 
    close(fd);
 
    return 0;
}

实验现象

1：点亮三盏灯

0：熄灭三盏灯