应用程序代码

#include<stdio.h>
#include<string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

int main (int argc, const char *argv[])
{
	char buf[128] = "";
	int fd = open("/dev/led0",O_RDWR);
	if(fd < 0)
	{
		printf("打开文件失败\n");
		return -1;
	}
	while(1)
	{
		memset(buf,0,sizeof(buf));
		read(fd,buf,sizeof(buf));
		printf("%s\n",buf);
	}

	close(fd);
	return 0;
}	

驱动代码

#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/gpio.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/uaccess.h>

struct cdev *cdev;
unsigned int irqnum;
unsigned int major;
unsigned int minor;
dev_t devnum;
struct class *cls;
struct device *dev;
struct device_node *dnode;
//gpio结构体
struct gpio_desc *gpionum;
//定义等待队列头
wait_queue_head_t wq_head;
unsigned int number = 0;
char kbuf[128] = "";
unsigned int condition=0;
//中断处理函数
irqreturn_t myirq_handler(int irqnum,void *dev_id)
{
    number = !number;
    gpiod_set_value(gpionum,!gpiod_get_value(gpionum));
     condition=1;//表示硬件数据就绪
    wake_up_interruptible(&wq_head);//唤醒休眠的进程
    return IRQ_HANDLED;
}
int mycdev_open (struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);
    return 0;

}
ssize_t mycdev_read (struct file *file, char __user *ubuf, size_t size, loff_t * lof)
{
    
    int ret;
    if(sizeof(kbuf) < size)
    {
        size = sizeof(kbuf);
    }
    wait_event_interruptible(wq_head,condition);//将进程切换为休眠
    ret = copy_to_user(ubuf,kbuf,size);
    if(ret)
    {
        printk("copy_tO_user filed\n");
        return -EIO;
    }
    printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);
    condition=0;//表示下一次硬件数据没有准备好
    return 0;
}
int mycdev_close (struct inode *inode, struct file *file)
{
    printk("%s:%s:%d\n",__FILE__,__func__,__LINE__);
    return 0;
}
struct file_operations fops=
{
    .open = mycdev_open,
    .read = mycdev_read,
    .release = mycdev_close,
};
static int __init mycdev_init(void)
{
    int ret;
    //初始化等待队列头
    init_waitqueue_head(&wq_head);
    //申请字符设备对象空间
    cdev = cdev_alloc();
    if(cdev == NULL)
    {
        printk("为字符设备对象申请空间失败\n");
        return -EIO;
    }
    printk("为字符设备对象申请空间成功\n");
    //初始化字符设备对象
    cdev_init(cdev,&fops);
    //申请设备号
    //动态申请
    ret = alloc_chrdev_region(&devnum,0,1,"myled");
    if(ret < 0)
    {
        printk("led灯申请设备号失败\n");
        ret = -EFAULT;
        return ret;
    }
    major = MAJOR(devnum);
    minor = MINOR(devnum);
     printk("led灯申请设备号成功，major = %d\n",major);
    //注册字符设备驱动
    ret = cdev_add(cdev,MKDEV(major,minor),1);
    if(ret < 0)
    {
        printk("注册字符设备驱动失败");
        return -EFAULT;
    }
    printk("注册字符设备驱动成功");
    //向上提交目录
    cls = class_create(THIS_MODULE,"myled");
    if(IS_ERR(cls))
    {
        printk("向上提交目录失败\n");
        ret = -PTR_ERR(cls);
        return ret;
    }
    printk("向上提交目录成功\n");
    dev = device_create(cls,NULL,MKDEV(major,minor),NULL,"led0");
    if(IS_ERR(dev))
    {
        printk("向上提交节点信息失败\n");
        ret = -PTR_ERR(dev);
        return ret;
    }
    printk("向上提交节点信息成功\n");
    //解析设备树节点信息
    dnode = of_find_node_by_name(NULL,"mydevs");
    if(dnode == NULL)
    {
        printk("解析设备树节点信息失败\n");
        return -ENXIO;
    }
    printk("解析设备树节点信息成功\n");
    //根据设备树节点解析led1  gpio结构体并向内核注册
    gpionum = gpiod_get_from_of_node(dnode,"led1",0,GPIOD_OUT_LOW,NULL);
    if(IS_ERR(gpionum))
    {
        printk("申请gpio失败\n");
        return -PTR_ERR(gpionum);
    }
    printk("申请gpio成功\n");
    //默认灭灯
    gpiod_set_value(gpionum,1);
    //获取软中断号
    irqnum = irq_of_parse_and_map(dnode,0);
    if(!irqnum)
    {
        printk("软中断号获取失败\n");
        return -ENOMEM;
    }
    printk("软中断号获取成功,irqnum = %d\n",irqnum);
    //注册中断
    ret = request_irq(irqnum,myirq_handler,IRQF_TRIGGER_FALLING,"key1",NULL);
    if(ret)
    {
        printk("注册中断失败\n");
        return ret;
    }
    printk("key1注册中断成功\n");
    return 0;
}
static void __exit mycdev_exit(void)
{
    //注销中断
    free_irq(irqnum,NULL);
    //灭灯
    gpiod_set_value(gpionum,0);
    //注销gpio信息
    gpiod_put(gpionum);
    //释放设备树节点信息
    device_destroy(cls,MKDEV(major,minor));
    class_destroy(cls);
    //注销字符设备驱动
    cdev_del(cdev);
    //释放申请的设备号
    unregister_chrdev_region(MKDEV(major,minor),1);
    //释放字符驱动对象空间
    kfree(cdev);

}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");