驱动程序

#include <linux/init.h>
#include <linux/module.h>
#include<linux/fs.h>
#include<linux/device.h>
#include<linux/cdev.h>
#include<linux/slab.h>
#include<linux/uaccess.h>
#include<linux/of.h>
#include<linux/of_irq.h>
#include<linux/interrupt.h>
#include<linux/of_gpio.h>
#include<linux/gpio.h>
struct cdev *cdev;
struct gpio_desc *gpiono1;
unsigned int major=500;
unsigned int minor=0;//次设备号的起始值
dev_t devno;
struct class *cls;
struct device *dev;
char kbuf[128]={0};
static int number=0;
unsigned int irqno;
struct device_node *dnodel;
//定义等待队列头
wait_queue_head_t wq_head;
unsigned int condition=0;
//中断处理函数
irqreturn_t myirq_handler(int irqno, void *dev_id)
{   
 
    number=!number;
    printk("key1 interrupt\n");
    gpiod_set_value(gpiono1,!gpiod_get_value(gpiono1)); 
    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 *ubuf, size_t size, loff_t *lof)
{
    int ret;
    if(sizeof(number)<size)
        size=sizeof(number);
    wait_event_interruptible(wq_head,condition);//将进程切换为休眠
    
    ret=copy_to_user(ubuf,&number,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;
}

// 定义操作方法结构体变量并赋值
struct file_operations fops = {
    .open = mycdev_open,
    .read=mycdev_read,
    .release = mycdev_close,
};

static int __init mycdev_init(void)
{
    int ret,i;
    //初始化等待队列头
    init_waitqueue_head(&wq_head);
    //1.分配字符设备驱动对象空间  cdev_alloc
    cdev=cdev_alloc();
    if(cdev==NULL)
    {
        printk("申请字符设备驱动对象空间失败\n");
        ret=-EFAULT;
        goto out1;
    }
    printk("字符设备驱动对象申请成功\n");
    //2.字符设备驱动对象部分初始化  cdev_init
    cdev_init(cdev,&fops);
    //3.申请设备号  register_chrdev_region/alloc_chrdev_region
    if(major>0)//静态申请设备号
    {
        ret=register_chrdev_region(MKDEV(major,minor),3,"myled");
        if(ret)
        {
            printk("静态指定设备号失败\n");
            goto out2;
        }
    }
    else//动态申请设备号
    {
        ret=alloc_chrdev_region(&devno,minor,3,"myled");
         if(ret)
        {
            printk("动态申请设备号失败\n");
            goto out2;
        }
        major=MAJOR(devno);//根据设备号得到主设备号
        minor=MINOR(devno);//根据设备号得到次设备号
    }
    printk("申请设备号成功\n");
    //4.注册字符设备驱动对象  cdev_add()
    ret=cdev_add(cdev,MKDEV(major,minor),3);
    if(ret)
    {
        printk("注册字符设备驱动对象失败\n");
        goto out3;
    }
    printk("注册字符设备驱动对象成功\n");
    //5.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);
        goto out4;
    }
    printk("向上提交目录成功\n");
    //6.向上提交设备节点
    for(i=0;i<3;i++)
    {
        dev=device_create(cls,NULL,MKDEV(major,i),NULL,"myled%d",i);
        if(IS_ERR(dev))
        {
            printk("向上提交节点信息失败\n");
            ret=-PTR_ERR(dev);
            goto out5;
        }
    }
    printk("向上提交设备节点信息成功\n");
    //解析led灯key的设备树节点
    dnodel=of_find_node_by_path("/mylandks");
    if(dnodel==NULL)
    {
    printk("解析设备树节点失败\n");
    return -ENXIO;
    }
    printk("解析设备树节点成功\n");
    //根据设备树节点解析led1 gpio结构体并向内核注册
    gpiono1=gpiod_get_from_of_node(dnodel,"led1",0,GPIOD_OUT_LOW,NULL); 
    if(IS_ERR(gpiono1))
    {
        printk("申请gpio失败\n");
        return -PTR_ERR(gpiono1);
    }  
    //获取软中断号
    irqno=irq_of_parse_and_map(dnodel,0);
    if(!irqno)
    {
        printk("软中断号获取失败\n");
        return -ENOMEM;
    }
    printk("软中断号获取成功irqno=%d\n",irqno);
    //注册中断
    ret=request_irq(irqno,myirq_handler,IRQF_TRIGGER_FALLING,"key1",NULL);
    if(ret)
    {
        printk("注册驱动失败\n");
        return ret;
    }
    printk("key1中断注册成功\n");
    return 0;
out5:
    for(--i;i>=0;i--)
    {
        //销毁上面提交的设备信息
        device_destroy(cls,MKDEV(major,i));
    }
    class_destroy(cls);
out4:
    cdev_del(cdev);
out3:
    unregister_chrdev_region(MKDEV(major,minor),3);
out2:
    kfree(cdev);
out1:
    return ret;
}
static void __exit mycdev_exit(void)
{
    //1.销毁设备信息  device_destroy
    int i;
    for(i=0;i<3;i++)
    {
        device_destroy(cls,MKDEV(major,i));
    }
    //2.销毁目录  class_destroy
    class_destroy(cls);
    //3.注销对象  cdev_del()
    cdev_del(cdev);
    //4.释放设备号   unregister_chrdev_region()
    unregister_chrdev_region(MKDEV(major,minor),3);
    //5.释放对象空间  kfree()
    kfree(cdev);
    //注销中断
    free_irq(irqno,NULL);
    //释放gpio编号
    gpiod_put(gpiono1);

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

测试程序

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
unsigned int number;
int main(int argc, char const *argv[])
{
    char buf[128] = {0};
    int fd = open("/dev/myled0", O_RDWR);
    if (fd < 0)
    {
        printf("打开设备文件失败\n");
        exit(-1);
    }
    while (1)
    {
        read(fd, &number, sizeof(number));
        printf("number:%d\n",number);
    }
    close(fd);
    return 0;
}

实验现象