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/gpio.h>
#include <linux/of_gpio.h>

struct cdev *cdev;
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;
// 定义等待队列头
wait_queue_head_t wq_head;
unsigned int condition = 0;

unsigned int number;
struct device_node *dnode;
unsigned int irqno;
struct gpio_desc *gpiono;

// 中断处理函数
irqreturn_t myirq_handler(int irqno, void *dev_id)
{
    if (number == 0)
    {
        number = 1;
        gpiod_set_value(gpiono, 1); // 亮灯
    }
    else
    {
        number = 0;
        gpiod_set_value(gpiono, 0); // 灭灯
    }
    condition=1;//表示硬件数据就绪
    wake_up_interruptible(&wq_head);//唤醒休眠的进程
    //printk("number = %d\n", number); // 打印此时的number的值
    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)
{
    printk("%s:%s:%d\n", __FILE__, __func__, __LINE__);
    int ret;
    // 向用户空间读取拷贝
    if (size > sizeof(number)) // 用户空间期待读取的大小内核满足不了，那就给内核支持的最大大小
        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) // 拷贝失败
    {
        printk("copy_to_user filed\n");
        return ret;
    }
    condition = 0; // 表示下一次硬件数据没有准备好
    return 0;
}

ssize_t mycdev_write(struct file *file, const char *ubuf, size_t size, loff_t *lof)
{
    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,
    .write = mycdev_write,
    .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, "mykeys");
        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, "mykeys");
        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, "mykeys");
    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, "mykeys%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");

    // 解析设备树节点
    dnode = of_find_node_by_name(NULL, "mykeys");
    if (dnode == 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");

    // 获取软中断号
    irqno = irq_of_parse_and_map(dnode, 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");

    // 根据设备树节点解析led1 gpio结构体并向内核注册
    gpiono = gpiod_get_from_of_node(dnode, "led1", 0, GPIOD_OUT_LOW, NULL);
    if (IS_ERR(gpiono))
    {
        printk("申请gpio失败\n");
        return -PTR_ERR(gpiono);
    }

    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);
    // 注销gpio信息
    gpiod_put(gpiono);
}
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

应用程序

#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
 
 
int main(int argc, char const *argv[])
{
    unsigned int number;
    int fd = open("/dev/mykeys0", O_RDWR);
    if (fd < 0)
    {
        printf("打开设备文件失败\n");
        exit(-1);
    }
    
        while(1)
        {
        read(fd,&number,sizeof(number));//读取数据
        printf("number = %d\n",number);
    
        }
    close(fd);
 
    return 0;
}

实验现象