作业：通过platform总线驱动实现

a.应用程序通过阻塞的io模型来读取number变量的值
b.number是内核驱动中的一个变量
c.number的值随着按键按下而改变（按键中断） 例如number=0 按下按键number=1 ,再次按下按键number=0
d.在按下按键的时候需要同时将led1的状态取反
e.驱动中需要编写字符设备驱动
f.驱动中需要自动创建设备节点
g.这个驱动需要的所有设备信息放在设备树的同一个节点中

驱动程序：my_platform.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/mod_devicetable.h>
#include <linux/of_gpio.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <linux/wait.h>

struct cdev *cdev;
unsigned int major = 0;
unsigned int minor = 0;
dev_t devno;
module_param(major, uint, 0664); //方便命令行传递major的值
struct class *cls;
struct device *dev;
struct resource *res;
unsigned int irqno;
struct gpio_desc *gpiono;
wait_queue_head_t wq_head; //定义一个等待队列头
unsigned int number = 0;
unsigned int condition = 0;

//定义中断处理函数
irqreturn_t key_handler(int irq, void *dev)
{
    gpiod_set_value(gpiono, !gpiod_get_value(gpiono));
    if (number == 0)
    {
        number = 1;
        condition = 1;
        wake_up_interruptible(&wq_head);
    }
    else
    {
        number = 0;
        condition = 1;
        wake_up_interruptible(&wq_head);
    }
    return IRQ_HANDLED;
}

//封装操作方法
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;
    //判断IO方式
    if (file->f_flags & O_NONBLOCK) //非阻塞
    {
    }
    else
    {                                                 //阻塞
        wait_event_interruptible(wq_head, condition); //先检查condition再将进程休眠
    }
    ret = copy_to_user(ubuf, &number, size);
    if (ret)
    {
        printk("copy_to_user err\n");
        return -EIO;
    }
    condition = 0; //下一次硬件数据没有就绪
    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;
}

//定义一个操作方法结构体对象并初始化
struct file_operations fops = {
    .open = mycdev_open,
    .read = mycdev_read,
    .write = mycdev_write,
    .release = mycdev_close,
};

//封装probe函数
int pdrv_probe(struct platform_device *pdev)
{
    //初始化等待队列
    init_waitqueue_head(&wq_head);

    int ret;
    //1.为字符设备驱动对象申请空间
    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("申请字符设备驱动对象空间成功\n");

    //2.初始化字符设备驱动对象
    cdev_init(cdev, &fops);
    printk("初始化字符设备驱动对象成功\n");

    //3.申请设备号
    if (major > 0) //静态指定设备号
    {
        ret = register_chrdev_region(MKDEV(major, minor), 3, "myled");
        if (ret)
        {
            printk("静态申请设备号失败\n");
            goto out2;
        }
    }
    else if (major == 0)
    { //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); //获取主设备号
        minor = MINOR(devno); //获取次设备号
    }
    printk("申请设备号成功\n");

    //4.注册字符设备驱动对象
    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");

    //向上提交目录信息
    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");

    //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, "myled%d", i);
        if (IS_ERR(dev))
        {
            printk("向上提交设备节点信息失败\n");
            ret = -PTR_ERR(dev);
            goto out5;
        }
    }
    printk("向上提交设备信息成功\n");

    //platform
    //获取MEM类型的资源
    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (res == NULL)
    {
        printk("获取MEM类型资源失败\n");
        return -ENXIO;
    }

    //获取中断类型的资源
    irqno = platform_get_irq(pdev, 0);
    if (irqno < 0)
    {
        printk("获取中断类型资源失败\n");
        return -ENXIO;
    }

    //设备树匹配成功后，设备树结点指针可以通过pdev->dev.of_node获取
    //基于设备树节点信息获取gpio_desc对象指针
    gpiono = gpiod_get_from_of_node(pdev->dev.of_node, "led1-gpio", 0, GPIOD_OUT_LOW, NULL);
    if (IS_ERR(gpiono))
    {
        printk("解析GPIO管脚信息失败\n");
        return -ENXIO;
    }
    printk("解析GPIO管脚信息成功\n");

    //注册按键中断
    ret = request_irq(irqno, key_handler, IRQF_TRIGGER_FALLING, "key_init", NULL);
    if (ret < 0)
    {
        printk("注册按键%d中断失败\n", i);
        return ret;
    }
    printk("注册按键中断成功\n");

    return 0;

out5:
    //释放前一次提交成功的设备信息
    for (--i; i >= 0; i--)
    {
        device_destroy(cls, MKDEV(major, i));
    }
    class_destroy(cls); //释放目录
out4:
    //注销字符设备驱动对象
    cdev_del(cdev);
out3:
    //释放设备号
    unregister_chrdev_region(MKDEV(major, minor), 3);
out2:
    //释放设备驱动对象空间
    kfree(cdev);
out1:
    return ret;
}

//封装remove函数
int pdrv_remove(struct platform_device *pdev)
{
    //注销中断
    free_irq(irqno, NULL);
    //释放GPIO信息
    gpiod_put(gpiono);
    int i;
    //释放设备节点信息
    for (i = 0; i < 3; i++)
    {
        device_destroy(cls, MKDEV(major, i));
    }
    //销毁目录
    class_destroy(cls);
    //注销字符设备驱动对象
    cdev_del(cdev);
    //释放设备号
    unregister_chrdev_region(MKDEV(major, minor), 3);
    //释放设备驱动对象空间
    kfree(cdev);
    return 0;
}

//构建设备树匹配表
struct of_device_id oftable[] = {
    {.compatible = "hqyj,myplatform"},
    {}, //防止数组越界
};

//定义platform驱动信息对象并初始化
struct platform_driver pdrv = {
    .probe = pdrv_probe,
    .remove = pdrv_remove,
    .driver = {
        .name = "bbbbb",
        .of_match_table = oftable, //用于设备树匹配
    },
};

//一键注册platform宏
module_platform_driver(pdrv);
MODULE_LICENSE("GPL");

应用程序：test.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
int main(){
    unsigned int number;
	int fd = open("/dev/myled0", O_RDWR);
	if(fd < 0){
		printf("设备文件打开失败\n");
		exit(-1);
	}
	while(1){
		read(fd, &number, sizeof(number));
		printf("number = %d\n", number);
	}


	close(fd);

	return 0;
}

实验现象：