platform总线驱动

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

 驱动代码：

#include 
#include 
#include
#include
#include
#include 
#include
#include
#include
#include
 
int major;//接收主设备号
struct class *cls;//句柄
struct device *dev;
char kbuf[128]={};  //定义数组用于存放和用户之间拷贝的数据
wait_queue_head_t wq_head;
unsigned int condition=0;//判断是否有数据准备好的标识变量
struct resource *res;
int irqno;  //中断号
struct gpio_desc *desc;
int number=1;  //1亮，0灭
int mycdev_open(struct inode *inode, struct file *file)
{
      return 0;
}
ssize_t mycdev_read(struct file *file, char __user *ubuf, size_t size, loff_t *loff)
{
    //size参数是用户期待读到的字节长度
    if(size>sizeof(kbuf))
    size=sizeof(kbuf);
    if(copy_to_user(ubuf,&number,size))//内核发送number给用户
    {
        printk("数据从内核向用户拷贝失败\n");
        return -EIO;
    }
    condition = 0;
    wait_event_interruptible(wq_head, condition);//发送完成进入阻塞
    return size;
}
ssize_t mycdev_write(struct file *file, const char __user *ubuf, size_t size, loff_t *loff)
{
    if(size>sizeof(kbuf))
    size=sizeof(kbuf);
    if(copy_from_user(kbuf,ubuf,size))
    {
        printk("用户向内核写数据失败\n");
        return -EIO;
    }
    return size;
}
int mycdev_close(struct inode *inode, struct file *file)
{
    return 0;
}
struct file_operations fops={
    .open=mycdev_open,
    .read=mycdev_read,
    .write=mycdev_write,
    .release=mycdev_close,
};
 
irqreturn_t irq_handel(int irq, void *dev)
{
    number = (number+1)%2;
    gpiod_set_value(desc,!gpiod_get_value(desc));//led2状态取反
    condition = 1;
    wake_up(&wq_head);  //唤醒阻塞
    return IRQ_HANDLED;
}
int pdrv_probe(struct platform_device *pdr)
{
      //获取中断号
      irqno=platform_get_irq(pdr,0);
      if(irqno<0)
      {
            printk("获取中断号失败\n");
            return irqno;
      }
      //注册中断
      if(request_irq(irqno,irq_handel,IRQF_TRIGGER_FALLING,"key2_interrupt",NULL))
      {
            printk("注册中断失败\n");
            return -1;
      }
      //获取GPIO编号
      desc=gpiod_get_from_of_node(pdr->dev.of_node,"led2",0,GPIOD_OUT_LOW,NULL);
      if(IS_ERR(desc))
      {
            printk("获取GPIO编号失败\n");
            return PTR_ERR(desc);
      }
      return 0;
}
 
 int pdrv_remove(struct platform_device *pdr)
 {
      return 0;
 }
 //定义compatible表
 struct of_device_id oftable[]={
      {.compatible="hqyj, fsmp1a"},
      {},
 };
MODULE_DEVICE_TABLE(of,oftable);
//定义并初始化对象
struct platform_driver pdrv ={
      .probe  = pdrv_probe,
      .remove = pdrv_remove,
      .driver = {
            .name = "test",
            .of_match_table = oftable,//设备树匹配 
      },
 };
static int __init mycdev_init(void)
{
      //动态注册字符设备驱动
      major=register_chrdev(0,"mycdev",&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);
      //自动创建设备节点
      cls=class_create(THIS_MODULE,"MYCDEV");  //向上提交节点目录
      if(IS_ERR(cls))
      {
            printk("向上提交目录失败\n");
            return PTR_ERR(cls);
      }
      dev=device_create(cls,NULL,MKDEV(major,0),NULL,"pdrv");  //创建设备节点
      if(IS_ERR(dev))
      {
            printk("创建节点失败\n");
            return PTR_ERR(dev);
      }
      printk("创建节点成功\n");
 
      //注册对象
      platform_driver_register(&pdrv);
      //初始化等待队列
      init_waitqueue_head(&wq_head);
      return 0;
}
 
static void __exit mycdev_exit(void)
{
      free_irq(irqno,NULL);                //注销中断号
      gpiod_direction_output(desc,0);      //关闭灯
      gpiod_put(desc);                     //释放GPIO编号
      platform_driver_unregister(&pdrv);   //注销
      device_destroy(cls,MKDEV(major,0));  //销毁节点
      class_destroy(cls);                  //销毁目录
      unregister_chrdev(major,"mycdev");   //注销字符设备驱动
}
 
module_init(mycdev_init);
module_exit(mycdev_exit);
MODULE_LICENSE("GPL");

添加的设备树节点：

my_platform_irq_led{
		compatible = "hqyj, fsmp1a";
		reg = <0x33221100 0x20>;
		interrupt-parent = <&gpiof>;
		interrupts = <7 0>;
		led2 = <&gpiof 10 0>;
	};

测试代码：

#include 
#include 
#include 
#include 
#include 
#include 
int main(int argc, char const *argv[])
{
    //打开节点
    int fd = open("/dev/pdrv",O_RDWR);
    if(fd<0)
    {
        printf("打开设备节点失败\n");
        return -1;
    }
    int number;
    while(1)
    {
        read(fd,&number,sizeof(number));//读取内核中number的值
        printf("number=%d\n",number);
    }
    close(fd);
    return 0;
}

测试结果：