在dev目录创建一个字符设备驱动的流程

Posted 2020-08-15 夕相待

1.struct file_operations 字符设备文件接口

   1:  static int mpu_open(struct inode *inode, struct file *file)

   2:  {    

   3:      return 0;

   4:  }

   5:   

   6:   

   7:   

   8:  static int mpu_close(struct inode *inode, struct file *file)

   9:  {

  10:      return 0;

  11:  }

  12:   

  13:   

  14:  static long mpu_ioctl ( struct file *filp, unsigned int cmd, unsigned long arg)

  15:  {

  16:      return 0;

  17:  }

  18:   

  19:  static ssize_t mpu_read(struct file * filp, char __user *buffer, size_t size, loff_t *off)

  20:  {

  21:      return 0;

  22:  }

  23:   

  24:  static ssize_t mpu_write(struct file *filp, const char __user *buffer, size_t size, loff_t *off)

  25:  {

  26:      return 0;

  27:  }

//结构

   1:  struct file_operations mpu_ops = {

   2:      .owner =  THIS_MODULE,

   3:      .open =   mpu_open,

   4:      .unlocked_ioctl =  mpu_ioctl,

   5:      .release = mpu_close, 

   6:      .read = mpu_read,

   7:      .write = mpu_write,

   8:  };

2.向内核注册字符设备框架

   1:  //根据设备号与设备名注册字符设备  

   2:      ret = register_chrdev(253, "dt-mpu", &mpu_ops);   

   3:      if (ret < 0) {  

   4:          printk("Unable to register character device %d!\n", 253);  

   5:          return ret;  

   6:      }  

 

3.在/sys/class下面注册一个类

   1:  mcls = class_create(THIS_MODULE, "dt-mpu"); 

   2:      if (!mcls) {

   3:          printk("class_create dt-mpu failure...\n");

   4:          goto un_register;

   5:      }

4.在/dev/目录创建dt-mpu设备文件

 //创建一个设备节点，节点名为DEVICE_NAME
    dev = device_create(mcls, NULL, MKDEV(253, 0), NULL, "dt-mpu");
    if (!dev) {
        printk("device_create dt-mpu failure...\n");
        goto des_class;
    }