标签: sys

通过一个实例，说明udev、sys动态创建设备结点的方法。注意代码中红色的部分是为了实现动态创建设备结点添加的。          #include          #include          #include          #include          #include          #include          #include          MODULE_LICENSE ("GPL");          int hello_major = 252;          int hello_minor = 0;          int number_of_devices = 1;          char data ="foobar not equal to barfoo";          struct cdev cdev;          dev_t dev = 0;          static int hello_open (struct inode *inode, struct file *file)          {          printk (KERN_INFO "Hey! device opened\n");          return 0;          }          static int hello_release (struct inode *inode, struct file *file)          {          printk (KERN_INFO "Hmmm... device closed\n");          return 0;          }          ssize_t hello_read (struct file *filp, char *buff, size_t count, loff_t *offp)          {          ssize_t result = 0;          if (copy_to_user (buff, data, sizeof(data)-1))          result = -EFAULT;          else          printk (KERN_INFO "wrote %d bytes\n", count);          return result;          }          ssize_t hello_write (struct file *filp, const char *buf, size_t count, loff_t *f_pos)          {          ssize_t ret = 0;          printk (KERN_INFO "Writing %d bytes\n", count);          if (count127) return -ENOMEM;          if (count0) return -EINVAL;          if (copy_from_user (data, buf, count)) {          ret = -EFAULT;          }          else {          data ='\0';          printk (KERN_INFO"Received: %s\n", data);          ret = count;          }          return ret;          }          struct file_operations hello_fops = { .         owner = THIS_MODULE, .         open = hello_open, .         release = hello_release, .         read = hello_read, .         write = hello_write          };          struct class *my_class;          static void char_reg_setup_cdev (void)          {          int error, devno = MKDEV (hello_major, hello_minor);          cdev_init (cdev, hello_fops);          cdev.owner = THIS_MODULE;          cdev.ops = hello_fops;          error = cdev_add (cdev, devno , 1);          if (error)          printk (KERN_NOTICE "Error %d adding char_reg_setup_cdev", error);          /* creating your own class */          my_class =class_create(THIS_MODULE, "farsight_class");//add by lht          if(IS_ERR(my_class)) {          printk("Err: failed in creating class.\n");          return ;          }          /* register your own device in sysfs, and this will cause udevd to create corresponding device node */          class_device_create(my_class,NULL, devno, NULL,"farsight_dev");          // device_create(my_class,NULL, devno,"farsight_dev");          }          static int __init hello_2_init (void)          {          int result;          dev = MKDEV (hello_major, hello_minor);          result = register_chrdev_region (dev, number_of_devices, "test");          if (result0) {          printk (KERN_WARNING "hello: can't get major number %d\n", hello_major);          return result;          }          char_reg_setup_cdev ();          printk (KERN_INFO "char device registered\n");          return 0;          }          static void __exit hello_2_exit (void)          {          dev_t devno = MKDEV (hello_major, hello_minor);          cdev_del (cdev);          unregister_chrdev_region (devno, number_of_devices);          class_device_destroy(my_class, devno);          class_destroy(my_class);          }          module_init (hello_2_init);          module_exit (hello_2_exit);v 在编译了驱动后，可以查看/dev/farsight_dev设备结点，和 /sys/class/farsight_class/farsight_dev/ 本代码的测试环境是Ubantu7.04，内核版本是2.6.20-15-generi。在不同版本的内核中，有些系统函数的参数可能不太一样。