利用udev在/dev下动态生成/移除设备文件

2020-06-15 00:00:00 创建 专区 订阅 付费 销毁

用udev在/dev/下动态生成设备文件，这样用户就不用手工调用mknod了。


利用的kernel API：

class_create : 创建class
class_destroy : 销毁class
class_device_create : 创建device
class_device_destroy : 销毁device


注意，这些API是2.6.13开始有的，在2.6.13之前，应当使用

class_simple_create
class_simple_destroy
class_simple_device_add
class_simple_device_remove

这一系列，也就是ldd3第14章描述的。 详见:

https://lwn.net/Articles/128644/

Output:
===========================================
[root@localhost dynamic_dev_node]# insmod ./dummy_dev.ko
[root@localhost dynamic_dev_node]# file /dev/dummy_dev0
/dev/dummy_dev0: character special (250/0)
[root@localhost dynamic_dev_node]# rmmod dummy_dev.ko
[root@localhost dynamic_dev_node]# file /dev/dummy_dev0
/dev/dummy_dev0: ERROR: cannot open `/dev/dummy_dev0' (No such file or directory)



  3. #include <linux/kernel.h>
  4. #include <linux/module.h>
  5. #include <linux/init.h>
  6. #include <linux/mm.h>
  7. #include <linux/fs.h>
  8. #include <linux/*.h>
  9. #include <linux/delay.h>
  10. #include <linux/moduleparam.h>
  11. #include <linux/slab.h>
  12. #include <linux/errno.h>
  13. #include <linux/ioctl.h>
  14. #include <linux/cdev.h>
  15. #include <linux/string.h>
  16. #include <linux/list.h>
  17. #include <linux/pci.h>
  18. #include <asm/uaccess.h>
  19. #include <asm/atomic.h>
  20. #include <asm/unistd.h>



  24. #define THIS_DESCRIPTION "\
  25. This module is a dummy device driver, it register\n\
  26. \t\ta char device, and utilize udev to create/destroy \n\
  27. \t\tdevice node under /dev/ dynamicallly."


  30. MODULE_LICENSE("GPL");
  31. MODULE_AUTHOR("albcamus <albcamus@gmail.com>");
  32. MODULE_DESCRIPTION(THIS_DESCRIPTION);



  36. #define DUMMY_MAJOR 250
  37. #define DUMMY_MINOR 0
  38. #define DUMMY_NAME "dummy_dev"





  44. /**
  45. * the open routine of 'dummy_dev'
  46. */
  47. static int dummy_open(struct inode *inode, struct file *file)
  48. {
  49.     printk("Open OK\n");
  50.     return 0;
  51. }

  53. /**
  54. * the write routine of 'dummy_dev'
  55. */
  56. static ssize_t dummy_write(struct file *filp, const char *bp, size_t count, loff_t *ppos)
  57. {
  58.     printk("Don't Write!\n");
  59.     return 0;
  60. }

  62. /**
  63. * the read routine of 'dummy_dev'
  64. */
  65. static ssize_t dummy_read(struct file *filp, char *bp, size_t count, loff_t *ppos)
  66. {
  67.     return 0;
  68. }

  70. /**
  71. * the ioctl routine of 'dummy_dev'
  72. */
  73. static int dummy_ioctl(struct inode *inode, struct file *filep,
  74.             unsigned int cmd, unsigned long arg)
  75. {

  77.     return 0;
  78. }


  81. /**
  82. * file_operations of 'dummy_dev'
  83. */
  84. static struct file_operations dummy_dev_ops = {
  85.     .owner = THIS_MODULE,
  86.     .open = dummy_open,
  87.     .read = dummy_read,
  88.     .write = dummy_write,
  89.     .ioctl = dummy_ioctl,
  90. };


  93. /**
  94. * struct cdev of 'dummy_dev'
  95. */
  96. struct cdev *my_cdev;
  97. struct class *my_class;



  101. static int __init my_init(void)
  102. {
  103.     int err, devno = MKDEV(DUMMY_MAJOR, DUMMY_MINOR);


  106.     /* register the 'dummy_dev' char device */
  107.     my_cdev = cdev_alloc();
  108.     cdev_init(my_cdev, &dummy_dev_ops);

  110.     my_cdev->owner = THIS_MODULE;

  112.     err = cdev_add(my_cdev, devno, 1);
  113.     if (err != 0)
  114.         printk("dummy pci device register failed!\n");

  116.     /* creating your own class */
  117.     my_class = class_create(THIS_MODULE, "dummy_class");
  118.     if(IS_ERR(my_class)) {
  119.         printk("Err: failed in creating class.\n");
  120.         return -1;
  121.     }

  123.     /* register your own device in sysfs, and this will cause udevd to create corresponding device node */
  124.     class_device_create(my_class, NULL, MKDEV(DUMMY_MAJOR, DUMMY_MINOR), NULL, DUMMY_NAME "%d", DUMMY_MINOR );



  128.     return 0;
  129. }

  131. static void __exit my_fini(void)
  132. {
  133.     printk("bye\n");

  135.     cdev_del(my_cdev);
  136.     //kfree(my_cdev); no use. because that cdev_del() will call kfree if neccessary.


  139.     class_device_destroy(my_class, MKDEV(DUMMY_MAJOR, DUMMY_MINOR));
  140.     class_destroy(my_class);

  142. }




  147. module_init(my_init);
  148. module_exit(my_fini);

相关文章