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)
- #include <linux/kernel.h>
- #include <linux/module.h>
- #include <linux/init.h>
- #include <linux/mm.h>
- #include <linux/fs.h>
- #include <linux/*.h>
- #include <linux/delay.h>
- #include <linux/moduleparam.h>
- #include <linux/slab.h>
- #include <linux/errno.h>
- #include <linux/ioctl.h>
- #include <linux/cdev.h>
- #include <linux/string.h>
- #include <linux/list.h>
- #include <linux/pci.h>
- #include <asm/uaccess.h>
- #include <asm/atomic.h>
- #include <asm/unistd.h>
- #define THIS_DESCRIPTION "\
- This module is a dummy device driver, it register\n\
- \t\ta char device, and utilize udev to create/destroy \n\
- \t\tdevice node under /dev/ dynamicallly."
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("albcamus <albcamus@gmail.com>");
- MODULE_DESCRIPTION(THIS_DESCRIPTION);
- #define DUMMY_MAJOR 250
- #define DUMMY_MINOR 0
- #define DUMMY_NAME "dummy_dev"
- /**
- * the open routine of 'dummy_dev'
- */
- static int dummy_open(struct inode *inode, struct file *file)
- {
- printk("Open OK\n");
- return 0;
- }
- /**
- * the write routine of 'dummy_dev'
- */
- static ssize_t dummy_write(struct file *filp, const char *bp, size_t count, loff_t *ppos)
- {
- printk("Don't Write!\n");
- return 0;
- }
- /**
- * the read routine of 'dummy_dev'
- */
- static ssize_t dummy_read(struct file *filp, char *bp, size_t count, loff_t *ppos)
- {
- return 0;
- }
- /**
- * the ioctl routine of 'dummy_dev'
- */
- static int dummy_ioctl(struct inode *inode, struct file *filep,
- unsigned int cmd, unsigned long arg)
- {
- return 0;
- }
- /**
- * file_operations of 'dummy_dev'
- */
- static struct file_operations dummy_dev_ops = {
- .owner = THIS_MODULE,
- .open = dummy_open,
- .read = dummy_read,
- .write = dummy_write,
- .ioctl = dummy_ioctl,
- };
- /**
- * struct cdev of 'dummy_dev'
- */
- struct cdev *my_cdev;
- struct class *my_class;
- static int __init my_init(void)
- {
- int err, devno = MKDEV(DUMMY_MAJOR, DUMMY_MINOR);
- /* register the 'dummy_dev' char device */
- my_cdev = cdev_alloc();
- cdev_init(my_cdev, &dummy_dev_ops);
- my_cdev->owner = THIS_MODULE;
- err = cdev_add(my_cdev, devno, 1);
- if (err != 0)
- printk("dummy pci device register failed!\n");
- /* creating your own class */
- my_class = class_create(THIS_MODULE, "dummy_class");
- if(IS_ERR(my_class)) {
- printk("Err: failed in creating class.\n");
- return -1;
- }
- /* register your own device in sysfs, and this will cause udevd to create corresponding device node */
- class_device_create(my_class, NULL, MKDEV(DUMMY_MAJOR, DUMMY_MINOR), NULL, DUMMY_NAME "%d", DUMMY_MINOR );
- return 0;
- }
- static void __exit my_fini(void)
- {
- printk("bye\n");
- cdev_del(my_cdev);
- //kfree(my_cdev); no use. because that cdev_del() will call kfree if neccessary.
- class_device_destroy(my_class, MKDEV(DUMMY_MAJOR, DUMMY_MINOR));
- class_destroy(my_class);
- }
- module_init(my_init);
- module_exit(my_fini);
文章来源CU社区：利用udev在/dev下动态生成/移除设备文件
