利用udev在/dev下动态生成/移除设备文件

steprun

       
       
       
       
       
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
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#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 ");
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);
               
               
               

本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u/28407/showart_340485.html