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【转】利用udev在/dev/下动态生成/移除设备文件

Driver crifan 1320浏览 0评论

【转】利用udev在/dev/下动态生成/移除设备文件

利用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)

Code:
+++++++++++++++++++++++++++

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/types.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 registern
tta char device, and utilize udev to create/destroy n
ttdevice 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 OKn");
    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("byen");

     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);

注:这样实现之后,还需要去udev工具进行设置的,才能看到/dev下出现你要的设备的,详情参考:

http://linux.chinaunix.net/bbs/thread-1031291-2-1.html

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网友最新评论 (4)

  1. 谢谢!都是好东西啊!
    suzp198410年前 (2009-06-01)回复
  2. 自己参考:
    如何编写Linux设备驱动程序【转】
    http://hi.baidu.com/serial_story/blog/item/82be2f385c2921f1b311c734.html
    againinput410年前 (2009-05-31)回复
  3. 能给出上面的代码是怎样编译出*.ko内核驱动的吗?
    怎样用gcc编译的?
    强烈关注!!

    suzp198410年前 (2009-05-31)回复
  4. 最近,一直要学习udev,有无从下手,这篇文章好!!
    suzp198410年前 (2009-05-31)回复
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