利用udev在/dev下动态生成/移除设备文件

深藏阁楼爱情的钟 2022-03-26 15:36 215阅读 0赞

http://blog.chinaunix.net/space.php?uid=14163325&do=blog&id=64559  
  
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：  
  
2.6.27到现在  
  
    class\_create        :    创建class  
    class\_destroy        :    销毁class  
    device\_create         :    创建device  
    device\_destroy         :    销毁device     
  
2.6.13到2.6.26     
  
    class\_create        :    创建class  
    class\_destroy        :    销毁class  
    class\_device\_create    :    创建device  
    class\_device\_destroy    :    销毁device  
  
  
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/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 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);