在Linux 2.6內(nèi)核中，devfs被認(rèn)為是過時的方法，并最終被拋棄，udev取代了它。Devfs的一個很重要的特點就是可以動態(tài)創(chuàng)建設(shè)備結(jié)點。那我們現(xiàn)在如何通過udev和sys文件系統(tǒng)動態(tài)創(chuàng)建設(shè)備結(jié)點呢？

下面通過一個實例，說明udev、sys動態(tài)創(chuàng)建設(shè)備結(jié)點的方法。注意代碼中紅色的部分是為了實現(xiàn)動態(tài)創(chuàng)建設(shè)備結(jié)點添加的。

#include

#include

#include

#include

#include

#include

#include

MODULE_LICENSE ("GPL");

int hello_major = 252;

int hello_minor = 0;

int number_of_devices = 1;

char data[50]="foobar not equal to barfoo";

struct cdev cdev;

dev_t dev = 0;

static int hello_open (struct inode *inode, struct file *file)

{

printk (KERN_INFO "Hey! device opened ");

return 0;

}

static int hello_release (struct inode *inode, struct file *file)

{

printk (KERN_INFO "Hmmm... device closed ");

return 0;

}

ssize_t hello_read (struct file *filp, char *buff, size_t count, loff_t *offp)

{

ssize_t result = 0;

if (copy_to_user (buff, data, sizeof(data)-1))

result = -EFAULT;

else

printk (KERN_INFO "wrote %d bytes ", count);

return result;

}

ssize_t hello_write (struct file *filp, const char?*buf, size_t count, loff_t *f_pos)

{

ssize_t ret = 0;

printk (KERN_INFO "Writing %d bytes ", count);

if (count>127) return -ENOMEM;

if (count<0) return -EINVAL;

if (copy_from_user (data, buf, count)) {

ret = -EFAULT;

}

else {

data[127]='