在Linux2.6內(nèi)核中，devfs被認(rèn)為是過(guò)時(shí)的方法，并最終被拋棄，udev取代了它。Devfs的一個(gè)很重要的特點(diǎn)就是可以動(dòng)態(tài)創(chuàng)建設(shè)備結(jié)點(diǎn)。那我們現(xiàn)在如何通過(guò)udev和sys文件系統(tǒng)動(dòng)態(tài)創(chuàng)建設(shè)備結(jié)點(diǎn)呢?

下面通過(guò)一個(gè)實(shí)例，說(shuō)明udev、sys動(dòng)態(tài)創(chuàng)建設(shè)備結(jié)點(diǎn)的方法。注意代碼中紅色的部分是為了實(shí)現(xiàn)動(dòng)態(tài)創(chuàng)建設(shè)備結(jié)點(diǎn)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 openedn);

return 0;

}

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

{

printk (KERN_INFO Hmmm... device closedn);

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 bytesn, 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 bytesn, count);

if (count>127) return -ENOMEM;

if (count0) return -EINVAL;

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

ret = -EFAULT;

}

else {

data[127]='