利用udev、sys动态创建linux设备结点

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在Linux 2.6内核中，devfs被认为是过时的方法，并最终被抛弃，udev取代了它。Devfs的一个很重要的特点就是可以动态创建设备结点。那我们现在如何通过udev和sys文件系统动态创建设备结点呢？

　　下面通过一个实例，说明udev、sys动态创建设备结点的方法。注意代码中红色的部分是为了实现动态创建设备结点添加的。

利用udev、sys动态创建<a <a class= class="tags" href="/tags/LINUX.html" title=linux>linux设备结点" />　

#include <class="tags" href="/tags/LINUX.html" title=linux>linux/module.h> #include <class="tags" href="/tags/LINUX.html" title=linux>linux/kernel.h> #include <class="tags" href="/tags/LINUX.html" title=linux>linux/init.h> #include <class="tags" href="/tags/LINUX.html" title=linux>linux/fs.h> #include <class="tags" href="/tags/LINUX.html" title=linux>linux/cdev.h> #include <asm/uaccess.h> #include <class="tags" href="/tags/LINUX.html" title=linux>linux/device.h> MODULE_LICENSE ("GPL"); 　　 int hello_major = 252; int hello_minor = 0; int number_of_devices = 1; char data[50]="foobar not equal to barfoo"; 　　 class="tags" href="/tags/STRUCT.html" title=struct>struct cdev cdev; dev_t dev = 0; static int hello_open (class="tags" href="/tags/STRUCT.html" title=struct>struct inode *inode, class="tags" href="/tags/STRUCT.html" title=struct>struct file *file) { printk (KERN_INFO "Hey! device openedn"); return 0; } 　　 static int hello_release (class="tags" href="/tags/STRUCT.html" title=struct>struct inode *inode, class="tags" href="/tags/STRUCT.html" title=struct>struct file *file) { printk (KERN_INFO "Hmmm... device closedn"); return 0; } ssize_t hello_read (class="tags" href="/tags/STRUCT.html" title=struct>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 (class="tags" href="/tags/STRUCT.html" title=struct>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 (count<0) return -EINVAL; if (copy_from_user (data, buf, count)) { 　　ret = -EFAULT; } else { 　　data[127]=''; 　　printk (KERN_INFO"Received: %sn", data); 　　ret = count; } return ret; } class="tags" href="/tags/STRUCT.html" title=struct>struct file_operations hello_fops = { .owner = THIS_MODULE, .open= hello_open, .release = hello_release, .read= hello_read, .write = hello_write }; class="tags" href="/tags/STRUCT.html" title=struct>struct class *my_class; static void char_reg_setup_cdev (void) { int error, devno = MKDEV (hello_major, hello_minor); cdev_init (&cdev, &hello_fops); cdev.owner = THIS_MODULE; cdev.ops = &hello_fops; error = cdev_add (&cdev, devno , 1); if (error) 　　printk (KERN_NOTICE "Error %d adding char_reg_setup_cdev", error); 　　　 /* creating your own class */ my_class =class_create(THIS_MODULE, "farsight_class");//add by lht if(IS_ERR(my_class)) { 　　　　 printk("Err: failed in creating class.n"); 　　　　 return ; } 　 /* register your own device in sysfs, and this will cause udevd to create corresponding device node */ class_device_create(my_class,NULL, devno, NULL,"farsight_dev"); 　　//device_create(my_class,NULL, devno,"farsight_dev"); } 　　 static int __init hello_2_init (void) { int result; dev = MKDEV (hello_major, hello_minor); result = register_chrdev_region (dev, number_of_devices, "test"); if (result<0) { 　　printk (KERN_WARNING "hello: can't get major number %dn", hello_major); 　　return result; } char_reg_setup_cdev (); printk (KERN_INFO "char device registeredn"); return 0; } static void __exit hello_2_exit (void) { 　dev_t devno = MKDEV (hello_major, hello_minor); 　cdev_del (&cdev); 　unregister_chrdev_region (devno, number_of_devices); 　 class_device_destroy(my_class, devno); 　 class_destroy(my_class); } module_init (hello_2_init); module_exit (hello_2_exit);