最近在鼓捣lnux字符设备驱动，在网上搜集的各种关于linux设备驱动的代码和注释，要么是针对2.4的，要么是错误百出，根本就不能运行成功，真希望大家在发博客的时候能认真核对下代码的正确性，特别是要把代码的运行环境和依赖条件列举出来，否则会对读者造成很大的误解。
以下代码的运行环境为：
操作系统:debian 6
内核版本:2.6.32(amd 64)
gcc版本：4.4.5
源代码如下所示(源代码确保编译可通过，运行无bug)：
#include#include #include #include #include #include #include MODULE_LICENSE("GPL");static int yang_open(struct inode*, struct file*);static int yang_release(struct inode*, struct file*);static ssize_t yang_read(struct file*, char *,size_t, loff_t*);static ssize_t yang_write(struct file*,const char*, size_t,loff_t*);loff_t yang_llseek(struct file *filp, loff_t off, int whence);static int major;static int device_open = 0;static char *device_name = "myvar";static dev_t devid;static struct mydev *my_cdev;struct mydev{ char *data; struct cdev cdev; unsigned long size;};static struct file_operations fops = { .owner = THIS_MODULE, .read = yang_read, .write = yang_write, .open = yang_open, .release = yang_release, .llseek = yang_llseek};int init_yang_module(void){ struct mydev *dev = (struct mydev *)kmalloc(sizeof(struct mydev),GFP_KERNEL); my_cdev = dev;//注册为全局变量，便于模块卸载 memset(dev, 0, sizeof(struct mydev)); dev->size = 10; int err; alloc_chrdev_region(&devid, 0, 1, "myvar"); major = MAJOR(devid); cdev_init(&dev->cdev, &fops); err = cdev_add(&dev->cdev, devid, 1); if(err) { printk(KERN_INFO"I was major number %d.\n",major); return -1; } printk("major number is %d\n",MAJOR(devid)); dev->data = (char*)kmalloc(dev->size * sizeof(char),GFP_KERNEL); memset(dev->data,0,dev->size * sizeof(char)); return 0;}void cleanup_yang_module(void){ cdev_del(&my_cdev->cdev); unregister_chrdev_region(devid, 1); printk("cleanup done\n");}loff_t yang_llseek(struct file *filp, loff_t off, int whence){ struct mydev *dev = filp->private_data; loff_t newpos; switch(whence) { case SEEK_SET: newpos = off; case SEEK_CUR: newpos = filp->f_pos + off; case SEEK_END: newpos = dev->size + off; break; default: return -EINVAL; } if(newpos < 0) return -EINVAL; filp->f_pos = newpos; return newpos;}static int yang_open(struct inode* inode, struct file* file){ struct mydev *dev; dev = container_of(inode->i_cdev, struct mydev, cdev); file->private_data = dev; return 0;}static int yang_release(struct inode* inode, struct file* file){ return 0;}static ssize_t yang_read(struct file* filp, char *buffer,size_t length, loff_t* off){ struct mydev *dev = filp->private_data; if(*off >= dev->size) { return 0; } if(*off + length > dev->size) length = dev->size - *off; if(copy_to_user(buffer,dev->data + *off,length * sizeof(char))) { return -EFAULT; } *off += length; return length;}static ssize_t yang_write(struct file* filp,const char* buffer, size_t length,loff_t* off){ struct mydev *dev = filp->private_data; if(length > dev->size) { return -EFAULT; } if(copy_from_user(dev->data,buffer,dev->size * sizeof(char))) { return -EFAULT; } *off += length; return dev->size;}module_init(init_yang_module); module_exit(cleanup_yang_module);
以后有时间我再把注释加上，如果有兄弟刚刚学习linux设备驱动，这份源代码是最好的礼物。