基本scull模块驱动程序

    还是太懒惰，总是不能找到足够的时间来看书和做总结，今天终于有时间把ldd3第三章的部分完整调试和总结下了。直接贴源代码吧，希望将来还能看懂。

1. scull.h头文件:

#ifndef _SCULL_H_#define _SCULL_H_#include <linux/ioctl.h>#ifndef SCULL_MAJOR#define SCULL_MAJOR 0#endif#ifndef SCULL_NR_DEVS#define SCULL_NR_DEVS 4 /* scull0 ~ scull3 */#endif#ifndef SCULL_QUANTUM#define SCULL_QUANTUM 4000#endif#ifndef SCULL_QSET#define SCULL_QSET 1000#endifstruct scull_qset{void **data;struct scull_qset *next;};struct scull_dev{struct scull_qset *data;int quantum;int qset;unsigned long size;unsigned int access_key;struct semaphore sem;struct cdev cdev;};#define TYPE(minor)((minor)>>4) && 0xff)#define NUM(minor) ((minor) & 0xf)extern int scull_major;/* main.c */extern int scull_nr_devs;extern int scull_quantum;extern int scull_qset;int scull_trim(struct scull_dev *dev);ssize_t scull_read(struct file *filep,char __user *buf, size_t count,loff_t *offp);ssize_t scull_write(struct file *filep, const char __user *buff, size_t count,loff_t *offp);loff_t scull_llseek(struct file *filep,loff_t off,int whence);int scull_ioctl(struct inode *inode,struct file *filep,unsigned int cmd,unsigned long arg);#define SCULL_IOC_MAXNR 14#endif      

2. scull.c文件:

//#include <linux/config.h>#include <linux/module.h>#include <linux/moduleparam.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/slab.h> #include <linux/fs.h>#include <linux/errno.h>#include <linux/types.h>#include <linux/proc_fs.h>#include <linux/fcntl.h>#include <linux/seq_file.h>#include <linux/cdev.h>#include <asm/system.h>#include <asm/uaccess.h>#include "scull.h"int scull_major = SCULL_MAJOR;int scull_minor = 0;int scull_nr_devs = SCULL_NR_DEVS;int scull_quantum = SCULL_QUANTUM;int scull_qset = SCULL_QSET;module_param(scull_major,int,S_IRUGO);module_param(scull_minor,int,S_IRUGO);module_param(scull_nr_devs,int,S_IRUGO);MODULE_LICENSE("Dual BSD/GPL");struct scull_dev *scull_devices;/* empty out the scull device; must be called with the device semaphore held*//* scull_trim 负责释放整个数据区，并且在文件以写入放送打开时由scull_open调用，它简单遍历链表，并释放所有找到的 量子和量子集 */int scull_trim(struct scull_dev *dev){struct scull_qset *next,*dptr;int qset = dev->qset;int i;for(dptr = dev->data;dptr;dptr=next){if(dptr->data){for(i = 0; i < qset; i++)kfree(dptr->data[i]);kfree(dptr->data);dptr->data = NULL;}next = dptr->next;kfree(dptr);}dev->size = 0;dev->quantum = scull_quantum;dev->qset = scull_qset;dev->data = NULL;return 0;}/* 若设备以写方式打开，它的长度截0，未锁信号量*/int scull_open(struct inode *inode,struct file *filep){struct scull_dev *dev;dev = container_of(inode->i_cdev,struct scull_dev,cdev);filep->private_data = dev;if((filep->f_flags & O_ACCMODE) == O_WRONLY){ /*if(down_interruptible(&dev->sem))return -ERESTARTSYS; */scull_trim(dev);/*up(&dev->sem); */}return 0;}int scull_release(struct inode *inode, struct file *filep){return 0;}struct scull_qset *scull_follow(struct scull_dev *dev,int n){struct scull_qset *qs = dev->data;if(!qs){qs = dev->data = kmalloc(sizeof(struct scull_qset),GFP_KERNEL);if(qs == NULL)return NULL;memset(qs,0,sizeof(struct scull_qset));}while(n--){if(!qs->next){qs->next = kmalloc(sizeof(struct scull_qset),GFP_KERNEL);if(qs->next == NULL)return NULL;memset(qs->next,0,sizeof(struct scull_qset));}qs = qs->next;continue;}return qs;}ssize_t scull_read(struct file *filep, char __user *buf, size_t count,loff_t *f_pos){struct scull_dev *dev = filep->private_data;struct scull_qset *dptr;int quantum = dev->quantum,qset = dev->qset;int itemsize = quantum * qset;int item, s_pos, q_pos,rest;ssize_t retval = 0;if(down_interruptible(&dev->sem))return -ERESTARTSYS;if(*f_pos>=dev->size)goto out;if(*f_pos + count > dev->size)count = dev->size - *f_pos;item = (long)*f_pos / itemsize;rest = (long)*f_pos % itemsize;s_pos = rest / quantum; q_pos = rest % quantum;dptr = scull_follow(dev,item);if(dptr == NULL || !dptr->data || !dptr->data[s_pos])goto out;if(count > quantum - q_pos)count = quantum - q_pos;if(copy_to_user(buf,dptr->data[s_pos] + q_pos,count)){retval = -EFAULT;goto out;}*f_pos += count;retval = count;out:up(&dev->sem);return retval;}ssize_t scull_write(struct file *filep,const char __user *buf,size_t count,loff_t *f_pos){struct scull_dev *dev = filep->private_data;struct scull_qset *dptr;int quantum = dev->quantum,qset = dev->qset;int itemsize = quantum * qset;int item,s_pos,q_pos,rest;ssize_t retval = -ENOMEM;/*if(down_interruptible(&dev->sem))return -ERESTARTSYS;*/item = (long)*f_pos / itemsize;rest = (long)*f_pos % itemsize;s_pos = rest / quantum; q_pos = rest % quantum;dptr = scull_follow(dev,item);if(dptr == NULL)goto out;if(!dptr->data){dptr->data[s_pos] = kmalloc(quantum,GFP_KERNEL);if(!dptr->data[s_pos])goto out;}if(count > quantum - q_pos)count = quantum - q_pos;if(copy_from_user(dptr->data[s_pos]+q_pos,buf,count)){retval = -EFAULT;goto out;}*f_pos += count;retval = count;if(dev->size < *f_pos)dev->size = *f_pos;out://up(&dev->sem);return retval;}/* scull_llseek方法用来修改文件的当前读写位置,并将新位置作为返回值返回*/loff_t scull_llseek(struct file *filep, loff_t off, int whence){struct scull_dev *dev = filep->private_data;loff_t newpos;switch(whence){case 0:newpos = off;break;case 1:newpos = filep->f_pos +off;break;case 2:newpos = dev->size + off;break;default:return -EINVAL;}if(newpos < 0)return -EINVAL;filep->f_pos = newpos;return newpos;}// scull设备的文件操作struct file_operations scull_fops = {.owner = THIS_MODULE,.llseek = scull_llseek,.read = scull_read,.write = scull_write,/*.ioctl = scull_ioctl,*/.open =scull_open,.release = scull_release,};void scull_cleanup_module(void){int i;dev_t devno = MKDEV(scull_major,scull_minor);if(scull_devices){for(i = 0; i < scull_nr_devs; i++){scull_trim(scull_devices + 1);cdev_del(&scull_devices[i].cdev);}kfree(scull_devices);}unregister_chrdev_region(devno,scull_nr_devs);}static void scull_setup_cdev(struct scull_dev *dev,int index){int err, devno = MKDEV(scull_major,scull_minor + index);cdev_init(&dev->cdev,&scull_fops);dev->cdev.owner = THIS_MODULE;dev->cdev.ops = &scull_fops;err = cdev_add(&dev->cdev,devno,1);if(err)printk(KERN_NOTICE "Error %d adding scull %d",err,index);}int scull_init_module(void){int result,i;dev_t dev = 0;// 获取主设备号if(scull_major){dev = MKDEV(scull_major,scull_minor);result = register_chrdev_region(dev,scull_nr_devs,"scull");}else{result = alloc_chrdev_region(&dev,scull_minor,scull_nr_devs,"scull");scull_major = MAJOR(dev);}if(result < 0){printk(KERN_WARNING "scull: can't get major %d /n", scull_major);return result;}scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev),GFP_KERNEL);if(!scull_devices){result = -ENOMEM;goto fail;}memset(scull_devices,0,scull_nr_devs * sizeof(struct scull_dev));printk(KERN_ALERT "The length of scull_dev is %d",sizeof(struct scull_dev));for(i = 0; i < scull_nr_devs; i++){scull_devices[i].quantum = scull_quantum;scull_devices[i].qset = scull_qset;//init_MUTEX(&scull_devices[i].sem);scull_setup_cdev(&scull_devices[i],i);}dev = MKDEV(scull_major,scull_minor + scull_nr_devs);return 0;fail:scull_cleanup_module();return result;}module_init(scull_init_module);module_exit(scull_cleanup_module);  

3. 加载设备脚本:

#!/bin/shmodule="scull"device="scull"mode="664"/sbin/insmod ./$module.ko $* || exit 1rm -f /dev/${device}[0-3]major=$(awk "/$2==/"$module/" {print /$1}" /proc/devices)mknod /dev/${device}0 c $major 0mknod /dev/${device}1 c $major 1mknod /dev/${device}2 c $major 2mknod /dev/${device}3 c $major 3

 4. 卸载设备脚本:

#!/bin/shmodule="scull"device="scull"/sbin/rmmod $module $* || exit 1rm -f /dev/${device} /dev/${device}[0-3]

5. 代码思路及调试办法

   1. 每个设备从module_init()开始，在scull设备中，module_init()首先分配设备号，然后分配内存，最后初始化cdev。

   2. 注意struct scull_dev的定义及全局变量struct file_operations scull_fops的初始化

   3. scull_trim()函数由scull_open()调用，scull_follow()由scull_write()和scull_read（0调用

   4. 注意要用chmod +x 命令将scull_load和scull_onload属性更改为可执行

   5. 执行scull_load，可用lsmod命令查看当前运行的模块，将看到多了个scull驱动程序，用ls /dev |more 将看到多了4个设备(scull0~scull3),注意，若用insmod直接加载模块，则在/dev下看不到scull0~scull3，只能用lsmod看到多了个scull设备驱动程序