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

 4. 卸载设备脚本:

#!/bin/sh module="scull" device="scull" /sbin/rmmod $module $* || exit 1 rm -f /dev/${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