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#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/kernel.h> /*printk()*/
#include <linux/slab.h> /*kmalloc()*/
#include <linux/fs.h> /*everything...*/
#include <linux/errno.h> /*error codes*/
#include <linux/types.h> /*size_t*/
#include <linux/cdev.h> /*cdev struct*/
#include <asm/system.h> /*cli(),*_flags*/
#include <asm/uaccess.h> /*copy_ ....*/
#include "scull_t1.h" /*attention to the "" and <>*/
/*
*Our parameters which can be set at load time.
*
*/
int scull_major = SCULL_MAJOR;
int scull_minor = 0;
int scull_nr_devs = SCULL_NR_DEVS; /*number of bare scull devs*/
int scull_quantum = SCULL_QUANTUM; /*every one of quantum array has a quantum size*/
int scull_qset = SCULL_QSET; /*the longth of quantum-set*/
module_param(scull_major,int,S_IRUGO); /*knowledge 1*/
module_param(scull_monor,int,S_IRUGO);
module_param(scull_nr_devs,int,S_IRUGO);
module_param(scull_quantum,int,S_IRUGO);
module_param(scull_qset,int,S_IRUGO);
struct scull_dev *scull_devices; /*allocated in scull_init_module*/
/*
*Empty out (like "clean up")the scull device
*/
int scull_trim(struct scull_dev *dev) /*知識點(diǎn)4*/
{
struct scull_qset *next,*dptr;
int qset = dev->qset; /*amount of quantum*/
int i;
for(dptr = dev->data;dptr;dptr = next) /*循環(huán)scull_qset list 個數(shù)*/
{
if(dptr->data)
{
for(i = 0; i<qset; i++)
kfree(dptr->data[i]); /*釋放dptr指向的數(shù)組的每個數(shù)組元素指向的quantum空間*/
kfree(dptr->data);/* 釋放當(dāng)前的scull_set的量子集的空間*/
dptr->data = NULL;/* 釋放一個scull_set中的void **data指針*/
/*其實(shí)就我個人寫的話下面那句指向空會漏掉*/
}
next = dptr->next; /*下一個scull_qset list開始*/
kfree(dptr); /*knowledge 2*/
}
dev->size =0; /*amount of data store here 為0*/
dev->quantum = scull_quantum; /*set the quantum'size*//*你不是清空不，怎么還來設(shè)置它的大小啊*/
dev->qset = scull_qset; /*set the number of quantum in a array*//*同上的疑問*/
dev->data = NULL; /*釋放當(dāng)前的scull_device的struct scull_qset *data指針*/
return 0;
}
/********************************************************************/
/*
*Open and close
*/
int scull_open(struct inode *inode,struct file *filp)
{
struct scull_dev *dev; /*the information of this dev*/
dev = contairner_of(inode->i_cdev,struct scull_dev, cdev); /*知識點(diǎn)3*/
flip->private_data = dev; /*.將獲得的dev保存到filp->private_data*/
/*如果是以只讀模式打開則調(diào)用scull_trim()截短設(shè)備為0*/
if((filp->f_flags&O_ACCMODE) == O_WRONLY) /*這里注意是檢測打開的方式不是讀寫權(quán)限f_mode*/
{
if(down_interruptible(&dev->sem)) /* 對訪問區(qū)域加鎖*/
return -ERESTARTSYS; /*猜想應(yīng)該是信號量不可用的意思吧??*/
scull_trim(dev);
up(&dev->sem); /* 解鎖*/
}
}
int scull_release(struct inode *inode, struct file *filp)
{
return 0;
/*由于前面定義了scull是一個全局且持久的內(nèi)存區(qū)，所以他的release什么都不做*/
}
/*
*Follow the list
*/
struct scull_qset *scull_follow(struct scull_dev *dev,int n)
{
struct scull_qset *qs = dev->data;
/*Allocate frist qset explicitly if need be*/
if(! qs) /*當(dāng)list為null時*/
{
qs = dev->data = kmalloc(sizeof(struct scull_qset),GFP_KERNEL);
if(qs == NULL)
return NULL; /*??*/
memset(qs,0,sizeof(struct scull_qset));
}
/*follow the list*/
while(n--)
{
if(!qs->next)
{
qs->next = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
if (qs->next == NULL)
return NULL; /* Never mind */
memset(qs->next, 0, sizeof(struct scull_qset));
}
qs = qs->next;
continue; /*這下我傻了*/
return qs;
}
}
/*
*read and write
*/
ssize_t scull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
struct scull_dev *dev = filp->private_data; /*獲得已經(jīng)保存在其中的設(shè)備結(jié)構(gòu)體入口指針*/
struct scull_qset *dptr; /*the first listitem*/
int quantum = dev->quantum,qset = dev->qset;
int itemsize = quantum *qset; /*這句很怪哦 不同的部分相互賦值干嗎啊??*/
int item,s_pos,q_pos,rest;
ssize_t retval = 0;
if(down_interruptible(&dev->sem))
return -ERESTARSYS;
if(*f_pos >= dev->size) /*判讀off_t *f_pos參數(shù)是否超越了設(shè)備存儲的范圍*/
goto out;
if(*f_pos+count > dev->size)
count = dev->size - *f_pos;
/*find listitem,qset index,and offset in the quantum*//* 根據(jù)數(shù)組結(jié)構(gòu)得出相應(yīng)數(shù)據(jù) */
item = (long)*f_pos/ itemsize; /*long???why???*/
rest = (long)*f_pos%itemsize;
s_pos = rest/quantum; /*no long ??why??*/
q_pos = rest%quantum;
/*follow the list up to the right position(defined elsewhere)*/
dptr = scull_follow(dev,item);
/*判斷各個數(shù)值的合法性并做修正*/
if(dptr == NULL||!dptr->data||!dptr->data||!dptr->data[s_pos])
goto out;
/*read only up to the end of this quantum*/
if(count>quantum - q_pos)
count = quantum -q_pos;
/*將內(nèi)核數(shù)據(jù)復(fù)制到用戶區(qū)域*/
if(copy_to_user(buf, dptr->data[s_pos]+q_pos,count))/*發(fā)現(xiàn)自己對返回值還是不足*/
{
retval = -EFUALT; /*上面應(yīng)該是成功返回0非成功返回非0即真*/
goto out;
}
*f_pos += count;
retval = count;
out:
up(&dev->sem);
return retval;
}
ssize_t scull_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos )
{
struct scull_dev *dev = filp->private_data;
struct scull_qset *dptr;
int quantum = dev->quantum,qset = dev->qset;
int itemsize = quantum * qset; /*這句還是沒懂*/
int item,s_pos,q_pos,rest;
ssize_t retval = -ENOMEM; /*no mem used in "goto out"*/
if(down_interruptible(&dev->sem))
return -ERESTART;
/*同read*/
item = (long)*f_pos / itemsize;
rest = (long)*f_pos % itemsize;
s_pos = rest / quantum;
q_pos = rest % quantum;
/* follow the list up to the right position */
/*同read*/
dptr = scull_follow(dev, item);
if (dptr == NULL)
goto out;
if (!dptr->data)
{
dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL);
if (!dptr->data)
goto out;
memset(dptr->data, 0, qset * sizeof(char *));
}
if (!dptr->data[s_pos])
{
dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL);
if (!dptr->data[s_pos])
goto out;
}
if (count > quantum - q_pos)
count = quantum - q_pos;
/*注意假如內(nèi)核訪問用戶區(qū)域,由于user域存在分頁機(jī)制,
進(jìn)程有可能被休眠以等待不再當(dāng)前頁中的數(shù)據(jù),所以需要
copy_from_user函數(shù)是可重入的.*/
if(copy_from_user(dptr->data[s_pos]+q_pos, buf, count))
{
retval = -EFAULT; /*bad address*/
goto out;
}
*f_pos +=count;
retval = count;
/*updata the size*/
/*實(shí)際上大多數(shù)情況讀寫函數(shù)是不能完全讀寫完的，所以做更新方便讀寫完的操作*/
if(dev->size< *f_pos)
dev->size = *f_pos;
out:
up(&dev->sem);
return retval;
}
/*set file_operations*/
struct file_operations scull_fops =
{
.owner = THIS_MODULE,
.read = scull_read,
.write = scull_write,
.open = scull_open,
.release = scull_release,
};
/*init and exit*/
void scull_cleanup_module(void)
{
int i;
dev_t devno = MKDEV(scull_major,scull_minor);/*獲取設(shè)備號*/
/*get rid of dev entries*/
if(scull_devices)
{
for(i = 0; i<scull_nr_devs; i++ )
{
scull_trim(scull_devices +i);
cdev_del(&scull_devices[i].cdev);
}
kfree(scull_devices);
}
unregister_chrdev_region(devno, scull_nr_devs);
}
/*
*set up the char_dev structure for this device
*/
static void scull_setup_cdev(struct scull_dev *dev, int index)
{
int err,devno = MKDEV(scull_major,scull_minor+index);
/*初始化cdev,主要是指定其fops */
cdev_init(&dev->cdev,&scull_fops); /*注冊設(shè)備結(jié)構(gòu)體*//*知識點(diǎn)5*/
dev->cdev.owner = THIS_MODULE; /*注意這里是先注冊再初始化有些元素，原因有待查*/
dev->cdev.ops = &scull_fops; /*cdev->init里面已經(jīng)初始化了 可省略*/
err = cdev_add(&dev->cdev, devno,1) /*告知內(nèi)核該結(jié)構(gòu)體信息，設(shè)備注冊到這里才算真的激活*/
if(err)
printk(KERN_NOTICE "Error %d adding scull%d",err,index); /*這個失敗的可能很小書上這么提到why??*/
}
int scull_init_module(void)
{
int result,i;
dev_t dev = 0;
if (scull_major) /*選擇是否自動獲取設(shè)備號*/
{
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;
}
/*
*allocate the devices we can't have them static,as the number
*can be specified at load time
*/
scull_devices = kmalloc(scull_nr_devs*sizeof(struct scull_dev), GFP_KERNEL);/*分配nr個scull_dev的內(nèi)存*/
if(!scull_devices)
{
result = -ENOMEM; /*NO enogh memory */
goto fail;
}
memset(scull_devices,0,scull_nr_devs*sizeof(struct scull_dev)); /*kmalloc不清空*/
/*init each device*/
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); /*初始化旗幟變量 用于down_interruptible up(&xxx_dev->sem);*/
scull_setup_cdev(&scull_devices[i],i); /*這個一定記得放于最后*/
}
return 0; /*succeed*/
fail: /*知識點(diǎn)6 goto*/
scull_cleanup_module();
return result;
}
/*加載 注銷*/
module_init(scull_init_module);
module_exit(scull_cleanup_module);
/*程序信息*/
MODULE_AUTHOR("小獸");
MODULE_LICENSE("Dual BSD/GPL"); /*聽說不寫這個會有警告，等下編譯的時候試驗(yàn)下*/
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