ldd3代码分析（高级字符驱动）
2007-02-08 00:31
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/**//*
* main.c -- the bare scull char module
*
* 此代码为ldd3例子，自己加了些注释;希望可以和更多和我同样有兴趣的鸟儿们一块学习讨论。
* 哪有注释的不对的地方请发mail给我，或留言；
*
* author : liyangth@gmail.com
*
* date: 2007-2-7
*
* Note：注释的每一个关键的段都以[tag00]作了标签，大家可以按照tag的顺序阅读；
* e.g: 搜索 "Tag000"
*/
#include <linux/config.h>
#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/proc_fs.h>
#include <linux/fcntl.h> /**//* O_ACCMODE */
#include <linux/seq_file.h>
#include <linux/cdev.h>
#include <asm/system.h> /**//* cli(), *_flags */
#include <asm/uaccess.h> /**//* copy_*_user */
#include "scull.h" /**//* local definitions */
/**//*
* 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 devices */
int scull_quantum = SCULL_QUANTUM;
int scull_qset = SCULL_QSET;
/**//*
* 模块参数，可在模块转载时赋值，很灵活方便；
* e.g:
* insmod scull.ko scull_major=111 scull_nr_devs=3 scull_quantum=1000
*
*[形参说明]
* 1 -- 变量名；
* 2 -- 变量类型；
* 3 -- sysfs入口项的访问许可掩码（一般用S_IRUGO就成）；
*/
module_param(scull_major, 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);
MODULE_AUTHOR("Alessandro Rubini, Jonathan Corbet");
MODULE_LICENSE("Dual BSD/GPL");
struct scull_dev *scull_devices; /**//* allocated in scull_init_module */
/**//* Note: 不要把它理解成一个指向scull_dev结构的指针, 它其实是一个scull_dev结构数组,等待下面kmalloc分配多个我们scull设备空间 */
/**//*
* Empty out the scull device; 就像销毁链表,和理解如何编写一个字符驱动没有关系,可以不看;
*
* must be called with the device semaphore held. 要注意一下了,肯定是要同步的;
*
*/
int scull_trim(struct scull_dev *dev)
...{
struct scull_qset *next, *dptr;
int qset = dev->qset; /**//* "dev" is not-null */
int i;
for (dptr = dev->data; dptr; dptr = next) ...{ /**//* all the list items */
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;
}
//Start: [Tag003] proc的实现,可以先不看;
#ifdef SCULL_DEBUG /**//* use proc only if debugging */
/**//*
* The proc filesystem: function to read and entry
*/
int scull_read_procmem(char *buf, char **start, off_t offset,
int count, int *eof, void *data)
...{
int i, j, len = 0;
int limit = count - 80; /**//* Don't print more than this */
for (i = 0; i < scull_nr_devs && len <= limit; i++) ...{
struct scull_dev *d = &scull_devices[i];
struct scull_qset *qs = d->data;
if (down_interruptible(&d->sem))
return -ERESTARTSYS;
len += sprintf(buf+len," Device %i: qset %i, q %i, sz %li ",
i, d->qset, d->quantum, d->size);
for (; qs && len <= limit; qs = qs->next) ...{ /**//* scan the list */
len += sprintf(buf + len, " item at %p, qset at %p ",
qs, qs->data);
if (qs->data && !qs->next) /**//* dump only the last item */
for (j = 0; j < d->qset; j++) ...{
if (qs->data[j])
len += sprintf(buf + len,
" % 4i: %8p ",
j, qs->data[j]);
}
}
up(&scull_devices[i].sem);
}
*eof = 1;
return len;
}
/**//*
* For now, the seq_file implementation will exist in parallel. The
* older read_procmem function should maybe go away, though.
*/
/**//*
* Here are our sequence iteration methods. Our "position" is
* simply the device number.
*/
static void *scull_seq_start(struct seq_file *s, loff_t *pos)
...{
if (*pos >= scull_nr_devs)
return NULL; /**//* No more to read */
return scull_devices + *pos;
}
static void *scull_seq_next(struct seq_file *s, void *v, loff_t *pos)
...{
(*pos)++;
if (*pos >= scull_nr_devs)
return NULL;
return scull_devices + *pos;
}
static void scull_seq_stop(struct seq_file *s, void *v)
...{
/**//* Actually, there's nothing to do here */
}
static int scull_seq_show(struct seq_file *s, void *v)
...{
struct scull_dev *dev = (struct scull_dev *) v;
struct scull_qset *d;
int i;
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
seq_printf(s, " Device %i: qset %i, q %i, sz %li ",
(int) (dev - scull_devices), dev->qset,
dev->quantum, dev->size);
for (d = dev->data; d; d = d->next) ...{ /**//* scan the list */
seq_printf(s, " item at %p, qset at %p ", d, d->data);
if (d->data && !d->next) /**//* dump only the last item */
for (i = 0; i < dev->qset; i++) ...{
if (d->data[i])
seq_printf(s, " % 4i: %8p ",
i, d->data[i]);
}
}
up(&dev->sem);
return 0;
}
/**//*
* Tie the sequence operators up.
*/
static struct seq_operations scull_seq_ops = ...{
.start = scull_seq_start,
.next = scull_seq_next,
.stop = scull_seq_stop,
.show = scull_seq_show
};
/**//*
* Now to implement the /proc file we need only make an open
* method which sets up the sequence operators.
*/
static int scull_proc_open(struct inode *inode, struct file *file)
...{
return seq_open(file, &scull_seq_ops);
}
/**//*
* Create a set of file operations for our proc file.
*/
static struct file_operations scull_proc_ops = ...{
.owner = THIS_MODULE,
.open = scull_proc_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release
};
/**//*
* Actually create (and remove) the /proc file(s).
*/
static void scull_create_proc(void)
...{
struct proc_dir_entry *entry;
create_proc_read_entry("scullmem", 0 /**//* default mode */,
NULL /**//* parent dir */, scull_read_procmem,
NULL /**//* client data */);
entry = create_proc_entry("scullseq", 0, NULL);
if (entry)
entry->proc_fops = &scull_proc_ops;
}
static void scull_remove_proc(void)
...{
/**//* no problem if it was not registered */
remove_proc_entry("scullmem", NULL /**//* parent dir */);
remove_proc_entry("scullseq", NULL);
}
#endif /* SCULL_DEBUG */
//End
/**//* 开始实现对设备操作的方法集了,关键!!! */
/**//*
* Open and close
*/
//[Tag004]
/**//*
open应完成的工作有：
1.检查设备特定的错误（诸如设备未就绪或类似的硬件问题）
2.如果设备是首次打开，则对其进行初始化；
3.如有必要，更新f_op指针；
4.分配并填写filp->private_data；（在这里我们只实现这项即可）
*/
/**//*
[形参说明]
struct inode *inode -- 用它的i_cdev成员得到dev;
struct file *filp -- 将得到的dev存放到他的成员private_data中；
*/
int scull_open(struct inode *inode, struct file *filp)
...{
struct scull_dev *dev; /**//* device information */
dev = container_of(inode->i_cdev, struct scull_dev, cdev);
/**//*
[说明]
1.我们要填充的应该是我们自己的特殊设备，而不是钳在他里面的字符设备结构；
2.inode结构的i_cdev成员这能提供基本字符设备结构；
3.这里利用了定义在<linux/kernel.h>中的宏来实现通过cdev得到dev;
*/
/**//*
以后read , write ,等操作的实现中就靠他来得到dev了；
*/
filp->private_data = dev; /**//* for other methods */
/**//* now trim to 0 the length of the device if open was write-only */
if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) ...{
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
scull_trim(dev); /**//* ignore errors */
up(&dev->sem);
}
return 0; /**//* success */
}
/**//* close device file, in here we do nothing */
/**//*
* [Tag005]
* close应完成的工作有：
* 1.释放由open分配的，保存在filp->private_data中的所有内容；
* 2.在最后一次关闭操作时关闭设备；
* [注意：]并不是每次的close系统调用都会去调用到release. 在open时，也仅在open时才会创建
* 一个新的数据结构；在fork, dup时只是增加了这个结构中维护的一个引用计数；
* 所以当这个引用计数为0时，调用的close才意味着要释放设备数据结构，此时release才会被调用；
*/
int scull_release(struct inode *inode, struct file *filp)
...{
return 0;
}
/**//*
* Follow the list
*
* 第一次调用时用于创建链表；
* 然后就是找到第n个节点；
* 对编写驱动程序关系不大；
*/
struct scull_qset *scull_follow(struct scull_dev *dev, int n)
...{
struct scull_qset *qs = dev->data;
/**//* Allocate first qset explicitly if need be */
if (! qs) ...{
qs = dev->data = kmalloc(sizeof(struct scull_qset), GFP_KERNEL);
if (qs == NULL)
return NULL; /**//* Never mind */
memset(qs, 0, sizeof(struct scull_qset));
}
/**//* Then 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;
}
return qs;
}
/**//*[Tag006]
* Data management: read and write
* [read和write的参数]
* 1] filp -- 文件指针；用它的成员filp->private_data得到dev;
* 2] buf -- 都是来自用户空间的指针；
* 3] count -- 缓冲区大小；(希望传输的字节数目)
* 4] f_pos -- 指向一个长偏移量对象的指针，这个对象指明了用户在文件中进行存取
* 操作的位置；
*
*[返回值]
* 1]如果返回值等于count，则完成了所请求数目的字节传输；
* 2]如果返回值是正，但小于count,则继续读或写余下的数据；
* 3]如果为0，则证明已经到了文件尾；
* 4]如果为负，则发生了错误。会返回一个错误码，该值指明了发生了什么错误。
* 错误码在<linux/errno.h>中定义；
* 例如：-EINTR (系统调用被中断)
* -EFAULT (无效地址)
*/
ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
loff_t *f_pos)
...{
struct scull_dev *dev = filp->private_data;
struct scull_qset *dptr; /**//* the first listitem */
int quantum = dev->quantum, qset = dev->qset;
int itemsize = quantum * qset; /**//* how many bytes in the listitem */
int item, s_pos, q_pos, rest;
ssize_t retval = 0;
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
if (*f_pos >= dev->size) //操作位置到文件尾，或超出文件尾了
goto out;
if (*f_pos + count > dev->size) //在当前位置所要读的数目超过文件尾了
count = dev->size - *f_pos; //减小这次的期望读取数目
/**//* find listitem, qset index, and offset in the quantum */
item = (long)*f_pos / itemsize; //确定是哪个链表项下，即哪个节点下；
rest = (long)*f_pos % itemsize; //在这个链表项的什么位置（偏移量），用于下面找qset索引和偏移量；
s_pos = rest / quantum; //在这个节点里**data这个指针数组的第几行；
q_pos = rest % quantum; //在这行，即这个量子里的偏移量；
/**//* follow the list up to the right position (defined elsewhere) */
dptr = scull_follow(dev, item); //找到这个链表项
if (dptr == NULL || !dptr->data || ! dptr->data[s_pos])
goto out; /**//* don't fill holes */
//以一个量子为单位传，简化了代码；
/**//* read only up to the end of this quantum */
if (count > quantum - q_pos)
count = quantum - q_pos;
/**//*
* 上面为这步准备了具体在哪个链表项的指针数组的第几行的第几列（即dptr->data[s_pos] + q_pos）
* 从这个位置的内核态的buf中拷给用户态
*/
//关键一步，将数据拷给用户空间
if (copy_to_user(buf, dptr->data[s_pos] + q_pos, count)) ...{
retval = -EFAULT;
goto out;
}
*f_pos += count; //更新文件指针
retval = count;
out:
up(&dev->sem);
return retval;
}
//与read的实现类似
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;
int item, s_pos, q_pos, rest;
ssize_t retval = -ENOMEM; /**//* value used in "goto out" statements */
if (down_interruptible(&dev->sem))
return -ERESTARTSYS;
/**//* find listitem, qset index and offset in the quantum */
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 */
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;
}
/**//* write only up to the end of this quantum */
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;
/**//* update the size */
if (dev->size < *f_pos)
dev->size = *f_pos;
out:
up(&dev->sem);
return retval;
}
/**//*
* The ioctl() implementation
*/
int scull_ioctl(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg)
...{
int err = 0, tmp;
int retval = 0;
/**//*
* extract the type and number bitfields, and don't decode
* wrong cmds: return ENOTTY (inappropriate ioctl) before access_ok()
*/
if (_IOC_TYPE(cmd) != SCULL_IOC_MAGIC) return -ENOTTY;
if (_IOC_NR(cmd) > SCULL_IOC_MAXNR) return -ENOTTY;
/**//*
* the direction is a bitmask, and VERIFY_WRITE catches R/W
* transfers. `Type' is user-oriented, while
* access_ok is kernel-oriented, so the concept of "read" and
* "write" is reversed
*/
if (_IOC_DIR(cmd) & _IOC_READ)
err = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd));
else if (_IOC_DIR(cmd) & _IOC_WRITE)
err = !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd));
if (err) return -EFAULT;
switch(cmd) ...{
case SCULL_IOCRESET:
scull_quantum = SCULL_QUANTUM;
scull_qset = SCULL_QSET;
break;
case SCULL_IOCSQUANTUM: /**//* Set: arg points to the value */
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
retval = __get_user(scull_quantum, (int __user *)arg);
break;
case SCULL_IOCTQUANTUM: /**//* Tell: arg is the value */
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
scull_quantum = arg;
break;
case SCULL_IOCGQUANTUM: /**//* Get: arg is pointer to result */
retval = __put_user(scull_quantum, (int __user *)arg);
break;
case SCULL_IOCQQUANTUM: /**//* Query: return it (it's positive) */
return scull_quantum;
case SCULL_IOCXQUANTUM: /**//* eXchange: use arg as pointer */
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
tmp = scull_quantum;
retval = __get_user(scull_quantum, (int __user *)arg);
if (retval == 0)
retval = __put_user(tmp, (int __user *)arg);
break;
case SCULL_IOCHQUANTUM: /**//* sHift: like Tell + Query */
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
tmp = scull_quantum;
scull_quantum = arg;
return tmp;
case SCULL_IOCSQSET:
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
retval = __get_user(scull_qset, (int __user *)arg);
break;
case SCULL_IOCTQSET:
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
scull_qset = arg;
break;
case SCULL_IOCGQSET:
retval = __put_user(scull_qset, (int __user *)arg);
break;
case SCULL_IOCQQSET:
return scull_qset;
case SCULL_IOCXQSET:
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
tmp = scull_qset;
retval = __get_user(scull_qset, (int __user *)arg);
if (retval == 0)
retval = put_user(tmp, (int __user *)arg);
break;
case SCULL_IOCHQSET:
if (! capable (CAP_SYS_ADMIN))
return -EPERM;
tmp = scull_qset;
scull_qset = arg;
return tmp;
/**//*
* The following two change the buffer size for scullpipe.
* The scullpipe device uses this same ioctl method, just to
* write less code. Actually, it's the same driver, isn't it?
*/
case SCULL_P_IOCTSIZE:
scull_p_buffer = arg;
break;
case SCULL_P_IOCQSIZE:
return scull_p_buffer;
default: /**//* redundant, as cmd was checked against MAXNR */
return -ENOTTY;
}
return retval;
}
/**//*
* The "extended" operations -- only seek
*/
loff_t scull_llseek(struct file *filp, loff_t off, int whence)
...{
struct scull_dev *dev = filp->private_data;
loff_t newpos;
switch(whence) ...{
case 0: /**//* SEEK_SET */
newpos = off;
break;
case 1: /**//* SEEK_CUR */
newpos = filp->f_pos + off;
break;
case 2: /**//* SEEK_END */
newpos = dev->size + off;
break;
default: /**//* can't happen */
return -EINVAL;
}
if (newpos < 0) return -EINVAL;
filp->f_pos = newpos;
return newpos;
}
//[Tag007]将这组操作打包为一个对象；
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,
};
/**//*
* Finally, the module stuff
*/
//[Tag008]模块卸载或goto fail时；
/**//*
* The cleanup function is used to handle initialization failures as well.
* Thefore, it must be careful to work correctly even if some of the items
* have not been initialized
*/
void scull_cleanup_module(void)
...{
int i;
dev_t devno = MKDEV(scull_major, scull_minor);
/**//* Get rid of our char dev entries */
if (scull_devices) ...{
for (i = 0; i < scull_nr_devs; i++) ...{
scull_trim(scull_devices + i);
cdev_del(&scull_devices[i].cdev); //[???]是一个内核函数么？
}
kfree(scull_devices);
}
#ifdef SCULL_DEBUG /**//* use proc only if debugging */
scull_remove_proc();
#endif
/**//* cleanup_module is never called if registering failed */
unregister_chrdev_region(devno, scull_nr_devs);
/**//* and call the cleanup functions for friend devices */
scull_p_cleanup();
scull_access_cleanup();
}
/**//* [Tag002]
这里主要干了2件事;
在内核内部使用struct cdev结构来表示字符设备;
[1]在这里因为我们将cdev结构嵌入到自己的scull_dev设备下了,所以我们用下面这个方法来
初始化已分配的结构;
cdev_init(&dev->cdev, &scull_fops);
[2]告诉内核我们新结构的信息;
*/
/**//*
* 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);
// [1]
cdev_init(&dev->cdev, &scull_fops); /**//* 初始化, 字符设备和给它一组在它上面操作的方法集 */
/**//* 填充基本字符设备的成员 */
dev->cdev.owner = THIS_MODULE; //模块计数
dev->cdev.ops = &scull_fops; //附上一组操作自己的方法集
// [2]
err = cdev_add (&dev->cdev, devno, 1);
/**//*
函数说明:
cdev -- 字符设备的结构指针,我们就是要把他告诉给内核;
devno -- 设备编号,用MKDEV利用全局的主设备号和次设备号生成的;
1 -- 是应该和该设备关联的设备编号的数量, 一般情况下都为1;
一般我们都是一个设备编号对应一个设备;
*/
/**//*
注意:
在调用cdev_add后,我们的设备就被添加到系统了,他"活"了. 附加的操作集也就可以被内核调用了
,因此,在驱动程序还没有完全准备好处理设备上的操作时,就不能调用cdev_add!
*/
/**//* Fail gracefully if need be */
if (err)
printk(KERN_NOTICE "Error %d adding scull%d", err, index);
}
/**//*[Tag000]
* 当模块加载时，调用；但是为什么要放在最后来实现他呢，看到Tag002时，你应该就明白了；
*/
int scull_init_module(void)
...{
int result, i;
dev_t dev = 0;
/**//* [Tag001] */
/**//* [1]分配设备编号 */
/**//*
* Get a range of minor numbers to work with, asking for a dynamic
* major unless directed otherwise at load time.
*/
if (scull_major) ...{ /**//* 预先自己指定了主设备号 */
dev = MKDEV(scull_major, scull_minor); /**//* 利用主设备号,找到设备编号给方法1用 */
result = register_chrdev_region(dev, scull_nr_devs, "scull");
} else ...{ /**//* 动态自己生成设备编号,然后再利用设备编号得到主设备号;
记住如果用这个方法那么就要后建设备文件了,因为不能提前知道主号
当然也可以利用ldd3书中提供的脚本,巨方便&&通用 */
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 ", scull_major);
return result;
}
/**//*[2]设备对象实例化*/
/**//*
* 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);
if (!scull_devices) ...{
result = -ENOMEM;
goto fail; /**//* Make this more graceful */
}
memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev));
/**//* [3]在这里初始化设备用了2.6的新方法,在scull_setup_cdev里完成 */
/**//* Initialize each device. */
for (i = 0; i < scull_nr_devs; i++) ...{
scull_devices[i].quantum = scull_quantum; /**//* 可以根据自己insmod时传参
来自己改变量子和量子集(指针数组)的大小 */
scull_devices[i].qset = scull_qset;
init_MUTEX(&scull_devices[i].sem);
scull_setup_cdev(&scull_devices[i], i); /**//* 在分别完主设备编号后goto Tag002 设备注册 */
}
/**//* At this point call the init function for any friend device */
dev = MKDEV(scull_major, scull_minor + scull_nr_devs);
dev += scull_p_init(dev);
dev += scull_access_init(dev);
#ifdef SCULL_DEBUG /**//* only when debugging */
scull_create_proc();
#endif
return 0; /**//* succeed */
fail:
scull_cleanup_module();
return result;
}
module_init(scull_init_module); //insmod
module_exit(scull_cleanup_module); //rmmod
/**//*
* scull.h -- definitions for the char module
*
* Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet
* Copyright (C) 2001 O'Reilly & Associates
*
* The source code in this file can be freely used, adapted,
* and redistributed in source or binary form, so long as an
* acknowledgment appears in derived source files. The citation
* should list that the code comes from the book "Linux Device
* Drivers" by Alessandro Rubini and Jonathan Corbet, published
* by O'Reilly & Associates. No warranty is attached;
* we cannot take responsibility for errors or fitness for use.
*
* $Id: scull.h,v 1.15 2004/11/04 17:51:18 rubini Exp $
*/
#ifndef _SCULL_H_
#define _SCULL_H_
#include <linux/ioctl.h> /**//* needed for the _IOW etc stuff used later */
/**//*
* Macros to help debugging
*/
#undef PDEBUG /* undef it, just in case */
#ifdef SCULL_DEBUG
# ifdef __KERNEL__
/**//* This one if debugging is on, and kernel space */
# define PDEBUG(fmt, args...) printk( KERN_DEBUG "scull: " fmt, ## args)
# else
/**//* This one for user space */
# define PDEBUG(fmt, args...) fprintf(stderr, fmt, ## args)
# endif
#else
# define PDEBUG(fmt, args...) /**//* not debugging: nothing */
#endif
#undef PDEBUGG
#define PDEBUGG(fmt, args...) /* nothing: it's a placeholder */
#ifndef SCULL_MAJOR
#define SCULL_MAJOR 0 /* dynamic major by default */
#endif
#ifndef SCULL_NR_DEVS
#define SCULL_NR_DEVS 4 /* scull0 through scull3 */
#endif
#ifndef SCULL_P_NR_DEVS
#define SCULL_P_NR_DEVS 4 /* scullpipe0 through scullpipe3 */
#endif
/**//*
* The bare device is a variable-length region of memory.
* Use a linked list of indirect blocks.
*
* "scull_dev->data" points to an array of pointers, each
* pointer refers to a memory area of SCULL_QUANTUM bytes.
*
* The array (quantum-set) is SCULL_QSET long.
*/
#ifndef SCULL_QUANTUM
#define SCULL_QUANTUM 4000 /* 每个指针(量子)指向一个4000字节的区域 */
#endif
#ifndef SCULL_QSET
#define SCULL_QSET 1000 /* 一个有1000个(量子)的指针数组 */
#endif
/**//*
* The pipe device is a simple circular buffer. Here its default size
*/
#ifndef SCULL_P_BUFFER
#define SCULL_P_BUFFER 4000
#endif
/**//*
* Representation of scull quantum sets.
* 一个链表项
*/
struct scull_qset ...{
void **data;
struct scull_qset *next; /**//* 下一个链表节点（链表项） */
};
/**//* 我们自己的设备(包含了基本的cdev字符设备结构) */
struct scull_dev ...{
struct scull_qset *data; /**//* Pointer to first quantum set (链表的头)*/
int quantum; /**//* the current quantum size */
int qset; /**//* the current array size */
unsigned long size; /**//* amount of data stored here (保存在其中的数据总量)*/
unsigned int access_key; /**//* used by sculluid and scullpriv */
struct semaphore sem; /**//* mutual exclusion semaphore */
struct cdev cdev; /**//* Char device structure */
};
/**//*
* Split minors in two parts
*/
#define TYPE(minor) (((minor) >> 4) & 0xf) /* high nibble */
#define NUM(minor) ((minor) & 0xf) /* low nibble */
/**//*
* The different configurable parameters
*/
extern int scull_major; /**//* main.c */
extern int scull_nr_devs;
extern int scull_quantum;
extern int scull_qset;
extern int scull_p_buffer; /**//* pipe.c */
/**//*
* Prototypes for shared functions
*/
int scull_p_init(dev_t dev);
void scull_p_cleanup(void);
int scull_access_init(dev_t dev);
void scull_access_cleanup(void);
int scull_trim(struct scull_dev *dev);
ssize_t scull_read(struct file *filp, char __user *buf, size_t count,
loff_t *f_pos);
ssize_t scull_write(struct file *filp, const char __user *buf, size_t count,
loff_t *f_pos);
loff_t scull_llseek(struct file *filp, loff_t off, int whence);
int scull_ioctl(struct inode *inode, struct file *filp,
unsigned int cmd, unsigned long arg);
/**//*
* Ioctl definitions
*/
/**//* Use 'k' as magic number */
#define SCULL_IOC_MAGIC 'k'
/**//* Please use a different 8-bit number in your code */
#define SCULL_IOCRESET _IO(SCULL_IOC_MAGIC, 0)
/**//*
* S means "Set" through a ptr,
* T means "Tell" directly with the argument value
* G means "Get": reply by setting through a pointer
* Q means "Query": response is on the return value
* X means "eXchange": switch G and S atomically
* H means "sHift": switch T and Q atomically
*/
#define SCULL_IOCSQUANTUM _IOW(SCULL_IOC_MAGIC, 1, int)
#define SCULL_IOCSQSET _IOW(SCULL_IOC_MAGIC, 2, int)
#define SCULL_IOCTQUANTUM _IO(SCULL_IOC_MAGIC, 3)
#define SCULL_IOCTQSET _IO(SCULL_IOC_MAGIC, 4)
#define SCULL_IOCGQUANTUM _IOR(SCULL_IOC_MAGIC, 5, int)
#define SCULL_IOCGQSET _IOR(SCULL_IOC_MAGIC, 6, int)
#define SCULL_IOCQQUANTUM _IO(SCULL_IOC_MAGIC, 7)
#define SCULL_IOCQQSET _IO(SCULL_IOC_MAGIC, 8)
#define SCULL_IOCXQUANTUM _IOWR(SCULL_IOC_MAGIC, 9, int)
#define SCULL_IOCXQSET _IOWR(SCULL_IOC_MAGIC,10, int)
#define SCULL_IOCHQUANTUM _IO(SCULL_IOC_MAGIC, 11)
#define SCULL_IOCHQSET _IO(SCULL_IOC_MAGIC, 12)
/**//*
* The other entities only have "Tell" and "Query", because they're
* not printed in the book, and there's no need to have all six.
* (The previous stuff was only there to show different ways to do it.
*/
#define SCULL_P_IOCTSIZE _IO(SCULL_IOC_MAGIC, 13)
#define SCULL_P_IOCQSIZE _IO(SCULL_IOC_MAGIC, 14)
/**//* ... more to come */
#define SCULL_IOC_MAXNR 14
#endif /* _SCULL_H_ */
linux设备驱动（第三版）的例子里还提供了几个非常通用和灵活的脚本，还有一个标准的Makefile.
大家可以利用下面的文件，修改一下运行试试效果。如果想了解读写的具体过程可以试试用strace命令来追踪；
e.g : strace ls -l >/dev/scull0
# Comment/uncomment the following line to disable/enable debugging
#非常标准的Makefile，稍加修改就可以用在很多驱动上
#将这个开关打开，看proc的输出。在这个例子分别有二个用于输出的proc文件。一个是用老方法实现的
#/proc/scullmem
#新方法 /proc/scullseq
DEBUG = y
# Add your debugging flag (or not) to CFLAGS
ifeq ($(DEBUG),y)
DEBFLAGS = -O -g -DSCULL_DEBUG # "-O" is needed to expand inlines
else
DEBFLAGS = -O2
endif
CFLAGS += $(DEBFLAGS)
CFLAGS += -I$(LDDINC)
ifneq ($(KERNELRELEASE),)
# call from kernel build system
scull-objs := main.o pipe.o access.o
obj-m := scull.o
else
KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
modules:
$(MAKE) -C $(KERNELDIR) M=$(PWD) LDDINC=$(PWD)/../include modules
endif
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
depend .depend dep:
$(CC) $(CFLAGS) -M *.c > .depend
ifeq (.depend,$(wildcard .depend))
include .depend
endif
下面这个是load,因为在2.6的新方法中我们是先动态分配主设备号，然后再根据/proc/modules来建立设备文件的
看下面这个脚本的实现就知道了。
#!/bin/sh
# $Id: scull_load,v 1.4 2004/11/03 06:19:49 rubini Exp $
module="scull"
device="scull"
mode="664"
# Group: since distributions do it differently, look for wheel or use staff
if grep -q '^staff:' /etc/group; then
group="staff"
else
group="wheel"
fi
# invoke insmod with all arguments we got
# and use a pathname, as insmod doesn't look in . by default
/sbin/insmod ./$module.ko $* || exit 1
# retrieve major number
major=$(awk "/$2=="$module" {print /$1}" /proc/devices)
# Remove stale nodes and replace them, then give gid and perms
# Usually the script is shorter, it's scull that has several devices in it.
rm -f /dev/$...{device}[0-3]
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
ln -sf $...{device}0 /dev/$...{device}
chgrp $group /dev/$...{device}[0-3]
chmod $mode /dev/$...{device}[0-3]
rm -f /dev/$...{device}pipe[0-3]
mknod /dev/$...{device}pipe0 c $major 4
mknod /dev/$...{device}pipe1 c $major 5
mknod /dev/$...{device}pipe2 c $major 6
mknod /dev/$...{device}pipe3 c $major 7
ln -sf $...{device}pipe0 /dev/$...{device}pipe
chgrp $group /dev/$...{device}pipe[0-3]
chmod $mode /dev/$...{device}pipe[0-3]
rm -f /dev/$...{device}single
mknod /dev/$...{device}single c $major 8
chgrp $group /dev/$...{device}single
chmod $mode /dev/$...{device}single
rm -f /dev/$...{device}uid
mknod /dev/$...{device}uid c $major 9
chgrp $group /dev/$...{device}uid
chmod $mode /dev/$...{device}uid
rm -f /dev/$...{device}wuid
mknod /dev/$...{device}wuid c $major 10
chgrp $group /dev/$...{device}wuid
chmod $mode /dev/$...{device}wuid
rm -f /dev/$...{device}priv
mknod /dev/$...{device}priv c $major 11
chgrp $group /dev/$...{device}priv
chmod $mode /dev/$...{device}priv
下面这个用于卸载
#!/bin/sh
module="scull"
device="scull"
# invoke rmmod with all arguments we got
/sbin/rmmod $module $* || exit 1
# Remove stale nodes
rm -f /dev/$...{device} /dev/$...{device}[0-3]
rm -f /dev/$...{device}priv
rm -f /dev/$...{device}pipe /dev/$...{device}pipe[0-3]
rm -f /dev/$...{device}single
rm -f /dev/$...{device}uid
rm -f /dev/$...{device}wuid
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