/********************
 * 字符設(shè)備驅(qū)動
 ********************/

#include <linux/fs.h>
int register_chrdev_region(dev_t first, unsigned int count, char *name);
//first:要分配的設(shè)備編號范圍的起始值(次設(shè)備號常設(shè)為0)
//count: 所請求的連續(xù)編號范圍
//name: 和編號關(guān)聯(lián)的設(shè)備名稱(見/proc/devices)

int alloc_chrdev_region(dev_t *dev, unsigned int firstminor, unsigned int count, char *name);
//firstminor: 通常為0
//*dev: 存放內(nèi)核返回的設(shè)備號

void unregister_chrdev_region(dev_t first, unsigned int count);
//在模塊的清除函數(shù)中調(diào)用

struct file_operations my_fops = {
.owner = THIS_MODULE,
.llseek = my_llseek,
.read = my_read,
.write = my_write,
.ioctl = my_ioctl,
.open = my_open,
.release = my_release,
}

struct file_operations my_fops = {
owner: THIS_MODULE,
llseek: my_llseek,
...
}

struct scull_dev{
...
struct cdev cdev; /* 字符設(shè)備結(jié)構(gòu) */
}

void cdev_init(struct cdev *cdev, struct file_operations *fops)

int cdev_add(struct cdev *dev, dev_t num, unsigned int count);
//num: 設(shè)備對應(yīng)的第一個編號
//count: 和設(shè)備關(guān)聯(lián)的設(shè)備編號的數(shù)量，常取1
//一旦cdev_add返回，內(nèi)核就認(rèn)為設(shè)備可以使用了，所以要在調(diào)用之前完成設(shè)備的硬件初始化。

int register_chrdev(unsigned int major,
  const char *name,
  struct file_operations *fops);
//為給定的主設(shè)備號注冊0~255作為次設(shè)備號，并為每個設(shè)備建立一個對應(yīng)的默認(rèn)cdev結(jié)構(gòu)

int unregister_chrdev(unsigned int major,
  const char *name);

int (*open) (struct inode *inode, struct file *filp);
//在open中通過inode獲得dev指針，并將其賦給file->private_data
//struct scull_dev *dev;
//dev = contain_of(inode->i_cdev, struct scull_dev, cdev);
//filp->private_data = dev;
//(如果dev是靜態(tài)分配的，則在open或write等方法中可以直接訪問dev，但如果dev是在module_init時動態(tài)分配的，則只能通過上面的方法獲得其指針)

ssize_t read(struct file *filp, char __user *buff, size_t count, loff_t *offp);
ssize_t write(struct file *filp, const char __user *buff, size_t count, loff_t *offp);
//buff: 用戶空間的緩沖區(qū)指針
//offp: 用戶在文件中進(jìn)行存取操作的位置
//在read和write中，拷貝完數(shù)據(jù)后，應(yīng)該更新offp，并將實(shí)際完成的拷貝字節(jié)數(shù)返回。

#include <linux/kdev_t.h>
#define MAJOR(dev) ((unsigned int) ((dev) >> MINORBITS)) //根據(jù)設(shè)備號獲取主設(shè)備號
#define MINOR(dev) ((unsigned int) ((dev) & MINORMASK)) //獲取次設(shè)備號
#define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))     //根據(jù)指定的主設(shè)備和次設(shè)備號生成設(shè)備號
#include <linux/fs.h> 
//靜態(tài)：申請指定的設(shè)備號, from指設(shè)備號, count指使用該驅(qū)動有多少個設(shè)備(次設(shè)備號), 設(shè)備名 
int register_chrdev_region(dev_t from, unsigned count, const char *name);
//name的長度不能超過64字節(jié) 
//動態(tài)申請?jiān)O(shè)備號, 由內(nèi)核分配沒有使用的主設(shè)備號, 分配好的設(shè)備存在dev, baseminor指次設(shè)備號從多少開始, count指設(shè)備數(shù)， name設(shè)備名 
int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
const char *name)
//釋放設(shè)備號, from指設(shè)備號， count指設(shè)備數(shù)
void unregister_chrdev_region(dev_t from, unsigned count)
//cat /proc/devices 可查看設(shè)備使用情況
在內(nèi)核源碼的documentations/devices.txt可查看設(shè)備號的靜態(tài)分配情況
///內(nèi)核里使用struct cdev來描述一個字符設(shè)備驅(qū)動 
#include <linux/cdev.h>
struct cdev {
struct kobject kobj;    //內(nèi)核用于管理字符設(shè)備驅(qū)動 
struct module *owner;   //通常設(shè)為THIS_MODULE, 用于防止驅(qū)動在使用中時卸載驅(qū)動模塊
const struct file_operations *ops; //怎樣操作(vfs)
struct list_head list;   //因多個設(shè)備可以使用同一個驅(qū)動， 用鏈表來記錄
dev_t dev;         //設(shè)備號
unsigned int count;    //設(shè)備數(shù)
};

struct cdev mycdev; 
//定義一個file_operations的文件操作對象
struct file_operations fops = {
.owner = THIS_MODULE,
.read = 讀函數(shù)
....
};

cdev_init(&mycdev, &fops); //mycdev.ops = &fops;
mycdev.owner = THIS_MODULE; 

cdev_del(&mycdev);
///////////創(chuàng)建設(shè)備文件
mknod /dev/設(shè)備文件名 c 主設(shè)備號 次設(shè)備號
////////inode節(jié)點(diǎn)對象描述一個文件/設(shè)備文件, 包括權(quán)限，設(shè)備號等信息
struct inode {
...
dev_t i_rdev;   //設(shè)備文件對應(yīng)的設(shè)備號
struct cdev *i_cdev; //指向?qū)?yīng)的設(shè)備驅(qū)動對象的地址
...
};
////file對象描述文件描述符, 在文件打開時創(chuàng)建, 關(guān)閉時銷毀
struct file {
...
const struct file_operations *f_op; //對應(yīng)的文件操作對象的地址
unsigned int f_flags; //文件打開的標(biāo)志
fmode_t f_mode; //權(quán)限
loff_t f_pos;  //文件描述符的偏移
struct fown_struct f_owner; //屬于哪個進(jìn)程
unsigned int f_uid, f_gid; 
void *private_data; //給驅(qū)動程序員使用
...
};

static inline unsigned long __must_check copy_to_user(void __user *to, const
void *from, unsigned long n)
{
if (access_ok(VERIFY_WRITE, to, n))
n = __copy_to_user(to, from, n);
return n; //返回值為剩下多少字節(jié)沒拷貝
}

extern inline long copy_from_user(void *to, const void __user *from, long n)

///////////
///動態(tài)申請內(nèi)存, 并清零. size為申請多大(不要超過128K),
//flags為標(biāo)志(常為GFP_KERNEL). 成功返回地址， 失敗返回NULL
// GFP_ATOMIC, 使用系統(tǒng)的內(nèi)存緊急池
void *kmalloc(size_t size, gfp_t flags);//申請后要內(nèi)存要清零
void *kzalloc(size_t size, gfp_t flags); //申請出來的內(nèi)存已清零
void kfree(const void *objp); //回收kmalloc/kzalloc的內(nèi)存
void *vmalloc(unsigned long size); //申請大內(nèi)存空間
void vfree(const void *addr); //回收vmalloc的內(nèi)存
// kmalloc申請出來的內(nèi)存是物理地址連續(xù)的, vmalloc不一定是連續(xù)的
///// container_of(ptr, type, member) type包括member成員的結(jié)構(gòu)體,
//ptr是type類型 結(jié)構(gòu)體的member成員的地址.
//此宏根據(jù)結(jié)構(gòu)體成員的地址獲取結(jié)構(gòu)體變量的首地址
#define container_of(ptr, type, member) ({ \
const typeof( ((type *)0)->member ) *__mptr = (ptr); \
(type *)( (char *)__mptr - offsetof(type,member) );})
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
 15 typedef struct led_dev_t {
 16     dev_t mydevid;
 17     unsigned int *rLEDCON;
 18     unsigned int *rLEDDAT;
 19     struct cdev mycdev;
 20 }LED_DEV;
 LED_DEV myled;
 //ind->i_cdev是指向myled.mycdev成員的地址
 //結(jié)構(gòu)體變量myled首地址可由container_of(ind->i_cdev, LED_DEV, mycdev)獲取;

#include <linux/device.h>

struct class *cl; 
cl = class_create(owner, name) ; //owner指屬于哪個模塊, name類名
//創(chuàng)建出來后可以查看 /sys/class/類名
void class_destroy(struct class *cls); //用于銷毀創(chuàng)建出來的類

struct device *device_create(struct class *cls, struct device *parent,
  dev_t devt, void *drvdata,
  const char *fmt, ...)
  __attribute__((format(printf, 5, 6)));
device_create(所屬的類, NULL, 設(shè)備號, NULL, "mydev%d", 88); //在/dev/目錄下產(chǎn)生名字為mydev88的設(shè)備文件
void device_destroy(struct class *cls, dev_t devt); //用于銷毀創(chuàng)建出來的設(shè)備文件
////////
int register_chrdev(unsigned int major, const char *name,
  const struct file_operations *fops) ; //注冊設(shè)備號并創(chuàng)建驅(qū)動對象
void unregister_chrdev(unsigned int major, const char *name); //反注冊設(shè)備號并刪除驅(qū)動對象
static inline int register_chrdev(unsigned int major, const char *name,
 const struct file_operations *fops)
{
return __register_chrdev(major, 0, 256, name, fops);
}
int __register_chrdev(unsigned int major, unsigned int baseminor,
   unsigned int count, const char *name,
   const struct file_operations *fops)
{
struct char_device_struct *cd;
struct cdev *cdev;
int err = -ENOMEM;
cd = __register_chrdev_region(major, baseminor, count, name);
if (IS_ERR(cd))
return PTR_ERR(cd);
cdev = cdev_alloc();
if (!cdev)
goto out2;
cdev->owner = fops->owner;
cdev->ops = fops;
kobject_set_name(&cdev->kobj, "%s", name);
err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
if (err)
goto out;
cd->cdev = cdev;
return major ? 0 : cd->major;
out:
kobject_put(&cdev->kobj);
out2:
kfree(__unregister_chrdev_region(cd->major, baseminor, count));
return err;
}