设备驱动程序：以内核模块的形式存在也就是*.ko
设备驱动程序和系统调用关系.
系统调用：应有程序和操作系统（内核） 之间的接口(应用程序与内核的交互)
设备驱动程序：内核和设备硬件之间接口（内核与硬件的交互）
整个过程实现了应用程序间接访问了底层的硬件。
test.c中调用open-----》系统调用（sys_open()）----->file_operation{.open = led_open}:调用驱动函数中的自定义的open
---------------------------------------------------------------
linux设备驱动的三种类型：
1.字符设备:LED，显卡，声卡，键盘，触摸屏。。。
2.块设备：硬盘，nandflash,SD,U盘....
3.网络设备:网卡(无线，有线)
---------------------------------------------------------------
二。字符设备特点
1.应用程序和设备进行数据交互时，是以字节单位进行的。
2。访问的数据是连续时，实时。
3.不带缓存，块设备驱动带有缓存.
三。字符设备的描述
1。cdev结构
struct cdev {
struct kobject kobj;
struct module *owner;
const struct file_operations *ops;
struct list_head list; //内核链表
dev_t dev;
unsigned int count;//当前设备下有多少个次设备
};
cdev是描述一个字符设备，每写一字符设备，创建一个cdev结构，每个字符设备都有自已的cdev
--struct kobject kobj;
不关心的，是由内核管理设备使用，
--struct module *owner;
cdev属于那个体module,一般写THIS_MODULE;
--const struct file_operations *ops;
操作集(设备驱动),是应用程序访问设备的驱动接口
--struct list_head list;
内核链表：将当前cdev放到一链表，方便内核管理cdev
--dev_t dev;
typedef u_long dev_t;
typedef unsigned long u_long;
设备号.每个字符设备都有自已的设备号，设备号在当内核中是唯一，在32 BITs,32无符号整形
--unsigned int count;
在当设备下有多少个次设备...
struct file_operations {
struct module *owner;
loff_t (*llseek) (struct file *, loff_t, int);
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
ssize_t (*aio_read) (struct kiocb *, const struct iovec *, unsigned long, loff_t);
ssize_t (*aio_write) (struct kiocb *, const struct iovec *, unsigned long,
loff_t);
int (*readdir) (struct file *, void *, filldir_t);
unsigned int (*poll) (struct file *, struct poll_table_struct *);
int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
int (*open) (struct inode *, struct file *);
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);
-----------------------------------------------
};
------------------------------------------------------------------
cdev中的设备号：
2.1定义
typedef u_long dev_t;
typedef unsigned long u_long;
设备号.每个字符设备都有自已的设备号，设备号在当内核中是唯一，在32 BITs,32无符号整形。
2.2设备号由主设备号和次设备号组成:
主设备号:某类型类的设备 [31:20]
次设备号:该类型的设备下，具体那个设备实例.[19:0]
2.3相关函数（宏）：由设备号的得到主次设备号
#define MAJOR(dev) ((unsigned int) ((dev) >> MINORBITS))
#define MINOR(dev) ((unsigned int) ((dev) & MINORMASK))
由主次设备号得到设备号：
#define MKDEV(ma,mi) (((ma) << MINORBITS) | (mi))
ma-->主设备号
mi-->次设备号
向内核中注册设备号：
定义一个CDEV时候，首先在内核中申请一个设备号，获得设备号的方法有两种。
1、向内核中静态注册一个设备号：自已定制一个设备号，向内核注册（申请）,如果内核中没有占用设备号，代注册成功。
* register_chrdev_region() - register a range of device numbers
* @from: the first in the desired range of device numbers; must include
* the major number.
* @count: the number of consecutive device numbers required
* @name: the name of the device or driver.
*
* Return value is zero on success, a negative error code on failure.
*/
int register_chrdev_region(dev_t from, unsigned count, const char *name)
参数说明:
from-->设备号的值
count-->次设备的数量
name->设备的名称.
返回值：
成功:0
失败：负数
例：
[@GEC2103 /]# ls /dev/s3c241* -l
crw-rw---- 1 0 0 204, 64 Jan 1 00:00 /dev/s3c2410_serial0
crw-rw---- 1 0 0 204, 65 Jan 1 00:00 /dev/s3c2410_serial1
crw-rw---- 1 0 0 204, 66 Jan 1 00:00 /dev/s3c2410_serial2
crw-rw---- 1 0 0 204, 67 Jan 1 00:00 /dev/s3c2410_serial3
register_chrdev_region（MKDEV（204，64），4，“s3c2410_serial”）
#cat /proc/devices
204 s3c2410_serial
2、让内核动态分配一个空闲设备号
/**
* alloc_chrdev_region() - register a range of char device numbers
* @dev: output parameter for first assigned number
* @baseminor: first of the requested range of minor numbers
* @count: the number of minor numbers required
* @name: the name of the associated device or driver
*
* Allocates a range of char device numbers. The major number will be
* chosen dynamically, and returned (along with the first minor number)
* in @dev. Returns zero or a negative error code.
*/
int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,const char *name)
参数：
*dev:-->申请设备号
baseminor-->申请设备号第一个次设备号
count-->申请次设备的数量
name-->设备名称
返回值：
成功:0
失败：负数
注意：一定判断申请是成功
dev_t det;
alloc_chrdev_region(&det,0,2,"test");
3、注销设备号
3.3注销一个已经注册的设备号
当驱动程序移除时，一定先注销设备号
/**
* unregister_chrdev_region() - return a range of device numbers
* @from: the first in the range of numbers to unregister
* @count: the number of device numbers to unregister
*
* This function will unregister a range of @count device numbers,
* starting with @from. The caller should normally be the one who
* allocated those numbers in the first place...
*/
void unregister_chrdev_region(dev_t from, unsigned count)
参数：from-->设备号的值,第一个设备号
count-->次设备号的数量
--------------------------------------------------------------------------
3.文件操作集
struct file_operations
文件操作集是内核管理cdev那设备的驱动接口, 驱动程序提供应用程序一个接口
int testopen(struct inode *inode, struct file *file)
{
}
int testclose (struct inode *inode, struct file *file);
{
}
ssize_t testread(struct file *, char __user *, size_t, loff_t *)
{
}
struct file_operations fops= --->结构体初始化 .---???????????????
{ .owner=THIS_MODULE,
.open=testopen,
.read=testread,
.release=testclose,
}
----------------------------------------------------------------------
4.cdev初始化和注册
4.1.cdev的初始化函数
/**
* cdev_init() - initialize a cdev structure
* @cdev: the structure to initialize
* @fops: the file_operations for this device
*
* Initializes @cdev, remembering @fops, making it ready to add to the
* system with cdev_add().
*/
void cdev_init(struct cdev *cdev, const struct file_operations *fops)
参数：
cdev-->要初始化cdev
fops-->cdev的文件操作集
4.2.注册cdev到内核的函数
/**
* cdev_add() - add a char device to the system
* @p: the cdev structure for the device
* @dev: the first device number for which this device is responsible
* @count: the number of consecutive minor numbers corresponding to this
* device
*
* cdev_add() adds the device represented by @p to the system, making it
* live immediately. A negative error code is returned on failure.
*/
int cdev_add(struct cdev *p, dev_t dev, unsigned count)
参数：p --->注册那个cdev
dev--->设备号
count-->次设备个数
返回值：
成功:0
失败：负数
例：
strcut cdev cd;
cdev_init(&cd,&fops)
cd.owner=THIS_MODULE;
cdev_add(&cd,dev,1);
--------------------------------------------------------------
4.3cdev的注销函数
/**
* cdev_del() - remove a cdev from the system
* @p: the cdev structure to be removed
*
* cdev_del() removes @p from the system, possibly freeing the structure
* itself.
*/
void cdev_del(struct cdev *p)
p-->要注销那个cdev .
注意：在linux驱动设计时候，我们使用的函数，一般都成对，申请<--->释放 注册--->注销
------------------------------------------------------------------------
5。字符设备的设计流程
5.1定义一个cdev
struct cdev chrdev3;
5.2申请一个设备号
例:
unsigned int TestMajor=0;
unsigned int TestMinor=0;
dev_t dev_no;
int ret;
dev_no =MKDEV(TestMajor,TestMinor)
if(dev_no>0)
{
ret=register_chrdev_region(dev_no, 1,"chrdev_test");//静态注册设备号
}
else //动态申请设备号
{
alloc_chrdev_region(&dev_no,TestMinor, 1,"chrdev_test");
}
if(ret<0)
{
return ret;
}
5.3定义文件操作集
int testopen(struct inode *inode, struct file *file)
{
}
int testclose (struct inode *inode, struct file *file);
{
}
ssize_t testwrtie(struct file *, char __user *, size_t, loff_t *)
{
}
struct file_operations fops= --->结构体初始化 .---???????????????
{ .owner=THIS_MODULE,
.open=testopen,
.write=testwrite,
.release=testclose,
}
5.4cdev初始化
cdev_init(&chrdev3,&fops);
5.5cdev注册到内核
cdev_add(&chrdev3,dev_no,1);先初始化设备号，然后注册cdev
5.6设备号和cdev注销
unregister_chrdev_region(dev_no, 1);
cdev_dev(&chrdev3);
-------------------------------------------------------------------------
.结合模块规则：写字符设备驱动程序
test.c
#include <linux/module.h>
#include <linux/kernel.h>
#include<linux/cdev.h>
struct cdev chrdev3;
unsigned int TestMajor=0;
unsigned int TestMinor=0;
dev_t dev_no;
int testopen(struct inode *inode, struct file *file)
{
//LED输出
printk("led init
");
}
int testclose (struct inode *inode, struct file *file);
{
printk("close");
return 0;
}
ssize_t testwrtie(struct file *, char __user *usr, size_t len, loff_t *offf)
{
char buf[12];
copy_from_user(buf,usr,);
buf[12];
//if(buf[]=='1')
// led点明
printk(,buf);
}
ssize_t testread(struct file *, char __user *usr, size_t len, loff_t *);
{
char buf='r';
read_led;
copy_to_user(usr,buf,);
}
struct file_operations fops= --->结构体初始化 .---???????????????
{ .owner=THIS_MODULE,
.open=testopen,
.write=testwrite,
.release=testclose,
}
static int __init test_init(void) //入口函数
{
printk("hello world!
"); //相当于printf()
int ret;
dev_no =MKDEV(TestMajor,TestMinor)
if(dev_no>0)
{
ret=register_chrdev_region(dev_no, 1,"chrdev_test");//静态注册设备号
}
else //动态申请设备号
{
alloc_chrdev_region(&dev_no,TestMinor, 1,"chrdev_test");
}
if(ret<0)
{
return ret;
}
cdev_init(&chrdev3,&fops);
cdev.owner=THIS_MODULE;
cdev_add(&chrdev3,dev_no,1);
return 0;
}
static void __exit test_exit(void) //出口函数
{
unregister_chrdev_region(dev_no, 1);
cdev_del(&chrdev3);
}
module_init(test_init); //驱动的入口 #insmod *.ko
module_exit(test_exit); //驱动的出口 #rmmod *.ko
//#modinfo *.ko 可以查看module的信息
MODULE_AUTHOR("fbx@GEC");
MODULE_DESCRIPTION("the first module of drivers");
MODULE_LICENSE("GPL");
MODULE_VERSION("V1.0");
---------------------------------------------------------------------
8.linux用户空间与内核空间交互函数。
8.1将内核空间数据copy用户空间
unsigned long copy_to_user(void __user *to, const void *from, unsigned long n)
8.2用户空间数据copy内核空间
unsigned long copy_from_user(void *to, const void __user *from, unsigned long n) ---> write
练习：应用调用write写一个字符到内核空间，内核那驱动程序的.write---》 PRINTK（）;
应用调用read把一个数据从内核读到用户，用户空间打印出来
chrdev.c
#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/cdev.h>
#include<linux/fs.h>
#include<linux/kdev_t.h>
#include<linux/types.h>
#include<linux/uaccess.h>
#include<linux/string.h>
struct cdev chrdev;
unsigned int TestMajor=0;
unsigned int TestMinor=0;
dev_t dev_no;
int ret;
int testopen(struct inode *inode,struct file *file)
{
printk("cdev init ");
return 0;
}
ssize_t testwrite(struct file *file, const char __user *usr, size_t len, loff_t *off)
{
char buf[12];
copy_from_user(buf,usr,strlen(usr));
printk("%s ",buf);
}
ssize_t testread(struct file *file, char __user *usr, size_t len, loff_t *off)
{
char *buf = "hello,user!";
copy_to_user(usr,buf,20);
}
int testrelease(struct inode *inode, struct file *file)
{
printk("close ");
return 0;
}
struct file_operations fops=
{
.owner=THIS_MODULE,
.open = testopen,
.write = testwrite,
.read = testread,
.release = testrelease,
};
static int __init test_init(void)
{
dev_no = MKDEV(TestMajor,TestMinor);
if(dev_no>0)
{
ret = register_chrdev_region(dev_no,1,"chrdev_test");
}
else
{
alloc_chrdev_region(&dev_no,0,1,"chrdev_test");
}
if(ret<0)
{
return ret;
}
cdev_init(&chrdev,&fops);
chrdev.owner=THIS_MODULE;
cdev_add(&chrdev,dev_no,1);
return 0;
}
static int __exit test_exit(void)
{
unregister_chrdev_region(dev_no,1);
cdev_del(&chrdev);
return 0;
}
module_init(test_init);
module_exit(test_exit);
MODULE_AUTHOR("FENG");
MODULE_DESCRIPTION("the first module of char drivers");
MODULE_LICENSE("GPL");
MODULE_VERSION("V1.0");
7.字符设备的调试 7。1安装驱动 [@GEC2103 /]# insmod chrdev.ko 7.2查看分配的设备号 [@GEC2103 /]# cat /proc/devices
250 chrdev_test
7.3手动创建设备文件 mknod /dev/chrdev c 250 0
[@GEC2103 /]# ls /dev/chrdev -l crw-r--r-- 1 0 0 250, 0 Jan 1 00:45 /dev/chrdev 7.4应用程序来/dev/chrdev设备文件，等效操作设备文件对应那个设备
int main() { fd=open("/dev/chrdev",O_RDWR); write(fd,usrbuf,sizeof(usrbuf)) close(fd);
}
--------------------------------------------------------------------------------
test.c
#include<stdio.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
int main()
{
char buf[20];
char buf1[20];
int fd = open("/dev/chrdev_test",O_RDWR);
if(fd<0)
perror("open() error! ");
bzero(buf1,20);
strcpy(buf1,"hello kernel!");
write(fd,buf1,strlen(buf1)+1);
sleep(1);
read(fd,buf,20);
printf("%s ",buf);
}
9。字符设备设计老的方法 优点：比新简洁，比较好理解.
1.使用函数 1)注册字符设备 static inline int register_chrdev(unsigned int major, const char *name,const struct file_operations *fops); 参数： major--->主设备号,如果major>0,静态注册 =0 动态分配
name-->设备名称 /proc/devices
fops-->文件操作集
返回值: major >0 成功:0 失败:负数 major =0 成功：分配后主设备号 失败：负数
2)注销字符设备 static inline void unregister_chrdev(unsigned int major, const char *name) major->主设备号 name-->设备名称
2.使用旧方法设计字符设备驱动的流程 2.1unsigned int Testmajor =0;//251
2.2定义文件操作集 int testopen(struct inode *inode, struct file *file) {
} int testclose (struct inode *inode, struct file *file); {
} ssize_t testwrtie(struct file *, char __user *, size_t, loff_t *) {
}
struct file_operations fops= --->结构体初始化 .---??????????????? { .owner=THIS_MODULE, .open=testopen, .write=testwrite, .release=testclose, }
2.3注册一个字符设备
ret=register_chrdev(Testmajor,"chrdev_test",&fops);//注册字符设备到内核 if(ret<0) { printk("register error") }
if(Testmajor==0) { Testmajor =ret;
}
#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/cdev.h>
#include<linux/fs.h>
#include<linux/kdev_t.h>
#include<linux/types.h>
#include<linux/uaccess.h>
#include<linux/string.h>
dev_t dev_no = 0;
int ret;
int testopen(struct inode *inode,struct file *file)
{
printk("cdev init ");
return 0;
}
ssize_t testwrite(struct file *file, const char __user *usr, size_t len, loff_t *off)
{
char buf[12];
copy_from_user(buf,usr,len);
printk("%s ",buf);
}
ssize_t testread(struct file *file, char __user *usr, size_t len, loff_t *off)
{
char buf[20] = "hello,user!";
copy_to_user(usr,buf,len);
}
int testrelease(struct inode *inode, struct file *file)
{
printk("close ");
return 0;
}
struct file_operations fops=
{
.owner=THIS_MODULE,
.open = testopen,
.write = testwrite,
.read = testread,
.release = testrelease,
};
static int __init test_init(void)
{
ret = register_chrdev(dev_no,"chrdev_test",&fops);
if(ret < 0)
{
printk("register error! ");
}
if(dev_no==0)
{
dev_no = ret;
}
return 0;
}
static int __exit test_exit(void)
{
unregister_chrdev(dev_no,"chrdev_test");
return 0;
}
module_init(test_init);
module_exit(test_exit);
MODULE_AUTHOR("FENG");
MODULE_DESCRIPTION("the first module of char drivers");
MODULE_LICENSE("GPL");
MODULE_VERSION("V1.0");
http://www.cnblogs.com/defen/p/5462247.html