第三章 字符设备驱动程序框架
字符设备驱动程序框架简介
出入口函数
module_init(drv_init);//告诉内核入口函数
module_exit(drv_exit);//告诉内核出口函数
drv_init()
这个函数就变成了我们的驱动程序的入口函数了,drv_exit()
这个函数就变成了我们的驱动程序的出口函数了
给应用程序提供接口
- 定义
file_operations
结构体(该结构体是驱动和应用程序交互的接口) - 调用
register_chrdev()
函数将该结构体注册进内核
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 *);
int (*fsync) (struct file *, struct dentry *, int datasync);
int (*aio_fsync) (struct kiocb *, int datasync);
int (*fasync) (int, struct file *, int);
int (*lock) (struct file *, int, struct file_lock *);
ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
int (*check_flags)(int);
int (*flock) (struct file *, int, struct file_lock *);
ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
int (*setlease)(struct file *, long, struct file_lock **);
};
驱动程序要给应用程序提供哪些接口,就只需要填充相应的成员即可。
字符设备驱动程序框架实现
#include <linux/mm.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <linux/random.h>
#include <linux/init.h>
#include <linux/raw.h>
#include <linux/tty.h>
#include <linux/capability.h>
#include <linux/ptrace.h>
#include <linux/device.h>
#include <linux/highmem.h>
#include <linux/crash_dump.h>
#include <linux/backing-dev.h>
#include <linux/bootmem.h>
#include <linux/splice.h>
#include <linux/pfn.h>
#include <linux/export.h>
#include <linux/io.h>
#include <linux/aio.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/uaccess.h>
#include <linux/ioctl.h>
/**************** 基本定义 **********************/
//内核空间缓冲区定义
#if 0
#define KB_MAX_SIZE 20
#define kbuf[KB_MAX_SIZE]
#endif
//加密函数参数内容: _IOW(IOW_CHAR , IOW_NUMn , IOW_TYPE)
//加密函数用于xxx_ioctl函数中
//使用举例:ioctl(fd , _IOW('L',0x80,long) , 0x01);
//#define NUMn xxx , if you need!
#define IOW_CHAR 'L'
#define IOW_TYPE long
#define IOW_NUM1 0x80
//初始化函数必要资源定义
//device number;
dev_t dev_num;
//struct dev
struct cdev xxx_cdev;
//auto "mknode /dev/xxx c dev_num minor_num"
struct class *xxx_class = NULL;
struct device *xxx_device = NULL;
/**************** 结构体 file_operations 成员函数 *****************/
//open
static int xxx_open(struct inode *inode, struct file *file)
{
printk("xxx drive open...\n");
return 0;
}
//close
static int xxx_close(struct inode *inode , struct file *file)
{
printk("xxx drive close...\n");
return 0;
}
//read
static ssize_t xxx_read(struct file *file, char __user *buffer,
size_t len, loff_t *pos)
{
int ret_v = 0;
printk("xxx drive read...\n");
return ret_v;
}
//write
static ssize_t xxx_write( struct file *file , const char __user *buffer,
size_t len , loff_t *offset )
{
int ret_v = 0;
printk("xxx drive write...\n");
return ret_v;
}
//unlocked_ioctl
static int xxx_ioctl (struct file *filp , unsigned int cmd , unsigned long arg)
{
int ret_v = 0;
printk("xxx drive ioctl...\n");
switch(cmd)
{
//cmd值自行进行修改
case 0x01:
{
if(arg == 0x01) //第二条件
{
}
}
break;
//带密码保护:
//请在"基本定义"进行必要的定义
case _IOW(IOW_CHAR,IOW_NUM1,IOW_TYPE):
{
if(arg == 0x01) //第二条件
{
}
}
break;
default:
break;
}
return ret_v;
}
/***************** 结构体: file_operations ************************/
//struct
static const struct file_operations xxx_fops = {
.owner = THIS_MODULE,
.open = xxx_open,
.release = xxx_close,
.read = xxx_read,
.write = xxx_write,
.unlocked_ioctl = xxx_ioctl,
};
/************* functions: init , exit *******************/
//条件值变量,用于指示资源是否正常使用
unsigned char init_flag = 0;
unsigned char add_code_flag = 0;
//init
static __init int xxx_init(void)
{
int ret_v = 0;
printk("xxx drive init...\n");
//函数 alloc_chrdev_region 主要参数说明:
//参数2:次设备号
//参数3:创建多少个设备
if( ( ret_v = alloc_chrdev_region(&dev_num,0,1,"xxx") ) < 0 )
{
goto dev_reg_error;
}
init_flag = 1; //标示设备创建成功
printk("The drive info of xxx:\nmajor: %d\nminor: %d\n",
MAJOR(dev_num),MINOR(dev_num));
cdev_init(&xxx_cdev,&xxx_fops);
if( (ret_v = cdev_add(&xxx_cdev,dev_num,1)) != 0 )
{
goto cdev_add_error;
}
xxx_class = class_create(THIS_MODULE,"xxx");
if( IS_ERR(xxx_class) )
{
goto class_c_error;
}
xxx_device = device_create(xxx_class,NULL,dev_num,NULL,"xxx");
if( IS_ERR(xxx_device) )
{
goto device_c_error;
}
printk("auto mknod success!\n");
//----------------- 请在此添加您的初始化程序 -------------------//
//如果需要做错误处理,请:goto xxx_error;
add_code_flag = 1;
//------------------------ END --------------------------------//
goto init_success;
dev_reg_error:
printk("alloc_chrdev_region failed\n");
return ret_v;
cdev_add_error:
printk("cdev_add failed\n");
unregister_chrdev_region(dev_num, 1);
init_flag = 0;
return ret_v;
class_c_error:
printk("class_create failed\n");
cdev_del(&xxx_cdev);
unregister_chrdev_region(dev_num, 1);
init_flag = 0;
return PTR_ERR(xxx_class);
device_c_error:
printk("device_create failed\n");
cdev_del(&xxx_cdev);
unregister_chrdev_region(dev_num, 1);
class_destroy(xxx_class);
init_flag = 0;
return PTR_ERR(xxx_device);
//--------------------- 请在此添加您的错误处理内容 -------------------//
xxx_error:
add_code_flag = 0;
return -1;
//---------------------- END ----------------------//
init_success:
printk("xxx init success!\n");
return 0;
}
//exit
static __exit void xxx_exit(void)
{
printk("xxx drive exit...\n");
if(add_code_flag == 1)
{
//------------ 请在这里释放您的程序占有的资源 -------------//
printk("free your resources...\n");
printk("free finish\n");
//---------------------- END ----------------------//
}
if(init_flag == 1)
{
//释放初始化使用到的资源
cdev_del(&xxx_cdev);
unregister_chrdev_region(dev_num, 1);
device_unregister(xxx_device);
class_destroy(xxx_class);
}
}
/********************* module operations*************************/
//module loading
module_init(xxx_init);
module_exit(xxx_exit);
//some infomation
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("from Jafy");
MODULE_DESCRIPTION("xxx drive");
/*********************** The End *******************************/