杂项设备可以说是对一部分字符设备的封装，还有一部分不好归类驱动也归到杂项设备。
•1为什么会引入杂项设备？
•第一、节省主设备号
–如果所有的驱动都是用字符设备，那么所有的设备号很快就用完了，总共就255个主设备号。
•第二、驱动写起来相对简单
–如果直接使用封装好的杂项设备，那么就可以减少一步注册主设备号的过程
•2杂项设备初始化文件
杂项设备初始化部分源文件“drivers/char/ misc.c”，这一部分通过Makefile可知，是强制编译的。
•3 注册文件
include/linux/miscdevice.h 头文件
struct miscdevice {
int minor;•常用的参数,设备号
const char *name;•常用的参数,生成设备节点的名称
const struct file_operations *fops; •常用的参数, 指向一个设备节点文件
struct list_head list;
struct device *parent;
struct device *this_device;
const char *nodename;
mode_t mode;
};
/*
* NOTE:
* all file operations except setlease can be called without
* the big kernel lock held in all filesystems.
*/
/*头文件 include/linux/fs.h*/
struct file_operations {
struct module *owner;•必选的是参数,一般是THIS_MODULE
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 *);
/* remove by cym 20130408 support for MT660.ko */
#if 0
//#ifdef CONFIG_SMM6260_MODEM
#if 1// liang, Pixtree also need to use ioctl interface...
int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
#endif
#endif
/* end remove */
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);对GPIO的操作，应用向底层驱动传值
long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
int (*mmap) (struct file *, struct vm_area_struct *);
int (*open) (struct inode *, struct file *);•必选的是参数
int (*flush) (struct file *, fl_owner_t id);
int (*release) (struct inode *, struct file *);•必选的是参数
int (*fsync) (struct file *, 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 **);
long (*fallocate)(struct file *file, int mode, loff_t offset, loff_t len);
/* add by cym 20130408 support for MT6260 and Pixtree */
#if defined(CONFIG_SMM6260_MODEM) || defined(CONFIG_USE_GPIO_AS_I2C)
int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
#endif
/* end add */
};
4.例子(devicenode_linux_module.c)
#include
#include
/*驱动注册的头文件，包含驱动的结构体和注册和卸载的函数*
/#include
/*注册杂项设备头文件*/
#include
/*注册设备节点的文件结构体*/
#include
#define DRIVER_NAME "hello_ctl"
#define DEVICE_NAME "hello_ctl123"
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("TOPEET");
/*ioctl*/
static long hello_ioctl( struct file *files, unsigned int cmd, unsigned long arg){
printk("cmd is %d,arg is %d\n",cmd,arg);
return 0;
}
/*close*/
static int hello_release(struct inode *inode, struct file *file){
printk(KERN_EMERG "hello release\n");
return 0;
}
static int hello_open(struct inode *inode, struct file *file){
printk(KERN_EMERG "hello open\n");
return 0;
}
static struct file_operations hello_ops = {
.owner = THIS_MODULE,
.open = hello_open,
.release = hello_release,
.unlocked_ioctl = hello_ioctl,
};
static struct miscdevice hello_dev = {
.minor = MISC_DYNAMIC_MINOR,
.name = DEVICE_NAME,
.fops = &hello_ops,
};
static int hello_probe(struct platform_device *pdv){
printk(KERN_EMERG "\tprobe initialized\n");
misc_register(&hello_dev);
return 0;
}
static int hello_remove(struct platform_device *pdv){
printk(KERN_EMERG "\tremove\n");
misc_deregister(&hello_dev);
return 0;
}
static void hello_shutdown(struct platform_device *pdv){
;
}
static int hello_suspend(struct platform_device *pdv,pm_message_t pmt){
return 0;
}
static int hello_resume(struct platform_device *pdv){
return 0;
}
struct platform_driver hello_driver = {
.probe = hello_probe,
.remove = hello_remove,
.shutdown = hello_shutdown,
.suspend = hello_suspend,
.resume = hello_resume,
.driver = {
.name = DRIVER_NAME,
.owner = THIS_MODULE,
}
};
static int hello_init(void)
{
printk(KERN_EMERG "HELLO WORLD enter!\n");
int DriverState = platform_driver_register(&hello_driver);
printk(KERN_EMERG "\tDriverState is %d\n",DriverState);
return 0;
}
static void hello_exit(void)
{
printk(KERN_EMERG "HELLO WORLD exit!\n");
platform_driver_unregister(&hello_driver);
}
module_init(hello_init);
module_exit(hello_exit);
5.Makefile
#!/bin/bash
#通知编译器我们要编译模块的哪些源码
#这里是编译devicenode_linux_module.c这个文件编译成中间文件devicenode_linux_module.o
obj-m += devicenode_linux_module.o
#源码目录变量，这里用户需要根据实际情况选择路径
#作者是将Linux的源码拷贝到目录/home/topeet/android4.0下并解压的
KDIR := /home/topeet/android4.0/iTop4412_Kernel_3.0
#当前目录变量
PWD ?= $(shell pwd)
#make命名默认寻找第一个目标
#make -C就是指调用执行的路径
#$(KDIR)Linux源码目录，作者这里指的是/home/topeet/android4.0/iTop4412_Kernel_3.0
#$(PWD)当前目录变量
#modules要执行的操作
all:
make -C $(KDIR) M=$(PWD) modules
#make clean执行的操作是删除后缀为o的文件
clean:
rm -rf *.o
6.make,编译后同驱动注册一样