#include <linux/module.h>
#include <linux/types.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/mm.h>//内存管理头文件，含有页面大小定义和一些页面释放函数原型
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <asm/io.h>//I/O头文件，以宏的嵌入汇编程序形式定义对I/O端口操作的函数。
#include <asm/system.h>//系统头文件，定义了设置或修改描述符/中断门等的嵌入式汇编宏。
#include <asm/uaccess.h>//包含了copy_to_user、copy_from_user等内核访问用户进程内存地址的函数定义
#include <linux/slab.h>//包含了kcalloc、kzalloc内存分配函数的定义。
#include <linux/poll.h>//--------------platform_device------------
#include <linux/platform_device.h>//-------------class_create,device_create------
#include <linux/device.h>/*用udev机制自动添加设备节点*/
struct class *globalfifo_class;#define GLOBALFIFO_SIZE    0x1000    /*全局内存最大4K字节*/
#define MEM_CLEAR 0x1  /*清0全局内存*/
#define GLOBALFIFO_MAJOR 0    /*预设的globalfifo的主设备号*/#define DEVICE_NAME "globalfifo"static int globalfifo_major = GLOBALFIFO_MAJOR;/*globalfifo设备结构体*/
struct globalfifo_dev
{                                                        struct cdev cdev; /*cdev结构体*/                       unsigned char mem[GLOBALFIFO_SIZE]; /*全局内存*/ unsigned int current_len;/*fifo 有效数据长度*/struct semaphore sem;/*并发控制用的信号量*/wait_queue_head_t r_wait;/*阻塞读用的等待队列头*/wait_queue_head_t w_wait;/*阻塞写用的等待队列头*/struct fasync_struct *async_queue;/*异步结构体指针*/
};struct globalfifo_dev *globalfifo_devp; /*设备结构体指针*/
/*文件打开函数*/
int globalfifo_open(struct inode *inode, struct file *filp)
{/*将设备结构体指针赋值给文件私有数据指针*/struct globalfifo_dev *dev;dev=container_of(inode->i_cdev,struct globalfifo_dev,cdev);//通过结构体成员的指针找到对应结构体的指针filp->private_data = dev;return 0;
}/* ioctl设备控制函数 */
static int globalfifo_ioctl(struct inode *inodep, struct file *filp, unsignedint cmd, unsigned long arg)
{struct globalfifo_dev *dev = filp->private_data;/*获得设备结构体指针*/switch (cmd){case MEM_CLEAR:if(down_interruptible(&dev->sem))/*获取信号量*/return -ERESTARTSYS;memset(dev->mem, 0, GLOBALFIFO_SIZE);  //mem数组名，即空间首地址
up(&dev->sem);printk(KERN_INFO "globalfifo is set to zero\n");break;default:return  - EINVAL;}return 0;
}/*读函数*/
static ssize_t globalfifo_read(struct file *filp, char __user *buf, size_t size,loff_t *ppos)
{int ret = 0;struct globalfifo_dev *dev = filp->private_data; /*获得设备结构体指针*/DECLARE_WAITQUEUE(wait,current);/*define wait queue*/if(down_interruptible(&dev->sem))/*获得信号量*/{return -ERESTARTSYS;}add_wait_queue(&dev->r_wait,&wait);/*进入读等待队列头*//*等待fifo非空并检测用户空间是否要求非阻塞访问*/while(dev->current_len==0){if(filp->f_flags &O_NONBLOCK){ret = -EAGAIN;goto out;}__set_current_state(TASK_INTERRUPTIBLE);/*改变进程状态为睡眠*//*********************************************************/up(&dev->sem);/*释放信号量，防止死锁*//*********************************************************/schedule();/*调度其他进程执行，开始睡眠*/if(signal_pending(current))/*如果是因为信号唤醒*/{ret = -ERESTARTSYS;/*重新执行系统调用*/goto out2;} else if(down_interruptible(&dev->sem)){return -ERESTARTSYS;}}/*内核空间->用户空间*/if(size>dev->current_len)size=dev->current_len;if (copy_to_user(buf,dev->mem,size)){ret =  - EFAULT;   /* Bad address */goto out;}else{memcpy(dev->mem,dev->mem+size,size);/*fifo数据前移*/dev->current_len -=size;/*有效数据长度减少*/printk(KERN_INFO"read %d bytes(s),current_len:%d \n",size,dev->current_len);wake_up_interruptible(&dev->w_wait);/*唤醒写等待队列*/ret= size;}out:up(&dev->sem);/*释放信号量*/out2:remove_wait_queue(&dev->r_wait,&wait);__set_current_state(TASK_RUNNING);return ret;
}/*写函数*/
static ssize_t globalfifo_write(struct file *filp, const char __user *buf,size_t size, loff_t *ppos)
{int ret = 0;struct globalfifo_dev *dev = filp->private_data; /*获得设备结构体指针*/DECLARE_WAITQUEUE(wait,current);/*define wait queue*/if(down_interruptible(&dev->sem))/*获得信号量*/{return -ERESTARTSYS;}add_wait_queue(&dev->w_wait,&wait);/*进入写等待队列*//*等待fifo非满并检测用户空间是否要求非阻塞访问*/while(dev->current_len==GLOBALFIFO_SIZE){if(filp->f_flags &O_NONBLOCK){ret = -EAGAIN;goto out;}__set_current_state(TASK_INTERRUPTIBLE);/*改变进程状态为睡眠*/up(&dev->sem);/*释放信号量，防止死锁*/schedule();/*调度其他进程执行，开始睡眠*/if(signal_pending(current)){ret = -ERESTARTSYS;goto out2;} else if(down_interruptible(&dev->sem)){return -ERESTARTSYS;}}/*内核空间<-用户空间*/if(size>GLOBALFIFO_SIZE-dev->current_len)size=GLOBALFIFO_SIZE-dev->current_len;if (copy_from_user(dev->mem+dev->current_len,buf,size)){ret =  - EFAULT;   /* Bad address */goto out;}else{dev->current_len +=size;/*有效数据长度减少*/printk(KERN_INFO"write %d bytes(s),current_len:%d \n",size,dev->current_len);wake_up_interruptible(&dev->r_wait);/*唤醒读等待队列*//*产生异步读信号*/if(dev->async_queue)kill_fasync(&dev->async_queue,SIGIO,POLL_IN);ret= size;}out:up(&dev->sem);/*释放信号量*/out2:remove_wait_queue(&dev->w_wait,&wait);__set_current_state(TASK_RUNNING);return ret;
}static unsigned int globalfifo_poll(struct file *filp,poll_table *wait)
{unsigned int mask=0;struct globalfifo_dev *dev=filp->private_data;if(down_interruptible(&dev->sem)){return -ERESTARTSYS;}poll_wait(filp,&dev->w_wait,wait);/*将对应的等待队列头添加到poll_table*/poll_wait(filp,&dev->w_wait,wait);/*fifo非空*/if(dev->current_len!=0)mask |=POLLIN|POLLRDNORM;/*标示数据可获得*//*fifo非满*/if(dev->current_len!=GLOBALFIFO_SIZE)mask |=POLLOUT|POLLWRNORM;/*标示数据可获得*/up(&dev->sem);return mask;}static int globalfifo_fasync(int fd,struct file *filp,int mode)
{struct globalfifo_dev *dev =filp->private_data;return fasync_helper(fd,filp,mode,&dev->async_queue);
}/*文件释放函数*/
int globalfifo_release(struct inode *inode, struct file *filp)
{/*将文件从异步通知列表里删除*/globalfifo_fasync(-1,filp,0);return 0;
}/*文件操作结构体*/
static const struct file_operations globalfifo_fops =
{.owner = THIS_MODULE,.read = globalfifo_read,.write = globalfifo_write,.ioctl = globalfifo_ioctl,.open = globalfifo_open,.release = globalfifo_release,.poll = globalfifo_poll,.fasync=globalfifo_fasync,
};/*初始化并注册cdev*/
static void globalfifo_setup_cdev(struct globalfifo_dev *dev, int index)
{int err, devno = MKDEV(globalfifo_major, index);cdev_init(&dev->cdev, &globalfifo_fops);dev->cdev.owner = THIS_MODULE;dev->cdev.ops = &globalfifo_fops;err = cdev_add(&dev->cdev, devno, 1);if (err)printk(KERN_NOTICE "Error %d ", err);
}static int __devinit globalfifo_probe(struct platform_device *pdev)
{printk("in the globalfifo_probe!!\n");int result;dev_t devno = MKDEV(globalfifo_major, 0);/* 申请设备号*/if (globalfifo_major)result = register_chrdev_region(devno, 1, DEVICE_NAME);else  /* 动态申请设备号 */{result = alloc_chrdev_region(&devno, 0, 1,DEVICE_NAME);globalfifo_major = MAJOR(devno);}  if (result < 0)return result;/* 动态申请设备结构体的内存*/globalfifo_devp = kmalloc(sizeof(struct globalfifo_dev), GFP_KERNEL);//kmalloc()内核空间；malloc()用户空间。返回起始地址if (!globalfifo_devp)     /*申请失败*/{result =    - ENOMEM;goto fail_malloc;}memset(globalfifo_devp, 0, sizeof(struct globalfifo_dev));//把此内存空间清零
    globalfifo_setup_cdev(globalfifo_devp, 0);//注册设备/*udev机制可以自动添加设备节点，只需要添加xxx_class这个类，以及device_create()*/globalfifo_class = class_create(THIS_MODULE, "globalfifo_class");/*在sys目录下创建xx_class这个类,/sys/class/~*/device_create(globalfifo_class, NULL, globalfifo_devp->cdev.dev,  DEVICE_NAME, DEVICE_NAME);/*自动创建设备/dev/$DEVICE_NAME*/init_MUTEX(&globalfifo_devp->sem);/*初始化信号量*/init_waitqueue_head(&globalfifo_devp->r_wait);/*初始化读写等待队列*/init_waitqueue_head(&globalfifo_devp->w_wait);printk("globalfifo driver installed!\n");printk("globalfifo_major is:%d\n",globalfifo_major);printk("the device name is %s\n",DEVICE_NAME);return 0;fail_malloc: unregister_chrdev_region(devno, 1);return result;}static int __devexit globalfifo_remove(struct platform_device *pdev)
{printk("in the globalfifo_remove!!\n");device_destroy(globalfifo_class, globalfifo_devp->cdev.dev);class_destroy(globalfifo_class);cdev_del(&globalfifo_devp->cdev);    /*注销cdev*/kfree(globalfifo_devp);     /*释放设备结构体内存*/unregister_chrdev_region(MKDEV(globalfifo_major, 0), 1); /*释放设备号*/printk("globalfifo driver uninstalled!\n");return 0;}static struct platform_driver globalfifo_device_driver={.probe=globalfifo_probe,.remove=globalfifo_remove,.driver={.name=DEVICE_NAME,.owner=THIS_MODULE,},
};/*设备驱动模块加载函数*/
static int __init globalfifo_init(void)
{return platform_driver_register(&globalfifo_device_driver);
}/*模块卸载函数*/
static void __exit globalfifo_exit(void)
{platform_driver_unregister(&globalfifo_device_driver);
}MODULE_AUTHOR("mhb@SEU");
MODULE_LICENSE("Dual BSD/GPL");module_param(globalfifo_major, int, S_IRUGO);module_init(globalfifo_init);
module_exit(globalfifo_exit);

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <signal.h>void input_handler(int signum)
{printf("signum is ；%d\n",signum);
}int main()
{int fd,oflags;fd=open("/dev/globalfifo",O_RDWR,S_IRUSR|S_IWUSR);if(fd != -1) {/*启动信号驱动机制*/signal(SIGIO,input_handler);/*让input_handler 处理SIGIO信号*/fcntl(fd,F_SETOWN,getpid());oflags=fcntl(fd,F_GETFL);fcntl(fd,F_SETFL,oflags|FASYNC);while(1){sleep(100);}} else{printf("device open failed!\n");}return 0;    }