驱动：
#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 ;
} /* ioctl设备控制函数 */
static int globalfifo_ioctl(struct inode *inodep, struct file *filp, unsigned
int 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, , 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 ;
} /*读函数*/
static ssize_t globalfifo_read(struct file *filp, char __user *buf, size_t size,
loff_t *ppos)
{ int ret = ;
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==)
{
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 = ;
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=;
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!=)
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(-,filp,);
return ;
} /*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, );
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, ); /* 申请设备号*/
if (globalfifo_major)
result = register_chrdev_region(devno, , DEVICE_NAME);
else /* 动态申请设备号 */
{
result = alloc_chrdev_region(&devno, , ,DEVICE_NAME);
globalfifo_major = MAJOR(devno);
}
if (result < )
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, , sizeof(struct globalfifo_dev));//把此内存空间清零 globalfifo_setup_cdev(globalfifo_devp, );//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 ; fail_malloc: unregister_chrdev_region(devno, );
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, ), ); /*释放设备号*/
printk("globalfifo driver uninstalled!\n");
return ; } 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);
测试程序：
#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 != -) {
/*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()
{
sleep();
}
} else
{
printf("device open failed!\n");
} return ; }