#include <linux/module.h> #include <linux/types.h> #include <linux/fs.h> #include <linux/errno.h> #include <linux/mm.h> #include <linux/sched.h> #include <linux/init.h> #include <linux/cdev.h> #include <asm/io.h> #include <asm/system.h> #include <asm/uaccess.h> #include <linux/slab.h> #include <linux/poll.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 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; } /*文件释放函数*/ int globalfifo_release(struct inode *inode, struct file *filp) { return 0; } /* 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: memset(dev->mem, 0, GLOBALFIFO_SIZE); //mem数组名，即空间首地址 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);/*唤醒写等待队列*/ 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; } /*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, }; /*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); } /*设备驱动模块加载函数*/ int globalfifo_init(void) { 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; } /*模块卸载函数*/ void globalfifo_exit(void) { 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"); } MODULE_AUTHOR("mhb@SEU"); MODULE_LICENSE("Dual BSD/GPL"); module_param(globalfifo_major, int, S_IRUGO); module_init(globalfifo_init); module_exit(globalfifo_exit);
轮询测试代码：
#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <fcntl.h> #include <sys/ioctl.h> #include <sys/select.h> #include <string.h> #define FIFO_CLEAR 0x1 #define BUFFER_LEN 20 int main() { int fd,num; char rd_ch[BUFFER_LEN]; fd_set rfds,wfds;/*读写文件描述符集*/ /*以非阻塞方式打开设备文件*/ fd=open("/dev/globalfifo",O_RDONLY|O_NONBLOCK); if(fd!=-1) { /*fifo清0*/ if(ioctl(fd,FIFO_CLEAR,0)<0) printf("ioctl command failed!!\n"); while(1) { FD_ZERO(&rfds); FD_ZERO(&wfds); FD_SET(fd,&rfds); FD_SET(fd,&wfds); select(fd+1,&rfds,&wfds,NULL,NULL); /*数据可获得*/ if(FD_ISSET(fd,&rfds)) printf("poll monitor ；can be read !!\n"); /*数据可写入*/ if(FD_ISSET(fd,&wfds)) printf("poll monitor ；can be write!!\n"); } }else { printf("device open failure!!\n"); } return 0; }