8--2支持阻塞操作的globalfifo设备驱动

在用户空间验证 globalfifo的读写：

 

编译 globalfifo.c并insmod模块即创建设备文件节点'/dev/globalfifo'后，启动两个进程，一个进程"cat /dev/globalfifo&",在后台执行

另一个进程echo 字符串 >/dev/globalfifo"在前台执行  如果想从后台到前台 执行 fg

 

1.当执行 cat /dev/globalfifo  时，没有后台操作，光标会在等待，进程进入睡眠。。

2.当 cat /dev/globalfifo  还在后台操作时，如果 rmmod globalfifo.ko  这时，不能卸载模块，因为还在后台操作，进程还在执行。

3.显示后台操作任务：jobs -l             后台到前台，需要 fg

4.当执行了 fg 后，进程在前台执行，但是  globalfifo 进程 还是在睡眠状态 需要 等待输入字符。

    控制界面，不能进行其他的操作了。

5 ctrl +c  取消 进程。就可以 继续其他 进程的操作了。

 

[root@EmbedSky /xiangjie]# ls4_book.ko globalmem_lock.ko helloglobalfifo.ko globalmem_two.ko hello.txt[root@EmbedSky /xiangjie]# insmod globalfifo.ko [root@EmbedSky /xiangjie]# cat /proc/devices Character devices: 1 mem 4 /dev/vc/0 4 tty 5 /dev/tty 5 /dev/console 5 /dev/ptmx 7 vcs 10 misc 13 input 14 sound 29 fb 81 video4linux 89 i2c 90 mtd116 alsa128 ptm136 pts180 usb188 ttyUSB189 usb_device204 tq2440_serial247 globalfifo253 usb_endpoint254 rtcBlock devices:259 blkext 7 loop 31 mtdblock179 mmc[root@EmbedSky /xiangjie]# mknod /dev/globalfifo c 247 0[root@EmbedSky /xiangjie]# cat /dev/globalfifo ^[[A^C[root@EmbedSky /xiangjie]# cat /dev/globalfifo&[root@EmbedSky /xiangjie]# ps PID USER VSZ STAT COMMAND 1 root 2068 S init 2 root 0 SW< [kthreadd] 3 root 0 SW< [ksoftirqd/0] 4 root 0 SW< [watchdog/0] 5 root 0 SW< [events/0] 6 root 0 SW< [khelper] 12 root 0 SW< [async/mgr] 135 root 0 SW< [kblockd/0] 141 root 0 SW< [ksuspend_usbd] 146 root 0 SW< [khubd] 153 root 0 SW< [kmmcd] 174 root 0 SW [khungtaskd] 175 root 0 SW [pdflush] 176 root 0 SW [pdflush] 177 root 0 SW< [kswapd0] 178 root 0 SW< [aio/0] 179 root 0 SW< [nfsiod] 281 root 0 SW< [mtdblockd] 348 root 0 SW< [usbhid_resumer] 362 root 0 SW< [rpciod/0] 370 root 0 DW< [yaffs_c395a000] 387 root 2072 S /bin/sh /bin/qtopia 389 root 15136 S /opt/Qtopia/bin/qpe 392 root 2068 S /usr/sbin/telnetd -l /bin/login 395 root 2072 S -/bin/sh 402 root 8728 S < /opt/Qtopia/bin/qss 403 root 10996 S N /opt/Qtopia/bin/quicklauncher 457 root 2068 S cat /dev/globalfifo 458 root 2072 R ps [root@EmbedSky /xiangjie]# echo 'i want to be '> /dev/globalfifo written 14 bytes(s),current_len:14read 14 bytes(s),current_len:0i want to be [root@EmbedSky /xiangjie]# echo 'a great chinese linux driver engineer' > /dev/globalfifo written 38 bytes(s),current_len:38read 38 bytes(s),current_len:0a great chinese linux driver engineer[root@EmbedSky /xiangjie]# rmmod globalfifo.ko rmmod: cannot unload 'globalfifo': Resource temporarily unavailable[root@EmbedSky /xiangjie]# jobs -l[1] + 457 Running cat /dev/globalfifo[root@EmbedSky /xiangjie]# fgcat /dev/globalfifo^C[root@EmbedSky /xiangjie]# rmmod globalfifo.ko [root@EmbedSky /xiangjie]#

 

 

 

/*====================================================================== A globalfifo driver as an example of char device drivers This example is to introduce poll,blocking and non-blocking access The initial developer of the original code is Baohua Song <[e-mail]>. All Rights Reserved.======================================================================*/#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/poll.h>#define GLOBALFIFO_SIZE0x1000/*全局fifo最大4K字节*/#define FIFO_CLEAR 0x1 /*清0全局内存的长度*/#define GLOBALFIFO_MAJOR 253 /*预设的globalfifo的主设备号*/static int globalfifo_major = GLOBALFIFO_MAJOR;/*globalfifo设备结构体*/struct globalfifo_dev { struct cdev cdev; /*cdev结构体*/ unsigned int current_len; /*fifo有效数据长度*/ unsigned char mem[GLOBALFIFO_SIZE]; /*全局内存*/ 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*/ filp->private_data = globalfifo_devp; 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 FIFO_CLEAR: down(&dev->sem); //获得信号量 dev->current_len = 0; memset(dev->mem,0,GLOBALFIFO_SIZE); up(&dev->sem); //释放信号量 printk(KERN_INFO "globalfifo is set to zero/n"); break; default: return - EINVAL; } return 0;}static unsigned int globalfifo_poll(struct file *filp, poll_table *wait){ unsigned int mask = 0; struct globalfifo_dev *dev = filp->private_data; /*获得设备结构体指针*/ down(&dev->sem); poll_wait(filp, &dev->r_wait, wait); 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; /*标示数据可写入*/ } up(&dev->sem); return mask;}/*globalfifo读函数*/static ssize_t globalfifo_read(struct file *filp, char __user *buf, size_t count, 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); //定义等待队列 down(&dev->sem); //获得信号量 add_wait_queue(&dev->r_wait, &wait); //进入读等待队列头 /* 等待FIFO非空 */ 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); schedule(); //调度其他进程执行 if (signal_pending(current)) //如果是因为信号唤醒 { ret = - ERESTARTSYS; goto out2; } down(&dev->sem); } /* 拷贝到用户空间 */ if (count > dev->current_len) count = dev->current_len; if (copy_to_user(buf, dev->mem, count)) { ret = - EFAULT; goto out; } else { memcpy(dev->mem, dev->mem + count, dev->current_len - count); //fifo数据前移 dev->current_len -= count; //有效数据长度减少 printk(KERN_INFO "read %d bytes(s),current_len:%d/n", count, dev->current_len); wake_up_interruptible(&dev->w_wait); //唤醒写等待队列 ret = count; } out: up(&dev->sem); //释放信号量 out2:remove_wait_queue(&dev->w_wait, &wait); //从附属的等待队列头移除 set_current_state(TASK_RUNNING); return ret;}/*globalfifo写操作*/static ssize_t globalfifo_write(struct file *filp, const char __user *buf, size_t count, loff_t *ppos){ struct globalfifo_dev *dev = filp->private_data; //获得设备结构体指针 int ret; DECLARE_WAITQUEUE(wait, current); //定义等待队列 down(&dev->sem); //获取信号量 add_wait_queue(&dev->w_wait, &wait); //进入写等待队列头 /* 等待FIFO非满 */ while (dev->current_len == GLOBALFIFO_SIZE) { if (filp->f_flags &O_NONBLOCK) //如果是非阻塞访问 { ret = - EAGAIN; goto out; } __set_current_state(TASK_INTERRUPTIBLE); //改变进程状态为睡眠 up(&dev->sem); schedule(); //调度其他进程执行 if (signal_pending(current)) //如果是因为信号唤醒 { ret = - ERESTARTSYS; goto out2; } down(&dev->sem); //获得信号量 } /*从用户空间拷贝到内核空间*/ if (count > GLOBALFIFO_SIZE - dev->current_len) count = GLOBALFIFO_SIZE - dev->current_len; if (copy_from_user(dev->mem + dev->current_len, buf, count)) { ret = - EFAULT; goto out; } else { dev->current_len += count; printk(KERN_INFO "written %d bytes(s),current_len:%d/n", count, dev ->current_len); wake_up_interruptible(&dev->r_wait); //唤醒读等待队列 ret = count; } out: up(&dev->sem); //释放信号量 out2:remove_wait_queue(&dev->w_wait, &wait); //从附属的等待队列头移除 set_current_state(TASK_RUNNING); return ret;}/*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, .poll = globalfifo_poll, .open = globalfifo_open, .release = globalfifo_release,};/*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 adding LED%d", err, index);}/*设备驱动模块加载函数*/int globalfifo_init(void){ int ret; dev_t devno = MKDEV(globalfifo_major, 0); /* 申请设备号*/ if (globalfifo_major) ret = register_chrdev_region(devno, 1, "globalfifo"); else /* 动态申请设备号 */ { ret = alloc_chrdev_region(&devno, 0, 1, "globalfifo"); globalfifo_major = MAJOR(devno); } if (ret < 0) return ret; /* 动态申请设备结构体的内存*/ globalfifo_devp = kmalloc(sizeof(struct globalfifo_dev), GFP_KERNEL); if (!globalfifo_devp) /*申请失败*/ { ret = - ENOMEM; goto fail_malloc; } memset(globalfifo_devp, 0, sizeof(struct globalfifo_dev)); globalfifo_setup_cdev(globalfifo_devp, 0); init_MUTEX(&globalfifo_devp->sem); /*初始化信号量*/ init_waitqueue_head(&globalfifo_devp->r_wait); /*初始化读等待队列头*/ init_waitqueue_head(&globalfifo_devp->w_wait); /*初始化写等待队列头*/ return 0; fail_malloc: unregister_chrdev_region(devno, 1); return ret;}/*模块卸载函数*/void globalfifo_exit(void){ 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*/}MODULE_AUTHOR("Song Baohua");MODULE_LICENSE("Dual BSD/GPL");module_param(globalfifo_major, int, S_IRUGO);module_init(globalfifo_init);module_exit(globalfifo_exit);