支持异步通知的globalfifo平台设备驱动程序及其测试代码

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 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:
      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
");
      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 
",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 
",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!!
");
    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!
");
    printk("globalfifo_major is:%d
",globalfifo_major);
    printk("the device name is %s
",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!!
");
    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!
");
    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);

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
",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!
");
        }


    return 0;    

}