2.6内核字符驱动示例程序（3）（转载）

int chardev_ioctl(struct inode *inode,struct file *file,unsigned int cmd,unsigned long arg)
{
        struct my_dev *dev = file->private_data;
        int retval = 0, tmp = 0;
        if( _IOC_TYPE(cmd) != KF701_IOC_MAGIC )
                return -ENOTTY;
        if( _IOC_NR(cmd) > KF701_IOC_MAXNR )
                return -ENOTTY;

        switch(cmd)
        {
                case KF701_IO_RESET:
                        printk(KERN_DEBUG "%s:IO_RESET CMD\n",DEVICE);
                        break;
                case KF701_IO_R:
                        printk(KERN_DEBUG "%s:IO READ CMD\n",DEVICE);
                        retval = put_user(dev->index, (int __user *)arg);
                        break;
                case KF701_IO_W:
                        printk(KERN_DEBUG "%s:IO WRITE CMD\n",DEVICE);
                        retval = get_user(tmp, (int __user *)arg);
                        printk(KERN_DEBUG "CMD ARG = %d\n", tmp);
                        break;
                case KF701_IO_RW:
                        printk(KERN_DEBUG "%s:IO W-R CMD\n",DEVICE);
                        break;
                default:
                        return -ENOTTY;
        }
        return retval;
}

unsigned int chardev_poll(struct file * file, poll_table * wait)
{
        struct my_dev *dev = file->private_data;
        unsigned int mask = 0;
        down(&dev->sem);
        poll_wait(file,&dev->rq,wait);
        if( 0 != dev->index )
                mask |= POLLIN | POLLRDNORM;
        up(&dev->sem);
        return mask;
}

// 此函数在进程上下文之外运行，类似中断上下文，因此：
// 1. 不能访问用户空间
// 2. current指针没有意义
// 3. 不能调用可能引起体眠和调度的代码，信号量也不行。
// 4. 最好使用 spinlock

void timer_function(unsigned long arg)
{
        struct my_dev *dev = (struct my_dev*)arg;
        if( dev->index >= (dev->size - 1) )
                return;
        if( dev->timer_char > 'Z' )
                dev->timer_char = 'A';
        if( '\n' == dev->buf[dev->index-1] )
                dev->index--;
        dev->buf[dev->index++] = (dev->timer_char)++;
        dev->buf[dev->index++] = '\n';

        // 唤醒阻塞在 read 和 select 上的进程
        wake_up_interruptible(&dev->rq);
        dev->timer.expires += dev->timer_interval;
        add_timer( &dev->timer );
}

module_init(chardev_init);
module_exit(chardev_exit);

MODULE_AUTHOR("kf701.ye at gmail.com");
MODULE_DESCRIPTION("Study for kf701");
MODULE_SUPPORTED_DEVICE(DEVICE);
MODULE_LICENSE("GPL");