n_hdlc.c

linux 内核源代码

 * n_hdlc_tty_receive - Called by tty driver when receive data is available
 * @tty	- pointer to tty instance data
 * @data - pointer to received data
 * @flags - pointer to flags for data
 * @count - count of received data in bytes
 *
 * Called by tty low level driver when receive data is available. Data is
 * interpreted as one HDLC frame.
 */
static void n_hdlc_tty_receive(struct tty_struct *tty, const __u8 *data,
			       char *flags, int count)
{
	register struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	register struct n_hdlc_buf *buf;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_receive() called count=%d\n",
			__FILE__,__LINE__, count);
		
	/* This can happen if stuff comes in on the backup tty */
	if (n_hdlc == 0 || tty != n_hdlc->tty)
		return;
		
	/* verify line is using HDLC discipline */
	if (n_hdlc->magic != HDLC_MAGIC) {
		printk("%s(%d) line not using HDLC discipline\n",
			__FILE__,__LINE__);
		return;
	}
	
	if ( count>maxframe ) {
		if (debuglevel >= DEBUG_LEVEL_INFO)	
			printk("%s(%d) rx count>maxframesize, data discarded\n",
			       __FILE__,__LINE__);
		return;
	}

	/* get a free HDLC buffer */	
	buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);
	if (!buf) {
		/* no buffers in free list, attempt to allocate another rx buffer */
		/* unless the maximum count has been reached */
		if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)
			buf = kmalloc(N_HDLC_BUF_SIZE, GFP_ATOMIC);
	}
	
	if (!buf) {
		if (debuglevel >= DEBUG_LEVEL_INFO)	
			printk("%s(%d) no more rx buffers, data discarded\n",
			       __FILE__,__LINE__);
		return;
	}
		
	/* copy received data to HDLC buffer */
	memcpy(buf->buf,data,count);
	buf->count=count;

	/* add HDLC buffer to list of received frames */
	n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);
	
	/* wake up any blocked reads and perform async signalling */
	wake_up_interruptible (&tty->read_wait);
	if (n_hdlc->tty->fasync != NULL)
		kill_fasync (&n_hdlc->tty->fasync, SIGIO, POLL_IN);

}	/* end of n_hdlc_tty_receive() */

/**
 * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
 * @tty - pointer to tty instance data
 * @file - pointer to open file object
 * @buf - pointer to returned data buffer
 * @nr - size of returned data buffer
 * 	
 * Returns the number of bytes returned or error code.
 */
static ssize_t n_hdlc_tty_read(struct tty_struct *tty, struct file *file,
			   __u8 __user *buf, size_t nr)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc(tty);
	int ret;
	struct n_hdlc_buf *rbuf;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_read() called\n",__FILE__,__LINE__);
		
	/* Validate the pointers */
	if (!n_hdlc)
		return -EIO;

	/* verify user access to buffer */
	if (!access_ok(VERIFY_WRITE, buf, nr)) {
		printk(KERN_WARNING "%s(%d) n_hdlc_tty_read() can't verify user "
		"buffer\n", __FILE__, __LINE__);
		return -EFAULT;
	}

	for (;;) {
		if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
			return -EIO;

		n_hdlc = tty2n_hdlc (tty);
		if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC ||
			 tty != n_hdlc->tty)
			return 0;

		rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);
		if (rbuf)
			break;
			
		/* no data */
		if (file->f_flags & O_NONBLOCK)
			return -EAGAIN;
			
		interruptible_sleep_on (&tty->read_wait);
		if (signal_pending(current))
			return -EINTR;
	}
		
	if (rbuf->count > nr)
		/* frame too large for caller's buffer (discard frame) */
		ret = -EOVERFLOW;
	else {
		/* Copy the data to the caller's buffer */
		if (copy_to_user(buf, rbuf->buf, rbuf->count))
			ret = -EFAULT;
		else
			ret = rbuf->count;
	}
	
	/* return HDLC buffer to free list unless the free list */
	/* count has exceeded the default value, in which case the */
	/* buffer is freed back to the OS to conserve memory */
	if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)
		kfree(rbuf);
	else	
		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,rbuf);
	
	return ret;
	
}	/* end of n_hdlc_tty_read() */

/**
 * n_hdlc_tty_write - write a single frame of data to device
 * @tty	- pointer to associated tty device instance data
 * @file - pointer to file object data
 * @data - pointer to transmit data (one frame)
 * @count - size of transmit frame in bytes
 * 		
 * Returns the number of bytes written (or error code).
 */
static ssize_t n_hdlc_tty_write(struct tty_struct *tty, struct file *file,
			    const unsigned char *data, size_t count)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	int error = 0;
	DECLARE_WAITQUEUE(wait, current);
	struct n_hdlc_buf *tbuf;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_write() called count=%Zd\n",
			__FILE__,__LINE__,count);
		
	/* Verify pointers */
	if (!n_hdlc)
		return -EIO;

	if (n_hdlc->magic != HDLC_MAGIC)
		return -EIO;

	/* verify frame size */
	if (count > maxframe ) {
		if (debuglevel & DEBUG_LEVEL_INFO)
			printk (KERN_WARNING
				"n_hdlc_tty_write: truncating user packet "
				"from %lu to %d\n", (unsigned long) count,
				maxframe );
		count = maxframe;
	}
	
	add_wait_queue(&tty->write_wait, &wait);
	set_current_state(TASK_INTERRUPTIBLE);
	
	/* Allocate transmit buffer */
	/* sleep until transmit buffer available */		
	while (!(tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list))) {
		schedule();
			
		n_hdlc = tty2n_hdlc (tty);
		if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC || 
		    tty != n_hdlc->tty) {
			printk("n_hdlc_tty_write: %p invalid after wait!\n", n_hdlc);
			error = -EIO;
			break;
		}
			
		if (signal_pending(current)) {
			error = -EINTR;
			break;
		}
	}

	set_current_state(TASK_RUNNING);
	remove_wait_queue(&tty->write_wait, &wait);

	if (!error) {		
		/* Retrieve the user's buffer */
		memcpy(tbuf->buf, data, count);

		/* Send the data */
		tbuf->count = error = count;
		n_hdlc_buf_put(&n_hdlc->tx_buf_list,tbuf);
		n_hdlc_send_frames(n_hdlc,tty);
	}

	return error;
	
}	/* end of n_hdlc_tty_write() */

/**
 * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
 * @tty - pointer to tty instance data
 * @file - pointer to open file object for device
 * @cmd - IOCTL command code
 * @arg - argument for IOCTL call (cmd dependent)
 *
 * Returns command dependent result.
 */
static int n_hdlc_tty_ioctl(struct tty_struct *tty, struct file *file,
			    unsigned int cmd, unsigned long arg)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	int error = 0;
	int count;
	unsigned long flags;
	
	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_ioctl() called %d\n",
			__FILE__,__LINE__,cmd);
		
	/* Verify the status of the device */
	if (!n_hdlc || n_hdlc->magic != HDLC_MAGIC)
		return -EBADF;

	switch (cmd) {
	case FIONREAD:
		/* report count of read data available */
		/* in next available frame (if any) */
		spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock,flags);
		if (n_hdlc->rx_buf_list.head)
			count = n_hdlc->rx_buf_list.head->count;
		else
			count = 0;
		spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock,flags);
		error = put_user(count, (int __user *)arg);
		break;

	case TIOCOUTQ:
		/* get the pending tx byte count in the driver */
		count = tty->driver->chars_in_buffer ?
				tty->driver->chars_in_buffer(tty) : 0;
		/* add size of next output frame in queue */
		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock,flags);
		if (n_hdlc->tx_buf_list.head)
			count += n_hdlc->tx_buf_list.head->count;
		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock,flags);
		error = put_user(count, (int __user *)arg);
		break;

	default:
		error = n_tty_ioctl (tty, file, cmd, arg);
		break;
	}
	return error;
	
}	/* end of n_hdlc_tty_ioctl() */

/**
 * n_hdlc_tty_poll - TTY callback for poll system call
 * @tty - pointer to tty instance data
 * @filp - pointer to open file object for device
 * @poll_table - wait queue for operations
 * 
 * Determine which operations (read/write) will not block and return info
 * to caller.
 * Returns a bit mask containing info on which ops will not block.
 */
static unsigned int n_hdlc_tty_poll(struct tty_struct *tty, struct file *filp,
				    poll_table *wait)
{
	struct n_hdlc *n_hdlc = tty2n_hdlc (tty);
	unsigned int mask = 0;

	if (debuglevel >= DEBUG_LEVEL_INFO)	
		printk("%s(%d)n_hdlc_tty_poll() called\n",__FILE__,__LINE__);
		
	if (n_hdlc && n_hdlc->magic == HDLC_MAGIC && tty == n_hdlc->tty) {
		/* queue current process into any wait queue that */
		/* may awaken in the future (read and write) */

		poll_wait(filp, &tty->read_wait, wait);
		poll_wait(filp, &tty->write_wait, wait);

		/* set bits for operations that won't block */
		if (n_hdlc->rx_buf_list.head)
			mask |= POLLIN | POLLRDNORM;	/* readable */
		if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
			mask |= POLLHUP;
		if (tty_hung_up_p(filp))
			mask |= POLLHUP;
		if (!tty_is_writelocked(tty) &&
				n_hdlc->tx_free_buf_list.head)
			mask |= POLLOUT | POLLWRNORM;	/* writable */
	}
	return mask;
}	/* end of n_hdlc_tty_poll() */

/**
 * n_hdlc_alloc - allocate an n_hdlc instance data structure
 *
 * Returns a pointer to newly created structure if success, otherwise %NULL
 */
static struct n_hdlc *n_hdlc_alloc(void)
{
	struct n_hdlc_buf *buf;
	int i;
	struct n_hdlc *n_hdlc = kmalloc(sizeof(*n_hdlc), GFP_KERNEL);

	if (!n_hdlc)
		return NULL;

	memset(n_hdlc, 0, sizeof(*n_hdlc));

	n_hdlc_buf_list_init(&n_hdlc->rx_free_buf_list);
	n_hdlc_buf_list_init(&n_hdlc->tx_free_buf_list);
	n_hdlc_buf_list_init(&n_hdlc->rx_buf_list);
	n_hdlc_buf_list_init(&n_hdlc->tx_buf_list);
	
	/* allocate free rx buffer list */
	for(i=0;i<DEFAULT_RX_BUF_COUNT;i++) {
		buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
		if (buf)
			n_hdlc_buf_put(&n_hdlc->rx_free_buf_list,buf);
		else if (debuglevel >= DEBUG_LEVEL_INFO)	
			printk("%s(%d)n_hdlc_alloc(), kalloc() failed for rx buffer %d\n",__FILE__,__LINE__, i);
	}
	
	/* allocate free tx buffer list */
	for(i=0;i<DEFAULT_TX_BUF_COUNT;i++) {
		buf = kmalloc(N_HDLC_BUF_SIZE, GFP_KERNEL);
		if (buf)
			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list,buf);
		else if (debuglevel >= DEBUG_LEVEL_INFO)	
			printk("%s(%d)n_hdlc_alloc(), kalloc() failed for tx buffer %d\n",__FILE__,__LINE__, i);
	}
	
	/* Initialize the control block */
	n_hdlc->magic  = HDLC_MAGIC;
	n_hdlc->flags  = 0;
	
	return n_hdlc;
	
}	/* end of n_hdlc_alloc() */

/**
 * n_hdlc_buf_list_init - initialize specified HDLC buffer list
 * @list - pointer to buffer list
 */
static void n_hdlc_buf_list_init(struct n_hdlc_buf_list *list)
{
	memset(list, 0, sizeof(*list));
	spin_lock_init(&list->spinlock);
}	/* end of n_hdlc_buf_list_init() */

/**
 * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
 * @list - pointer to buffer list
 * @buf	- pointer to buffer
 */
static void n_hdlc_buf_put(struct n_hdlc_buf_list *list,
			   struct n_hdlc_buf *buf)
{
	unsigned long flags;
	spin_lock_irqsave(&list->spinlock,flags);
	
	buf->link=NULL;
	if (list->tail)
		list->tail->link = buf;
	else
		list->head = buf;
	list->tail = buf;
	(list->count)++;
	
	spin_unlock_irqrestore(&list->spinlock,flags);
	
}	/* end of n_hdlc_buf_put() */

/**
 * n_hdlc_buf_get - remove and return an HDLC buffer from list
 * @list - pointer to HDLC buffer list
 * 
 * Remove and return an HDLC buffer from the head of the specified HDLC buffer
 * list.
 * Returns a pointer to HDLC buffer if available, otherwise %NULL.
 */
static struct n_hdlc_buf* n_hdlc_buf_get(struct n_hdlc_buf_list *list)
{
	unsigned long flags;
	struct n_hdlc_buf *buf;
	spin_lock_irqsave(&list->spinlock,flags);
	
	buf = list->head;
	if (buf) {
		list->head = buf->link;
		(list->count)--;
	}
	if (!list->head)
		list->tail = NULL;
	
	spin_unlock_irqrestore(&list->spinlock,flags);
	return buf;
	
}	/* end of n_hdlc_buf_get() */

static char hdlc_banner[] __initdata =
	KERN_INFO "HDLC line discipline: version " HDLC_VERSION
	", maxframe=%u\n";
static char hdlc_register_ok[] __initdata =
	KERN_INFO "N_HDLC line discipline registered.\n";
static char hdlc_register_fail[] __initdata =
	KERN_ERR "error registering line discipline: %d\n";
static char hdlc_init_fail[] __initdata =
	KERN_INFO "N_HDLC: init failure %d\n";

static int __init n_hdlc_init(void)
{
	int status;

	/* range check maxframe arg */
	if (maxframe < 4096)
		maxframe = 4096;
	else if (maxframe > 65535)
		maxframe = 65535;

	printk(hdlc_banner, maxframe);

	status = tty_register_ldisc(N_HDLC, &n_hdlc_ldisc);
	if (!status)
		printk(hdlc_register_ok);
	else
		printk(hdlc_register_fail, status);

	if (status)
		printk(hdlc_init_fail, status);
	return status;
	
}	/* end of init_module() */

static char hdlc_unregister_ok[] __exitdata =
	KERN_INFO "N_HDLC: line discipline unregistered\n";
static char hdlc_unregister_fail[] __exitdata =
	KERN_ERR "N_HDLC: can't unregister line discipline (err = %d)\n";

static void __exit n_hdlc_exit(void)
{
	/* Release tty registration of line discipline */
	int status = tty_unregister_ldisc(N_HDLC);

	if (status)
		printk(hdlc_unregister_fail, status);
	else
		printk(hdlc_unregister_ok);
}

module_init(n_hdlc_init);
module_exit(n_hdlc_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul Fulghum [e-mail]");
module_param(debuglevel, int, 0);
module_param(maxframe, int, 0);
MODULE_ALIAS_LDISC(N_HDLC);