1 // SPDX-License-Identifier: GPL-1.0+
16  * tty device drivers that support bit-synchronous HDLC communications.
18  * All HDLC data is frame oriented which means:
20  * 1. tty write calls represent one complete transmit frame of data
21  *    The device driver should accept the complete frame or none of
22  *    the frame (busy) in the write method. Each write call should have
23  *    a byte count in the range of 2-65535 bytes (2 is min HDLC frame
26  *    CCITT CRC32, 4 crc bytes are required, so the maximum size frame
28  *    CRC16, the maximum application frame size would be 65533.
32  *    one received frame. The device driver should bypass
33  *    the tty flip buffer and call the line discipline receive
41  * 3. tty read calls returns an entire frame of data or nothing.
49  *    otherwise the count of the next available frame is returned.
50  *    (instead of the sum of all received frame counts).
54  * this line discipline (or another line discipline that is frame
64  * and frame orientation of HDLC communications.
126  * struct n_hdlc - per device instance data structure
130  * @tx_buf_list: list of pending transmit frame buffers
131  * @rx_buf_list: list of received frame buffers
132  * @tx_free_buf_list: list unused transmit frame buffers
133  * @rx_free_buf_list: list unused received frame buffers
148  * HDLC buffer list manipulation functions
161 /* max frame size for memory allocations */
166 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_rx_queue()
169 	while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))  in flush_rx_queue()
170 		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);  in flush_rx_queue()
175 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_tx_queue()
178 	while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))  in flush_tx_queue()
179 		n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);  in flush_tx_queue()
193  * n_hdlc_tty_close - line discipline close
201 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_close()
203 	if (n_hdlc->magic != HDLC_MAGIC) {  in n_hdlc_tty_close()
208 	clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_close()
210 	tty->disc_data = NULL;  in n_hdlc_tty_close()
213 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_close()
214 	wake_up_interruptible(&tty->write_wait);  in n_hdlc_tty_close()
216 	cancel_work_sync(&n_hdlc->write_work);  in n_hdlc_tty_close()
218 	n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);  in n_hdlc_tty_close()
219 	n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);  in n_hdlc_tty_close()
220 	n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);  in n_hdlc_tty_close()
221 	n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);  in n_hdlc_tty_close()
226  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
233 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_open()
235 	pr_debug("%s() called (device=%s)\n", __func__, tty->name);  in n_hdlc_tty_open()
240 		return -EEXIST;  in n_hdlc_tty_open()
246 		return -ENFILE;  in n_hdlc_tty_open()
249 	INIT_WORK(&n_hdlc->write_work, n_hdlc_tty_write_work);  in n_hdlc_tty_open()
250 	n_hdlc->tty_for_write_work = tty;  in n_hdlc_tty_open()
251 	tty->disc_data = n_hdlc;  in n_hdlc_tty_open()
252 	tty->receive_room = 65536;  in n_hdlc_tty_open()
255 	set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_open()
265  * n_hdlc_send_frames - send frames on pending send buffer list
269  * Send frames on pending send buffer list until the driver does not accept a
270  * frame (busy) this function is called after adding a frame to the send buffer
281 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
282 	if (n_hdlc->tbusy) {  in n_hdlc_send_frames()
283 		n_hdlc->woke_up = true;  in n_hdlc_send_frames()
284 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
287 	n_hdlc->tbusy = true;  in n_hdlc_send_frames()
288 	n_hdlc->woke_up = false;  in n_hdlc_send_frames()
289 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
291 	tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);  in n_hdlc_send_frames()
293 		pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count);  in n_hdlc_send_frames()
296 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
297 		actual = tty->ops->write(tty, tbuf->buf, tbuf->count);  in n_hdlc_send_frames()
300 		if (actual == -ERESTARTSYS) {  in n_hdlc_send_frames()
301 			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_send_frames()
304 		/* if transmit error, throw frame away by */  in n_hdlc_send_frames()
307 			actual = tbuf->count;  in n_hdlc_send_frames()
309 		if (actual == tbuf->count) {  in n_hdlc_send_frames()
310 			pr_debug("frame %p completed\n", tbuf);  in n_hdlc_send_frames()
312 			/* free current transmit buffer */  in n_hdlc_send_frames()
313 			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);  in n_hdlc_send_frames()
316 			wake_up_interruptible(&tty->write_wait);  in n_hdlc_send_frames()
318 			/* get next pending transmit buffer */  in n_hdlc_send_frames()
319 			tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);  in n_hdlc_send_frames()
321 			pr_debug("frame %p pending\n", tbuf);  in n_hdlc_send_frames()
324 			 * the buffer was not accepted by driver,  in n_hdlc_send_frames()
327 			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_send_frames()
333 		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
335 	/* Clear the re-entry flag */  in n_hdlc_send_frames()
336 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
337 	n_hdlc->tbusy = false;  in n_hdlc_send_frames()
338 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
340 	if (n_hdlc->woke_up)  in n_hdlc_send_frames()
345  * n_hdlc_tty_write_work - Asynchronous callback for transmit wakeup
353 	struct tty_struct *tty = n_hdlc->tty_for_write_work;  in n_hdlc_tty_write_work()
359  * n_hdlc_tty_wakeup - Callback for transmit wakeup
366 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_wakeup()
368 	schedule_work(&n_hdlc->write_work);  in n_hdlc_tty_wakeup()
372  * n_hdlc_tty_receive - Called by tty driver when receive data is available
379  * interpreted as one HDLC frame.
384 	register struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_receive()
390 	if (n_hdlc->magic != HDLC_MAGIC) {  in n_hdlc_tty_receive()
400 	/* get a free HDLC buffer */  in n_hdlc_tty_receive()
401 	buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);  in n_hdlc_tty_receive()
405 		 * buffer unless the maximum count has been reached  in n_hdlc_tty_receive()
407 		if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)  in n_hdlc_tty_receive()
417 	/* copy received data to HDLC buffer */  in n_hdlc_tty_receive()
418 	memcpy(buf->buf, data, count);  in n_hdlc_tty_receive()
419 	buf->count = count;  in n_hdlc_tty_receive()
421 	/* add HDLC buffer to list of received frames */  in n_hdlc_tty_receive()
422 	n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);  in n_hdlc_tty_receive()
425 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_receive()
426 	if (tty->fasync != NULL)  in n_hdlc_tty_receive()
427 		kill_fasync(&tty->fasync, SIGIO, POLL_IN);  in n_hdlc_tty_receive()
432  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
435  * @buf: pointer to returned data buffer
436  * @nr: size of returned data buffer
444 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_read()
454 	add_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
457 		if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {  in n_hdlc_tty_read()
458 			ret = -EIO;  in n_hdlc_tty_read()
466 		rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);  in n_hdlc_tty_read()
472 			ret = -EAGAIN;  in n_hdlc_tty_read()
479 			ret = -EINTR;  in n_hdlc_tty_read()
484 	remove_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
493 	if (offset >= rbuf->count)  in n_hdlc_tty_read()
497 	ret = -EOVERFLOW;  in n_hdlc_tty_read()
502 	ret = rbuf->count - offset;  in n_hdlc_tty_read()
505 	memcpy(kbuf, rbuf->buf+offset, ret);  in n_hdlc_tty_read()
509 	if (offset < rbuf->count)  in n_hdlc_tty_read()
515 	if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)  in n_hdlc_tty_read()
518 		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);  in n_hdlc_tty_read()
525  * n_hdlc_tty_write - write a single frame of data to device
528  * @data: pointer to transmit data (one frame)
529  * @count: size of transmit frame in bytes
536 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_write()
543 	if (n_hdlc->magic != HDLC_MAGIC)  in n_hdlc_tty_write()
544 		return -EIO;  in n_hdlc_tty_write()
546 	/* verify frame size */  in n_hdlc_tty_write()
553 	add_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
558 		tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);  in n_hdlc_tty_write()
563 			error = -EAGAIN;  in n_hdlc_tty_write()
569 			error = -EINTR;  in n_hdlc_tty_write()
575 	remove_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
578 		/* Retrieve the user's buffer */  in n_hdlc_tty_write()
579 		memcpy(tbuf->buf, data, count);  in n_hdlc_tty_write()
582 		tbuf->count = error = count;  in n_hdlc_tty_write()
583 		n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_tty_write()
592  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
603 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_ioctl()
612 	if (n_hdlc->magic != HDLC_MAGIC)  in n_hdlc_tty_ioctl()
613 		return -EBADF;  in n_hdlc_tty_ioctl()
618 		/* in next available frame (if any) */  in n_hdlc_tty_ioctl()
619 		spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
620 		buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,  in n_hdlc_tty_ioctl()
623 			count = buf->count;  in n_hdlc_tty_ioctl()
626 		spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
633 		/* add size of next output frame in queue */  in n_hdlc_tty_ioctl()
634 		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
635 		buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,  in n_hdlc_tty_ioctl()
638 			count += buf->count;  in n_hdlc_tty_ioctl()
639 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
660  * n_hdlc_tty_poll - TTY callback for poll system call
672 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_poll()
675 	if (n_hdlc->magic != HDLC_MAGIC)  in n_hdlc_tty_poll()
682 	poll_wait(filp, &tty->read_wait, wait);  in n_hdlc_tty_poll()
683 	poll_wait(filp, &tty->write_wait, wait);  in n_hdlc_tty_poll()
686 	if (!list_empty(&n_hdlc->rx_buf_list.list))  in n_hdlc_tty_poll()
688 	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))  in n_hdlc_tty_poll()
693 			!list_empty(&n_hdlc->tx_free_buf_list.list))  in n_hdlc_tty_poll()
708 			pr_debug("%s(), kmalloc() failed for %s buffer %u\n",  in n_hdlc_alloc_buf()
717  * n_hdlc_alloc - allocate an n_hdlc instance data structure
728 	spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);  in n_hdlc_alloc()
729 	spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);  in n_hdlc_alloc()
730 	spin_lock_init(&n_hdlc->rx_buf_list.spinlock);  in n_hdlc_alloc()
731 	spin_lock_init(&n_hdlc->tx_buf_list.spinlock);  in n_hdlc_alloc()
733 	INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);  in n_hdlc_alloc()
734 	INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);  in n_hdlc_alloc()
735 	INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);  in n_hdlc_alloc()
736 	INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);  in n_hdlc_alloc()
738 	n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");  in n_hdlc_alloc()
739 	n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");  in n_hdlc_alloc()
742 	n_hdlc->magic  = HDLC_MAGIC;  in n_hdlc_alloc()
749  * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
750  * @buf_list: pointer to the buffer list
751  * @buf: pointer to the buffer
758 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_return()
760 	list_add(&buf->list_item, &buf_list->list);  in n_hdlc_buf_return()
761 	buf_list->count++;  in n_hdlc_buf_return()
763 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_return()
767  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
768  * @buf_list: pointer to buffer list
769  * @buf: pointer to buffer
776 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_put()
778 	list_add_tail(&buf->list_item, &buf_list->list);  in n_hdlc_buf_put()
779 	buf_list->count++;  in n_hdlc_buf_put()
781 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_put()
785  * n_hdlc_buf_get - remove and return an HDLC buffer from list
786  * @buf_list: pointer to HDLC buffer list
788  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
790  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
797 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_get()
799 	buf = list_first_entry_or_null(&buf_list->list,  in n_hdlc_buf_get()
802 		list_del(&buf->list_item);  in n_hdlc_buf_get()
803 		buf_list->count--;  in n_hdlc_buf_get()
806 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_get()