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.
123  * struct n_hdlc - per device instance data structure
126  * @tx_buf_list: list of pending transmit frame buffers
127  * @rx_buf_list: list of received frame buffers
128  * @tx_free_buf_list: list unused transmit frame buffers
129  * @rx_free_buf_list: list unused received frame buffers
143  * HDLC buffer list manipulation functions
156 /* max frame size for memory allocations */
161 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_rx_queue()
164 	while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))  in flush_rx_queue()
165 		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);  in flush_rx_queue()
170 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_tx_queue()
173 	while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))  in flush_tx_queue()
174 		n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);  in flush_tx_queue()
188  * n_hdlc_tty_close - line discipline close
196 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_close()
199 	clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_close()
201 	tty->disc_data = NULL;  in n_hdlc_tty_close()
204 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_close()
205 	wake_up_interruptible(&tty->write_wait);  in n_hdlc_tty_close()
207 	cancel_work_sync(&n_hdlc->write_work);  in n_hdlc_tty_close()
209 	n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);  in n_hdlc_tty_close()
210 	n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);  in n_hdlc_tty_close()
211 	n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);  in n_hdlc_tty_close()
212 	n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);  in n_hdlc_tty_close()
217  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
224 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_open()
226 	pr_debug("%s() called (device=%s)\n", __func__, tty->name);  in n_hdlc_tty_open()
231 		return -EEXIST;  in n_hdlc_tty_open()
237 		return -ENFILE;  in n_hdlc_tty_open()
240 	INIT_WORK(&n_hdlc->write_work, n_hdlc_tty_write_work);  in n_hdlc_tty_open()
241 	n_hdlc->tty_for_write_work = tty;  in n_hdlc_tty_open()
242 	tty->disc_data = n_hdlc;  in n_hdlc_tty_open()
243 	tty->receive_room = 65536;  in n_hdlc_tty_open()
246 	set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_open()
256  * n_hdlc_send_frames - send frames on pending send buffer list
260  * Send frames on pending send buffer list until the driver does not accept a
261  * frame (busy) this function is called after adding a frame to the send buffer
272 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
273 	if (n_hdlc->tbusy) {  in n_hdlc_send_frames()
274 		n_hdlc->woke_up = true;  in n_hdlc_send_frames()
275 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
278 	n_hdlc->tbusy = true;  in n_hdlc_send_frames()
279 	n_hdlc->woke_up = false;  in n_hdlc_send_frames()
280 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
282 	tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);  in n_hdlc_send_frames()
284 		pr_debug("sending frame %p, count=%zu\n", tbuf, tbuf->count);  in n_hdlc_send_frames()
287 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
288 		actual = tty->ops->write(tty, tbuf->buf, tbuf->count);  in n_hdlc_send_frames()
291 		if (actual == -ERESTARTSYS) {  in n_hdlc_send_frames()
292 			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_send_frames()
295 		/* if transmit error, throw frame away by */  in n_hdlc_send_frames()
298 			actual = tbuf->count;  in n_hdlc_send_frames()
300 		if (actual == tbuf->count) {  in n_hdlc_send_frames()
301 			pr_debug("frame %p completed\n", tbuf);  in n_hdlc_send_frames()
303 			/* free current transmit buffer */  in n_hdlc_send_frames()
304 			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);  in n_hdlc_send_frames()
307 			wake_up_interruptible(&tty->write_wait);  in n_hdlc_send_frames()
309 			/* get next pending transmit buffer */  in n_hdlc_send_frames()
310 			tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);  in n_hdlc_send_frames()
312 			pr_debug("frame %p pending\n", tbuf);  in n_hdlc_send_frames()
315 			 * the buffer was not accepted by driver,  in n_hdlc_send_frames()
318 			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_send_frames()
324 		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
326 	/* Clear the re-entry flag */  in n_hdlc_send_frames()
327 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
328 	n_hdlc->tbusy = false;  in n_hdlc_send_frames()
329 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
331 	if (n_hdlc->woke_up)  in n_hdlc_send_frames()
336  * n_hdlc_tty_write_work - Asynchronous callback for transmit wakeup
344 	struct tty_struct *tty = n_hdlc->tty_for_write_work;  in n_hdlc_tty_write_work()
350  * n_hdlc_tty_wakeup - Callback for transmit wakeup
357 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_wakeup()
359 	schedule_work(&n_hdlc->write_work);  in n_hdlc_tty_wakeup()
363  * n_hdlc_tty_receive - Called by tty driver when receive data is available
370  * interpreted as one HDLC frame.
375 	register struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_receive()
385 	/* get a free HDLC buffer */  in n_hdlc_tty_receive()
386 	buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);  in n_hdlc_tty_receive()
390 		 * buffer unless the maximum count has been reached  in n_hdlc_tty_receive()
392 		if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)  in n_hdlc_tty_receive()
402 	/* copy received data to HDLC buffer */  in n_hdlc_tty_receive()
403 	memcpy(buf->buf, data, count);  in n_hdlc_tty_receive()
404 	buf->count = count;  in n_hdlc_tty_receive()
406 	/* add HDLC buffer to list of received frames */  in n_hdlc_tty_receive()
407 	n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);  in n_hdlc_tty_receive()
410 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_receive()
411 	if (tty->fasync != NULL)  in n_hdlc_tty_receive()
412 		kill_fasync(&tty->fasync, SIGIO, POLL_IN);  in n_hdlc_tty_receive()
417  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
420  * @kbuf: pointer to returned data buffer
421  * @nr: size of returned data buffer
423  * @offset: offset into the data buffer
431 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_read()
441 	add_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
444 		if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {  in n_hdlc_tty_read()
445 			ret = -EIO;  in n_hdlc_tty_read()
453 		rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);  in n_hdlc_tty_read()
459 			ret = -EAGAIN;  in n_hdlc_tty_read()
466 			ret = -EINTR;  in n_hdlc_tty_read()
471 	remove_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
480 	if (offset >= rbuf->count)  in n_hdlc_tty_read()
484 	ret = -EOVERFLOW;  in n_hdlc_tty_read()
489 	ret = rbuf->count - offset;  in n_hdlc_tty_read()
492 	memcpy(kbuf, rbuf->buf+offset, ret);  in n_hdlc_tty_read()
496 	if (offset < rbuf->count)  in n_hdlc_tty_read()
502 	if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)  in n_hdlc_tty_read()
505 		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);  in n_hdlc_tty_read()
512  * n_hdlc_tty_write - write a single frame of data to device
515  * @data: pointer to transmit data (one frame)
516  * @count: size of transmit frame in bytes
523 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_write()
530 	/* verify frame size */  in n_hdlc_tty_write()
537 	add_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
542 		tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);  in n_hdlc_tty_write()
547 			error = -EAGAIN;  in n_hdlc_tty_write()
553 			error = -EINTR;  in n_hdlc_tty_write()
559 	remove_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
562 		/* Retrieve the user's buffer */  in n_hdlc_tty_write()
563 		memcpy(tbuf->buf, data, count);  in n_hdlc_tty_write()
566 		tbuf->count = error = count;  in n_hdlc_tty_write()
567 		n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_tty_write()
576  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
586 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_ioctl()
597 		/* in next available frame (if any) */  in n_hdlc_tty_ioctl()
598 		spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
599 		buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,  in n_hdlc_tty_ioctl()
602 			count = buf->count;  in n_hdlc_tty_ioctl()
605 		spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
612 		/* add size of next output frame in queue */  in n_hdlc_tty_ioctl()
613 		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
614 		buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,  in n_hdlc_tty_ioctl()
617 			count += buf->count;  in n_hdlc_tty_ioctl()
618 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
639  * n_hdlc_tty_poll - TTY callback for poll system call
651 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_poll()
658 	poll_wait(filp, &tty->read_wait, wait);  in n_hdlc_tty_poll()
659 	poll_wait(filp, &tty->write_wait, wait);  in n_hdlc_tty_poll()
662 	if (!list_empty(&n_hdlc->rx_buf_list.list))  in n_hdlc_tty_poll()
664 	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))  in n_hdlc_tty_poll()
669 			!list_empty(&n_hdlc->tx_free_buf_list.list))  in n_hdlc_tty_poll()
684 			pr_debug("%s(), kmalloc() failed for %s buffer %u\n",  in n_hdlc_alloc_buf()
693  * n_hdlc_alloc - allocate an n_hdlc instance data structure
704 	spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);  in n_hdlc_alloc()
705 	spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);  in n_hdlc_alloc()
706 	spin_lock_init(&n_hdlc->rx_buf_list.spinlock);  in n_hdlc_alloc()
707 	spin_lock_init(&n_hdlc->tx_buf_list.spinlock);  in n_hdlc_alloc()
709 	INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);  in n_hdlc_alloc()
710 	INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);  in n_hdlc_alloc()
711 	INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);  in n_hdlc_alloc()
712 	INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);  in n_hdlc_alloc()
714 	n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");  in n_hdlc_alloc()
715 	n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");  in n_hdlc_alloc()
722  * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
723  * @buf_list: pointer to the buffer list
724  * @buf: pointer to the buffer
731 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_return()
733 	list_add(&buf->list_item, &buf_list->list);  in n_hdlc_buf_return()
734 	buf_list->count++;  in n_hdlc_buf_return()
736 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_return()
740  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
741  * @buf_list: pointer to buffer list
742  * @buf: pointer to buffer
749 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_put()
751 	list_add_tail(&buf->list_item, &buf_list->list);  in n_hdlc_buf_put()
752 	buf_list->count++;  in n_hdlc_buf_put()
754 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_put()
758  * n_hdlc_buf_get - remove and return an HDLC buffer from list
759  * @buf_list: pointer to HDLC buffer list
761  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
763  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
770 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_get()
772 	buf = list_first_entry_or_null(&buf_list->list,  in n_hdlc_buf_get()
775 		list_del(&buf->list_item);  in n_hdlc_buf_get()
776 		buf_list->count--;  in n_hdlc_buf_get()
779 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_get()