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
146  * HDLC buffer list manipulation functions
158 /* max frame size for memory allocations */
163 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_rx_queue()
166 	while ((buf = n_hdlc_buf_get(&n_hdlc->rx_buf_list)))  in flush_rx_queue()
167 		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, buf);  in flush_rx_queue()
172 	struct n_hdlc *n_hdlc = tty->disc_data;  in flush_tx_queue()
175 	while ((buf = n_hdlc_buf_get(&n_hdlc->tx_buf_list)))  in flush_tx_queue()
176 		n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, buf);  in flush_tx_queue()
190  * n_hdlc_tty_close - line discipline close
198 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_close()
200 	if (n_hdlc->magic != HDLC_MAGIC) {  in n_hdlc_tty_close()
205 	clear_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_close()
207 	tty->disc_data = NULL;  in n_hdlc_tty_close()
210 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_close()
211 	wake_up_interruptible(&tty->write_wait);  in n_hdlc_tty_close()
213 	n_hdlc_free_buf_list(&n_hdlc->rx_free_buf_list);  in n_hdlc_tty_close()
214 	n_hdlc_free_buf_list(&n_hdlc->tx_free_buf_list);  in n_hdlc_tty_close()
215 	n_hdlc_free_buf_list(&n_hdlc->rx_buf_list);  in n_hdlc_tty_close()
216 	n_hdlc_free_buf_list(&n_hdlc->tx_buf_list);  in n_hdlc_tty_close()
221  * n_hdlc_tty_open - called when line discipline changed to n_hdlc
228 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_open()
230 	pr_debug("%s() called (device=%s)\n", __func__, tty->name);  in n_hdlc_tty_open()
235 		return -EEXIST;  in n_hdlc_tty_open()
241 		return -ENFILE;  in n_hdlc_tty_open()
244 	tty->disc_data = n_hdlc;  in n_hdlc_tty_open()
245 	tty->receive_room = 65536;  in n_hdlc_tty_open()
248 	set_bit(TTY_NO_WRITE_SPLIT, &tty->flags);  in n_hdlc_tty_open()
258  * n_hdlc_send_frames - send frames on pending send buffer list
262  * Send frames on pending send buffer list until the driver does not accept a
263  * frame (busy) this function is called after adding a frame to the send buffer
274 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
275 	if (n_hdlc->tbusy) {  in n_hdlc_send_frames()
276 		n_hdlc->woke_up = true;  in n_hdlc_send_frames()
277 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
280 	n_hdlc->tbusy = true;  in n_hdlc_send_frames()
281 	n_hdlc->woke_up = false;  in n_hdlc_send_frames()
282 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
284 	tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);  in n_hdlc_send_frames()
286 		pr_debug("sending frame %p, count=%d\n", tbuf, tbuf->count);  in n_hdlc_send_frames()
289 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
290 		actual = tty->ops->write(tty, tbuf->buf, tbuf->count);  in n_hdlc_send_frames()
293 		if (actual == -ERESTARTSYS) {  in n_hdlc_send_frames()
294 			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_send_frames()
297 		/* if transmit error, throw frame away by */  in n_hdlc_send_frames()
300 			actual = tbuf->count;  in n_hdlc_send_frames()
302 		if (actual == tbuf->count) {  in n_hdlc_send_frames()
303 			pr_debug("frame %p completed\n", tbuf);  in n_hdlc_send_frames()
305 			/* free current transmit buffer */  in n_hdlc_send_frames()
306 			n_hdlc_buf_put(&n_hdlc->tx_free_buf_list, tbuf);  in n_hdlc_send_frames()
309 			wake_up_interruptible(&tty->write_wait);  in n_hdlc_send_frames()
311 			/* get next pending transmit buffer */  in n_hdlc_send_frames()
312 			tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);  in n_hdlc_send_frames()
314 			pr_debug("frame %p pending\n", tbuf);  in n_hdlc_send_frames()
317 			 * the buffer was not accepted by driver,  in n_hdlc_send_frames()
320 			n_hdlc_buf_return(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_send_frames()
326 		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);  in n_hdlc_send_frames()
328 	/* Clear the re-entry flag */  in n_hdlc_send_frames()
329 	spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
330 	n_hdlc->tbusy = false;  in n_hdlc_send_frames()
331 	spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_send_frames()
333 	if (n_hdlc->woke_up)  in n_hdlc_send_frames()
338  * n_hdlc_tty_wakeup - Callback for transmit wakeup
345 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_wakeup()
351  * n_hdlc_tty_receive - Called by tty driver when receive data is available
358  * interpreted as one HDLC frame.
363 	register struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_receive()
369 	if (n_hdlc->magic != HDLC_MAGIC) {  in n_hdlc_tty_receive()
379 	/* get a free HDLC buffer */  in n_hdlc_tty_receive()
380 	buf = n_hdlc_buf_get(&n_hdlc->rx_free_buf_list);  in n_hdlc_tty_receive()
384 		 * buffer unless the maximum count has been reached  in n_hdlc_tty_receive()
386 		if (n_hdlc->rx_buf_list.count < MAX_RX_BUF_COUNT)  in n_hdlc_tty_receive()
396 	/* copy received data to HDLC buffer */  in n_hdlc_tty_receive()
397 	memcpy(buf->buf, data, count);  in n_hdlc_tty_receive()
398 	buf->count = count;  in n_hdlc_tty_receive()
400 	/* add HDLC buffer to list of received frames */  in n_hdlc_tty_receive()
401 	n_hdlc_buf_put(&n_hdlc->rx_buf_list, buf);  in n_hdlc_tty_receive()
404 	wake_up_interruptible(&tty->read_wait);  in n_hdlc_tty_receive()
405 	if (tty->fasync != NULL)  in n_hdlc_tty_receive()
406 		kill_fasync(&tty->fasync, SIGIO, POLL_IN);  in n_hdlc_tty_receive()
411  * n_hdlc_tty_read - Called to retrieve one frame of data (if available)
414  * @kbuf: pointer to returned data buffer
415  * @nr: size of returned data buffer
417  * @offset: offset into the data buffer
425 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_read()
435 	add_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
438 		if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {  in n_hdlc_tty_read()
439 			ret = -EIO;  in n_hdlc_tty_read()
447 		rbuf = n_hdlc_buf_get(&n_hdlc->rx_buf_list);  in n_hdlc_tty_read()
453 			ret = -EAGAIN;  in n_hdlc_tty_read()
460 			ret = -EINTR;  in n_hdlc_tty_read()
465 	remove_wait_queue(&tty->read_wait, &wait);  in n_hdlc_tty_read()
474 	if (offset >= rbuf->count)  in n_hdlc_tty_read()
478 	ret = -EOVERFLOW;  in n_hdlc_tty_read()
483 	ret = rbuf->count - offset;  in n_hdlc_tty_read()
486 	memcpy(kbuf, rbuf->buf+offset, ret);  in n_hdlc_tty_read()
490 	if (offset < rbuf->count)  in n_hdlc_tty_read()
496 	if (n_hdlc->rx_free_buf_list.count > DEFAULT_RX_BUF_COUNT)  in n_hdlc_tty_read()
499 		n_hdlc_buf_put(&n_hdlc->rx_free_buf_list, rbuf);  in n_hdlc_tty_read()
506  * n_hdlc_tty_write - write a single frame of data to device
509  * @data: pointer to transmit data (one frame)
510  * @count: size of transmit frame in bytes
517 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_write()
524 	if (n_hdlc->magic != HDLC_MAGIC)  in n_hdlc_tty_write()
525 		return -EIO;  in n_hdlc_tty_write()
527 	/* verify frame size */  in n_hdlc_tty_write()
534 	add_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
539 		tbuf = n_hdlc_buf_get(&n_hdlc->tx_free_buf_list);  in n_hdlc_tty_write()
544 			error = -EAGAIN;  in n_hdlc_tty_write()
550 			error = -EINTR;  in n_hdlc_tty_write()
556 	remove_wait_queue(&tty->write_wait, &wait);  in n_hdlc_tty_write()
559 		/* Retrieve the user's buffer */  in n_hdlc_tty_write()
560 		memcpy(tbuf->buf, data, count);  in n_hdlc_tty_write()
563 		tbuf->count = error = count;  in n_hdlc_tty_write()
564 		n_hdlc_buf_put(&n_hdlc->tx_buf_list, tbuf);  in n_hdlc_tty_write()
573  * n_hdlc_tty_ioctl - process IOCTL system call for the tty device.
584 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_ioctl()
593 	if (n_hdlc->magic != HDLC_MAGIC)  in n_hdlc_tty_ioctl()
594 		return -EBADF;  in n_hdlc_tty_ioctl()
599 		/* in next available frame (if any) */  in n_hdlc_tty_ioctl()
600 		spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
601 		buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,  in n_hdlc_tty_ioctl()
604 			count = buf->count;  in n_hdlc_tty_ioctl()
607 		spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
614 		/* add size of next output frame in queue */  in n_hdlc_tty_ioctl()
615 		spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
616 		buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,  in n_hdlc_tty_ioctl()
619 			count += buf->count;  in n_hdlc_tty_ioctl()
620 		spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);  in n_hdlc_tty_ioctl()
641  * n_hdlc_tty_poll - TTY callback for poll system call
653 	struct n_hdlc *n_hdlc = tty->disc_data;  in n_hdlc_tty_poll()
656 	if (n_hdlc->magic != HDLC_MAGIC)  in n_hdlc_tty_poll()
663 	poll_wait(filp, &tty->read_wait, wait);  in n_hdlc_tty_poll()
664 	poll_wait(filp, &tty->write_wait, wait);  in n_hdlc_tty_poll()
667 	if (!list_empty(&n_hdlc->rx_buf_list.list))  in n_hdlc_tty_poll()
669 	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))  in n_hdlc_tty_poll()
674 			!list_empty(&n_hdlc->tx_free_buf_list.list))  in n_hdlc_tty_poll()
689 			pr_debug("%s(), kmalloc() failed for %s buffer %u\n",  in n_hdlc_alloc_buf()
698  * n_hdlc_alloc - allocate an n_hdlc instance data structure
709 	spin_lock_init(&n_hdlc->rx_free_buf_list.spinlock);  in n_hdlc_alloc()
710 	spin_lock_init(&n_hdlc->tx_free_buf_list.spinlock);  in n_hdlc_alloc()
711 	spin_lock_init(&n_hdlc->rx_buf_list.spinlock);  in n_hdlc_alloc()
712 	spin_lock_init(&n_hdlc->tx_buf_list.spinlock);  in n_hdlc_alloc()
714 	INIT_LIST_HEAD(&n_hdlc->rx_free_buf_list.list);  in n_hdlc_alloc()
715 	INIT_LIST_HEAD(&n_hdlc->tx_free_buf_list.list);  in n_hdlc_alloc()
716 	INIT_LIST_HEAD(&n_hdlc->rx_buf_list.list);  in n_hdlc_alloc()
717 	INIT_LIST_HEAD(&n_hdlc->tx_buf_list.list);  in n_hdlc_alloc()
719 	n_hdlc_alloc_buf(&n_hdlc->rx_free_buf_list, DEFAULT_RX_BUF_COUNT, "rx");  in n_hdlc_alloc()
720 	n_hdlc_alloc_buf(&n_hdlc->tx_free_buf_list, DEFAULT_TX_BUF_COUNT, "tx");  in n_hdlc_alloc()
723 	n_hdlc->magic  = HDLC_MAGIC;  in n_hdlc_alloc()
730  * n_hdlc_buf_return - put the HDLC buffer after the head of the specified list
731  * @buf_list: pointer to the buffer list
732  * @buf: pointer to the buffer
739 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_return()
741 	list_add(&buf->list_item, &buf_list->list);  in n_hdlc_buf_return()
742 	buf_list->count++;  in n_hdlc_buf_return()
744 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_return()
748  * n_hdlc_buf_put - add specified HDLC buffer to tail of specified list
749  * @buf_list: pointer to buffer list
750  * @buf: pointer to buffer
757 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_put()
759 	list_add_tail(&buf->list_item, &buf_list->list);  in n_hdlc_buf_put()
760 	buf_list->count++;  in n_hdlc_buf_put()
762 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_put()
766  * n_hdlc_buf_get - remove and return an HDLC buffer from list
767  * @buf_list: pointer to HDLC buffer list
769  * Remove and return an HDLC buffer from the head of the specified HDLC buffer
771  * Returns a pointer to HDLC buffer if available, otherwise %NULL.
778 	spin_lock_irqsave(&buf_list->spinlock, flags);  in n_hdlc_buf_get()
780 	buf = list_first_entry_or_null(&buf_list->list,  in n_hdlc_buf_get()
783 		list_del(&buf->list_item);  in n_hdlc_buf_get()
784 		buf_list->count--;  in n_hdlc_buf_get()
787 	spin_unlock_irqrestore(&buf_list->spinlock, flags);  in n_hdlc_buf_get()