1 files changed, 330 insertions, 167 deletions

diff --git a/drivers/usb/host/xhci-dbgtty.c b/drivers/usb/host/xhci-dbgtty.c
index be726c791323..57cdda4e09c8 100644
--- a/drivers/usb/host/xhci-dbgtty.c
+++ b/drivers/usb/host/xhci-dbgtty.c
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
-/**
+/*
  * xhci-dbgtty.c - tty glue for xHCI debug capability
  *
  * Copyright (C) 2017 Intel Corporation
@@ -10,24 +10,44 @@
 #include <linux/slab.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
+#include <linux/idr.h>
 
 #include "xhci.h"
 #include "xhci-dbgcap.h"
 
+static struct tty_driver *dbc_tty_driver;
+static struct idr dbc_tty_minors;
+static DEFINE_MUTEX(dbc_tty_minors_lock);
+
+static inline struct dbc_port *dbc_to_port(struct xhci_dbc *dbc)
+{
+	return dbc->priv;
+}
+
 static unsigned int
-dbc_send_packet(struct dbc_port *port, char *packet, unsigned int size)
+dbc_kfifo_to_req(struct dbc_port *port, char *packet)
 {
-	unsigned int		len;
-
-	len = kfifo_len(&port->write_fifo);
-	if (len < size)
-		size = len;
-	if (size != 0)
-		size = kfifo_out(&port->write_fifo, packet, size);
-	return size;
+	unsigned int	len;
+
+	len = kfifo_len(&port->port.xmit_fifo);
+
+	if (len == 0)
+		return 0;
+
+	len = min(len, DBC_MAX_PACKET);
+
+	if (port->tx_boundary)
+		len = min(port->tx_boundary, len);
+
+	len = kfifo_out(&port->port.xmit_fifo, packet, len);
+
+	if (port->tx_boundary)
+		port->tx_boundary -= len;
+
+	return len;
 }
 
-static int dbc_start_tx(struct dbc_port *port)
+static int dbc_do_start_tx(struct dbc_port *port)
 	__releases(&port->port_lock)
 	__acquires(&port->port_lock)
 {
@@ -37,9 +57,11 @@ static int dbc_start_tx(struct dbc_port *port)
 	bool			do_tty_wake = false;
 	struct list_head	*pool = &port->write_pool;
 
+	port->tx_running = true;
+
 	while (!list_empty(pool)) {
 		req = list_entry(pool->next, struct dbc_request, list_pool);
-		len = dbc_send_packet(port, req->buf, DBC_MAX_PACKET);
+		len = dbc_kfifo_to_req(port, req->buf);
 		if (len == 0)
 			break;
 		do_tty_wake = true;
@@ -48,7 +70,7 @@ static int dbc_start_tx(struct dbc_port *port)
 		list_del(&req->list_pool);
 
 		spin_unlock(&port->port_lock);
-		status = dbc_ep_queue(port->out, req, GFP_ATOMIC);
+		status = dbc_ep_queue(req);
 		spin_lock(&port->port_lock);
 
 		if (status) {
@@ -57,12 +79,25 @@ static int dbc_start_tx(struct dbc_port *port)
 		}
 	}
 
+	port->tx_running = false;
+
 	if (do_tty_wake && port->port.tty)
 		tty_wakeup(port->port.tty);
 
 	return status;
 }
 
+/* must be called with port->port_lock held */
+static int dbc_start_tx(struct dbc_port *port)
+{
+	lockdep_assert_held(&port->port_lock);
+
+	if (port->tx_running)
+		return -EBUSY;
+
+	return dbc_do_start_tx(port);
+}
+
 static void dbc_start_rx(struct dbc_port *port)
 	__releases(&port->port_lock)
 	__acquires(&port->port_lock)
@@ -80,7 +115,7 @@ static void dbc_start_rx(struct dbc_port *port)
 		req->length = DBC_MAX_PACKET;
 
 		spin_unlock(&port->port_lock);
-		status = dbc_ep_queue(port->in, req, GFP_ATOMIC);
+		status = dbc_ep_queue(req);
 		spin_lock(&port->port_lock);
 
 		if (status) {
@@ -90,24 +125,81 @@ static void dbc_start_rx(struct dbc_port *port)
 	}
 }
 
+/*
+ * Queue received data to tty buffer and push it.
+ *
+ * Returns nr of remaining bytes that didn't fit tty buffer, i.e. 0 if all
+ * bytes sucessfullt moved. In case of error returns negative errno.
+ * Call with lock held
+ */
+static int dbc_rx_push_buffer(struct dbc_port *port, struct dbc_request *req)
+{
+	char		*packet = req->buf;
+	unsigned int	n, size = req->actual;
+	int		count;
+
+	if (!req->actual)
+		return 0;
+
+	/* if n_read is set then request was partially moved to tty buffer */
+	n = port->n_read;
+	if (n) {
+		packet += n;
+		size -= n;
+	}
+
+	count = tty_insert_flip_string(&port->port, packet, size);
+	if (count)
+		tty_flip_buffer_push(&port->port);
+	if (count != size) {
+		port->n_read += count;
+		return size - count;
+	}
+
+	port->n_read = 0;
+	return 0;
+}
+
 static void
-dbc_read_complete(struct xhci_hcd *xhci, struct dbc_request *req)
+dbc_read_complete(struct xhci_dbc *dbc, struct dbc_request *req)
 {
 	unsigned long		flags;
-	struct xhci_dbc		*dbc = xhci->dbc;
-	struct dbc_port		*port = &dbc->port;
+	struct dbc_port		*port = dbc_to_port(dbc);
+	struct tty_struct	*tty;
+	int			untransferred;
+
+	tty = port->port.tty;
 
 	spin_lock_irqsave(&port->port_lock, flags);
+
+	/*
+	 * Only defer copyig data to tty buffer in case:
+	 * - !list_empty(&port->read_queue), there are older pending data
+	 * - tty is throttled
+	 * - failed to copy all data to buffer, defer remaining part
+	 */
+
+	if (list_empty(&port->read_queue) && tty && !tty_throttled(tty)) {
+		untransferred = dbc_rx_push_buffer(port, req);
+		if (untransferred == 0) {
+			list_add_tail(&req->list_pool, &port->read_pool);
+			if (req->status != -ESHUTDOWN)
+				dbc_start_rx(port);
+			goto out;
+		}
+	}
+
+	/* defer moving data from req to tty buffer to a tasklet */
 	list_add_tail(&req->list_pool, &port->read_queue);
 	tasklet_schedule(&port->push);
+out:
 	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
-static void dbc_write_complete(struct xhci_hcd *xhci, struct dbc_request *req)
+static void dbc_write_complete(struct xhci_dbc *dbc, struct dbc_request *req)
 {
 	unsigned long		flags;
-	struct xhci_dbc		*dbc = xhci->dbc;
-	struct dbc_port		*port = &dbc->port;
+	struct dbc_port		*port = dbc_to_port(dbc);
 
 	spin_lock_irqsave(&port->port_lock, flags);
 	list_add(&req->list_pool, &port->write_pool);
@@ -118,35 +210,36 @@ static void dbc_write_complete(struct xhci_hcd *xhci, struct dbc_request *req)
 	case -ESHUTDOWN:
 		break;
 	default:
-		xhci_warn(xhci, "unexpected write complete status %d\n",
+		dev_warn(dbc->dev, "unexpected write complete status %d\n",
 			  req->status);
 		break;
 	}
 	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
-static void xhci_dbc_free_req(struct dbc_ep *dep, struct dbc_request *req)
+static void xhci_dbc_free_req(struct dbc_request *req)
 {
 	kfree(req->buf);
-	dbc_free_request(dep, req);
+	dbc_free_request(req);
 }
 
 static int
-xhci_dbc_alloc_requests(struct dbc_ep *dep, struct list_head *head,
-			void (*fn)(struct xhci_hcd *, struct dbc_request *))
+xhci_dbc_alloc_requests(struct xhci_dbc *dbc, unsigned int direction,
+			struct list_head *head,
+			void (*fn)(struct xhci_dbc *, struct dbc_request *))
 {
 	int			i;
 	struct dbc_request	*req;
 
 	for (i = 0; i < DBC_QUEUE_SIZE; i++) {
-		req = dbc_alloc_request(dep, GFP_KERNEL);
+		req = dbc_alloc_request(dbc, direction, GFP_KERNEL);
 		if (!req)
 			break;
 
 		req->length = DBC_MAX_PACKET;
 		req->buf = kmalloc(req->length, GFP_KERNEL);
 		if (!req->buf) {
-			dbc_free_request(dep, req);
+			dbc_free_request(req);
 			break;
 		}
 
@@ -158,20 +251,27 @@ xhci_dbc_alloc_requests(struct dbc_ep *dep, struct list_head *head,
 }
 
 static void
-xhci_dbc_free_requests(struct dbc_ep *dep, struct list_head *head)
+xhci_dbc_free_requests(struct list_head *head)
 {
 	struct dbc_request	*req;
 
 	while (!list_empty(head)) {
 		req = list_entry(head->next, struct dbc_request, list_pool);
 		list_del(&req->list_pool);
-		xhci_dbc_free_req(dep, req);
+		xhci_dbc_free_req(req);
 	}
 }
 
 static int dbc_tty_install(struct tty_driver *driver, struct tty_struct *tty)
 {
-	struct dbc_port		*port = driver->driver_state;
+	struct dbc_port		*port;
+
+	mutex_lock(&dbc_tty_minors_lock);
+	port = idr_find(&dbc_tty_minors, tty->index);
+	mutex_unlock(&dbc_tty_minors_lock);
+
+	if (!port)
+		return -ENXIO;
 
 	tty->driver_data = port;
 
@@ -192,30 +292,47 @@ static void dbc_tty_close(struct tty_struct *tty, struct file *file)
 	tty_port_close(&port->port, tty, file);
 }
 
-static int dbc_tty_write(struct tty_struct *tty,
-			 const unsigned char *buf,
-			 int count)
+static ssize_t dbc_tty_write(struct tty_struct *tty, const u8 *buf,
+			     size_t count)
 {
 	struct dbc_port		*port = tty->driver_data;
 	unsigned long		flags;
+	unsigned int		written = 0;
 
 	spin_lock_irqsave(&port->port_lock, flags);
-	if (count)
-		count = kfifo_in(&port->write_fifo, buf, count);
-	dbc_start_tx(port);
+
+	/*
+	 * Treat tty write as one usb transfer. Make sure the writes are turned
+	 * into TRB request having the same size boundaries as the tty writes.
+	 * Don't add data to kfifo before previous write is turned into TRBs
+	 */
+	if (port->tx_boundary) {
+		spin_unlock_irqrestore(&port->port_lock, flags);
+		return 0;
+	}
+
+	if (count) {
+		written = kfifo_in(&port->port.xmit_fifo, buf, count);
+
+		if (written == count)
+			port->tx_boundary = kfifo_len(&port->port.xmit_fifo);
+
+		dbc_start_tx(port);
+	}
+
 	spin_unlock_irqrestore(&port->port_lock, flags);
 
-	return count;
+	return written;
 }
 
-static int dbc_tty_put_char(struct tty_struct *tty, unsigned char ch)
+static int dbc_tty_put_char(struct tty_struct *tty, u8 ch)
 {
 	struct dbc_port		*port = tty->driver_data;
 	unsigned long		flags;
 	int			status;
 
 	spin_lock_irqsave(&port->port_lock, flags);
-	status = kfifo_put(&port->write_fifo, ch);
+	status = kfifo_put(&port->port.xmit_fifo, ch);
 	spin_unlock_irqrestore(&port->port_lock, flags);
 
 	return status;
@@ -231,27 +348,31 @@ static void dbc_tty_flush_chars(struct tty_struct *tty)
 	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
-static int dbc_tty_write_room(struct tty_struct *tty)
+static unsigned int dbc_tty_write_room(struct tty_struct *tty)
 {
 	struct dbc_port		*port = tty->driver_data;
 	unsigned long		flags;
-	int			room = 0;
+	unsigned int		room;
 
 	spin_lock_irqsave(&port->port_lock, flags);
-	room = kfifo_avail(&port->write_fifo);
+	room = kfifo_avail(&port->port.xmit_fifo);
+
+	if (port->tx_boundary)
+		room = 0;
+
 	spin_unlock_irqrestore(&port->port_lock, flags);
 
 	return room;
 }
 
-static int dbc_tty_chars_in_buffer(struct tty_struct *tty)
+static unsigned int dbc_tty_chars_in_buffer(struct tty_struct *tty)
 {
 	struct dbc_port		*port = tty->driver_data;
 	unsigned long		flags;
-	int			chars = 0;
+	unsigned int		chars;
 
 	spin_lock_irqsave(&port->port_lock, flags);
-	chars = kfifo_len(&port->write_fifo);
+	chars = kfifo_len(&port->port.xmit_fifo);
 	spin_unlock_irqrestore(&port->port_lock, flags);
 
 	return chars;
@@ -279,64 +400,15 @@ static const struct tty_operations dbc_tty_ops = {
 	.unthrottle		= dbc_tty_unthrottle,
 };
 
-static struct tty_driver *dbc_tty_driver;
-
-int xhci_dbc_tty_register_driver(struct xhci_hcd *xhci)
-{
-	int			status;
-	struct xhci_dbc		*dbc = xhci->dbc;
-
-	dbc_tty_driver = tty_alloc_driver(1, TTY_DRIVER_REAL_RAW |
-					  TTY_DRIVER_DYNAMIC_DEV);
-	if (IS_ERR(dbc_tty_driver)) {
-		status = PTR_ERR(dbc_tty_driver);
-		dbc_tty_driver = NULL;
-		return status;
-	}
-
-	dbc_tty_driver->driver_name = "dbc_serial";
-	dbc_tty_driver->name = "ttyDBC";
-
-	dbc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
-	dbc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
-	dbc_tty_driver->init_termios = tty_std_termios;
-	dbc_tty_driver->init_termios.c_cflag =
-			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
-	dbc_tty_driver->init_termios.c_ispeed = 9600;
-	dbc_tty_driver->init_termios.c_ospeed = 9600;
-	dbc_tty_driver->driver_state = &dbc->port;
-
-	tty_set_operations(dbc_tty_driver, &dbc_tty_ops);
-
-	status = tty_register_driver(dbc_tty_driver);
-	if (status) {
-		xhci_err(xhci,
-			 "can't register dbc tty driver, err %d\n", status);
-		put_tty_driver(dbc_tty_driver);
-		dbc_tty_driver = NULL;
-	}
-
-	return status;
-}
-
-void xhci_dbc_tty_unregister_driver(void)
-{
-	if (dbc_tty_driver) {
-		tty_unregister_driver(dbc_tty_driver);
-		put_tty_driver(dbc_tty_driver);
-		dbc_tty_driver = NULL;
-	}
-}
-
-static void dbc_rx_push(unsigned long _port)
+static void dbc_rx_push(struct tasklet_struct *t)
 {
 	struct dbc_request	*req;
 	struct tty_struct	*tty;
 	unsigned long		flags;
-	bool			do_push = false;
 	bool			disconnect = false;
-	struct dbc_port		*port = (void *)_port;
+	struct dbc_port		*port = from_tasklet(port, t, push);
 	struct list_head	*queue = &port->read_queue;
+	int			untransferred;
 
 	spin_lock_irqsave(&port->port_lock, flags);
 	tty = port->port.tty;
@@ -358,42 +430,15 @@ static void dbc_rx_push(unsigned long _port)
 			break;
 		}
 
-		if (req->actual) {
-			char		*packet = req->buf;
-			unsigned int	n, size = req->actual;
-			int		count;
-
-			n = port->n_read;
-			if (n) {
-				packet += n;
-				size -= n;
-			}
-
-			count = tty_insert_flip_string(&port->port, packet,
-						       size);
-			if (count)
-				do_push = true;
-			if (count != size) {
-				port->n_read += count;
-				break;
-			}
-			port->n_read = 0;
-		}
+		untransferred = dbc_rx_push_buffer(port, req);
+		if (untransferred > 0)
+			break;
 
-		list_move(&req->list_pool, &port->read_pool);
+		list_move_tail(&req->list_pool, &port->read_pool);
 	}
 
-	if (do_push)
-		tty_flip_buffer_push(&port->port);
-
-	if (!list_empty(queue) && tty) {
-		if (!tty_throttled(tty)) {
-			if (do_push)
-				tasklet_schedule(&port->push);
-			else
-				pr_warn("ttyDBC0: RX not scheduled?\n");
-		}
-	}
+	if (!list_empty(queue))
+		tasklet_schedule(&port->push);
 
 	if (!disconnect)
 		dbc_start_rx(port);
@@ -418,17 +463,15 @@ static const struct tty_port_operations dbc_port_ops = {
 };
 
 static void
-xhci_dbc_tty_init_port(struct xhci_hcd *xhci, struct dbc_port *port)
+xhci_dbc_tty_init_port(struct xhci_dbc *dbc, struct dbc_port *port)
 {
 	tty_port_init(&port->port);
 	spin_lock_init(&port->port_lock);
-	tasklet_init(&port->push, dbc_rx_push, (unsigned long)port);
+	tasklet_setup(&port->push, dbc_rx_push);
 	INIT_LIST_HEAD(&port->read_pool);
 	INIT_LIST_HEAD(&port->read_queue);
 	INIT_LIST_HEAD(&port->write_pool);
 
-	port->in =		get_in_ep(xhci);
-	port->out =		get_out_ep(xhci);
 	port->port.ops =	&dbc_port_ops;
 	port->n_read =		0;
 }
@@ -440,66 +483,186 @@ xhci_dbc_tty_exit_port(struct dbc_port *port)
 	tty_port_destroy(&port->port);
 }
 
-int xhci_dbc_tty_register_device(struct xhci_hcd *xhci)
+static int xhci_dbc_tty_register_device(struct xhci_dbc *dbc)
 {
 	int			ret;
 	struct device		*tty_dev;
-	struct xhci_dbc		*dbc = xhci->dbc;
-	struct dbc_port		*port = &dbc->port;
+	struct dbc_port		*port = dbc_to_port(dbc);
 
-	xhci_dbc_tty_init_port(xhci, port);
-	tty_dev = tty_port_register_device(&port->port,
-					   dbc_tty_driver, 0, NULL);
-	if (IS_ERR(tty_dev)) {
-		ret = PTR_ERR(tty_dev);
-		goto register_fail;
+	if (port->registered)
+		return -EBUSY;
+
+	xhci_dbc_tty_init_port(dbc, port);
+
+	mutex_lock(&dbc_tty_minors_lock);
+	port->minor = idr_alloc(&dbc_tty_minors, port, 0, 64, GFP_KERNEL);
+	mutex_unlock(&dbc_tty_minors_lock);
+
+	if (port->minor < 0) {
+		ret = port->minor;
+		goto err_idr;
 	}
 
-	ret = kfifo_alloc(&port->write_fifo, DBC_WRITE_BUF_SIZE, GFP_KERNEL);
+	ret = kfifo_alloc(&port->port.xmit_fifo, DBC_WRITE_BUF_SIZE,
+			  GFP_KERNEL);
 	if (ret)
-		goto buf_alloc_fail;
+		goto err_exit_port;
 
-	ret = xhci_dbc_alloc_requests(port->in, &port->read_pool,
+	ret = xhci_dbc_alloc_requests(dbc, BULK_IN, &port->read_pool,
 				      dbc_read_complete);
 	if (ret)
-		goto request_fail;
+		goto err_free_fifo;
 
-	ret = xhci_dbc_alloc_requests(port->out, &port->write_pool,
+	ret = xhci_dbc_alloc_requests(dbc, BULK_OUT, &port->write_pool,
 				      dbc_write_complete);
 	if (ret)
-		goto request_fail;
+		goto err_free_requests;
+
+	tty_dev = tty_port_register_device(&port->port,
+					   dbc_tty_driver, port->minor, NULL);
+	if (IS_ERR(tty_dev)) {
+		ret = PTR_ERR(tty_dev);
+		goto err_free_requests;
+	}
 
 	port->registered = true;
 
 	return 0;
 
-request_fail:
-	xhci_dbc_free_requests(port->in, &port->read_pool);
-	xhci_dbc_free_requests(port->out, &port->write_pool);
-	kfifo_free(&port->write_fifo);
-
-buf_alloc_fail:
-	tty_unregister_device(dbc_tty_driver, 0);
-
-register_fail:
+err_free_requests:
+	xhci_dbc_free_requests(&port->read_pool);
+	xhci_dbc_free_requests(&port->write_pool);
+err_free_fifo:
+	kfifo_free(&port->port.xmit_fifo);
+err_exit_port:
+	idr_remove(&dbc_tty_minors, port->minor);
+err_idr:
 	xhci_dbc_tty_exit_port(port);
 
-	xhci_err(xhci, "can't register tty port, err %d\n", ret);
+	dev_err(dbc->dev, "can't register tty port, err %d\n", ret);
 
 	return ret;
 }
 
-void xhci_dbc_tty_unregister_device(struct xhci_hcd *xhci)
+static void xhci_dbc_tty_unregister_device(struct xhci_dbc *dbc)
 {
-	struct xhci_dbc		*dbc = xhci->dbc;
-	struct dbc_port		*port = &dbc->port;
+	struct dbc_port		*port = dbc_to_port(dbc);
+
+	if (!port->registered)
+		return;
+	/*
+	 * Hang up the TTY. This wakes up any blocked
+	 * writers and causes subsequent writes to fail.
+	 */
+	tty_vhangup(port->port.tty);
 
-	tty_unregister_device(dbc_tty_driver, 0);
+	tty_unregister_device(dbc_tty_driver, port->minor);
 	xhci_dbc_tty_exit_port(port);
 	port->registered = false;
 
-	kfifo_free(&port->write_fifo);
-	xhci_dbc_free_requests(get_out_ep(xhci), &port->read_pool);
-	xhci_dbc_free_requests(get_out_ep(xhci), &port->read_queue);
-	xhci_dbc_free_requests(get_in_ep(xhci), &port->write_pool);
+	mutex_lock(&dbc_tty_minors_lock);
+	idr_remove(&dbc_tty_minors, port->minor);
+	mutex_unlock(&dbc_tty_minors_lock);
+
+	kfifo_free(&port->port.xmit_fifo);
+	xhci_dbc_free_requests(&port->read_pool);
+	xhci_dbc_free_requests(&port->read_queue);
+	xhci_dbc_free_requests(&port->write_pool);
+}
+
+static const struct dbc_driver dbc_driver = {
+	.configure		= xhci_dbc_tty_register_device,
+	.disconnect		= xhci_dbc_tty_unregister_device,
+};
+
+int xhci_dbc_tty_probe(struct device *dev, void __iomem *base, struct xhci_hcd *xhci)
+{
+	struct xhci_dbc		*dbc;
+	struct dbc_port		*port;
+	int			status;
+
+	if (!dbc_tty_driver)
+		return -ENODEV;
+
+	port = kzalloc(sizeof(*port), GFP_KERNEL);
+	if (!port)
+		return -ENOMEM;
+
+	dbc = xhci_alloc_dbc(dev, base, &dbc_driver);
+
+	if (!dbc) {
+		status = -ENOMEM;
+		goto out2;
+	}
+
+	dbc->priv = port;
+
+	/* get rid of xhci once this is a real driver binding to a device */
+	xhci->dbc = dbc;
+
+	return 0;
+out2:
+	kfree(port);
+
+	return status;
+}
+
+/*
+ * undo what probe did, assume dbc is stopped already.
+ * we also assume tty_unregister_device() is called before this
+ */
+void xhci_dbc_tty_remove(struct xhci_dbc *dbc)
+{
+	struct dbc_port         *port = dbc_to_port(dbc);
+
+	xhci_dbc_remove(dbc);
+	kfree(port);
+}
+
+int dbc_tty_init(void)
+{
+	int		ret;
+
+	idr_init(&dbc_tty_minors);
+
+	dbc_tty_driver = tty_alloc_driver(64, TTY_DRIVER_REAL_RAW |
+					  TTY_DRIVER_DYNAMIC_DEV);
+	if (IS_ERR(dbc_tty_driver)) {
+		idr_destroy(&dbc_tty_minors);
+		return PTR_ERR(dbc_tty_driver);
+	}
+
+	dbc_tty_driver->driver_name = "dbc_serial";
+	dbc_tty_driver->name = "ttyDBC";
+
+	dbc_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
+	dbc_tty_driver->subtype = SERIAL_TYPE_NORMAL;
+	dbc_tty_driver->init_termios = tty_std_termios;
+	dbc_tty_driver->init_termios.c_lflag &= ~ECHO;
+	dbc_tty_driver->init_termios.c_cflag =
+			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
+	dbc_tty_driver->init_termios.c_ispeed = 9600;
+	dbc_tty_driver->init_termios.c_ospeed = 9600;
+
+	tty_set_operations(dbc_tty_driver, &dbc_tty_ops);
+
+	ret = tty_register_driver(dbc_tty_driver);
+	if (ret) {
+		pr_err("Can't register dbc tty driver\n");
+		tty_driver_kref_put(dbc_tty_driver);
+		idr_destroy(&dbc_tty_minors);
+	}
+
+	return ret;
+}
+
+void dbc_tty_exit(void)
+{
+	if (dbc_tty_driver) {
+		tty_unregister_driver(dbc_tty_driver);
+		tty_driver_kref_put(dbc_tty_driver);
+		dbc_tty_driver = NULL;
+	}
+
+	idr_destroy(&dbc_tty_minors);
 }