[PATCH v2 2/4] usb: common: Move u_serial from gadget/function to usb/common

[Lu Baolu]

The component u_serial provides a glue layer between TTY layer
and a USB gadget device needed to provide a basic serial port
functionality. Currently, u_serial sits under gadget/function
and depends on CONFIG_USB_GADGET to be compiled and used.

Most of the serial gadget devices are based on a UDC (USB device
controller) and implemented by making use of the Linux gadget
frameworks. But we are facing other implementions as well. One
example can be found with xHCI debug capability. The xHCI debug
capability implements a serial gadget with hardware and firmware,
and provides an interface similar with xHCI host for submitting
and reaping the transfer requests.

In order to make better use of u_serial when implementing xHCI
debug capability in xHCI driver, this patch moves u_serial.c
from gadget/function to usb/common, and moves u_serial.h from
gadget/function to include/linux/usb.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/usb/Kconfig                    |    3 +
 drivers/usb/Makefile                   |    3 +-
 drivers/usb/common/Makefile            |    1 +
 drivers/usb/common/u_serial.c          | 1604 +++++++++++++++++++++++++++++++
 drivers/usb/gadget/Kconfig             |    3 -
 drivers/usb/gadget/function/Makefile   |    1 -
 drivers/usb/gadget/function/f_acm.c    |    4 +-
 drivers/usb/gadget/function/f_obex.c   |    4 +-
 drivers/usb/gadget/function/f_serial.c |    3 +-
 drivers/usb/gadget/function/u_serial.c | 1606 --------------------------------
 drivers/usb/gadget/function/u_serial.h |   71 --
 drivers/usb/gadget/legacy/acm_ms.c     |    3 +-
 drivers/usb/gadget/legacy/cdc2.c       |    2 +-
 drivers/usb/gadget/legacy/dbgp.c       |    3 +-
 drivers/usb/gadget/legacy/multi.c      |    2 +-
 drivers/usb/gadget/legacy/nokia.c      |    2 +-
 drivers/usb/gadget/legacy/serial.c     |    3 +-
 include/linux/usb/u_serial.h           |   71 ++
 18 files changed, 1689 insertions(+), 1700 deletions(-)
 create mode 100644 drivers/usb/common/u_serial.c
 delete mode 100644 drivers/usb/gadget/function/u_serial.c
 delete mode 100644 drivers/usb/gadget/function/u_serial.h
 create mode 100644 include/linux/usb/u_serial.h

diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
index 939a63b..c39aceb 100644
--- a/drivers/usb/Kconfig
+++ b/drivers/usb/Kconfig
@@ -35,6 +35,9 @@ config USB_COMMON
 config USB_ARCH_HAS_HCD
 	def_bool y
 
+config USB_U_SERIAL
+	tristate
+
 config USB
 	tristate "Support for Host-side USB"
 	depends on USB_ARCH_HAS_HCD
diff --git a/drivers/usb/Makefile b/drivers/usb/Makefile
index 9650b35..a3274aa 100644
--- a/drivers/usb/Makefile
+++ b/drivers/usb/Makefile
@@ -5,6 +5,7 @@
 # Object files in subdirectories
 
 obj-$(CONFIG_USB)		+= core/
+obj-$(CONFIG_USB_COMMON)	+= common/
 obj-$(CONFIG_USB_SUPPORT)	+= phy/
 
 obj-$(CONFIG_USB_DWC3)		+= dwc3/
@@ -59,8 +60,6 @@ obj-$(CONFIG_USB_CHIPIDEA)	+= chipidea/
 obj-$(CONFIG_USB_RENESAS_USBHS)	+= renesas_usbhs/
 obj-$(CONFIG_USB_GADGET)	+= gadget/
 
-obj-$(CONFIG_USB_COMMON)	+= common/
-
 obj-$(CONFIG_USBIP_CORE)	+= usbip/
 
 obj-$(CONFIG_TYPEC)		+= typec/
diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
index 6bbb3ec..dff720b 100644
--- a/drivers/usb/common/Makefile
+++ b/drivers/usb/common/Makefile
@@ -8,3 +8,4 @@ usb-common-$(CONFIG_USB_LED_TRIG) += led.o
 
 obj-$(CONFIG_USB_OTG_FSM) += usb-otg-fsm.o
 obj-$(CONFIG_USB_ULPI_BUS)	+= ulpi.o
+obj-$(CONFIG_USB_U_SERIAL)	+= u_serial.o
diff --git a/drivers/usb/common/u_serial.c b/drivers/usb/common/u_serial.c
new file mode 100644
index 0000000..da09602
--- /dev/null
+++ b/drivers/usb/common/u_serial.c
@@ -0,0 +1,1604 @@
+/*
+ * u_serial.c - utilities for USB gadget "serial port"/TTY support
+ *
+ * Copyright (C) 2003 Al Borchers (alborchers@xxxxxxxxxxxxxxxx)
+ * Copyright (C) 2008 David Brownell
+ * Copyright (C) 2008 by Nokia Corporation
+ *
+ * This code also borrows from usbserial.c, which is
+ * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@xxxxxxxxx)
+ * Copyright (C) 2000 Peter Berger (pberger@xxxxxxxxxxx)
+ * Copyright (C) 2000 Al Borchers (alborchers@xxxxxxxxxxxxxxxx)
+ *
+ * This software is distributed under the terms of the GNU General
+ * Public License ("GPL") as published by the Free Software Foundation,
+ * either version 2 of that License or (at your option) any later version.
+ */
+
+/* #define VERBOSE_DEBUG */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/delay.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/slab.h>
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/console.h>
+#include <linux/kthread.h>
+#include <linux/usb/u_serial.h>
+
+/*
+ * This component encapsulates the TTY layer glue needed to provide basic
+ * "serial port" functionality through the USB gadget stack.  Each such
+ * port is exposed through a /dev/ttyGS* node.
+ *
+ * After this module has been loaded, the individual TTY port can be requested
+ * (gserial_alloc_line()) and it will stay available until they are removed
+ * (gserial_free_line()). Each one may be connected to a USB function
+ * (gserial_connect), or disconnected (with gserial_disconnect) when the USB
+ * host issues a config change event. Data can only flow when the port is
+ * connected to the host.
+ *
+ * A given TTY port can be made available in multiple configurations.
+ * For example, each one might expose a ttyGS0 node which provides a
+ * login application.  In one case that might use CDC ACM interface 0,
+ * while another configuration might use interface 3 for that.  The
+ * work to handle that (including descriptor management) is not part
+ * of this component.
+ *
+ * Configurations may expose more than one TTY port.  For example, if
+ * ttyGS0 provides login service, then ttyGS1 might provide dialer access
+ * for a telephone or fax link.  And ttyGS2 might be something that just
+ * needs a simple byte stream interface for some messaging protocol that
+ * is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
+ *
+ *
+ * gserial is the lifecycle interface, used by USB functions
+ * gs_port is the I/O nexus, used by the tty driver
+ * tty_struct links to the tty/filesystem framework
+ *
+ * gserial <---> gs_port ... links will be null when the USB link is
+ * inactive; managed by gserial_{connect,disconnect}().  each gserial
+ * instance can wrap its own USB control protocol.
+ *	gserial->ioport == usb_ep->driver_data ... gs_port
+ *	gs_port->port_usb ... gserial
+ *
+ * gs_port <---> tty_struct ... links will be null when the TTY file
+ * isn't opened; managed by gs_open()/gs_close()
+ *	gserial->port_tty ... tty_struct
+ *	tty_struct->driver_data ... gserial
+ */
+
+/* RX and TX queues can buffer QUEUE_SIZE packets before they hit the
+ * next layer of buffering.  For TX that's a circular buffer; for RX
+ * consider it a NOP.  A third layer is provided by the TTY code.
+ */
+#define QUEUE_SIZE		16
+#define WRITE_BUF_SIZE		8192		/* TX only */
+#define GS_CONSOLE_BUF_SIZE	8192
+
+/* circular buffer */
+struct gs_buf {
+	unsigned		buf_size;
+	char			*buf_buf;
+	char			*buf_get;
+	char			*buf_put;
+};
+
+/* console info */
+struct gscons_info {
+	struct gs_port		*port;
+	struct task_struct	*console_thread;
+	struct gs_buf		con_buf;
+	/* protect the buf and busy flag */
+	spinlock_t		con_lock;
+	int			req_busy;
+	struct usb_request	*console_req;
+};
+
+/*
+ * The port structure holds info for each port, one for each minor number
+ * (and thus for each /dev/ node).
+ */
+struct gs_port {
+	struct tty_port		port;
+	spinlock_t		port_lock;	/* guard port_* access */
+
+	struct gserial		*port_usb;
+
+	bool			openclose;	/* open/close in progress */
+	u8			port_num;
+
+	struct list_head	read_pool;
+	int read_started;
+	int read_allocated;
+	struct list_head	read_queue;
+	unsigned		n_read;
+	struct tasklet_struct	push;
+
+	struct list_head	write_pool;
+	int write_started;
+	int write_allocated;
+	struct gs_buf		port_write_buf;
+	wait_queue_head_t	drain_wait;	/* wait while writes drain */
+	bool                    write_busy;
+	wait_queue_head_t	close_wait;
+
+	/* REVISIT this state ... */
+	struct usb_cdc_line_coding port_line_coding;	/* 8-N-1 etc */
+};
+
+static struct portmaster {
+	struct mutex	lock;			/* protect open/close */
+	struct gs_port	*port;
+} ports[MAX_U_SERIAL_PORTS];
+
+#define GS_CLOSE_TIMEOUT		15		/* seconds */
+
+
+
+#ifdef VERBOSE_DEBUG
+#ifndef pr_vdebug
+#define pr_vdebug(fmt, arg...) \
+	pr_debug(fmt, ##arg)
+#endif /* pr_vdebug */
+#else
+#ifndef pr_vdebug
+#define pr_vdebug(fmt, arg...) \
+	({ if (0) pr_debug(fmt, ##arg); })
+#endif /* pr_vdebug */
+#endif
+
+/*-------------------------------------------------------------------------*/
+
+/* Circular Buffer */
+
+/*
+ * gs_buf_alloc
+ *
+ * Allocate a circular buffer and all associated memory.
+ */
+static int gs_buf_alloc(struct gs_buf *gb, unsigned size)
+{
+	gb->buf_buf = kmalloc(size, GFP_KERNEL);
+	if (gb->buf_buf == NULL)
+		return -ENOMEM;
+
+	gb->buf_size = size;
+	gb->buf_put = gb->buf_buf;
+	gb->buf_get = gb->buf_buf;
+
+	return 0;
+}
+
+/*
+ * gs_buf_free
+ *
+ * Free the buffer and all associated memory.
+ */
+static void gs_buf_free(struct gs_buf *gb)
+{
+	kfree(gb->buf_buf);
+	gb->buf_buf = NULL;
+}
+
+/*
+ * gs_buf_clear
+ *
+ * Clear out all data in the circular buffer.
+ */
+static void gs_buf_clear(struct gs_buf *gb)
+{
+	gb->buf_get = gb->buf_put;
+	/* equivalent to a get of all data available */
+}
+
+/*
+ * gs_buf_data_avail
+ *
+ * Return the number of bytes of data written into the circular
+ * buffer.
+ */
+static unsigned gs_buf_data_avail(struct gs_buf *gb)
+{
+	return (gb->buf_size + gb->buf_put - gb->buf_get) % gb->buf_size;
+}
+
+/*
+ * gs_buf_space_avail
+ *
+ * Return the number of bytes of space available in the circular
+ * buffer.
+ */
+static unsigned gs_buf_space_avail(struct gs_buf *gb)
+{
+	return (gb->buf_size + gb->buf_get - gb->buf_put - 1) % gb->buf_size;
+}
+
+/*
+ * gs_buf_put
+ *
+ * Copy data data from a user buffer and put it into the circular buffer.
+ * Restrict to the amount of space available.
+ *
+ * Return the number of bytes copied.
+ */
+static unsigned
+gs_buf_put(struct gs_buf *gb, const char *buf, unsigned count)
+{
+	unsigned len;
+
+	len  = gs_buf_space_avail(gb);
+	if (count > len)
+		count = len;
+
+	if (count == 0)
+		return 0;
+
+	len = gb->buf_buf + gb->buf_size - gb->buf_put;
+	if (count > len) {
+		memcpy(gb->buf_put, buf, len);
+		memcpy(gb->buf_buf, buf+len, count - len);
+		gb->buf_put = gb->buf_buf + count - len;
+	} else {
+		memcpy(gb->buf_put, buf, count);
+		if (count < len)
+			gb->buf_put += count;
+		else /* count == len */
+			gb->buf_put = gb->buf_buf;
+	}
+
+	return count;
+}
+
+/*
+ * gs_buf_get
+ *
+ * Get data from the circular buffer and copy to the given buffer.
+ * Restrict to the amount of data available.
+ *
+ * Return the number of bytes copied.
+ */
+static unsigned
+gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
+{
+	unsigned len;
+
+	len = gs_buf_data_avail(gb);
+	if (count > len)
+		count = len;
+
+	if (count == 0)
+		return 0;
+
+	len = gb->buf_buf + gb->buf_size - gb->buf_get;
+	if (count > len) {
+		memcpy(buf, gb->buf_get, len);
+		memcpy(buf+len, gb->buf_buf, count - len);
+		gb->buf_get = gb->buf_buf + count - len;
+	} else {
+		memcpy(buf, gb->buf_get, count);
+		if (count < len)
+			gb->buf_get += count;
+		else /* count == len */
+			gb->buf_get = gb->buf_buf;
+	}
+
+	return count;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* I/O glue between TTY (upper) and USB function (lower) driver layers */
+
+/*
+ * gs_alloc_req
+ *
+ * Allocate a usb_request and its buffer.  Returns a pointer to the
+ * usb_request or NULL if there is an error.
+ */
+struct usb_request *
+gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
+{
+	struct usb_request *req;
+
+	req = usb_ep_alloc_request(ep, kmalloc_flags);
+
+	if (req != NULL) {
+		req->length = len;
+		req->buf = kmalloc(len, kmalloc_flags);
+		if (req->buf == NULL) {
+			usb_ep_free_request(ep, req);
+			return NULL;
+		}
+	}
+
+	return req;
+}
+EXPORT_SYMBOL_GPL(gs_alloc_req);
+
+/*
+ * gs_free_req
+ *
+ * Free a usb_request and its buffer.
+ */
+void gs_free_req(struct usb_ep *ep, struct usb_request *req)
+{
+	kfree(req->buf);
+	usb_ep_free_request(ep, req);
+}
+EXPORT_SYMBOL_GPL(gs_free_req);
+
+/*
+ * gs_send_packet
+ *
+ * If there is data to send, a packet is built in the given
+ * buffer and the size is returned.  If there is no data to
+ * send, 0 is returned.
+ *
+ * Called with port_lock held.
+ */
+static unsigned
+gs_send_packet(struct gs_port *port, char *packet, unsigned size)
+{
+	unsigned len;
+
+	len = gs_buf_data_avail(&port->port_write_buf);
+	if (len < size)
+		size = len;
+	if (size != 0)
+		size = gs_buf_get(&port->port_write_buf, packet, size);
+	return size;
+}
+
+/*
+ * gs_start_tx
+ *
+ * This function finds available write requests, calls
+ * gs_send_packet to fill these packets with data, and
+ * continues until either there are no more write requests
+ * available or no more data to send.  This function is
+ * run whenever data arrives or write requests are available.
+ *
+ * Context: caller owns port_lock; port_usb is non-null.
+ */
+static int gs_start_tx(struct gs_port *port)
+/*
+__releases(&port->port_lock)
+__acquires(&port->port_lock)
+*/
+{
+	struct list_head	*pool = &port->write_pool;
+	struct usb_ep		*in;
+	int			status = 0;
+	bool			do_tty_wake = false;
+
+	if (!port->port_usb)
+		return status;
+
+	in = port->port_usb->in;
+
+	while (!port->write_busy && !list_empty(pool)) {
+		struct usb_request	*req;
+		int			len;
+
+		if (port->write_started >= QUEUE_SIZE)
+			break;
+
+		req = list_entry(pool->next, struct usb_request, list);
+		len = gs_send_packet(port, req->buf, in->maxpacket);
+		if (len == 0) {
+			wake_up_interruptible(&port->drain_wait);
+			break;
+		}
+		do_tty_wake = true;
+
+		req->length = len;
+		list_del(&req->list);
+		req->zero = (gs_buf_data_avail(&port->port_write_buf) == 0);
+
+		pr_vdebug("ttyGS%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
+			  port->port_num, len, *((u8 *)req->buf),
+			  *((u8 *)req->buf+1), *((u8 *)req->buf+2));
+
+		/* Drop lock while we call out of driver; completions
+		 * could be issued while we do so.  Disconnection may
+		 * happen too; maybe immediately before we queue this!
+		 *
+		 * NOTE that we may keep sending data for a while after
+		 * the TTY closed (dev->ioport->port_tty is NULL).
+		 */
+		port->write_busy = true;
+		spin_unlock(&port->port_lock);
+		status = usb_ep_queue(in, req, GFP_ATOMIC);
+		spin_lock(&port->port_lock);
+		port->write_busy = false;
+
+		if (status) {
+			pr_debug("%s: %s %s err %d\n",
+					__func__, "queue", in->name, status);
+			list_add(&req->list, pool);
+			break;
+		}
+
+		port->write_started++;
+
+		/* abort immediately after disconnect */
+		if (!port->port_usb)
+			break;
+	}
+
+	if (do_tty_wake && port->port.tty)
+		tty_wakeup(port->port.tty);
+	return status;
+}
+
+/*
+ * Context: caller owns port_lock, and port_usb is set
+ */
+static unsigned gs_start_rx(struct gs_port *port)
+/*
+__releases(&port->port_lock)
+__acquires(&port->port_lock)
+*/
+{
+	struct list_head	*pool = &port->read_pool;
+	struct usb_ep		*out = port->port_usb->out;
+
+	while (!list_empty(pool)) {
+		struct usb_request	*req;
+		int			status;
+		struct tty_struct	*tty;
+
+		/* no more rx if closed */
+		tty = port->port.tty;
+		if (!tty)
+			break;
+
+		if (port->read_started >= QUEUE_SIZE)
+			break;
+
+		req = list_entry(pool->next, struct usb_request, list);
+		list_del(&req->list);
+		req->length = out->maxpacket;
+
+		/* drop lock while we call out; the controller driver
+		 * may need to call us back (e.g. for disconnect)
+		 */
+		spin_unlock(&port->port_lock);
+		status = usb_ep_queue(out, req, GFP_ATOMIC);
+		spin_lock(&port->port_lock);
+
+		if (status) {
+			pr_debug("%s: %s %s err %d\n",
+					__func__, "queue", out->name, status);
+			list_add(&req->list, pool);
+			break;
+		}
+		port->read_started++;
+
+		/* abort immediately after disconnect */
+		if (!port->port_usb)
+			break;
+	}
+	return port->read_started;
+}
+
+/*
+ * RX tasklet takes data out of the RX queue and hands it up to the TTY
+ * layer until it refuses to take any more data (or is throttled back).
+ * Then it issues reads for any further data.
+ *
+ * If the RX queue becomes full enough that no usb_request is queued,
+ * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
+ * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
+ * can be buffered before the TTY layer's buffers (currently 64 KB).
+ */
+static void gs_rx_push(unsigned long _port)
+{
+	struct gs_port		*port = (void *)_port;
+	struct tty_struct	*tty;
+	struct list_head	*queue = &port->read_queue;
+	bool			disconnect = false;
+	bool			do_push = false;
+
+	/* hand any queued data to the tty */
+	spin_lock_irq(&port->port_lock);
+	tty = port->port.tty;
+	while (!list_empty(queue)) {
+		struct usb_request	*req;
+
+		req = list_first_entry(queue, struct usb_request, list);
+
+		/* leave data queued if tty was rx throttled */
+		if (tty && tty_throttled(tty))
+			break;
+
+		switch (req->status) {
+		case -ESHUTDOWN:
+			disconnect = true;
+			pr_vdebug("ttyGS%d: shutdown\n", port->port_num);
+			break;
+
+		default:
+			/* presumably a transient fault */
+			pr_warn("ttyGS%d: unexpected RX status %d\n",
+				port->port_num, req->status);
+			/* FALLTHROUGH */
+		case 0:
+			/* normal completion */
+			break;
+		}
+
+		/* push data to (open) tty */
+		if (req->actual) {
+			char		*packet = req->buf;
+			unsigned	size = req->actual;
+			unsigned	n;
+			int		count;
+
+			/* we may have pushed part of this packet already... */
+			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) {
+				/* stop pushing; TTY layer can't handle more */
+				port->n_read += count;
+				pr_vdebug("ttyGS%d: rx block %d/%d\n",
+					  port->port_num, count, req->actual);
+				break;
+			}
+			port->n_read = 0;
+		}
+
+		list_move(&req->list, &port->read_pool);
+		port->read_started--;
+	}
+
+	/* Push from tty to ldisc; this is handled by a workqueue,
+	 * so we won't get callbacks and can hold port_lock
+	 */
+	if (do_push)
+		tty_flip_buffer_push(&port->port);
+
+
+	/* We want our data queue to become empty ASAP, keeping data
+	 * in the tty and ldisc (not here).  If we couldn't push any
+	 * this time around, there may be trouble unless there's an
+	 * implicit tty_unthrottle() call on its way...
+	 *
+	 * REVISIT we should probably add a timer to keep the tasklet
+	 * from starving ... but it's not clear that case ever happens.
+	 */
+	if (!list_empty(queue) && tty) {
+		if (!tty_throttled(tty)) {
+			if (do_push)
+				tasklet_schedule(&port->push);
+			else
+				pr_warn("ttyGS%d: RX not scheduled?\n",
+					port->port_num);
+		}
+	}
+
+	/* If we're still connected, refill the USB RX queue. */
+	if (!disconnect && port->port_usb)
+		gs_start_rx(port);
+
+	spin_unlock_irq(&port->port_lock);
+}
+
+static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct gs_port	*port = ep->driver_data;
+
+	/* Queue all received data until the tty layer is ready for it. */
+	spin_lock(&port->port_lock);
+	list_add_tail(&req->list, &port->read_queue);
+	tasklet_schedule(&port->push);
+	spin_unlock(&port->port_lock);
+}
+
+static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct gs_port	*port = ep->driver_data;
+
+	spin_lock(&port->port_lock);
+	list_add(&req->list, &port->write_pool);
+	port->write_started--;
+
+	switch (req->status) {
+	default:
+		/* presumably a transient fault */
+		pr_warn("%s: unexpected %s status %d\n",
+			__func__, ep->name, req->status);
+		/* FALL THROUGH */
+	case 0:
+		/* normal completion */
+		gs_start_tx(port);
+		break;
+
+	case -ESHUTDOWN:
+		/* disconnect */
+		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
+		break;
+	}
+
+	spin_unlock(&port->port_lock);
+}
+
+static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
+							 int *allocated)
+{
+	struct usb_request	*req;
+
+	while (!list_empty(head)) {
+		req = list_entry(head->next, struct usb_request, list);
+		list_del(&req->list);
+		gs_free_req(ep, req);
+		if (allocated)
+			(*allocated)--;
+	}
+}
+
+static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
+		void (*fn)(struct usb_ep *, struct usb_request *),
+		int *allocated)
+{
+	int			i;
+	struct usb_request	*req;
+	int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
+
+	/* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
+	 * do quite that many this time, don't fail ... we just won't
+	 * be as speedy as we might otherwise be.
+	 */
+	for (i = 0; i < n; i++) {
+		req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
+		if (!req)
+			return list_empty(head) ? -ENOMEM : 0;
+		req->complete = fn;
+		list_add_tail(&req->list, head);
+		if (allocated)
+			(*allocated)++;
+	}
+	return 0;
+}
+
+/**
+ * gs_start_io - start USB I/O streams
+ * @dev: encapsulates endpoints to use
+ * Context: holding port_lock; port_tty and port_usb are non-null
+ *
+ * We only start I/O when something is connected to both sides of
+ * this port.  If nothing is listening on the host side, we may
+ * be pointlessly filling up our TX buffers and FIFO.
+ */
+static int gs_start_io(struct gs_port *port)
+{
+	struct list_head	*head = &port->read_pool;
+	struct usb_ep		*ep = port->port_usb->out;
+	int			status;
+	unsigned		started;
+
+	/* Allocate RX and TX I/O buffers.  We can't easily do this much
+	 * earlier (with GFP_KERNEL) because the requests are coupled to
+	 * endpoints, as are the packet sizes we'll be using.  Different
+	 * configurations may use different endpoints with a given port;
+	 * and high speed vs full speed changes packet sizes too.
+	 */
+	status = gs_alloc_requests(ep, head, gs_read_complete,
+		&port->read_allocated);
+	if (status)
+		return status;
+
+	status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
+			gs_write_complete, &port->write_allocated);
+	if (status) {
+		gs_free_requests(ep, head, &port->read_allocated);
+		return status;
+	}
+
+	/* queue read requests */
+	port->n_read = 0;
+	started = gs_start_rx(port);
+
+	/* unblock any pending writes into our circular buffer */
+	if (started) {
+		tty_wakeup(port->port.tty);
+	} else {
+		gs_free_requests(ep, head, &port->read_allocated);
+		gs_free_requests(port->port_usb->in, &port->write_pool,
+			&port->write_allocated);
+		status = -EIO;
+	}
+
+	return status;
+}
+
+/*-------------------------------------------------------------------------*/
+
+/* TTY Driver */
+
+/*
+ * gs_open sets up the link between a gs_port and its associated TTY.
+ * That link is broken *only* by TTY close(), and all driver methods
+ * know that.
+ */
+static int gs_open(struct tty_struct *tty, struct file *file)
+{
+	int		port_num = tty->index;
+	struct gs_port	*port;
+	int		status;
+
+	do {
+		mutex_lock(&ports[port_num].lock);
+		port = ports[port_num].port;
+		if (!port)
+			status = -ENODEV;
+		else {
+			spin_lock_irq(&port->port_lock);
+
+			/* already open?  Great. */
+			if (port->port.count) {
+				status = 0;
+				port->port.count++;
+
+			/* currently opening/closing? wait ... */
+			} else if (port->openclose) {
+				status = -EBUSY;
+
+			/* ... else we do the work */
+			} else {
+				status = -EAGAIN;
+				port->openclose = true;
+			}
+			spin_unlock_irq(&port->port_lock);
+		}
+		mutex_unlock(&ports[port_num].lock);
+
+		switch (status) {
+		default:
+			/* fully handled */
+			return status;
+		case -EAGAIN:
+			/* must do the work */
+			break;
+		case -EBUSY:
+			/* wait for EAGAIN task to finish */
+			msleep(1);
+			/* REVISIT could have a waitchannel here, if
+			 * concurrent open performance is important
+			 */
+			break;
+		}
+	} while (status != -EAGAIN);
+
+	/* Do the "real open" */
+	spin_lock_irq(&port->port_lock);
+
+	/* allocate circular buffer on first open */
+	if (port->port_write_buf.buf_buf == NULL) {
+
+		spin_unlock_irq(&port->port_lock);
+		status = gs_buf_alloc(&port->port_write_buf, WRITE_BUF_SIZE);
+		spin_lock_irq(&port->port_lock);
+
+		if (status) {
+			pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
+				port->port_num, tty, file);
+			port->openclose = false;
+			goto exit_unlock_port;
+		}
+	}
+
+	/* REVISIT if REMOVED (ports[].port NULL), abort the open
+	 * to let rmmod work faster (but this way isn't wrong).
+	 */
+
+	/* REVISIT maybe wait for "carrier detect" */
+
+	tty->driver_data = port;
+	port->port.tty = tty;
+
+	port->port.count = 1;
+	port->openclose = false;
+
+	/* if connected, start the I/O stream */
+	if (port->port_usb) {
+		struct gserial	*gser = port->port_usb;
+
+		pr_debug("gs_open: start ttyGS%d\n", port->port_num);
+		gs_start_io(port);
+
+		if (gser->connect)
+			gser->connect(gser);
+	}
+
+	pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
+
+	status = 0;
+
+exit_unlock_port:
+	spin_unlock_irq(&port->port_lock);
+	return status;
+}
+
+static int gs_writes_finished(struct gs_port *p)
+{
+	int cond;
+
+	/* return true on disconnect or empty buffer */
+	spin_lock_irq(&p->port_lock);
+	cond = (p->port_usb == NULL) || !gs_buf_data_avail(&p->port_write_buf);
+	spin_unlock_irq(&p->port_lock);
+
+	return cond;
+}
+
+static void gs_close(struct tty_struct *tty, struct file *file)
+{
+	struct gs_port *port = tty->driver_data;
+	struct gserial	*gser;
+
+	spin_lock_irq(&port->port_lock);
+
+	if (port->port.count != 1) {
+		if (port->port.count == 0)
+			WARN_ON(1);
+		else
+			--port->port.count;
+		goto exit;
+	}
+
+	pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
+
+	/* mark port as closing but in use; we can drop port lock
+	 * and sleep if necessary
+	 */
+	port->openclose = true;
+	port->port.count = 0;
+
+	gser = port->port_usb;
+	if (gser && gser->disconnect)
+		gser->disconnect(gser);
+
+	/* wait for circular write buffer to drain, disconnect, or at
+	 * most GS_CLOSE_TIMEOUT seconds; then discard the rest
+	 */
+	if (gs_buf_data_avail(&port->port_write_buf) > 0 && gser) {
+		spin_unlock_irq(&port->port_lock);
+		wait_event_interruptible_timeout(port->drain_wait,
+					gs_writes_finished(port),
+					GS_CLOSE_TIMEOUT * HZ);
+		spin_lock_irq(&port->port_lock);
+		gser = port->port_usb;
+	}
+
+	/* Iff we're disconnected, there can be no I/O in flight so it's
+	 * ok to free the circular buffer; else just scrub it.  And don't
+	 * let the push tasklet fire again until we're re-opened.
+	 */
+	if (gser == NULL)
+		gs_buf_free(&port->port_write_buf);
+	else
+		gs_buf_clear(&port->port_write_buf);
+
+	port->port.tty = NULL;
+
+	port->openclose = false;
+
+	pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
+			port->port_num, tty, file);
+
+	wake_up(&port->close_wait);
+exit:
+	spin_unlock_irq(&port->port_lock);
+}
+
+static int gs_write(struct tty_struct *tty, const unsigned char *buf, int count)
+{
+	struct gs_port	*port = tty->driver_data;
+	unsigned long	flags;
+
+	pr_vdebug("gs_write: ttyGS%d (%p) writing %d bytes\n",
+			port->port_num, tty, count);
+
+	spin_lock_irqsave(&port->port_lock, flags);
+	if (count)
+		count = gs_buf_put(&port->port_write_buf, buf, count);
+	/* treat count == 0 as flush_chars() */
+	if (port->port_usb)
+		gs_start_tx(port);
+	spin_unlock_irqrestore(&port->port_lock, flags);
+
+	return count;
+}
+
+static int gs_put_char(struct tty_struct *tty, unsigned char ch)
+{
+	struct gs_port	*port = tty->driver_data;
+	unsigned long	flags;
+	int		status;
+
+	pr_vdebug("gs_put_char: (%d,%p) char=0x%x, called from %ps\n",
+		port->port_num, tty, ch, __builtin_return_address(0));
+
+	spin_lock_irqsave(&port->port_lock, flags);
+	status = gs_buf_put(&port->port_write_buf, &ch, 1);
+	spin_unlock_irqrestore(&port->port_lock, flags);
+
+	return status;
+}
+
+static void gs_flush_chars(struct tty_struct *tty)
+{
+	struct gs_port	*port = tty->driver_data;
+	unsigned long	flags;
+
+	pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
+
+	spin_lock_irqsave(&port->port_lock, flags);
+	if (port->port_usb)
+		gs_start_tx(port);
+	spin_unlock_irqrestore(&port->port_lock, flags);
+}
+
+static int gs_write_room(struct tty_struct *tty)
+{
+	struct gs_port	*port = tty->driver_data;
+	unsigned long	flags;
+	int		room = 0;
+
+	spin_lock_irqsave(&port->port_lock, flags);
+	if (port->port_usb)
+		room = gs_buf_space_avail(&port->port_write_buf);
+	spin_unlock_irqrestore(&port->port_lock, flags);
+
+	pr_vdebug("gs_write_room: (%d,%p) room=%d\n",
+		port->port_num, tty, room);
+
+	return room;
+}
+
+static int gs_chars_in_buffer(struct tty_struct *tty)
+{
+	struct gs_port	*port = tty->driver_data;
+	unsigned long	flags;
+	int		chars = 0;
+
+	spin_lock_irqsave(&port->port_lock, flags);
+	chars = gs_buf_data_avail(&port->port_write_buf);
+	spin_unlock_irqrestore(&port->port_lock, flags);
+
+	pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%d\n",
+		port->port_num, tty, chars);
+
+	return chars;
+}
+
+/* undo side effects of setting TTY_THROTTLED */
+static void gs_unthrottle(struct tty_struct *tty)
+{
+	struct gs_port		*port = tty->driver_data;
+	unsigned long		flags;
+
+	spin_lock_irqsave(&port->port_lock, flags);
+	if (port->port_usb) {
+		/* Kickstart read queue processing.  We don't do xon/xoff,
+		 * rts/cts, or other handshaking with the host, but if the
+		 * read queue backs up enough we'll be NAKing OUT packets.
+		 */
+		tasklet_schedule(&port->push);
+		pr_vdebug("ttyGS%d: unthrottle\n", port->port_num);
+	}
+	spin_unlock_irqrestore(&port->port_lock, flags);
+}
+
+static int gs_break_ctl(struct tty_struct *tty, int duration)
+{
+	struct gs_port	*port = tty->driver_data;
+	int		status = 0;
+	struct gserial	*gser;
+
+	pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
+			port->port_num, duration);
+
+	spin_lock_irq(&port->port_lock);
+	gser = port->port_usb;
+	if (gser && gser->send_break)
+		status = gser->send_break(gser, duration);
+	spin_unlock_irq(&port->port_lock);
+
+	return status;
+}
+
+static const struct tty_operations gs_tty_ops = {
+	.open =			gs_open,
+	.close =		gs_close,
+	.write =		gs_write,
+	.put_char =		gs_put_char,
+	.flush_chars =		gs_flush_chars,
+	.write_room =		gs_write_room,
+	.chars_in_buffer =	gs_chars_in_buffer,
+	.unthrottle =		gs_unthrottle,
+	.break_ctl =		gs_break_ctl,
+};
+
+/*-------------------------------------------------------------------------*/
+
+static struct tty_driver *gs_tty_driver;
+
+#ifdef CONFIG_U_SERIAL_CONSOLE
+
+static struct gscons_info gscons_info;
+static struct console gserial_cons;
+
+static struct usb_request *gs_request_new(struct usb_ep *ep)
+{
+	struct usb_request *req = usb_ep_alloc_request(ep, GFP_ATOMIC);
+	if (!req)
+		return NULL;
+
+	req->buf = kmalloc(ep->maxpacket, GFP_ATOMIC);
+	if (!req->buf) {
+		usb_ep_free_request(ep, req);
+		return NULL;
+	}
+
+	return req;
+}
+
+static void gs_request_free(struct usb_request *req, struct usb_ep *ep)
+{
+	if (!req)
+		return;
+
+	kfree(req->buf);
+	usb_ep_free_request(ep, req);
+}
+
+static void gs_complete_out(struct usb_ep *ep, struct usb_request *req)
+{
+	struct gscons_info *info = &gscons_info;
+
+	switch (req->status) {
+	default:
+		pr_warn("%s: unexpected %s status %d\n",
+			__func__, ep->name, req->status);
+	case 0:
+		/* normal completion */
+		spin_lock(&info->con_lock);
+		info->req_busy = 0;
+		spin_unlock(&info->con_lock);
+
+		wake_up_process(info->console_thread);
+		break;
+	case -ESHUTDOWN:
+		/* disconnect */
+		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
+		break;
+	}
+}
+
+static int gs_console_connect(int port_num)
+{
+	struct gscons_info *info = &gscons_info;
+	struct gs_port *port;
+	struct usb_ep *ep;
+
+	if (port_num != gserial_cons.index) {
+		pr_err("%s: port num [%d] is not support console\n",
+		       __func__, port_num);
+		return -ENXIO;
+	}
+
+	port = ports[port_num].port;
+	ep = port->port_usb->in;
+	if (!info->console_req) {
+		info->console_req = gs_request_new(ep);
+		if (!info->console_req)
+			return -ENOMEM;
+		info->console_req->complete = gs_complete_out;
+	}
+
+	info->port = port;
+	spin_lock(&info->con_lock);
+	info->req_busy = 0;
+	spin_unlock(&info->con_lock);
+	pr_vdebug("port[%d] console connect!\n", port_num);
+	return 0;
+}
+
+static void gs_console_disconnect(struct usb_ep *ep)
+{
+	struct gscons_info *info = &gscons_info;
+	struct usb_request *req = info->console_req;
+
+	gs_request_free(req, ep);
+	info->console_req = NULL;
+}
+
+static int gs_console_thread(void *data)
+{
+	struct gscons_info *info = &gscons_info;
+	struct gs_port *port;
+	struct usb_request *req;
+	struct usb_ep *ep;
+	int xfer, ret, count, size;
+
+	do {
+		port = info->port;
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (!port || !port->port_usb
+		    || !port->port_usb->in || !info->console_req)
+			goto sched;
+
+		req = info->console_req;
+		ep = port->port_usb->in;
+
+		spin_lock_irq(&info->con_lock);
+		count = gs_buf_data_avail(&info->con_buf);
+		size = ep->maxpacket;
+
+		if (count > 0 && !info->req_busy) {
+			set_current_state(TASK_RUNNING);
+			if (count < size)
+				size = count;
+
+			xfer = gs_buf_get(&info->con_buf, req->buf, size);
+			req->length = xfer;
+
+			spin_unlock(&info->con_lock);
+			ret = usb_ep_queue(ep, req, GFP_ATOMIC);
+			spin_lock(&info->con_lock);
+			if (ret < 0)
+				info->req_busy = 0;
+			else
+				info->req_busy = 1;
+
+			spin_unlock_irq(&info->con_lock);
+		} else {
+			spin_unlock_irq(&info->con_lock);
+sched:
+			if (kthread_should_stop()) {
+				set_current_state(TASK_RUNNING);
+				break;
+			}
+			schedule();
+		}
+	} while (1);
+
+	return 0;
+}
+
+static int gs_console_setup(struct console *co, char *options)
+{
+	struct gscons_info *info = &gscons_info;
+	int status;
+
+	info->port = NULL;
+	info->console_req = NULL;
+	info->req_busy = 0;
+	spin_lock_init(&info->con_lock);
+
+	status = gs_buf_alloc(&info->con_buf, GS_CONSOLE_BUF_SIZE);
+	if (status) {
+		pr_err("%s: allocate console buffer failed\n", __func__);
+		return status;
+	}
+
+	info->console_thread = kthread_create(gs_console_thread,
+					      co, "gs_console");
+	if (IS_ERR(info->console_thread)) {
+		pr_err("%s: cannot create console thread\n", __func__);
+		gs_buf_free(&info->con_buf);
+		return PTR_ERR(info->console_thread);
+	}
+	wake_up_process(info->console_thread);
+
+	return 0;
+}
+
+static void gs_console_write(struct console *co,
+			     const char *buf, unsigned count)
+{
+	struct gscons_info *info = &gscons_info;
+	unsigned long flags;
+
+	spin_lock_irqsave(&info->con_lock, flags);
+	gs_buf_put(&info->con_buf, buf, count);
+	spin_unlock_irqrestore(&info->con_lock, flags);
+
+	wake_up_process(info->console_thread);
+}
+
+static struct tty_driver *gs_console_device(struct console *co, int *index)
+{
+	struct tty_driver **p = (struct tty_driver **)co->data;
+
+	if (!*p)
+		return NULL;
+
+	*index = co->index;
+	return *p;
+}
+
+static struct console gserial_cons = {
+	.name =		"ttyGS",
+	.write =	gs_console_write,
+	.device =	gs_console_device,
+	.setup =	gs_console_setup,
+	.flags =	CON_PRINTBUFFER,
+	.index =	-1,
+	.data =		&gs_tty_driver,
+};
+
+static void gserial_console_init(void)
+{
+	register_console(&gserial_cons);
+}
+
+static void gserial_console_exit(void)
+{
+	struct gscons_info *info = &gscons_info;
+
+	unregister_console(&gserial_cons);
+	if (!IS_ERR_OR_NULL(info->console_thread))
+		kthread_stop(info->console_thread);
+	gs_buf_free(&info->con_buf);
+}
+
+#else
+
+static int gs_console_connect(int port_num)
+{
+	return 0;
+}
+
+static void gs_console_disconnect(struct usb_ep *ep)
+{
+}
+
+static void gserial_console_init(void)
+{
+}
+
+static void gserial_console_exit(void)
+{
+}
+
+#endif
+
+static int
+gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
+{
+	struct gs_port	*port;
+	int		ret = 0;
+
+	mutex_lock(&ports[port_num].lock);
+	if (ports[port_num].port) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
+	if (port == NULL) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	tty_port_init(&port->port);
+	spin_lock_init(&port->port_lock);
+	init_waitqueue_head(&port->drain_wait);
+	init_waitqueue_head(&port->close_wait);
+
+	tasklet_init(&port->push, gs_rx_push, (unsigned long) port);
+
+	INIT_LIST_HEAD(&port->read_pool);
+	INIT_LIST_HEAD(&port->read_queue);
+	INIT_LIST_HEAD(&port->write_pool);
+
+	port->port_num = port_num;
+	port->port_line_coding = *coding;
+
+	ports[port_num].port = port;
+out:
+	mutex_unlock(&ports[port_num].lock);
+	return ret;
+}
+
+static int gs_closed(struct gs_port *port)
+{
+	int cond;
+
+	spin_lock_irq(&port->port_lock);
+	cond = (port->port.count == 0) && !port->openclose;
+	spin_unlock_irq(&port->port_lock);
+	return cond;
+}
+
+static void gserial_free_port(struct gs_port *port)
+{
+	tasklet_kill(&port->push);
+	/* wait for old opens to finish */
+	wait_event(port->close_wait, gs_closed(port));
+	WARN_ON(port->port_usb != NULL);
+	tty_port_destroy(&port->port);
+	kfree(port);
+}
+
+void gserial_free_line(unsigned char port_num)
+{
+	struct gs_port	*port;
+
+	mutex_lock(&ports[port_num].lock);
+	if (WARN_ON(!ports[port_num].port)) {
+		mutex_unlock(&ports[port_num].lock);
+		return;
+	}
+	port = ports[port_num].port;
+	ports[port_num].port = NULL;
+	mutex_unlock(&ports[port_num].lock);
+
+	gserial_free_port(port);
+	tty_unregister_device(gs_tty_driver, port_num);
+	gserial_console_exit();
+}
+EXPORT_SYMBOL_GPL(gserial_free_line);
+
+int gserial_alloc_line(unsigned char *line_num)
+{
+	struct usb_cdc_line_coding	coding;
+	struct device			*tty_dev;
+	int				ret;
+	int				port_num;
+
+	coding.dwDTERate = cpu_to_le32(9600);
+	coding.bCharFormat = 8;
+	coding.bParityType = USB_CDC_NO_PARITY;
+	coding.bDataBits = USB_CDC_1_STOP_BITS;
+
+	for (port_num = 0; port_num < MAX_U_SERIAL_PORTS; port_num++) {
+		ret = gs_port_alloc(port_num, &coding);
+		if (ret == -EBUSY)
+			continue;
+		if (ret)
+			return ret;
+		break;
+	}
+	if (ret)
+		return ret;
+
+	/* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
+
+	tty_dev = tty_port_register_device(&ports[port_num].port->port,
+			gs_tty_driver, port_num, NULL);
+	if (IS_ERR(tty_dev)) {
+		struct gs_port	*port;
+		pr_err("%s: failed to register tty for port %d, err %ld\n",
+				__func__, port_num, PTR_ERR(tty_dev));
+
+		ret = PTR_ERR(tty_dev);
+		port = ports[port_num].port;
+		ports[port_num].port = NULL;
+		gserial_free_port(port);
+		goto err;
+	}
+	*line_num = port_num;
+	gserial_console_init();
+err:
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gserial_alloc_line);
+
+/**
+ * gserial_connect - notify TTY I/O glue that USB link is active
+ * @gser: the function, set up with endpoints and descriptors
+ * @port_num: which port is active
+ * Context: any (usually from irq)
+ *
+ * This is called activate endpoints and let the TTY layer know that
+ * the connection is active ... not unlike "carrier detect".  It won't
+ * necessarily start I/O queues; unless the TTY is held open by any
+ * task, there would be no point.  However, the endpoints will be
+ * activated so the USB host can perform I/O, subject to basic USB
+ * hardware flow control.
+ *
+ * Caller needs to have set up the endpoints and USB function in @dev
+ * before calling this, as well as the appropriate (speed-specific)
+ * endpoint descriptors, and also have allocate @port_num by calling
+ * @gserial_alloc_line().
+ *
+ * Returns negative errno or zero.
+ * On success, ep->driver_data will be overwritten.
+ */
+int gserial_connect(struct gserial *gser, u8 port_num)
+{
+	struct gs_port	*port;
+	unsigned long	flags;
+	int		status;
+
+	if (port_num >= MAX_U_SERIAL_PORTS)
+		return -ENXIO;
+
+	port = ports[port_num].port;
+	if (!port) {
+		pr_err("serial line %d not allocated.\n", port_num);
+		return -EINVAL;
+	}
+	if (port->port_usb) {
+		pr_err("serial line %d is in use.\n", port_num);
+		return -EBUSY;
+	}
+
+	/* activate the endpoints */
+	status = usb_ep_enable(gser->in);
+	if (status < 0)
+		return status;
+	gser->in->driver_data = port;
+
+	status = usb_ep_enable(gser->out);
+	if (status < 0)
+		goto fail_out;
+	gser->out->driver_data = port;
+
+	/* then tell the tty glue that I/O can work */
+	spin_lock_irqsave(&port->port_lock, flags);
+	gser->ioport = port;
+	port->port_usb = gser;
+
+	/* REVISIT unclear how best to handle this state...
+	 * we don't really couple it with the Linux TTY.
+	 */
+	gser->port_line_coding = port->port_line_coding;
+
+	/* REVISIT if waiting on "carrier detect", signal. */
+
+	/* if it's already open, start I/O ... and notify the serial
+	 * protocol about open/close status (connect/disconnect).
+	 */
+	if (port->port.count) {
+		pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
+		gs_start_io(port);
+		if (gser->connect)
+			gser->connect(gser);
+	} else {
+		if (gser->disconnect)
+			gser->disconnect(gser);
+	}
+
+	status = gs_console_connect(port_num);
+	spin_unlock_irqrestore(&port->port_lock, flags);
+
+	return status;
+
+fail_out:
+	usb_ep_disable(gser->in);
+	return status;
+}
+EXPORT_SYMBOL_GPL(gserial_connect);
+/**
+ * gserial_disconnect - notify TTY I/O glue that USB link is inactive
+ * @gser: the function, on which gserial_connect() was called
+ * Context: any (usually from irq)
+ *
+ * This is called to deactivate endpoints and let the TTY layer know
+ * that the connection went inactive ... not unlike "hangup".
+ *
+ * On return, the state is as if gserial_connect() had never been called;
+ * there is no active USB I/O on these endpoints.
+ */
+void gserial_disconnect(struct gserial *gser)
+{
+	struct gs_port	*port = gser->ioport;
+	unsigned long	flags;
+
+	if (!port)
+		return;
+
+	/* tell the TTY glue not to do I/O here any more */
+	spin_lock_irqsave(&port->port_lock, flags);
+
+	/* REVISIT as above: how best to track this? */
+	port->port_line_coding = gser->port_line_coding;
+
+	port->port_usb = NULL;
+	gser->ioport = NULL;
+	if (port->port.count > 0 || port->openclose) {
+		wake_up_interruptible(&port->drain_wait);
+		if (port->port.tty)
+			tty_hangup(port->port.tty);
+	}
+	spin_unlock_irqrestore(&port->port_lock, flags);
+
+	/* disable endpoints, aborting down any active I/O */
+	usb_ep_disable(gser->out);
+	usb_ep_disable(gser->in);
+
+	/* finally, free any unused/unusable I/O buffers */
+	spin_lock_irqsave(&port->port_lock, flags);
+	if (port->port.count == 0 && !port->openclose)
+		gs_buf_free(&port->port_write_buf);
+	gs_free_requests(gser->out, &port->read_pool, NULL);
+	gs_free_requests(gser->out, &port->read_queue, NULL);
+	gs_free_requests(gser->in, &port->write_pool, NULL);
+
+	port->read_allocated = port->read_started =
+		port->write_allocated = port->write_started = 0;
+
+	gs_console_disconnect(gser->in);
+	spin_unlock_irqrestore(&port->port_lock, flags);
+}
+EXPORT_SYMBOL_GPL(gserial_disconnect);
+
+static int userial_init(void)
+{
+	unsigned			i;
+	int				status;
+
+	gs_tty_driver = alloc_tty_driver(MAX_U_SERIAL_PORTS);
+	if (!gs_tty_driver)
+		return -ENOMEM;
+
+	gs_tty_driver->driver_name = "g_serial";
+	gs_tty_driver->name = "ttyGS";
+	/* uses dynamically assigned dev_t values */
+
+	gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
+	gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
+	gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
+	gs_tty_driver->init_termios = tty_std_termios;
+
+	/* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
+	 * MS-Windows.  Otherwise, most of these flags shouldn't affect
+	 * anything unless we were to actually hook up to a serial line.
+	 */
+	gs_tty_driver->init_termios.c_cflag =
+			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
+	gs_tty_driver->init_termios.c_ispeed = 9600;
+	gs_tty_driver->init_termios.c_ospeed = 9600;
+
+	tty_set_operations(gs_tty_driver, &gs_tty_ops);
+	for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
+		mutex_init(&ports[i].lock);
+
+	/* export the driver ... */
+	status = tty_register_driver(gs_tty_driver);
+	if (status) {
+		pr_err("%s: cannot register, err %d\n",
+				__func__, status);
+		goto fail;
+	}
+
+	pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
+			MAX_U_SERIAL_PORTS,
+			(MAX_U_SERIAL_PORTS == 1) ? "" : "s");
+
+	return status;
+fail:
+	put_tty_driver(gs_tty_driver);
+	gs_tty_driver = NULL;
+	return status;
+}
+module_init(userial_init);
+
+static void userial_cleanup(void)
+{
+	tty_unregister_driver(gs_tty_driver);
+	put_tty_driver(gs_tty_driver);
+	gs_tty_driver = NULL;
+}
+module_exit(userial_cleanup);
+
+MODULE_LICENSE("GPL");
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 35cc641..304c9b4 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -152,9 +152,6 @@ config USB_F_ACM
 config USB_F_SS_LB
 	tristate
 
-config USB_U_SERIAL
-	tristate
-
 config USB_U_ETHER
 	tristate
 
diff --git a/drivers/usb/gadget/function/Makefile b/drivers/usb/gadget/function/Makefile
index 86e8252..57f5ed0 100644
--- a/drivers/usb/gadget/function/Makefile
+++ b/drivers/usb/gadget/function/Makefile
@@ -10,7 +10,6 @@ usb_f_acm-y			:= f_acm.o
 obj-$(CONFIG_USB_F_ACM)		+= usb_f_acm.o
 usb_f_ss_lb-y			:= f_loopback.o f_sourcesink.o
 obj-$(CONFIG_USB_F_SS_LB)	+= usb_f_ss_lb.o
-obj-$(CONFIG_USB_U_SERIAL)	+= u_serial.o
 usb_f_serial-y			:= f_serial.o
 obj-$(CONFIG_USB_F_SERIAL)	+= usb_f_serial.o
 usb_f_obex-y			:= f_obex.o
diff --git a/drivers/usb/gadget/function/f_acm.c b/drivers/usb/gadget/function/f_acm.c
index 5e3828d..5d00da1 100644
--- a/drivers/usb/gadget/function/f_acm.c
+++ b/drivers/usb/gadget/function/f_acm.c
@@ -19,9 +19,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/err.h>
-
-#include "u_serial.h"
-
+#include <linux/usb/u_serial.h>
 
 /*
  * This CDC ACM function support just wraps control functions and
diff --git a/drivers/usb/gadget/function/f_obex.c b/drivers/usb/gadget/function/f_obex.c
index d43e86c..6e7acd4 100644
--- a/drivers/usb/gadget/function/f_obex.c
+++ b/drivers/usb/gadget/function/f_obex.c
@@ -18,9 +18,7 @@
 #include <linux/kernel.h>
 #include <linux/device.h>
 #include <linux/module.h>
-
-#include "u_serial.h"
-
+#include <linux/usb/u_serial.h>
 
 /*
  * This CDC OBEX function support just packages a TTY-ish byte stream.
diff --git a/drivers/usb/gadget/function/f_serial.c b/drivers/usb/gadget/function/f_serial.c
index cb00ada..c589982 100644
--- a/drivers/usb/gadget/function/f_serial.c
+++ b/drivers/usb/gadget/function/f_serial.c
@@ -14,8 +14,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/device.h>
-
-#include "u_serial.h"
+#include <linux/usb/u_serial.h>
 
 
 /*
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
deleted file mode 100644
index 9b0805f..0000000
--- a/drivers/usb/gadget/function/u_serial.c
+++ /dev/null
@@ -1,1606 +0,0 @@
-/*
- * u_serial.c - utilities for USB gadget "serial port"/TTY support
- *
- * Copyright (C) 2003 Al Borchers (alborchers@xxxxxxxxxxxxxxxx)
- * Copyright (C) 2008 David Brownell
- * Copyright (C) 2008 by Nokia Corporation
- *
- * This code also borrows from usbserial.c, which is
- * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@xxxxxxxxx)
- * Copyright (C) 2000 Peter Berger (pberger@xxxxxxxxxxx)
- * Copyright (C) 2000 Al Borchers (alborchers@xxxxxxxxxxxxxxxx)
- *
- * This software is distributed under the terms of the GNU General
- * Public License ("GPL") as published by the Free Software Foundation,
- * either version 2 of that License or (at your option) any later version.
- */
-
-/* #define VERBOSE_DEBUG */
-
-#include <linux/kernel.h>
-#include <linux/sched.h>
-#include <linux/interrupt.h>
-#include <linux/device.h>
-#include <linux/delay.h>
-#include <linux/tty.h>
-#include <linux/tty_flip.h>
-#include <linux/slab.h>
-#include <linux/export.h>
-#include <linux/module.h>
-#include <linux/console.h>
-#include <linux/kthread.h>
-
-#include "u_serial.h"
-
-
-/*
- * This component encapsulates the TTY layer glue needed to provide basic
- * "serial port" functionality through the USB gadget stack.  Each such
- * port is exposed through a /dev/ttyGS* node.
- *
- * After this module has been loaded, the individual TTY port can be requested
- * (gserial_alloc_line()) and it will stay available until they are removed
- * (gserial_free_line()). Each one may be connected to a USB function
- * (gserial_connect), or disconnected (with gserial_disconnect) when the USB
- * host issues a config change event. Data can only flow when the port is
- * connected to the host.
- *
- * A given TTY port can be made available in multiple configurations.
- * For example, each one might expose a ttyGS0 node which provides a
- * login application.  In one case that might use CDC ACM interface 0,
- * while another configuration might use interface 3 for that.  The
- * work to handle that (including descriptor management) is not part
- * of this component.
- *
- * Configurations may expose more than one TTY port.  For example, if
- * ttyGS0 provides login service, then ttyGS1 might provide dialer access
- * for a telephone or fax link.  And ttyGS2 might be something that just
- * needs a simple byte stream interface for some messaging protocol that
- * is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
- *
- *
- * gserial is the lifecycle interface, used by USB functions
- * gs_port is the I/O nexus, used by the tty driver
- * tty_struct links to the tty/filesystem framework
- *
- * gserial <---> gs_port ... links will be null when the USB link is
- * inactive; managed by gserial_{connect,disconnect}().  each gserial
- * instance can wrap its own USB control protocol.
- *	gserial->ioport == usb_ep->driver_data ... gs_port
- *	gs_port->port_usb ... gserial
- *
- * gs_port <---> tty_struct ... links will be null when the TTY file
- * isn't opened; managed by gs_open()/gs_close()
- *	gserial->port_tty ... tty_struct
- *	tty_struct->driver_data ... gserial
- */
-
-/* RX and TX queues can buffer QUEUE_SIZE packets before they hit the
- * next layer of buffering.  For TX that's a circular buffer; for RX
- * consider it a NOP.  A third layer is provided by the TTY code.
- */
-#define QUEUE_SIZE		16
-#define WRITE_BUF_SIZE		8192		/* TX only */
-#define GS_CONSOLE_BUF_SIZE	8192
-
-/* circular buffer */
-struct gs_buf {
-	unsigned		buf_size;
-	char			*buf_buf;
-	char			*buf_get;
-	char			*buf_put;
-};
-
-/* console info */
-struct gscons_info {
-	struct gs_port		*port;
-	struct task_struct	*console_thread;
-	struct gs_buf		con_buf;
-	/* protect the buf and busy flag */
-	spinlock_t		con_lock;
-	int			req_busy;
-	struct usb_request	*console_req;
-};
-
-/*
- * The port structure holds info for each port, one for each minor number
- * (and thus for each /dev/ node).
- */
-struct gs_port {
-	struct tty_port		port;
-	spinlock_t		port_lock;	/* guard port_* access */
-
-	struct gserial		*port_usb;
-
-	bool			openclose;	/* open/close in progress */
-	u8			port_num;
-
-	struct list_head	read_pool;
-	int read_started;
-	int read_allocated;
-	struct list_head	read_queue;
-	unsigned		n_read;
-	struct tasklet_struct	push;
-
-	struct list_head	write_pool;
-	int write_started;
-	int write_allocated;
-	struct gs_buf		port_write_buf;
-	wait_queue_head_t	drain_wait;	/* wait while writes drain */
-	bool                    write_busy;
-	wait_queue_head_t	close_wait;
-
-	/* REVISIT this state ... */
-	struct usb_cdc_line_coding port_line_coding;	/* 8-N-1 etc */
-};
-
-static struct portmaster {
-	struct mutex	lock;			/* protect open/close */
-	struct gs_port	*port;
-} ports[MAX_U_SERIAL_PORTS];
-
-#define GS_CLOSE_TIMEOUT		15		/* seconds */
-
-
-
-#ifdef VERBOSE_DEBUG
-#ifndef pr_vdebug
-#define pr_vdebug(fmt, arg...) \
-	pr_debug(fmt, ##arg)
-#endif /* pr_vdebug */
-#else
-#ifndef pr_vdebug
-#define pr_vdebug(fmt, arg...) \
-	({ if (0) pr_debug(fmt, ##arg); })
-#endif /* pr_vdebug */
-#endif
-
-/*-------------------------------------------------------------------------*/
-
-/* Circular Buffer */
-
-/*
- * gs_buf_alloc
- *
- * Allocate a circular buffer and all associated memory.
- */
-static int gs_buf_alloc(struct gs_buf *gb, unsigned size)
-{
-	gb->buf_buf = kmalloc(size, GFP_KERNEL);
-	if (gb->buf_buf == NULL)
-		return -ENOMEM;
-
-	gb->buf_size = size;
-	gb->buf_put = gb->buf_buf;
-	gb->buf_get = gb->buf_buf;
-
-	return 0;
-}
-
-/*
- * gs_buf_free
- *
- * Free the buffer and all associated memory.
- */
-static void gs_buf_free(struct gs_buf *gb)
-{
-	kfree(gb->buf_buf);
-	gb->buf_buf = NULL;
-}
-
-/*
- * gs_buf_clear
- *
- * Clear out all data in the circular buffer.
- */
-static void gs_buf_clear(struct gs_buf *gb)
-{
-	gb->buf_get = gb->buf_put;
-	/* equivalent to a get of all data available */
-}
-
-/*
- * gs_buf_data_avail
- *
- * Return the number of bytes of data written into the circular
- * buffer.
- */
-static unsigned gs_buf_data_avail(struct gs_buf *gb)
-{
-	return (gb->buf_size + gb->buf_put - gb->buf_get) % gb->buf_size;
-}
-
-/*
- * gs_buf_space_avail
- *
- * Return the number of bytes of space available in the circular
- * buffer.
- */
-static unsigned gs_buf_space_avail(struct gs_buf *gb)
-{
-	return (gb->buf_size + gb->buf_get - gb->buf_put - 1) % gb->buf_size;
-}
-
-/*
- * gs_buf_put
- *
- * Copy data data from a user buffer and put it into the circular buffer.
- * Restrict to the amount of space available.
- *
- * Return the number of bytes copied.
- */
-static unsigned
-gs_buf_put(struct gs_buf *gb, const char *buf, unsigned count)
-{
-	unsigned len;
-
-	len  = gs_buf_space_avail(gb);
-	if (count > len)
-		count = len;
-
-	if (count == 0)
-		return 0;
-
-	len = gb->buf_buf + gb->buf_size - gb->buf_put;
-	if (count > len) {
-		memcpy(gb->buf_put, buf, len);
-		memcpy(gb->buf_buf, buf+len, count - len);
-		gb->buf_put = gb->buf_buf + count - len;
-	} else {
-		memcpy(gb->buf_put, buf, count);
-		if (count < len)
-			gb->buf_put += count;
-		else /* count == len */
-			gb->buf_put = gb->buf_buf;
-	}
-
-	return count;
-}
-
-/*
- * gs_buf_get
- *
- * Get data from the circular buffer and copy to the given buffer.
- * Restrict to the amount of data available.
- *
- * Return the number of bytes copied.
- */
-static unsigned
-gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
-{
-	unsigned len;
-
-	len = gs_buf_data_avail(gb);
-	if (count > len)
-		count = len;
-
-	if (count == 0)
-		return 0;
-
-	len = gb->buf_buf + gb->buf_size - gb->buf_get;
-	if (count > len) {
-		memcpy(buf, gb->buf_get, len);
-		memcpy(buf+len, gb->buf_buf, count - len);
-		gb->buf_get = gb->buf_buf + count - len;
-	} else {
-		memcpy(buf, gb->buf_get, count);
-		if (count < len)
-			gb->buf_get += count;
-		else /* count == len */
-			gb->buf_get = gb->buf_buf;
-	}
-
-	return count;
-}
-
-/*-------------------------------------------------------------------------*/
-
-/* I/O glue between TTY (upper) and USB function (lower) driver layers */
-
-/*
- * gs_alloc_req
- *
- * Allocate a usb_request and its buffer.  Returns a pointer to the
- * usb_request or NULL if there is an error.
- */
-struct usb_request *
-gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
-{
-	struct usb_request *req;
-
-	req = usb_ep_alloc_request(ep, kmalloc_flags);
-
-	if (req != NULL) {
-		req->length = len;
-		req->buf = kmalloc(len, kmalloc_flags);
-		if (req->buf == NULL) {
-			usb_ep_free_request(ep, req);
-			return NULL;
-		}
-	}
-
-	return req;
-}
-EXPORT_SYMBOL_GPL(gs_alloc_req);
-
-/*
- * gs_free_req
- *
- * Free a usb_request and its buffer.
- */
-void gs_free_req(struct usb_ep *ep, struct usb_request *req)
-{
-	kfree(req->buf);
-	usb_ep_free_request(ep, req);
-}
-EXPORT_SYMBOL_GPL(gs_free_req);
-
-/*
- * gs_send_packet
- *
- * If there is data to send, a packet is built in the given
- * buffer and the size is returned.  If there is no data to
- * send, 0 is returned.
- *
- * Called with port_lock held.
- */
-static unsigned
-gs_send_packet(struct gs_port *port, char *packet, unsigned size)
-{
-	unsigned len;
-
-	len = gs_buf_data_avail(&port->port_write_buf);
-	if (len < size)
-		size = len;
-	if (size != 0)
-		size = gs_buf_get(&port->port_write_buf, packet, size);
-	return size;
-}
-
-/*
- * gs_start_tx
- *
- * This function finds available write requests, calls
- * gs_send_packet to fill these packets with data, and
- * continues until either there are no more write requests
- * available or no more data to send.  This function is
- * run whenever data arrives or write requests are available.
- *
- * Context: caller owns port_lock; port_usb is non-null.
- */
-static int gs_start_tx(struct gs_port *port)
-/*
-__releases(&port->port_lock)
-__acquires(&port->port_lock)
-*/
-{
-	struct list_head	*pool = &port->write_pool;
-	struct usb_ep		*in;
-	int			status = 0;
-	bool			do_tty_wake = false;
-
-	if (!port->port_usb)
-		return status;
-
-	in = port->port_usb->in;
-
-	while (!port->write_busy && !list_empty(pool)) {
-		struct usb_request	*req;
-		int			len;
-
-		if (port->write_started >= QUEUE_SIZE)
-			break;
-
-		req = list_entry(pool->next, struct usb_request, list);
-		len = gs_send_packet(port, req->buf, in->maxpacket);
-		if (len == 0) {
-			wake_up_interruptible(&port->drain_wait);
-			break;
-		}
-		do_tty_wake = true;
-
-		req->length = len;
-		list_del(&req->list);
-		req->zero = (gs_buf_data_avail(&port->port_write_buf) == 0);
-
-		pr_vdebug("ttyGS%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
-			  port->port_num, len, *((u8 *)req->buf),
-			  *((u8 *)req->buf+1), *((u8 *)req->buf+2));
-
-		/* Drop lock while we call out of driver; completions
-		 * could be issued while we do so.  Disconnection may
-		 * happen too; maybe immediately before we queue this!
-		 *
-		 * NOTE that we may keep sending data for a while after
-		 * the TTY closed (dev->ioport->port_tty is NULL).
-		 */
-		port->write_busy = true;
-		spin_unlock(&port->port_lock);
-		status = usb_ep_queue(in, req, GFP_ATOMIC);
-		spin_lock(&port->port_lock);
-		port->write_busy = false;
-
-		if (status) {
-			pr_debug("%s: %s %s err %d\n",
-					__func__, "queue", in->name, status);
-			list_add(&req->list, pool);
-			break;
-		}
-
-		port->write_started++;
-
-		/* abort immediately after disconnect */
-		if (!port->port_usb)
-			break;
-	}
-
-	if (do_tty_wake && port->port.tty)
-		tty_wakeup(port->port.tty);
-	return status;
-}
-
-/*
- * Context: caller owns port_lock, and port_usb is set
- */
-static unsigned gs_start_rx(struct gs_port *port)
-/*
-__releases(&port->port_lock)
-__acquires(&port->port_lock)
-*/
-{
-	struct list_head	*pool = &port->read_pool;
-	struct usb_ep		*out = port->port_usb->out;
-
-	while (!list_empty(pool)) {
-		struct usb_request	*req;
-		int			status;
-		struct tty_struct	*tty;
-
-		/* no more rx if closed */
-		tty = port->port.tty;
-		if (!tty)
-			break;
-
-		if (port->read_started >= QUEUE_SIZE)
-			break;
-
-		req = list_entry(pool->next, struct usb_request, list);
-		list_del(&req->list);
-		req->length = out->maxpacket;
-
-		/* drop lock while we call out; the controller driver
-		 * may need to call us back (e.g. for disconnect)
-		 */
-		spin_unlock(&port->port_lock);
-		status = usb_ep_queue(out, req, GFP_ATOMIC);
-		spin_lock(&port->port_lock);
-
-		if (status) {
-			pr_debug("%s: %s %s err %d\n",
-					__func__, "queue", out->name, status);
-			list_add(&req->list, pool);
-			break;
-		}
-		port->read_started++;
-
-		/* abort immediately after disconnect */
-		if (!port->port_usb)
-			break;
-	}
-	return port->read_started;
-}
-
-/*
- * RX tasklet takes data out of the RX queue and hands it up to the TTY
- * layer until it refuses to take any more data (or is throttled back).
- * Then it issues reads for any further data.
- *
- * If the RX queue becomes full enough that no usb_request is queued,
- * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
- * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
- * can be buffered before the TTY layer's buffers (currently 64 KB).
- */
-static void gs_rx_push(unsigned long _port)
-{
-	struct gs_port		*port = (void *)_port;
-	struct tty_struct	*tty;
-	struct list_head	*queue = &port->read_queue;
-	bool			disconnect = false;
-	bool			do_push = false;
-
-	/* hand any queued data to the tty */
-	spin_lock_irq(&port->port_lock);
-	tty = port->port.tty;
-	while (!list_empty(queue)) {
-		struct usb_request	*req;
-
-		req = list_first_entry(queue, struct usb_request, list);
-
-		/* leave data queued if tty was rx throttled */
-		if (tty && tty_throttled(tty))
-			break;
-
-		switch (req->status) {
-		case -ESHUTDOWN:
-			disconnect = true;
-			pr_vdebug("ttyGS%d: shutdown\n", port->port_num);
-			break;
-
-		default:
-			/* presumably a transient fault */
-			pr_warn("ttyGS%d: unexpected RX status %d\n",
-				port->port_num, req->status);
-			/* FALLTHROUGH */
-		case 0:
-			/* normal completion */
-			break;
-		}
-
-		/* push data to (open) tty */
-		if (req->actual) {
-			char		*packet = req->buf;
-			unsigned	size = req->actual;
-			unsigned	n;
-			int		count;
-
-			/* we may have pushed part of this packet already... */
-			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) {
-				/* stop pushing; TTY layer can't handle more */
-				port->n_read += count;
-				pr_vdebug("ttyGS%d: rx block %d/%d\n",
-					  port->port_num, count, req->actual);
-				break;
-			}
-			port->n_read = 0;
-		}
-
-		list_move(&req->list, &port->read_pool);
-		port->read_started--;
-	}
-
-	/* Push from tty to ldisc; this is handled by a workqueue,
-	 * so we won't get callbacks and can hold port_lock
-	 */
-	if (do_push)
-		tty_flip_buffer_push(&port->port);
-
-
-	/* We want our data queue to become empty ASAP, keeping data
-	 * in the tty and ldisc (not here).  If we couldn't push any
-	 * this time around, there may be trouble unless there's an
-	 * implicit tty_unthrottle() call on its way...
-	 *
-	 * REVISIT we should probably add a timer to keep the tasklet
-	 * from starving ... but it's not clear that case ever happens.
-	 */
-	if (!list_empty(queue) && tty) {
-		if (!tty_throttled(tty)) {
-			if (do_push)
-				tasklet_schedule(&port->push);
-			else
-				pr_warn("ttyGS%d: RX not scheduled?\n",
-					port->port_num);
-		}
-	}
-
-	/* If we're still connected, refill the USB RX queue. */
-	if (!disconnect && port->port_usb)
-		gs_start_rx(port);
-
-	spin_unlock_irq(&port->port_lock);
-}
-
-static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
-{
-	struct gs_port	*port = ep->driver_data;
-
-	/* Queue all received data until the tty layer is ready for it. */
-	spin_lock(&port->port_lock);
-	list_add_tail(&req->list, &port->read_queue);
-	tasklet_schedule(&port->push);
-	spin_unlock(&port->port_lock);
-}
-
-static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
-{
-	struct gs_port	*port = ep->driver_data;
-
-	spin_lock(&port->port_lock);
-	list_add(&req->list, &port->write_pool);
-	port->write_started--;
-
-	switch (req->status) {
-	default:
-		/* presumably a transient fault */
-		pr_warn("%s: unexpected %s status %d\n",
-			__func__, ep->name, req->status);
-		/* FALL THROUGH */
-	case 0:
-		/* normal completion */
-		gs_start_tx(port);
-		break;
-
-	case -ESHUTDOWN:
-		/* disconnect */
-		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
-		break;
-	}
-
-	spin_unlock(&port->port_lock);
-}
-
-static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
-							 int *allocated)
-{
-	struct usb_request	*req;
-
-	while (!list_empty(head)) {
-		req = list_entry(head->next, struct usb_request, list);
-		list_del(&req->list);
-		gs_free_req(ep, req);
-		if (allocated)
-			(*allocated)--;
-	}
-}
-
-static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
-		void (*fn)(struct usb_ep *, struct usb_request *),
-		int *allocated)
-{
-	int			i;
-	struct usb_request	*req;
-	int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
-
-	/* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
-	 * do quite that many this time, don't fail ... we just won't
-	 * be as speedy as we might otherwise be.
-	 */
-	for (i = 0; i < n; i++) {
-		req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
-		if (!req)
-			return list_empty(head) ? -ENOMEM : 0;
-		req->complete = fn;
-		list_add_tail(&req->list, head);
-		if (allocated)
-			(*allocated)++;
-	}
-	return 0;
-}
-
-/**
- * gs_start_io - start USB I/O streams
- * @dev: encapsulates endpoints to use
- * Context: holding port_lock; port_tty and port_usb are non-null
- *
- * We only start I/O when something is connected to both sides of
- * this port.  If nothing is listening on the host side, we may
- * be pointlessly filling up our TX buffers and FIFO.
- */
-static int gs_start_io(struct gs_port *port)
-{
-	struct list_head	*head = &port->read_pool;
-	struct usb_ep		*ep = port->port_usb->out;
-	int			status;
-	unsigned		started;
-
-	/* Allocate RX and TX I/O buffers.  We can't easily do this much
-	 * earlier (with GFP_KERNEL) because the requests are coupled to
-	 * endpoints, as are the packet sizes we'll be using.  Different
-	 * configurations may use different endpoints with a given port;
-	 * and high speed vs full speed changes packet sizes too.
-	 */
-	status = gs_alloc_requests(ep, head, gs_read_complete,
-		&port->read_allocated);
-	if (status)
-		return status;
-
-	status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
-			gs_write_complete, &port->write_allocated);
-	if (status) {
-		gs_free_requests(ep, head, &port->read_allocated);
-		return status;
-	}
-
-	/* queue read requests */
-	port->n_read = 0;
-	started = gs_start_rx(port);
-
-	/* unblock any pending writes into our circular buffer */
-	if (started) {
-		tty_wakeup(port->port.tty);
-	} else {
-		gs_free_requests(ep, head, &port->read_allocated);
-		gs_free_requests(port->port_usb->in, &port->write_pool,
-			&port->write_allocated);
-		status = -EIO;
-	}
-
-	return status;
-}
-
-/*-------------------------------------------------------------------------*/
-
-/* TTY Driver */
-
-/*
- * gs_open sets up the link between a gs_port and its associated TTY.
- * That link is broken *only* by TTY close(), and all driver methods
- * know that.
- */
-static int gs_open(struct tty_struct *tty, struct file *file)
-{
-	int		port_num = tty->index;
-	struct gs_port	*port;
-	int		status;
-
-	do {
-		mutex_lock(&ports[port_num].lock);
-		port = ports[port_num].port;
-		if (!port)
-			status = -ENODEV;
-		else {
-			spin_lock_irq(&port->port_lock);
-
-			/* already open?  Great. */
-			if (port->port.count) {
-				status = 0;
-				port->port.count++;
-
-			/* currently opening/closing? wait ... */
-			} else if (port->openclose) {
-				status = -EBUSY;
-
-			/* ... else we do the work */
-			} else {
-				status = -EAGAIN;
-				port->openclose = true;
-			}
-			spin_unlock_irq(&port->port_lock);
-		}
-		mutex_unlock(&ports[port_num].lock);
-
-		switch (status) {
-		default:
-			/* fully handled */
-			return status;
-		case -EAGAIN:
-			/* must do the work */
-			break;
-		case -EBUSY:
-			/* wait for EAGAIN task to finish */
-			msleep(1);
-			/* REVISIT could have a waitchannel here, if
-			 * concurrent open performance is important
-			 */
-			break;
-		}
-	} while (status != -EAGAIN);
-
-	/* Do the "real open" */
-	spin_lock_irq(&port->port_lock);
-
-	/* allocate circular buffer on first open */
-	if (port->port_write_buf.buf_buf == NULL) {
-
-		spin_unlock_irq(&port->port_lock);
-		status = gs_buf_alloc(&port->port_write_buf, WRITE_BUF_SIZE);
-		spin_lock_irq(&port->port_lock);
-
-		if (status) {
-			pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
-				port->port_num, tty, file);
-			port->openclose = false;
-			goto exit_unlock_port;
-		}
-	}
-
-	/* REVISIT if REMOVED (ports[].port NULL), abort the open
-	 * to let rmmod work faster (but this way isn't wrong).
-	 */
-
-	/* REVISIT maybe wait for "carrier detect" */
-
-	tty->driver_data = port;
-	port->port.tty = tty;
-
-	port->port.count = 1;
-	port->openclose = false;
-
-	/* if connected, start the I/O stream */
-	if (port->port_usb) {
-		struct gserial	*gser = port->port_usb;
-
-		pr_debug("gs_open: start ttyGS%d\n", port->port_num);
-		gs_start_io(port);
-
-		if (gser->connect)
-			gser->connect(gser);
-	}
-
-	pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
-
-	status = 0;
-
-exit_unlock_port:
-	spin_unlock_irq(&port->port_lock);
-	return status;
-}
-
-static int gs_writes_finished(struct gs_port *p)
-{
-	int cond;
-
-	/* return true on disconnect or empty buffer */
-	spin_lock_irq(&p->port_lock);
-	cond = (p->port_usb == NULL) || !gs_buf_data_avail(&p->port_write_buf);
-	spin_unlock_irq(&p->port_lock);
-
-	return cond;
-}
-
-static void gs_close(struct tty_struct *tty, struct file *file)
-{
-	struct gs_port *port = tty->driver_data;
-	struct gserial	*gser;
-
-	spin_lock_irq(&port->port_lock);
-
-	if (port->port.count != 1) {
-		if (port->port.count == 0)
-			WARN_ON(1);
-		else
-			--port->port.count;
-		goto exit;
-	}
-
-	pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
-
-	/* mark port as closing but in use; we can drop port lock
-	 * and sleep if necessary
-	 */
-	port->openclose = true;
-	port->port.count = 0;
-
-	gser = port->port_usb;
-	if (gser && gser->disconnect)
-		gser->disconnect(gser);
-
-	/* wait for circular write buffer to drain, disconnect, or at
-	 * most GS_CLOSE_TIMEOUT seconds; then discard the rest
-	 */
-	if (gs_buf_data_avail(&port->port_write_buf) > 0 && gser) {
-		spin_unlock_irq(&port->port_lock);
-		wait_event_interruptible_timeout(port->drain_wait,
-					gs_writes_finished(port),
-					GS_CLOSE_TIMEOUT * HZ);
-		spin_lock_irq(&port->port_lock);
-		gser = port->port_usb;
-	}
-
-	/* Iff we're disconnected, there can be no I/O in flight so it's
-	 * ok to free the circular buffer; else just scrub it.  And don't
-	 * let the push tasklet fire again until we're re-opened.
-	 */
-	if (gser == NULL)
-		gs_buf_free(&port->port_write_buf);
-	else
-		gs_buf_clear(&port->port_write_buf);
-
-	port->port.tty = NULL;
-
-	port->openclose = false;
-
-	pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
-			port->port_num, tty, file);
-
-	wake_up(&port->close_wait);
-exit:
-	spin_unlock_irq(&port->port_lock);
-}
-
-static int gs_write(struct tty_struct *tty, const unsigned char *buf, int count)
-{
-	struct gs_port	*port = tty->driver_data;
-	unsigned long	flags;
-
-	pr_vdebug("gs_write: ttyGS%d (%p) writing %d bytes\n",
-			port->port_num, tty, count);
-
-	spin_lock_irqsave(&port->port_lock, flags);
-	if (count)
-		count = gs_buf_put(&port->port_write_buf, buf, count);
-	/* treat count == 0 as flush_chars() */
-	if (port->port_usb)
-		gs_start_tx(port);
-	spin_unlock_irqrestore(&port->port_lock, flags);
-
-	return count;
-}
-
-static int gs_put_char(struct tty_struct *tty, unsigned char ch)
-{
-	struct gs_port	*port = tty->driver_data;
-	unsigned long	flags;
-	int		status;
-
-	pr_vdebug("gs_put_char: (%d,%p) char=0x%x, called from %ps\n",
-		port->port_num, tty, ch, __builtin_return_address(0));
-
-	spin_lock_irqsave(&port->port_lock, flags);
-	status = gs_buf_put(&port->port_write_buf, &ch, 1);
-	spin_unlock_irqrestore(&port->port_lock, flags);
-
-	return status;
-}
-
-static void gs_flush_chars(struct tty_struct *tty)
-{
-	struct gs_port	*port = tty->driver_data;
-	unsigned long	flags;
-
-	pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
-
-	spin_lock_irqsave(&port->port_lock, flags);
-	if (port->port_usb)
-		gs_start_tx(port);
-	spin_unlock_irqrestore(&port->port_lock, flags);
-}
-
-static int gs_write_room(struct tty_struct *tty)
-{
-	struct gs_port	*port = tty->driver_data;
-	unsigned long	flags;
-	int		room = 0;
-
-	spin_lock_irqsave(&port->port_lock, flags);
-	if (port->port_usb)
-		room = gs_buf_space_avail(&port->port_write_buf);
-	spin_unlock_irqrestore(&port->port_lock, flags);
-
-	pr_vdebug("gs_write_room: (%d,%p) room=%d\n",
-		port->port_num, tty, room);
-
-	return room;
-}
-
-static int gs_chars_in_buffer(struct tty_struct *tty)
-{
-	struct gs_port	*port = tty->driver_data;
-	unsigned long	flags;
-	int		chars = 0;
-
-	spin_lock_irqsave(&port->port_lock, flags);
-	chars = gs_buf_data_avail(&port->port_write_buf);
-	spin_unlock_irqrestore(&port->port_lock, flags);
-
-	pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%d\n",
-		port->port_num, tty, chars);
-
-	return chars;
-}
-
-/* undo side effects of setting TTY_THROTTLED */
-static void gs_unthrottle(struct tty_struct *tty)
-{
-	struct gs_port		*port = tty->driver_data;
-	unsigned long		flags;
-
-	spin_lock_irqsave(&port->port_lock, flags);
-	if (port->port_usb) {
-		/* Kickstart read queue processing.  We don't do xon/xoff,
-		 * rts/cts, or other handshaking with the host, but if the
-		 * read queue backs up enough we'll be NAKing OUT packets.
-		 */
-		tasklet_schedule(&port->push);
-		pr_vdebug("ttyGS%d: unthrottle\n", port->port_num);
-	}
-	spin_unlock_irqrestore(&port->port_lock, flags);
-}
-
-static int gs_break_ctl(struct tty_struct *tty, int duration)
-{
-	struct gs_port	*port = tty->driver_data;
-	int		status = 0;
-	struct gserial	*gser;
-
-	pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
-			port->port_num, duration);
-
-	spin_lock_irq(&port->port_lock);
-	gser = port->port_usb;
-	if (gser && gser->send_break)
-		status = gser->send_break(gser, duration);
-	spin_unlock_irq(&port->port_lock);
-
-	return status;
-}
-
-static const struct tty_operations gs_tty_ops = {
-	.open =			gs_open,
-	.close =		gs_close,
-	.write =		gs_write,
-	.put_char =		gs_put_char,
-	.flush_chars =		gs_flush_chars,
-	.write_room =		gs_write_room,
-	.chars_in_buffer =	gs_chars_in_buffer,
-	.unthrottle =		gs_unthrottle,
-	.break_ctl =		gs_break_ctl,
-};
-
-/*-------------------------------------------------------------------------*/
-
-static struct tty_driver *gs_tty_driver;
-
-#ifdef CONFIG_U_SERIAL_CONSOLE
-
-static struct gscons_info gscons_info;
-static struct console gserial_cons;
-
-static struct usb_request *gs_request_new(struct usb_ep *ep)
-{
-	struct usb_request *req = usb_ep_alloc_request(ep, GFP_ATOMIC);
-	if (!req)
-		return NULL;
-
-	req->buf = kmalloc(ep->maxpacket, GFP_ATOMIC);
-	if (!req->buf) {
-		usb_ep_free_request(ep, req);
-		return NULL;
-	}
-
-	return req;
-}
-
-static void gs_request_free(struct usb_request *req, struct usb_ep *ep)
-{
-	if (!req)
-		return;
-
-	kfree(req->buf);
-	usb_ep_free_request(ep, req);
-}
-
-static void gs_complete_out(struct usb_ep *ep, struct usb_request *req)
-{
-	struct gscons_info *info = &gscons_info;
-
-	switch (req->status) {
-	default:
-		pr_warn("%s: unexpected %s status %d\n",
-			__func__, ep->name, req->status);
-	case 0:
-		/* normal completion */
-		spin_lock(&info->con_lock);
-		info->req_busy = 0;
-		spin_unlock(&info->con_lock);
-
-		wake_up_process(info->console_thread);
-		break;
-	case -ESHUTDOWN:
-		/* disconnect */
-		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
-		break;
-	}
-}
-
-static int gs_console_connect(int port_num)
-{
-	struct gscons_info *info = &gscons_info;
-	struct gs_port *port;
-	struct usb_ep *ep;
-
-	if (port_num != gserial_cons.index) {
-		pr_err("%s: port num [%d] is not support console\n",
-		       __func__, port_num);
-		return -ENXIO;
-	}
-
-	port = ports[port_num].port;
-	ep = port->port_usb->in;
-	if (!info->console_req) {
-		info->console_req = gs_request_new(ep);
-		if (!info->console_req)
-			return -ENOMEM;
-		info->console_req->complete = gs_complete_out;
-	}
-
-	info->port = port;
-	spin_lock(&info->con_lock);
-	info->req_busy = 0;
-	spin_unlock(&info->con_lock);
-	pr_vdebug("port[%d] console connect!\n", port_num);
-	return 0;
-}
-
-static void gs_console_disconnect(struct usb_ep *ep)
-{
-	struct gscons_info *info = &gscons_info;
-	struct usb_request *req = info->console_req;
-
-	gs_request_free(req, ep);
-	info->console_req = NULL;
-}
-
-static int gs_console_thread(void *data)
-{
-	struct gscons_info *info = &gscons_info;
-	struct gs_port *port;
-	struct usb_request *req;
-	struct usb_ep *ep;
-	int xfer, ret, count, size;
-
-	do {
-		port = info->port;
-		set_current_state(TASK_INTERRUPTIBLE);
-		if (!port || !port->port_usb
-		    || !port->port_usb->in || !info->console_req)
-			goto sched;
-
-		req = info->console_req;
-		ep = port->port_usb->in;
-
-		spin_lock_irq(&info->con_lock);
-		count = gs_buf_data_avail(&info->con_buf);
-		size = ep->maxpacket;
-
-		if (count > 0 && !info->req_busy) {
-			set_current_state(TASK_RUNNING);
-			if (count < size)
-				size = count;
-
-			xfer = gs_buf_get(&info->con_buf, req->buf, size);
-			req->length = xfer;
-
-			spin_unlock(&info->con_lock);
-			ret = usb_ep_queue(ep, req, GFP_ATOMIC);
-			spin_lock(&info->con_lock);
-			if (ret < 0)
-				info->req_busy = 0;
-			else
-				info->req_busy = 1;
-
-			spin_unlock_irq(&info->con_lock);
-		} else {
-			spin_unlock_irq(&info->con_lock);
-sched:
-			if (kthread_should_stop()) {
-				set_current_state(TASK_RUNNING);
-				break;
-			}
-			schedule();
-		}
-	} while (1);
-
-	return 0;
-}
-
-static int gs_console_setup(struct console *co, char *options)
-{
-	struct gscons_info *info = &gscons_info;
-	int status;
-
-	info->port = NULL;
-	info->console_req = NULL;
-	info->req_busy = 0;
-	spin_lock_init(&info->con_lock);
-
-	status = gs_buf_alloc(&info->con_buf, GS_CONSOLE_BUF_SIZE);
-	if (status) {
-		pr_err("%s: allocate console buffer failed\n", __func__);
-		return status;
-	}
-
-	info->console_thread = kthread_create(gs_console_thread,
-					      co, "gs_console");
-	if (IS_ERR(info->console_thread)) {
-		pr_err("%s: cannot create console thread\n", __func__);
-		gs_buf_free(&info->con_buf);
-		return PTR_ERR(info->console_thread);
-	}
-	wake_up_process(info->console_thread);
-
-	return 0;
-}
-
-static void gs_console_write(struct console *co,
-			     const char *buf, unsigned count)
-{
-	struct gscons_info *info = &gscons_info;
-	unsigned long flags;
-
-	spin_lock_irqsave(&info->con_lock, flags);
-	gs_buf_put(&info->con_buf, buf, count);
-	spin_unlock_irqrestore(&info->con_lock, flags);
-
-	wake_up_process(info->console_thread);
-}
-
-static struct tty_driver *gs_console_device(struct console *co, int *index)
-{
-	struct tty_driver **p = (struct tty_driver **)co->data;
-
-	if (!*p)
-		return NULL;
-
-	*index = co->index;
-	return *p;
-}
-
-static struct console gserial_cons = {
-	.name =		"ttyGS",
-	.write =	gs_console_write,
-	.device =	gs_console_device,
-	.setup =	gs_console_setup,
-	.flags =	CON_PRINTBUFFER,
-	.index =	-1,
-	.data =		&gs_tty_driver,
-};
-
-static void gserial_console_init(void)
-{
-	register_console(&gserial_cons);
-}
-
-static void gserial_console_exit(void)
-{
-	struct gscons_info *info = &gscons_info;
-
-	unregister_console(&gserial_cons);
-	if (!IS_ERR_OR_NULL(info->console_thread))
-		kthread_stop(info->console_thread);
-	gs_buf_free(&info->con_buf);
-}
-
-#else
-
-static int gs_console_connect(int port_num)
-{
-	return 0;
-}
-
-static void gs_console_disconnect(struct usb_ep *ep)
-{
-}
-
-static void gserial_console_init(void)
-{
-}
-
-static void gserial_console_exit(void)
-{
-}
-
-#endif
-
-static int
-gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
-{
-	struct gs_port	*port;
-	int		ret = 0;
-
-	mutex_lock(&ports[port_num].lock);
-	if (ports[port_num].port) {
-		ret = -EBUSY;
-		goto out;
-	}
-
-	port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
-	if (port == NULL) {
-		ret = -ENOMEM;
-		goto out;
-	}
-
-	tty_port_init(&port->port);
-	spin_lock_init(&port->port_lock);
-	init_waitqueue_head(&port->drain_wait);
-	init_waitqueue_head(&port->close_wait);
-
-	tasklet_init(&port->push, gs_rx_push, (unsigned long) port);
-
-	INIT_LIST_HEAD(&port->read_pool);
-	INIT_LIST_HEAD(&port->read_queue);
-	INIT_LIST_HEAD(&port->write_pool);
-
-	port->port_num = port_num;
-	port->port_line_coding = *coding;
-
-	ports[port_num].port = port;
-out:
-	mutex_unlock(&ports[port_num].lock);
-	return ret;
-}
-
-static int gs_closed(struct gs_port *port)
-{
-	int cond;
-
-	spin_lock_irq(&port->port_lock);
-	cond = (port->port.count == 0) && !port->openclose;
-	spin_unlock_irq(&port->port_lock);
-	return cond;
-}
-
-static void gserial_free_port(struct gs_port *port)
-{
-	tasklet_kill(&port->push);
-	/* wait for old opens to finish */
-	wait_event(port->close_wait, gs_closed(port));
-	WARN_ON(port->port_usb != NULL);
-	tty_port_destroy(&port->port);
-	kfree(port);
-}
-
-void gserial_free_line(unsigned char port_num)
-{
-	struct gs_port	*port;
-
-	mutex_lock(&ports[port_num].lock);
-	if (WARN_ON(!ports[port_num].port)) {
-		mutex_unlock(&ports[port_num].lock);
-		return;
-	}
-	port = ports[port_num].port;
-	ports[port_num].port = NULL;
-	mutex_unlock(&ports[port_num].lock);
-
-	gserial_free_port(port);
-	tty_unregister_device(gs_tty_driver, port_num);
-	gserial_console_exit();
-}
-EXPORT_SYMBOL_GPL(gserial_free_line);
-
-int gserial_alloc_line(unsigned char *line_num)
-{
-	struct usb_cdc_line_coding	coding;
-	struct device			*tty_dev;
-	int				ret;
-	int				port_num;
-
-	coding.dwDTERate = cpu_to_le32(9600);
-	coding.bCharFormat = 8;
-	coding.bParityType = USB_CDC_NO_PARITY;
-	coding.bDataBits = USB_CDC_1_STOP_BITS;
-
-	for (port_num = 0; port_num < MAX_U_SERIAL_PORTS; port_num++) {
-		ret = gs_port_alloc(port_num, &coding);
-		if (ret == -EBUSY)
-			continue;
-		if (ret)
-			return ret;
-		break;
-	}
-	if (ret)
-		return ret;
-
-	/* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
-
-	tty_dev = tty_port_register_device(&ports[port_num].port->port,
-			gs_tty_driver, port_num, NULL);
-	if (IS_ERR(tty_dev)) {
-		struct gs_port	*port;
-		pr_err("%s: failed to register tty for port %d, err %ld\n",
-				__func__, port_num, PTR_ERR(tty_dev));
-
-		ret = PTR_ERR(tty_dev);
-		port = ports[port_num].port;
-		ports[port_num].port = NULL;
-		gserial_free_port(port);
-		goto err;
-	}
-	*line_num = port_num;
-	gserial_console_init();
-err:
-	return ret;
-}
-EXPORT_SYMBOL_GPL(gserial_alloc_line);
-
-/**
- * gserial_connect - notify TTY I/O glue that USB link is active
- * @gser: the function, set up with endpoints and descriptors
- * @port_num: which port is active
- * Context: any (usually from irq)
- *
- * This is called activate endpoints and let the TTY layer know that
- * the connection is active ... not unlike "carrier detect".  It won't
- * necessarily start I/O queues; unless the TTY is held open by any
- * task, there would be no point.  However, the endpoints will be
- * activated so the USB host can perform I/O, subject to basic USB
- * hardware flow control.
- *
- * Caller needs to have set up the endpoints and USB function in @dev
- * before calling this, as well as the appropriate (speed-specific)
- * endpoint descriptors, and also have allocate @port_num by calling
- * @gserial_alloc_line().
- *
- * Returns negative errno or zero.
- * On success, ep->driver_data will be overwritten.
- */
-int gserial_connect(struct gserial *gser, u8 port_num)
-{
-	struct gs_port	*port;
-	unsigned long	flags;
-	int		status;
-
-	if (port_num >= MAX_U_SERIAL_PORTS)
-		return -ENXIO;
-
-	port = ports[port_num].port;
-	if (!port) {
-		pr_err("serial line %d not allocated.\n", port_num);
-		return -EINVAL;
-	}
-	if (port->port_usb) {
-		pr_err("serial line %d is in use.\n", port_num);
-		return -EBUSY;
-	}
-
-	/* activate the endpoints */
-	status = usb_ep_enable(gser->in);
-	if (status < 0)
-		return status;
-	gser->in->driver_data = port;
-
-	status = usb_ep_enable(gser->out);
-	if (status < 0)
-		goto fail_out;
-	gser->out->driver_data = port;
-
-	/* then tell the tty glue that I/O can work */
-	spin_lock_irqsave(&port->port_lock, flags);
-	gser->ioport = port;
-	port->port_usb = gser;
-
-	/* REVISIT unclear how best to handle this state...
-	 * we don't really couple it with the Linux TTY.
-	 */
-	gser->port_line_coding = port->port_line_coding;
-
-	/* REVISIT if waiting on "carrier detect", signal. */
-
-	/* if it's already open, start I/O ... and notify the serial
-	 * protocol about open/close status (connect/disconnect).
-	 */
-	if (port->port.count) {
-		pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
-		gs_start_io(port);
-		if (gser->connect)
-			gser->connect(gser);
-	} else {
-		if (gser->disconnect)
-			gser->disconnect(gser);
-	}
-
-	status = gs_console_connect(port_num);
-	spin_unlock_irqrestore(&port->port_lock, flags);
-
-	return status;
-
-fail_out:
-	usb_ep_disable(gser->in);
-	return status;
-}
-EXPORT_SYMBOL_GPL(gserial_connect);
-/**
- * gserial_disconnect - notify TTY I/O glue that USB link is inactive
- * @gser: the function, on which gserial_connect() was called
- * Context: any (usually from irq)
- *
- * This is called to deactivate endpoints and let the TTY layer know
- * that the connection went inactive ... not unlike "hangup".
- *
- * On return, the state is as if gserial_connect() had never been called;
- * there is no active USB I/O on these endpoints.
- */
-void gserial_disconnect(struct gserial *gser)
-{
-	struct gs_port	*port = gser->ioport;
-	unsigned long	flags;
-
-	if (!port)
-		return;
-
-	/* tell the TTY glue not to do I/O here any more */
-	spin_lock_irqsave(&port->port_lock, flags);
-
-	/* REVISIT as above: how best to track this? */
-	port->port_line_coding = gser->port_line_coding;
-
-	port->port_usb = NULL;
-	gser->ioport = NULL;
-	if (port->port.count > 0 || port->openclose) {
-		wake_up_interruptible(&port->drain_wait);
-		if (port->port.tty)
-			tty_hangup(port->port.tty);
-	}
-	spin_unlock_irqrestore(&port->port_lock, flags);
-
-	/* disable endpoints, aborting down any active I/O */
-	usb_ep_disable(gser->out);
-	usb_ep_disable(gser->in);
-
-	/* finally, free any unused/unusable I/O buffers */
-	spin_lock_irqsave(&port->port_lock, flags);
-	if (port->port.count == 0 && !port->openclose)
-		gs_buf_free(&port->port_write_buf);
-	gs_free_requests(gser->out, &port->read_pool, NULL);
-	gs_free_requests(gser->out, &port->read_queue, NULL);
-	gs_free_requests(gser->in, &port->write_pool, NULL);
-
-	port->read_allocated = port->read_started =
-		port->write_allocated = port->write_started = 0;
-
-	gs_console_disconnect(gser->in);
-	spin_unlock_irqrestore(&port->port_lock, flags);
-}
-EXPORT_SYMBOL_GPL(gserial_disconnect);
-
-static int userial_init(void)
-{
-	unsigned			i;
-	int				status;
-
-	gs_tty_driver = alloc_tty_driver(MAX_U_SERIAL_PORTS);
-	if (!gs_tty_driver)
-		return -ENOMEM;
-
-	gs_tty_driver->driver_name = "g_serial";
-	gs_tty_driver->name = "ttyGS";
-	/* uses dynamically assigned dev_t values */
-
-	gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
-	gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
-	gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
-	gs_tty_driver->init_termios = tty_std_termios;
-
-	/* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
-	 * MS-Windows.  Otherwise, most of these flags shouldn't affect
-	 * anything unless we were to actually hook up to a serial line.
-	 */
-	gs_tty_driver->init_termios.c_cflag =
-			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
-	gs_tty_driver->init_termios.c_ispeed = 9600;
-	gs_tty_driver->init_termios.c_ospeed = 9600;
-
-	tty_set_operations(gs_tty_driver, &gs_tty_ops);
-	for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
-		mutex_init(&ports[i].lock);
-
-	/* export the driver ... */
-	status = tty_register_driver(gs_tty_driver);
-	if (status) {
-		pr_err("%s: cannot register, err %d\n",
-				__func__, status);
-		goto fail;
-	}
-
-	pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
-			MAX_U_SERIAL_PORTS,
-			(MAX_U_SERIAL_PORTS == 1) ? "" : "s");
-
-	return status;
-fail:
-	put_tty_driver(gs_tty_driver);
-	gs_tty_driver = NULL;
-	return status;
-}
-module_init(userial_init);
-
-static void userial_cleanup(void)
-{
-	tty_unregister_driver(gs_tty_driver);
-	put_tty_driver(gs_tty_driver);
-	gs_tty_driver = NULL;
-}
-module_exit(userial_cleanup);
-
-MODULE_LICENSE("GPL");
diff --git a/drivers/usb/gadget/function/u_serial.h b/drivers/usb/gadget/function/u_serial.h
deleted file mode 100644
index c20210c..0000000
--- a/drivers/usb/gadget/function/u_serial.h
+++ /dev/null
@@ -1,71 +0,0 @@
-/*
- * u_serial.h - interface to USB gadget "serial port"/TTY utilities
- *
- * Copyright (C) 2008 David Brownell
- * Copyright (C) 2008 by Nokia Corporation
- *
- * This software is distributed under the terms of the GNU General
- * Public License ("GPL") as published by the Free Software Foundation,
- * either version 2 of that License or (at your option) any later version.
- */
-
-#ifndef __U_SERIAL_H
-#define __U_SERIAL_H
-
-#include <linux/usb/composite.h>
-#include <linux/usb/cdc.h>
-
-#define MAX_U_SERIAL_PORTS	4
-
-struct f_serial_opts {
-	struct usb_function_instance func_inst;
-	u8 port_num;
-};
-
-/*
- * One non-multiplexed "serial" I/O port ... there can be several of these
- * on any given USB peripheral device, if it provides enough endpoints.
- *
- * The "u_serial" utility component exists to do one thing:  manage TTY
- * style I/O using the USB peripheral endpoints listed here, including
- * hookups to sysfs and /dev for each logical "tty" device.
- *
- * REVISIT at least ACM could support tiocmget() if needed.
- *
- * REVISIT someday, allow multiplexing several TTYs over these endpoints.
- */
-struct gserial {
-	struct usb_function		func;
-
-	/* port is managed by gserial_{connect,disconnect} */
-	struct gs_port			*ioport;
-
-	struct usb_ep			*in;
-	struct usb_ep			*out;
-
-	/* REVISIT avoid this CDC-ACM support harder ... */
-	struct usb_cdc_line_coding port_line_coding;	/* 9600-8-N-1 etc */
-
-	/* notification callbacks */
-	void (*connect)(struct gserial *p);
-	void (*disconnect)(struct gserial *p);
-	int (*send_break)(struct gserial *p, int duration);
-};
-
-/* utilities to allocate/free request and buffer */
-struct usb_request *gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t flags);
-void gs_free_req(struct usb_ep *, struct usb_request *req);
-
-/* management of individual TTY ports */
-int gserial_alloc_line(unsigned char *port_line);
-void gserial_free_line(unsigned char port_line);
-
-/* connect/disconnect is handled by individual functions */
-int gserial_connect(struct gserial *, u8 port_num);
-void gserial_disconnect(struct gserial *);
-
-/* functions are bound to configurations by a config or gadget driver */
-int gser_bind_config(struct usb_configuration *c, u8 port_num);
-int obex_bind_config(struct usb_configuration *c, u8 port_num);
-
-#endif /* __U_SERIAL_H */
diff --git a/drivers/usb/gadget/legacy/acm_ms.c b/drivers/usb/gadget/legacy/acm_ms.c
index c39de65..5c63b95 100644
--- a/drivers/usb/gadget/legacy/acm_ms.c
+++ b/drivers/usb/gadget/legacy/acm_ms.c
@@ -16,8 +16,7 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
-
-#include "u_serial.h"
+#include <linux/usb/u_serial.h>
 
 #define DRIVER_DESC		"Composite Gadget (ACM + MS)"
 #define DRIVER_VERSION		"2011/10/10"
diff --git a/drivers/usb/gadget/legacy/cdc2.c b/drivers/usb/gadget/legacy/cdc2.c
index 51c0868..e06a88e 100644
--- a/drivers/usb/gadget/legacy/cdc2.c
+++ b/drivers/usb/gadget/legacy/cdc2.c
@@ -12,9 +12,9 @@
 
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/usb/u_serial.h>
 
 #include "u_ether.h"
-#include "u_serial.h"
 #include "u_ecm.h"
 
 
diff --git a/drivers/usb/gadget/legacy/dbgp.c b/drivers/usb/gadget/legacy/dbgp.c
index 99ca3da..ed8b9d4 100644
--- a/drivers/usb/gadget/legacy/dbgp.c
+++ b/drivers/usb/gadget/legacy/dbgp.c
@@ -12,8 +12,7 @@
 #include <linux/module.h>
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
-
-#include "u_serial.h"
+#include <linux/usb/u_serial.h>
 
 #define DRIVER_VENDOR_ID	0x0525 /* NetChip */
 #define DRIVER_PRODUCT_ID	0xc0de /* undefined */
diff --git a/drivers/usb/gadget/legacy/multi.c b/drivers/usb/gadget/legacy/multi.c
index a70a406..335eea9 100644
--- a/drivers/usb/gadget/legacy/multi.c
+++ b/drivers/usb/gadget/legacy/multi.c
@@ -16,8 +16,8 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
+#include <linux/usb/u_serial.h>
 
-#include "u_serial.h"
 #if defined USB_ETH_RNDIS
 #  undef USB_ETH_RNDIS
 #endif
diff --git a/drivers/usb/gadget/legacy/nokia.c b/drivers/usb/gadget/legacy/nokia.c
index b1e535f..135f075 100644
--- a/drivers/usb/gadget/legacy/nokia.c
+++ b/drivers/usb/gadget/legacy/nokia.c
@@ -18,8 +18,8 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/device.h>
+#include <linux/usb/u_serial.h>
 
-#include "u_serial.h"
 #include "u_ether.h"
 #include "u_phonet.h"
 #include "u_ecm.h"
diff --git a/drivers/usb/gadget/legacy/serial.c b/drivers/usb/gadget/legacy/serial.c
index 9d89adc..1ca8d58 100644
--- a/drivers/usb/gadget/legacy/serial.c
+++ b/drivers/usb/gadget/legacy/serial.c
@@ -15,8 +15,7 @@
 #include <linux/module.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
-
-#include "u_serial.h"
+#include <linux/usb/u_serial.h>
 
 
 /* Defines */
diff --git a/include/linux/usb/u_serial.h b/include/linux/usb/u_serial.h
new file mode 100644
index 0000000..c20210c
--- /dev/null
+++ b/include/linux/usb/u_serial.h
@@ -0,0 +1,71 @@
+/*
+ * u_serial.h - interface to USB gadget "serial port"/TTY utilities
+ *
+ * Copyright (C) 2008 David Brownell
+ * Copyright (C) 2008 by Nokia Corporation
+ *
+ * This software is distributed under the terms of the GNU General
+ * Public License ("GPL") as published by the Free Software Foundation,
+ * either version 2 of that License or (at your option) any later version.
+ */
+
+#ifndef __U_SERIAL_H
+#define __U_SERIAL_H
+
+#include <linux/usb/composite.h>
+#include <linux/usb/cdc.h>
+
+#define MAX_U_SERIAL_PORTS	4
+
+struct f_serial_opts {
+	struct usb_function_instance func_inst;
+	u8 port_num;
+};
+
+/*
+ * One non-multiplexed "serial" I/O port ... there can be several of these
+ * on any given USB peripheral device, if it provides enough endpoints.
+ *
+ * The "u_serial" utility component exists to do one thing:  manage TTY
+ * style I/O using the USB peripheral endpoints listed here, including
+ * hookups to sysfs and /dev for each logical "tty" device.
+ *
+ * REVISIT at least ACM could support tiocmget() if needed.
+ *
+ * REVISIT someday, allow multiplexing several TTYs over these endpoints.
+ */
+struct gserial {
+	struct usb_function		func;
+
+	/* port is managed by gserial_{connect,disconnect} */
+	struct gs_port			*ioport;
+
+	struct usb_ep			*in;
+	struct usb_ep			*out;
+
+	/* REVISIT avoid this CDC-ACM support harder ... */
+	struct usb_cdc_line_coding port_line_coding;	/* 9600-8-N-1 etc */
+
+	/* notification callbacks */
+	void (*connect)(struct gserial *p);
+	void (*disconnect)(struct gserial *p);
+	int (*send_break)(struct gserial *p, int duration);
+};
+
+/* utilities to allocate/free request and buffer */
+struct usb_request *gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t flags);
+void gs_free_req(struct usb_ep *, struct usb_request *req);
+
+/* management of individual TTY ports */
+int gserial_alloc_line(unsigned char *port_line);
+void gserial_free_line(unsigned char port_line);
+
+/* connect/disconnect is handled by individual functions */
+int gserial_connect(struct gserial *, u8 port_num);
+void gserial_disconnect(struct gserial *);
+
+/* functions are bound to configurations by a config or gadget driver */
+int gser_bind_config(struct usb_configuration *c, u8 port_num);
+int obex_bind_config(struct usb_configuration *c, u8 port_num);
+
+#endif /* __U_SERIAL_H */
-- 
2.7.4