u_serial.c

   1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * u_serial.c - utilities for USB gadget "serial port"/TTY support
   4 *
   5 * Copyright (C) 2003 Al Borchers (alborchers@steinerpoint.com)
   6 * Copyright (C) 2008 David Brownell
   7 * Copyright (C) 2008 by Nokia Corporation
   8 *
   9 * This code also borrows from usbserial.c, which is
  10 * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
  11 * Copyright (C) 2000 Peter Berger (pberger@brimson.com)
  12 * Copyright (C) 2000 Al Borchers (alborchers@steinerpoint.com)
  13 */
  14
  15/* #define VERBOSE_DEBUG */
  16
  17#include <linux/kernel.h>
  18#include <linux/sched.h>
  19#include <linux/device.h>
  20#include <linux/delay.h>
  21#include <linux/tty.h>
  22#include <linux/tty_flip.h>
  23#include <linux/slab.h>
  24#include <linux/string_choices.h>
  25#include <linux/export.h>
  26#include <linux/module.h>
  27#include <linux/console.h>
  28#include <linux/kstrtox.h>
  29#include <linux/kthread.h>
  30#include <linux/workqueue.h>
  31#include <linux/kfifo.h>
  32#include <linux/serial.h>
  33
  34#include "u_serial.h"
  35
  36
  37/*
  38 * This component encapsulates the TTY layer glue needed to provide basic
  39 * "serial port" functionality through the USB gadget stack.  Each such
  40 * port is exposed through a /dev/ttyGS* node.
  41 *
  42 * After this module has been loaded, the individual TTY port can be requested
  43 * (gserial_alloc_line()) and it will stay available until they are removed
  44 * (gserial_free_line()). Each one may be connected to a USB function
  45 * (gserial_connect), or disconnected (with gserial_disconnect) when the USB
  46 * host issues a config change event. Data can only flow when the port is
  47 * connected to the host.
  48 *
  49 * A given TTY port can be made available in multiple configurations.
  50 * For example, each one might expose a ttyGS0 node which provides a
  51 * login application.  In one case that might use CDC ACM interface 0,
  52 * while another configuration might use interface 3 for that.  The
  53 * work to handle that (including descriptor management) is not part
  54 * of this component.
  55 *
  56 * Configurations may expose more than one TTY port.  For example, if
  57 * ttyGS0 provides login service, then ttyGS1 might provide dialer access
  58 * for a telephone or fax link.  And ttyGS2 might be something that just
  59 * needs a simple byte stream interface for some messaging protocol that
  60 * is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
  61 *
  62 *
  63 * gserial is the lifecycle interface, used by USB functions
  64 * gs_port is the I/O nexus, used by the tty driver
  65 * tty_struct links to the tty/filesystem framework
  66 *
  67 * gserial <---> gs_port ... links will be null when the USB link is
  68 * inactive; managed by gserial_{connect,disconnect}().  each gserial
  69 * instance can wrap its own USB control protocol.
  70 *	gserial->ioport == usb_ep->driver_data ... gs_port
  71 *	gs_port->port_usb ... gserial
  72 *
  73 * gs_port <---> tty_struct ... links will be null when the TTY file
  74 * isn't opened; managed by gs_open()/gs_close()
  75 *	gserial->port_tty ... tty_struct
  76 *	tty_struct->driver_data ... gserial
  77 */
  78
  79/* RX and TX queues can buffer QUEUE_SIZE packets before they hit the
  80 * next layer of buffering.  For TX that's a circular buffer; for RX
  81 * consider it a NOP.  A third layer is provided by the TTY code.
  82 */
  83#define QUEUE_SIZE		16
  84#define WRITE_BUF_SIZE		8192		/* TX only */
  85#define GS_CONSOLE_BUF_SIZE	8192
  86
  87/* Prevents race conditions while accessing gser->ioport */
  88static DEFINE_SPINLOCK(serial_port_lock);
  89
  90/* console info */
  91struct gs_console {
  92	struct console		console;
  93	struct work_struct	work;
  94	spinlock_t		lock;
  95	struct usb_request	*req;
  96	struct kfifo		buf;
  97	size_t			missed;
  98};
  99
 100/*
 101 * The port structure holds info for each port, one for each minor number
 102 * (and thus for each /dev/ node).
 103 */
 104struct gs_port {
 105	struct tty_port		port;
 106	spinlock_t		port_lock;	/* guard port_* access */
 107
 108	struct gserial		*port_usb;
 109#ifdef CONFIG_U_SERIAL_CONSOLE
 110	struct gs_console	*console;
 111#endif
 112
 113	u8			port_num;
 114
 115	struct list_head	read_pool;
 116	int read_started;
 117	int read_allocated;
 118	struct list_head	read_queue;
 119	unsigned		n_read;
 120	struct delayed_work	push;
 121
 122	struct list_head	write_pool;
 123	int write_started;
 124	int write_allocated;
 125	struct kfifo		port_write_buf;
 126	wait_queue_head_t	drain_wait;	/* wait while writes drain */
 127	bool                    write_busy;
 128	wait_queue_head_t	close_wait;
 129	bool			suspended;	/* port suspended */
 130	bool			start_delayed;	/* delay start when suspended */
 131	struct async_icount	icount;
 132
 133	/* REVISIT this state ... */
 134	struct usb_cdc_line_coding port_line_coding;	/* 8-N-1 etc */
 135};
 136
 137static struct portmaster {
 138	struct mutex	lock;			/* protect open/close */
 139	struct gs_port	*port;
 140} ports[MAX_U_SERIAL_PORTS];
 141
 142#define GS_CLOSE_TIMEOUT		15		/* seconds */
 143
 144
 145
 146#ifdef VERBOSE_DEBUG
 147#ifndef pr_vdebug
 148#define pr_vdebug(fmt, arg...) \
 149	pr_debug(fmt, ##arg)
 150#endif /* pr_vdebug */
 151#else
 152#ifndef pr_vdebug
 153#define pr_vdebug(fmt, arg...) \
 154	({ if (0) pr_debug(fmt, ##arg); })
 155#endif /* pr_vdebug */
 156#endif
 157
 158/*-------------------------------------------------------------------------*/
 159
 160/* I/O glue between TTY (upper) and USB function (lower) driver layers */
 161
 162/*
 163 * gs_alloc_req
 164 *
 165 * Allocate a usb_request and its buffer.  Returns a pointer to the
 166 * usb_request or NULL if there is an error.
 167 */
 168struct usb_request *
 169gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
 170{
 171	struct usb_request *req;
 172
 173	req = usb_ep_alloc_request(ep, kmalloc_flags);
 174
 175	if (req != NULL) {
 176		req->length = len;
 177		req->buf = kmalloc(len, kmalloc_flags);
 178		if (req->buf == NULL) {
 179			usb_ep_free_request(ep, req);
 180			return NULL;
 181		}
 182	}
 183
 184	return req;
 185}
 186EXPORT_SYMBOL_GPL(gs_alloc_req);
 187
 188/*
 189 * gs_free_req
 190 *
 191 * Free a usb_request and its buffer.
 192 */
 193void gs_free_req(struct usb_ep *ep, struct usb_request *req)
 194{
 195	kfree(req->buf);
 196	usb_ep_free_request(ep, req);
 197}
 198EXPORT_SYMBOL_GPL(gs_free_req);
 199
 200/*
 201 * gs_send_packet
 202 *
 203 * If there is data to send, a packet is built in the given
 204 * buffer and the size is returned.  If there is no data to
 205 * send, 0 is returned.
 206 *
 207 * Called with port_lock held.
 208 */
 209static unsigned
 210gs_send_packet(struct gs_port *port, char *packet, unsigned size)
 211{
 212	unsigned len;
 213
 214	len = kfifo_len(&port->port_write_buf);
 215	if (len < size)
 216		size = len;
 217	if (size != 0)
 218		size = kfifo_out(&port->port_write_buf, packet, size);
 219	return size;
 220}
 221
 222/*
 223 * gs_start_tx
 224 *
 225 * This function finds available write requests, calls
 226 * gs_send_packet to fill these packets with data, and
 227 * continues until either there are no more write requests
 228 * available or no more data to send.  This function is
 229 * run whenever data arrives or write requests are available.
 230 *
 231 * Context: caller owns port_lock; port_usb is non-null.
 232 */
 233static int gs_start_tx(struct gs_port *port)
 234/*
 235__releases(&port->port_lock)
 236__acquires(&port->port_lock)
 237*/
 238{
 239	struct list_head	*pool = &port->write_pool;
 240	struct usb_ep		*in;
 241	int			status = 0;
 242	bool			do_tty_wake = false;
 243
 244	if (!port->port_usb)
 245		return status;
 246
 247	in = port->port_usb->in;
 248
 249	while (!port->write_busy && !list_empty(pool)) {
 250		struct usb_request	*req;
 251		int			len;
 252
 253		if (port->write_started >= QUEUE_SIZE)
 254			break;
 255
 256		req = list_entry(pool->next, struct usb_request, list);
 257		len = gs_send_packet(port, req->buf, in->maxpacket);
 258		if (len == 0) {
 259			wake_up_interruptible(&port->drain_wait);
 260			break;
 261		}
 262		do_tty_wake = true;
 263		port->icount.tx += len;
 264
 265		req->length = len;
 266		list_del(&req->list);
 267		req->zero = kfifo_is_empty(&port->port_write_buf);
 268
 269		pr_vdebug("ttyGS%d: tx len=%d, %3ph ...\n", port->port_num, len, req->buf);
 270
 271		/* Drop lock while we call out of driver; completions
 272		 * could be issued while we do so.  Disconnection may
 273		 * happen too; maybe immediately before we queue this!
 274		 *
 275		 * NOTE that we may keep sending data for a while after
 276		 * the TTY closed (dev->ioport->port_tty is NULL).
 277		 */
 278		port->write_busy = true;
 279		spin_unlock(&port->port_lock);
 280		status = usb_ep_queue(in, req, GFP_ATOMIC);
 281		spin_lock(&port->port_lock);
 282		port->write_busy = false;
 283
 284		if (status) {
 285			pr_debug("%s: %s %s err %d\n",
 286					__func__, "queue", in->name, status);
 287			list_add(&req->list, pool);
 288			break;
 289		}
 290
 291		port->write_started++;
 292
 293		/* abort immediately after disconnect */
 294		if (!port->port_usb)
 295			break;
 296	}
 297
 298	if (do_tty_wake)
 299		tty_port_tty_wakeup(&port->port);
 300	return status;
 301}
 302
 303/*
 304 * Context: caller owns port_lock, and port_usb is set
 305 */
 306static unsigned gs_start_rx(struct gs_port *port)
 307/*
 308__releases(&port->port_lock)
 309__acquires(&port->port_lock)
 310*/
 311{
 312	struct list_head	*pool = &port->read_pool;
 313	struct usb_ep		*out = port->port_usb->out;
 314
 315	while (!list_empty(pool)) {
 316		struct usb_request	*req;
 317		int			status;
 318		struct tty_struct	*tty;
 319
 320		/* no more rx if closed */
 321		tty = port->port.tty;
 322		if (!tty)
 323			break;
 324
 325		if (port->read_started >= QUEUE_SIZE)
 326			break;
 327
 328		req = list_entry(pool->next, struct usb_request, list);
 329		list_del(&req->list);
 330		req->length = out->maxpacket;
 331
 332		/* drop lock while we call out; the controller driver
 333		 * may need to call us back (e.g. for disconnect)
 334		 */
 335		spin_unlock(&port->port_lock);
 336		status = usb_ep_queue(out, req, GFP_ATOMIC);
 337		spin_lock(&port->port_lock);
 338
 339		if (status) {
 340			pr_debug("%s: %s %s err %d\n",
 341					__func__, "queue", out->name, status);
 342			list_add(&req->list, pool);
 343			break;
 344		}
 345		port->read_started++;
 346
 347		/* abort immediately after disconnect */
 348		if (!port->port_usb)
 349			break;
 350	}
 351	return port->read_started;
 352}
 353
 354/*
 355 * RX work takes data out of the RX queue and hands it up to the TTY
 356 * layer until it refuses to take any more data (or is throttled back).
 357 * Then it issues reads for any further data.
 358 *
 359 * If the RX queue becomes full enough that no usb_request is queued,
 360 * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
 361 * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
 362 * can be buffered before the TTY layer's buffers (currently 64 KB).
 363 */
 364static void gs_rx_push(struct work_struct *work)
 365{
 366	struct delayed_work	*w = to_delayed_work(work);
 367	struct gs_port		*port = container_of(w, struct gs_port, push);
 368	struct tty_struct	*tty;
 369	struct list_head	*queue = &port->read_queue;
 370	bool			disconnect = false;
 371	bool			do_push = false;
 372
 373	/* hand any queued data to the tty */
 374	spin_lock_irq(&port->port_lock);
 375	tty = port->port.tty;
 376	while (!list_empty(queue)) {
 377		struct usb_request	*req;
 378
 379		req = list_first_entry(queue, struct usb_request, list);
 380
 381		/* leave data queued if tty was rx throttled */
 382		if (tty && tty_throttled(tty))
 383			break;
 384
 385		switch (req->status) {
 386		case -ESHUTDOWN:
 387			disconnect = true;
 388			pr_vdebug("ttyGS%d: shutdown\n", port->port_num);
 389			break;
 390
 391		default:
 392			/* presumably a transient fault */
 393			pr_warn("ttyGS%d: unexpected RX status %d\n",
 394				port->port_num, req->status);
 395			fallthrough;
 396		case 0:
 397			/* normal completion */
 398			break;
 399		}
 400
 401		/* push data to (open) tty */
 402		if (req->actual && tty) {
 403			char		*packet = req->buf;
 404			unsigned	size = req->actual;
 405			unsigned	n;
 406			int		count;
 407
 408			/* we may have pushed part of this packet already... */
 409			n = port->n_read;
 410			if (n) {
 411				packet += n;
 412				size -= n;
 413			}
 414
 415			port->icount.rx += size;
 416			count = tty_insert_flip_string(&port->port, packet,
 417					size);
 418			if (count)
 419				do_push = true;
 420			if (count != size) {
 421				/* stop pushing; TTY layer can't handle more */
 422				port->n_read += count;
 423				pr_vdebug("ttyGS%d: rx block %d/%d\n",
 424					  port->port_num, count, req->actual);
 425				break;
 426			}
 427			port->n_read = 0;
 428		}
 429
 430		list_move(&req->list, &port->read_pool);
 431		port->read_started--;
 432	}
 433
 434	/* Push from tty to ldisc; this is handled by a workqueue,
 435	 * so we won't get callbacks and can hold port_lock
 436	 */
 437	if (do_push)
 438		tty_flip_buffer_push(&port->port);
 439
 440
 441	/* We want our data queue to become empty ASAP, keeping data
 442	 * in the tty and ldisc (not here).  If we couldn't push any
 443	 * this time around, RX may be starved, so wait until next jiffy.
 444	 *
 445	 * We may leave non-empty queue only when there is a tty, and
 446	 * either it is throttled or there is no more room in flip buffer.
 447	 */
 448	if (!list_empty(queue) && !tty_throttled(tty))
 449		schedule_delayed_work(&port->push, 1);
 450
 451	/* If we're still connected, refill the USB RX queue. */
 452	if (!disconnect && port->port_usb)
 453		gs_start_rx(port);
 454
 455	spin_unlock_irq(&port->port_lock);
 456}
 457
 458static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
 459{
 460	struct gs_port	*port = ep->driver_data;
 461
 462	/* Queue all received data until the tty layer is ready for it. */
 463	spin_lock(&port->port_lock);
 464	list_add_tail(&req->list, &port->read_queue);
 465	schedule_delayed_work(&port->push, 0);
 466	spin_unlock(&port->port_lock);
 467}
 468
 469static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
 470{
 471	struct gs_port	*port = ep->driver_data;
 472
 473	spin_lock(&port->port_lock);
 474	list_add(&req->list, &port->write_pool);
 475	port->write_started--;
 476
 477	switch (req->status) {
 478	default:
 479		/* presumably a transient fault */
 480		pr_warn("%s: unexpected %s status %d\n",
 481			__func__, ep->name, req->status);
 482		fallthrough;
 483	case 0:
 484		/* normal completion */
 485		gs_start_tx(port);
 486		break;
 487
 488	case -ESHUTDOWN:
 489		/* disconnect */
 490		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
 491		break;
 492	}
 493
 494	spin_unlock(&port->port_lock);
 495}
 496
 497static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
 498							 int *allocated)
 499{
 500	struct usb_request	*req;
 501
 502	while (!list_empty(head)) {
 503		req = list_entry(head->next, struct usb_request, list);
 504		list_del(&req->list);
 505		gs_free_req(ep, req);
 506		if (allocated)
 507			(*allocated)--;
 508	}
 509}
 510
 511static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
 512		void (*fn)(struct usb_ep *, struct usb_request *),
 513		int *allocated)
 514{
 515	int			i;
 516	struct usb_request	*req;
 517	int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
 518
 519	/* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
 520	 * do quite that many this time, don't fail ... we just won't
 521	 * be as speedy as we might otherwise be.
 522	 */
 523	for (i = 0; i < n; i++) {
 524		req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
 525		if (!req)
 526			return list_empty(head) ? -ENOMEM : 0;
 527		req->complete = fn;
 528		list_add_tail(&req->list, head);
 529		if (allocated)
 530			(*allocated)++;
 531	}
 532	return 0;
 533}
 534
 535/**
 536 * gs_start_io - start USB I/O streams
 537 * @port: port to use
 538 * Context: holding port_lock; port_tty and port_usb are non-null
 539 *
 540 * We only start I/O when something is connected to both sides of
 541 * this port.  If nothing is listening on the host side, we may
 542 * be pointlessly filling up our TX buffers and FIFO.
 543 */
 544static int gs_start_io(struct gs_port *port)
 545{
 546	struct list_head	*head = &port->read_pool;
 547	struct usb_ep		*ep = port->port_usb->out;
 548	int			status;
 549	unsigned		started;
 550
 551	/* Allocate RX and TX I/O buffers.  We can't easily do this much
 552	 * earlier (with GFP_KERNEL) because the requests are coupled to
 553	 * endpoints, as are the packet sizes we'll be using.  Different
 554	 * configurations may use different endpoints with a given port;
 555	 * and high speed vs full speed changes packet sizes too.
 556	 */
 557	status = gs_alloc_requests(ep, head, gs_read_complete,
 558		&port->read_allocated);
 559	if (status)
 560		return status;
 561
 562	status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
 563			gs_write_complete, &port->write_allocated);
 564	if (status) {
 565		gs_free_requests(ep, head, &port->read_allocated);
 566		return status;
 567	}
 568
 569	/* queue read requests */
 570	port->n_read = 0;
 571	started = gs_start_rx(port);
 572
 573	if (started) {
 574		gs_start_tx(port);
 575		/* Unblock any pending writes into our circular buffer, in case
 576		 * we didn't in gs_start_tx() */
 577		tty_port_tty_wakeup(&port->port);
 578	} else {
 579		/* Free reqs only if we are still connected */
 580		if (port->port_usb) {
 581			gs_free_requests(ep, head, &port->read_allocated);
 582			gs_free_requests(port->port_usb->in, &port->write_pool,
 583				&port->write_allocated);
 584		}
 585		status = -EIO;
 586	}
 587
 588	return status;
 589}
 590
 591static int gserial_wakeup_host(struct gserial *gser)
 592{
 593	struct usb_function	*func = &gser->func;
 594	struct usb_gadget	*gadget = func->config->cdev->gadget;
 595
 596	if (func->func_suspended)
 597		return usb_func_wakeup(func);
 598	else
 599		return usb_gadget_wakeup(gadget);
 600}
 601
 602/*-------------------------------------------------------------------------*/
 603
 604/* TTY Driver */
 605
 606/*
 607 * gs_open sets up the link between a gs_port and its associated TTY.
 608 * That link is broken *only* by TTY close(), and all driver methods
 609 * know that.
 610 */
 611static int gs_open(struct tty_struct *tty, struct file *file)
 612{
 613	int		port_num = tty->index;
 614	struct gs_port	*port;
 615	int		status = 0;
 616
 617	mutex_lock(&ports[port_num].lock);
 618	port = ports[port_num].port;
 619	if (!port) {
 620		status = -ENODEV;
 621		goto out;
 622	}
 623
 624	spin_lock_irq(&port->port_lock);
 625
 626	/* allocate circular buffer on first open */
 627	if (!kfifo_initialized(&port->port_write_buf)) {
 628
 629		spin_unlock_irq(&port->port_lock);
 630
 631		/*
 632		 * portmaster's mutex still protects from simultaneous open(),
 633		 * and close() can't happen, yet.
 634		 */
 635
 636		status = kfifo_alloc(&port->port_write_buf,
 637				     WRITE_BUF_SIZE, GFP_KERNEL);
 638		if (status) {
 639			pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
 640				 port_num, tty, file);
 641			goto out;
 642		}
 643
 644		spin_lock_irq(&port->port_lock);
 645	}
 646
 647	/* already open?  Great. */
 648	if (port->port.count++)
 649		goto exit_unlock_port;
 650
 651	tty->driver_data = port;
 652	port->port.tty = tty;
 653
 654	/* if connected, start the I/O stream */
 655	if (port->port_usb) {
 656		/* if port is suspended, wait resume to start I/0 stream */
 657		if (!port->suspended) {
 658			struct gserial	*gser = port->port_usb;
 659
 660			pr_debug("gs_open: start ttyGS%d\n", port->port_num);
 661			gs_start_io(port);
 662
 663			if (gser->connect)
 664				gser->connect(gser);
 665		} else {
 666			pr_debug("delay start of ttyGS%d\n", port->port_num);
 667			port->start_delayed = true;
 668		}
 669	}
 670
 671	pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
 672
 673exit_unlock_port:
 674	spin_unlock_irq(&port->port_lock);
 675out:
 676	mutex_unlock(&ports[port_num].lock);
 677	return status;
 678}
 679
 680static int gs_close_flush_done(struct gs_port *p)
 681{
 682	int cond;
 683
 684	/* return true on disconnect or empty buffer or if raced with open() */
 685	spin_lock_irq(&p->port_lock);
 686	cond = p->port_usb == NULL || !kfifo_len(&p->port_write_buf) ||
 687		p->port.count > 1;
 688	spin_unlock_irq(&p->port_lock);
 689
 690	return cond;
 691}
 692
 693static void gs_close(struct tty_struct *tty, struct file *file)
 694{
 695	struct gs_port *port = tty->driver_data;
 696	struct gserial	*gser;
 697
 698	spin_lock_irq(&port->port_lock);
 699
 700	if (port->port.count != 1) {
 701raced_with_open:
 702		if (port->port.count == 0)
 703			WARN_ON(1);
 704		else
 705			--port->port.count;
 706		goto exit;
 707	}
 708
 709	pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
 710
 711	gser = port->port_usb;
 712	if (gser && !port->suspended && gser->disconnect)
 713		gser->disconnect(gser);
 714
 715	/* wait for circular write buffer to drain, disconnect, or at
 716	 * most GS_CLOSE_TIMEOUT seconds; then discard the rest
 717	 */
 718	if (kfifo_len(&port->port_write_buf) > 0 && gser) {
 719		spin_unlock_irq(&port->port_lock);
 720		wait_event_interruptible_timeout(port->drain_wait,
 721					gs_close_flush_done(port),
 722					GS_CLOSE_TIMEOUT * HZ);
 723		spin_lock_irq(&port->port_lock);
 724
 725		if (port->port.count != 1)
 726			goto raced_with_open;
 727
 728		gser = port->port_usb;
 729	}
 730
 731	/* Iff we're disconnected, there can be no I/O in flight so it's
 732	 * ok to free the circular buffer; else just scrub it.  And don't
 733	 * let the push async work fire again until we're re-opened.
 734	 */
 735	if (gser == NULL)
 736		kfifo_free(&port->port_write_buf);
 737	else
 738		kfifo_reset(&port->port_write_buf);
 739
 740	port->start_delayed = false;
 741	port->port.count = 0;
 742	port->port.tty = NULL;
 743
 744	pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
 745			port->port_num, tty, file);
 746
 747	wake_up(&port->close_wait);
 748exit:
 749	spin_unlock_irq(&port->port_lock);
 750}
 751
 752static ssize_t gs_write(struct tty_struct *tty, const u8 *buf, size_t count)
 753{
 754	struct gs_port	*port = tty->driver_data;
 755	unsigned long	flags;
 756	int ret = 0;
 757	struct gserial  *gser = port->port_usb;
 758
 759	pr_vdebug("gs_write: ttyGS%d (%p) writing %zu bytes\n",
 760			port->port_num, tty, count);
 761
 762	spin_lock_irqsave(&port->port_lock, flags);
 763	if (count)
 764		count = kfifo_in(&port->port_write_buf, buf, count);
 765
 766	if (port->suspended) {
 767		spin_unlock_irqrestore(&port->port_lock, flags);
 768		ret = gserial_wakeup_host(gser);
 769		if (ret) {
 770			pr_debug("ttyGS%d: Remote wakeup failed:%d\n", port->port_num, ret);
 771			return count;
 772		}
 773		spin_lock_irqsave(&port->port_lock, flags);
 774	}
 775
 776	/* treat count == 0 as flush_chars() */
 777	if (port->port_usb)
 778		gs_start_tx(port);
 779	spin_unlock_irqrestore(&port->port_lock, flags);
 780
 781	return count;
 782}
 783
 784static int gs_put_char(struct tty_struct *tty, u8 ch)
 785{
 786	struct gs_port	*port = tty->driver_data;
 787	unsigned long	flags;
 788	int		status;
 789
 790	pr_vdebug("gs_put_char: (%d,%p) char=0x%x, called from %ps\n",
 791		port->port_num, tty, ch, __builtin_return_address(0));
 792
 793	spin_lock_irqsave(&port->port_lock, flags);
 794	status = kfifo_put(&port->port_write_buf, ch);
 795	spin_unlock_irqrestore(&port->port_lock, flags);
 796
 797	return status;
 798}
 799
 800static void gs_flush_chars(struct tty_struct *tty)
 801{
 802	struct gs_port	*port = tty->driver_data;
 803	unsigned long	flags;
 804	int ret = 0;
 805	struct gserial  *gser = port->port_usb;
 806
 807	pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
 808
 809	spin_lock_irqsave(&port->port_lock, flags);
 810	if (port->suspended) {
 811		spin_unlock_irqrestore(&port->port_lock, flags);
 812		ret = gserial_wakeup_host(gser);
 813		if (ret) {
 814			pr_debug("ttyGS%d: Remote wakeup failed:%d\n", port->port_num, ret);
 815			return;
 816		}
 817		spin_lock_irqsave(&port->port_lock, flags);
 818	}
 819
 820	if (port->port_usb)
 821		gs_start_tx(port);
 822	spin_unlock_irqrestore(&port->port_lock, flags);
 823}
 824
 825static unsigned int gs_write_room(struct tty_struct *tty)
 826{
 827	struct gs_port	*port = tty->driver_data;
 828	unsigned long	flags;
 829	unsigned int room = 0;
 830
 831	spin_lock_irqsave(&port->port_lock, flags);
 832	if (port->port_usb)
 833		room = kfifo_avail(&port->port_write_buf);
 834	spin_unlock_irqrestore(&port->port_lock, flags);
 835
 836	pr_vdebug("gs_write_room: (%d,%p) room=%u\n",
 837		port->port_num, tty, room);
 838
 839	return room;
 840}
 841
 842static unsigned int gs_chars_in_buffer(struct tty_struct *tty)
 843{
 844	struct gs_port	*port = tty->driver_data;
 845	unsigned long	flags;
 846	unsigned int	chars;
 847
 848	spin_lock_irqsave(&port->port_lock, flags);
 849	chars = kfifo_len(&port->port_write_buf);
 850	spin_unlock_irqrestore(&port->port_lock, flags);
 851
 852	pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%u\n",
 853		port->port_num, tty, chars);
 854
 855	return chars;
 856}
 857
 858/* undo side effects of setting TTY_THROTTLED */
 859static void gs_unthrottle(struct tty_struct *tty)
 860{
 861	struct gs_port		*port = tty->driver_data;
 862	unsigned long		flags;
 863
 864	spin_lock_irqsave(&port->port_lock, flags);
 865	if (port->port_usb) {
 866		/* Kickstart read queue processing.  We don't do xon/xoff,
 867		 * rts/cts, or other handshaking with the host, but if the
 868		 * read queue backs up enough we'll be NAKing OUT packets.
 869		 */
 870		pr_vdebug("ttyGS%d: unthrottle\n", port->port_num);
 871		schedule_delayed_work(&port->push, 0);
 872	}
 873	spin_unlock_irqrestore(&port->port_lock, flags);
 874}
 875
 876static int gs_break_ctl(struct tty_struct *tty, int duration)
 877{
 878	struct gs_port	*port = tty->driver_data;
 879	int		status = 0;
 880	struct gserial	*gser;
 881
 882	pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
 883			port->port_num, duration);
 884
 885	spin_lock_irq(&port->port_lock);
 886	gser = port->port_usb;
 887	if (gser && gser->send_break)
 888		status = gser->send_break(gser, duration);
 889	spin_unlock_irq(&port->port_lock);
 890
 891	return status;
 892}
 893
 894static int gs_get_icount(struct tty_struct *tty,
 895			 struct serial_icounter_struct *icount)
 896{
 897	struct gs_port *port = tty->driver_data;
 898	struct async_icount cnow;
 899	unsigned long flags;
 900
 901	spin_lock_irqsave(&port->port_lock, flags);
 902	cnow = port->icount;
 903	spin_unlock_irqrestore(&port->port_lock, flags);
 904
 905	icount->rx = cnow.rx;
 906	icount->tx = cnow.tx;
 907
 908	return 0;
 909}
 910
 911static const struct tty_operations gs_tty_ops = {
 912	.open =			gs_open,
 913	.close =		gs_close,
 914	.write =		gs_write,
 915	.put_char =		gs_put_char,
 916	.flush_chars =		gs_flush_chars,
 917	.write_room =		gs_write_room,
 918	.chars_in_buffer =	gs_chars_in_buffer,
 919	.unthrottle =		gs_unthrottle,
 920	.break_ctl =		gs_break_ctl,
 921	.get_icount =		gs_get_icount,
 922};
 923
 924/*-------------------------------------------------------------------------*/
 925
 926static struct tty_driver *gs_tty_driver;
 927
 928#ifdef CONFIG_U_SERIAL_CONSOLE
 929
 930static void gs_console_complete_out(struct usb_ep *ep, struct usb_request *req)
 931{
 932	struct gs_console *cons = req->context;
 933
 934	switch (req->status) {
 935	default:
 936		pr_warn("%s: unexpected %s status %d\n",
 937			__func__, ep->name, req->status);
 938		fallthrough;
 939	case 0:
 940		/* normal completion */
 941		spin_lock(&cons->lock);
 942		req->length = 0;
 943		schedule_work(&cons->work);
 944		spin_unlock(&cons->lock);
 945		break;
 946	case -ECONNRESET:
 947	case -ESHUTDOWN:
 948		/* disconnect */
 949		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
 950		break;
 951	}
 952}
 953
 954static void __gs_console_push(struct gs_console *cons)
 955{
 956	struct usb_request *req = cons->req;
 957	struct usb_ep *ep;
 958	size_t size;
 959
 960	if (!req)
 961		return;	/* disconnected */
 962
 963	if (req->length)
 964		return;	/* busy */
 965
 966	ep = cons->console.data;
 967	size = kfifo_out(&cons->buf, req->buf, ep->maxpacket);
 968	if (!size)
 969		return;
 970
 971	if (cons->missed && ep->maxpacket >= 64) {
 972		char buf[64];
 973		size_t len;
 974
 975		len = sprintf(buf, "\n[missed %zu bytes]\n", cons->missed);
 976		kfifo_in(&cons->buf, buf, len);
 977		cons->missed = 0;
 978	}
 979
 980	req->length = size;
 981
 982	spin_unlock_irq(&cons->lock);
 983	if (usb_ep_queue(ep, req, GFP_ATOMIC))
 984		req->length = 0;
 985	spin_lock_irq(&cons->lock);
 986}
 987
 988static void gs_console_work(struct work_struct *work)
 989{
 990	struct gs_console *cons = container_of(work, struct gs_console, work);
 991
 992	spin_lock_irq(&cons->lock);
 993
 994	__gs_console_push(cons);
 995
 996	spin_unlock_irq(&cons->lock);
 997}
 998
 999static void gs_console_write(struct console *co,
1000			     const char *buf, unsigned count)
1001{
1002	struct gs_console *cons = container_of(co, struct gs_console, console);
1003	unsigned long flags;
1004	size_t n;
1005
1006	spin_lock_irqsave(&cons->lock, flags);
1007
1008	n = kfifo_in(&cons->buf, buf, count);
1009	if (n < count)
1010		cons->missed += count - n;
1011
1012	if (cons->req && !cons->req->length)
1013		schedule_work(&cons->work);
1014
1015	spin_unlock_irqrestore(&cons->lock, flags);
1016}
1017
1018static struct tty_driver *gs_console_device(struct console *co, int *index)
1019{
1020	*index = co->index;
1021	return gs_tty_driver;
1022}
1023
1024static int gs_console_connect(struct gs_port *port)
1025{
1026	struct gs_console *cons = port->console;
1027	struct usb_request *req;
1028	struct usb_ep *ep;
1029
1030	if (!cons)
1031		return 0;
1032
1033	ep = port->port_usb->in;
1034	req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
1035	if (!req)
1036		return -ENOMEM;
1037	req->complete = gs_console_complete_out;
1038	req->context = cons;
1039	req->length = 0;
1040
1041	spin_lock(&cons->lock);
1042	cons->req = req;
1043	cons->console.data = ep;
1044	spin_unlock(&cons->lock);
1045
1046	pr_debug("ttyGS%d: console connected!\n", port->port_num);
1047
1048	schedule_work(&cons->work);
1049
1050	return 0;
1051}
1052
1053static void gs_console_disconnect(struct gs_port *port)
1054{
1055	struct gs_console *cons = port->console;
1056	struct usb_request *req;
1057	struct usb_ep *ep;
1058
1059	if (!cons)
1060		return;
1061
1062	spin_lock(&cons->lock);
1063
1064	req = cons->req;
1065	ep = cons->console.data;
1066	cons->req = NULL;
1067
1068	spin_unlock(&cons->lock);
1069
1070	if (!req)
1071		return;
1072
1073	usb_ep_dequeue(ep, req);
1074	gs_free_req(ep, req);
1075}
1076
1077static int gs_console_init(struct gs_port *port)
1078{
1079	struct gs_console *cons;
1080	int err;
1081
1082	if (port->console)
1083		return 0;
1084
1085	cons = kzalloc(sizeof(*port->console), GFP_KERNEL);
1086	if (!cons)
1087		return -ENOMEM;
1088
1089	strcpy(cons->console.name, "ttyGS");
1090	cons->console.write = gs_console_write;
1091	cons->console.device = gs_console_device;
1092	cons->console.flags = CON_PRINTBUFFER;
1093	cons->console.index = port->port_num;
1094
1095	INIT_WORK(&cons->work, gs_console_work);
1096	spin_lock_init(&cons->lock);
1097
1098	err = kfifo_alloc(&cons->buf, GS_CONSOLE_BUF_SIZE, GFP_KERNEL);
1099	if (err) {
1100		pr_err("ttyGS%d: allocate console buffer failed\n", port->port_num);
1101		kfree(cons);
1102		return err;
1103	}
1104
1105	port->console = cons;
1106	register_console(&cons->console);
1107
1108	spin_lock_irq(&port->port_lock);
1109	if (port->port_usb)
1110		gs_console_connect(port);
1111	spin_unlock_irq(&port->port_lock);
1112
1113	return 0;
1114}
1115
1116static void gs_console_exit(struct gs_port *port)
1117{
1118	struct gs_console *cons = port->console;
1119
1120	if (!cons)
1121		return;
1122
1123	unregister_console(&cons->console);
1124
1125	spin_lock_irq(&port->port_lock);
1126	if (cons->req)
1127		gs_console_disconnect(port);
1128	spin_unlock_irq(&port->port_lock);
1129
1130	cancel_work_sync(&cons->work);
1131	kfifo_free(&cons->buf);
1132	kfree(cons);
1133	port->console = NULL;
1134}
1135
1136ssize_t gserial_set_console(unsigned char port_num, const char *page, size_t count)
1137{
1138	struct gs_port *port;
1139	bool enable;
1140	int ret;
1141
1142	ret = kstrtobool(page, &enable);
1143	if (ret)
1144		return ret;
1145
1146	mutex_lock(&ports[port_num].lock);
1147	port = ports[port_num].port;
1148
1149	if (WARN_ON(port == NULL)) {
1150		ret = -ENXIO;
1151		goto out;
1152	}
1153
1154	if (enable)
1155		ret = gs_console_init(port);
1156	else
1157		gs_console_exit(port);
1158out:
1159	mutex_unlock(&ports[port_num].lock);
1160
1161	return ret < 0 ? ret : count;
1162}
1163EXPORT_SYMBOL_GPL(gserial_set_console);
1164
1165ssize_t gserial_get_console(unsigned char port_num, char *page)
1166{
1167	struct gs_port *port;
1168	ssize_t ret;
1169
1170	mutex_lock(&ports[port_num].lock);
1171	port = ports[port_num].port;
1172
1173	if (WARN_ON(port == NULL))
1174		ret = -ENXIO;
1175	else
1176		ret = sprintf(page, "%u\n", !!port->console);
1177
1178	mutex_unlock(&ports[port_num].lock);
1179
1180	return ret;
1181}
1182EXPORT_SYMBOL_GPL(gserial_get_console);
1183
1184#else
1185
1186static int gs_console_connect(struct gs_port *port)
1187{
1188	return 0;
1189}
1190
1191static void gs_console_disconnect(struct gs_port *port)
1192{
1193}
1194
1195static int gs_console_init(struct gs_port *port)
1196{
1197	return -ENOSYS;
1198}
1199
1200static void gs_console_exit(struct gs_port *port)
1201{
1202}
1203
1204#endif
1205
1206static int
1207gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
1208{
1209	struct gs_port	*port;
1210	int		ret = 0;
1211
1212	mutex_lock(&ports[port_num].lock);
1213	if (ports[port_num].port) {
1214		ret = -EBUSY;
1215		goto out;
1216	}
1217
1218	port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
1219	if (port == NULL) {
1220		ret = -ENOMEM;
1221		goto out;
1222	}
1223
1224	tty_port_init(&port->port);
1225	spin_lock_init(&port->port_lock);
1226	init_waitqueue_head(&port->drain_wait);
1227	init_waitqueue_head(&port->close_wait);
1228
1229	INIT_DELAYED_WORK(&port->push, gs_rx_push);
1230
1231	INIT_LIST_HEAD(&port->read_pool);
1232	INIT_LIST_HEAD(&port->read_queue);
1233	INIT_LIST_HEAD(&port->write_pool);
1234
1235	port->port_num = port_num;
1236	port->port_line_coding = *coding;
1237
1238	ports[port_num].port = port;
1239out:
1240	mutex_unlock(&ports[port_num].lock);
1241	return ret;
1242}
1243
1244static int gs_closed(struct gs_port *port)
1245{
1246	int cond;
1247
1248	spin_lock_irq(&port->port_lock);
1249	cond = port->port.count == 0;
1250	spin_unlock_irq(&port->port_lock);
1251
1252	return cond;
1253}
1254
1255static void gserial_free_port(struct gs_port *port)
1256{
1257	cancel_delayed_work_sync(&port->push);
1258	/* wait for old opens to finish */
1259	wait_event(port->close_wait, gs_closed(port));
1260	WARN_ON(port->port_usb != NULL);
1261	tty_port_destroy(&port->port);
1262	kfree(port);
1263}
1264
1265void gserial_free_line(unsigned char port_num)
1266{
1267	struct gs_port	*port;
1268
1269	mutex_lock(&ports[port_num].lock);
1270	if (!ports[port_num].port) {
1271		mutex_unlock(&ports[port_num].lock);
1272		return;
1273	}
1274	port = ports[port_num].port;
1275	gs_console_exit(port);
1276	ports[port_num].port = NULL;
1277	mutex_unlock(&ports[port_num].lock);
1278
1279	gserial_free_port(port);
1280	tty_unregister_device(gs_tty_driver, port_num);
1281}
1282EXPORT_SYMBOL_GPL(gserial_free_line);
1283
1284int gserial_alloc_line_no_console(unsigned char *line_num)
1285{
1286	struct usb_cdc_line_coding	coding;
1287	struct gs_port			*port;
1288	struct device			*tty_dev;
1289	int				ret;
1290	int				port_num;
1291
1292	coding.dwDTERate = cpu_to_le32(9600);
1293	coding.bCharFormat = 8;
1294	coding.bParityType = USB_CDC_NO_PARITY;
1295	coding.bDataBits = USB_CDC_1_STOP_BITS;
1296
1297	for (port_num = 0; port_num < MAX_U_SERIAL_PORTS; port_num++) {
1298		ret = gs_port_alloc(port_num, &coding);
1299		if (ret == -EBUSY)
1300			continue;
1301		if (ret)
1302			return ret;
1303		break;
1304	}
1305	if (ret)
1306		return ret;
1307
1308	/* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
1309
1310	port = ports[port_num].port;
1311	tty_dev = tty_port_register_device(&port->port,
1312			gs_tty_driver, port_num, NULL);
1313	if (IS_ERR(tty_dev)) {
1314		pr_err("%s: failed to register tty for port %d, err %ld\n",
1315				__func__, port_num, PTR_ERR(tty_dev));
1316
1317		ret = PTR_ERR(tty_dev);
1318		mutex_lock(&ports[port_num].lock);
1319		ports[port_num].port = NULL;
1320		mutex_unlock(&ports[port_num].lock);
1321		gserial_free_port(port);
1322		goto err;
1323	}
1324	*line_num = port_num;
1325err:
1326	return ret;
1327}
1328EXPORT_SYMBOL_GPL(gserial_alloc_line_no_console);
1329
1330int gserial_alloc_line(unsigned char *line_num)
1331{
1332	int ret = gserial_alloc_line_no_console(line_num);
1333
1334	if (!ret && !*line_num)
1335		gs_console_init(ports[*line_num].port);
1336
1337	return ret;
1338}
1339EXPORT_SYMBOL_GPL(gserial_alloc_line);
1340
1341/**
1342 * gserial_connect - notify TTY I/O glue that USB link is active
1343 * @gser: the function, set up with endpoints and descriptors
1344 * @port_num: which port is active
1345 * Context: any (usually from irq)
1346 *
1347 * This is called activate endpoints and let the TTY layer know that
1348 * the connection is active ... not unlike "carrier detect".  It won't
1349 * necessarily start I/O queues; unless the TTY is held open by any
1350 * task, there would be no point.  However, the endpoints will be
1351 * activated so the USB host can perform I/O, subject to basic USB
1352 * hardware flow control.
1353 *
1354 * Caller needs to have set up the endpoints and USB function in @dev
1355 * before calling this, as well as the appropriate (speed-specific)
1356 * endpoint descriptors, and also have allocate @port_num by calling
1357 * @gserial_alloc_line().
1358 *
1359 * Returns negative errno or zero.
1360 * On success, ep->driver_data will be overwritten.
1361 */
1362int gserial_connect(struct gserial *gser, u8 port_num)
1363{
1364	struct gs_port	*port;
1365	unsigned long	flags;
1366	int		status;
1367
1368	if (port_num >= MAX_U_SERIAL_PORTS)
1369		return -ENXIO;
1370
1371	port = ports[port_num].port;
1372	if (!port) {
1373		pr_err("serial line %d not allocated.\n", port_num);
1374		return -EINVAL;
1375	}
1376	if (port->port_usb) {
1377		pr_err("serial line %d is in use.\n", port_num);
1378		return -EBUSY;
1379	}
1380
1381	/* activate the endpoints */
1382	status = usb_ep_enable(gser->in);
1383	if (status < 0)
1384		return status;
1385	gser->in->driver_data = port;
1386
1387	status = usb_ep_enable(gser->out);
1388	if (status < 0)
1389		goto fail_out;
1390	gser->out->driver_data = port;
1391
1392	/* then tell the tty glue that I/O can work */
1393	spin_lock_irqsave(&port->port_lock, flags);
1394	gser->ioport = port;
1395	port->port_usb = gser;
1396
1397	/* REVISIT unclear how best to handle this state...
1398	 * we don't really couple it with the Linux TTY.
1399	 */
1400	gser->port_line_coding = port->port_line_coding;
1401
1402	/* REVISIT if waiting on "carrier detect", signal. */
1403
1404	/* if it's already open, start I/O ... and notify the serial
1405	 * protocol about open/close status (connect/disconnect).
1406	 */
1407	if (port->port.count) {
1408		pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
1409		gs_start_io(port);
1410		if (gser->connect)
1411			gser->connect(gser);
1412	} else {
1413		if (gser->disconnect)
1414			gser->disconnect(gser);
1415	}
1416
1417	status = gs_console_connect(port);
1418	spin_unlock_irqrestore(&port->port_lock, flags);
1419
1420	return status;
1421
1422fail_out:
1423	usb_ep_disable(gser->in);
1424	return status;
1425}
1426EXPORT_SYMBOL_GPL(gserial_connect);
1427/**
1428 * gserial_disconnect - notify TTY I/O glue that USB link is inactive
1429 * @gser: the function, on which gserial_connect() was called
1430 * Context: any (usually from irq)
1431 *
1432 * This is called to deactivate endpoints and let the TTY layer know
1433 * that the connection went inactive ... not unlike "hangup".
1434 *
1435 * On return, the state is as if gserial_connect() had never been called;
1436 * there is no active USB I/O on these endpoints.
1437 */
1438void gserial_disconnect(struct gserial *gser)
1439{
1440	struct gs_port	*port = gser->ioport;
1441	unsigned long	flags;
1442
1443	if (!port)
1444		return;
1445
1446	spin_lock_irqsave(&serial_port_lock, flags);
1447
1448	/* tell the TTY glue not to do I/O here any more */
1449	spin_lock(&port->port_lock);
1450
1451	gs_console_disconnect(port);
1452
1453	/* REVISIT as above: how best to track this? */
1454	port->port_line_coding = gser->port_line_coding;
1455
1456	port->port_usb = NULL;
1457	gser->ioport = NULL;
1458	if (port->port.count > 0) {
1459		wake_up_interruptible(&port->drain_wait);
1460		if (port->port.tty)
1461			tty_hangup(port->port.tty);
1462	}
1463	port->suspended = false;
1464	spin_unlock(&port->port_lock);
1465	spin_unlock_irqrestore(&serial_port_lock, flags);
1466
1467	/* disable endpoints, aborting down any active I/O */
1468	usb_ep_disable(gser->out);
1469	usb_ep_disable(gser->in);
1470
1471	/* finally, free any unused/unusable I/O buffers */
1472	spin_lock_irqsave(&port->port_lock, flags);
1473	if (port->port.count == 0)
1474		kfifo_free(&port->port_write_buf);
1475	gs_free_requests(gser->out, &port->read_pool, NULL);
1476	gs_free_requests(gser->out, &port->read_queue, NULL);
1477	gs_free_requests(gser->in, &port->write_pool, NULL);
1478
1479	port->read_allocated = port->read_started =
1480		port->write_allocated = port->write_started = 0;
1481
1482	spin_unlock_irqrestore(&port->port_lock, flags);
1483}
1484EXPORT_SYMBOL_GPL(gserial_disconnect);
1485
1486void gserial_suspend(struct gserial *gser)
1487{
1488	struct gs_port	*port;
1489	unsigned long	flags;
1490
1491	spin_lock_irqsave(&serial_port_lock, flags);
1492	port = gser->ioport;
1493
1494	if (!port) {
1495		spin_unlock_irqrestore(&serial_port_lock, flags);
1496		return;
1497	}
1498
1499	if (port->write_busy || port->write_started) {
1500		/* Wakeup to host if there are ongoing transfers */
1501		spin_unlock_irqrestore(&serial_port_lock, flags);
1502		if (!gserial_wakeup_host(gser))
1503			return;
1504		spin_lock_irqsave(&serial_port_lock, flags);
1505	}
1506
1507	spin_lock(&port->port_lock);
1508	spin_unlock(&serial_port_lock);
1509	port->suspended = true;
1510	port->start_delayed = true;
1511	spin_unlock_irqrestore(&port->port_lock, flags);
1512}
1513EXPORT_SYMBOL_GPL(gserial_suspend);
1514
1515void gserial_resume(struct gserial *gser)
1516{
1517	struct gs_port *port;
1518	unsigned long	flags;
1519
1520	spin_lock_irqsave(&serial_port_lock, flags);
1521	port = gser->ioport;
1522
1523	if (!port) {
1524		spin_unlock_irqrestore(&serial_port_lock, flags);
1525		return;
1526	}
1527
1528	spin_lock(&port->port_lock);
1529	spin_unlock(&serial_port_lock);
1530	port->suspended = false;
1531	if (!port->start_delayed) {
1532		spin_unlock_irqrestore(&port->port_lock, flags);
1533		return;
1534	}
1535
1536	pr_debug("delayed start ttyGS%d\n", port->port_num);
1537	gs_start_io(port);
1538	if (gser->connect)
1539		gser->connect(gser);
1540	port->start_delayed = false;
1541	spin_unlock_irqrestore(&port->port_lock, flags);
1542}
1543EXPORT_SYMBOL_GPL(gserial_resume);
1544
1545static int __init userial_init(void)
1546{
1547	struct tty_driver *driver;
1548	unsigned			i;
1549	int				status;
1550
1551	driver = tty_alloc_driver(MAX_U_SERIAL_PORTS, TTY_DRIVER_REAL_RAW |
1552			TTY_DRIVER_DYNAMIC_DEV);
1553	if (IS_ERR(driver))
1554		return PTR_ERR(driver);
1555
1556	driver->driver_name = "g_serial";
1557	driver->name = "ttyGS";
1558	/* uses dynamically assigned dev_t values */
1559
1560	driver->type = TTY_DRIVER_TYPE_SERIAL;
1561	driver->subtype = SERIAL_TYPE_NORMAL;
1562	driver->init_termios = tty_std_termios;
1563
1564	/* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
1565	 * MS-Windows.  Otherwise, most of these flags shouldn't affect
1566	 * anything unless we were to actually hook up to a serial line.
1567	 */
1568	driver->init_termios.c_cflag =
1569			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
1570	driver->init_termios.c_ispeed = 9600;
1571	driver->init_termios.c_ospeed = 9600;
1572
1573	tty_set_operations(driver, &gs_tty_ops);
1574	for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
1575		mutex_init(&ports[i].lock);
1576
1577	/* export the driver ... */
1578	status = tty_register_driver(driver);
1579	if (status) {
1580		pr_err("%s: cannot register, err %d\n",
1581				__func__, status);
1582		goto fail;
1583	}
1584
1585	gs_tty_driver = driver;
1586
1587	pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
1588			MAX_U_SERIAL_PORTS,
1589			str_plural(MAX_U_SERIAL_PORTS));
1590
1591	return status;
1592fail:
1593	tty_driver_kref_put(driver);
1594	return status;
1595}
1596module_init(userial_init);
1597
1598static void __exit userial_cleanup(void)
1599{
1600	tty_unregister_driver(gs_tty_driver);
1601	tty_driver_kref_put(gs_tty_driver);
1602	gs_tty_driver = NULL;
1603}
1604module_exit(userial_cleanup);
1605
1606MODULE_DESCRIPTION("utilities for USB gadget \"serial port\"/TTY support");
1607MODULE_LICENSE("GPL");