drivers/usb/gadget/function/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 ([email protected])
   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 ([email protected])
  11  * Copyright (C) 2000 Peter Berger ([email protected])
  12  * Copyright (C) 2000 Al Borchers ([email protected])
  13  */
  14
  15 /* #define VERBOSE_DEBUG */
  16
  17 #include <linux/kernel.h>
  18 #include <linux/sched.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/device.h>
  21 #include <linux/delay.h>
  22 #include <linux/tty.h>
  23 #include <linux/tty_flip.h>
  24 #include <linux/slab.h>
  25 #include <linux/export.h>
  26 #include <linux/module.h>
  27 #include <linux/console.h>
  28 #include <linux/kthread.h>
  29 #include <linux/kfifo.h>
  30
  31 #include "u_serial.h"
  32
  33
  34 /*
  35  * This component encapsulates the TTY layer glue needed to provide basic
  36  * "serial port" functionality through the USB gadget stack.  Each such
  37  * port is exposed through a /dev/ttyGS* node.
  38  *
  39  * After this module has been loaded, the individual TTY port can be requested
  40  * (gserial_alloc_line()) and it will stay available until they are removed
  41  * (gserial_free_line()). Each one may be connected to a USB function
  42  * (gserial_connect), or disconnected (with gserial_disconnect) when the USB
  43  * host issues a config change event. Data can only flow when the port is
  44  * connected to the host.
  45  *
  46  * A given TTY port can be made available in multiple configurations.
  47  * For example, each one might expose a ttyGS0 node which provides a
  48  * login application.  In one case that might use CDC ACM interface 0,
  49  * while another configuration might use interface 3 for that.  The
  50  * work to handle that (including descriptor management) is not part
  51  * of this component.
  52  *
  53  * Configurations may expose more than one TTY port.  For example, if
  54  * ttyGS0 provides login service, then ttyGS1 might provide dialer access
  55  * for a telephone or fax link.  And ttyGS2 might be something that just
  56  * needs a simple byte stream interface for some messaging protocol that
  57  * is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
  58  *
  59  *
  60  * gserial is the lifecycle interface, used by USB functions
  61  * gs_port is the I/O nexus, used by the tty driver
  62  * tty_struct links to the tty/filesystem framework
  63  *
  64  * gserial <---> gs_port ... links will be null when the USB link is
  65  * inactive; managed by gserial_{connect,disconnect}().  each gserial
  66  * instance can wrap its own USB control protocol.
  67  *      gserial->ioport == usb_ep->driver_data ... gs_port
  68  *      gs_port->port_usb ... gserial
  69  *
  70  * gs_port <---> tty_struct ... links will be null when the TTY file
  71  * isn't opened; managed by gs_open()/gs_close()
  72  *      gserial->port_tty ... tty_struct
  73  *      tty_struct->driver_data ... gserial
  74  */
  75
  76 /* RX and TX queues can buffer QUEUE_SIZE packets before they hit the
  77  * next layer of buffering.  For TX that's a circular buffer; for RX
  78  * consider it a NOP.  A third layer is provided by the TTY code.
  79  */
  80 #define QUEUE_SIZE              16
  81 #define WRITE_BUF_SIZE          8192            /* TX only */
  82 #define GS_CONSOLE_BUF_SIZE     8192
  83
  84 /* console info */
  85 struct gscons_info {
  86         struct gs_port          *port;
  87         struct task_struct      *console_thread;
  88         struct kfifo            con_buf;
  89         /* protect the buf and busy flag */
  90         spinlock_t              con_lock;
  91         int                     req_busy;
  92         struct usb_request      *console_req;
  93 };
  94
  95 /*
  96  * The port structure holds info for each port, one for each minor number
  97  * (and thus for each /dev/ node).
  98  */
  99 struct gs_port {
 100         struct tty_port         port;
 101         spinlock_t              port_lock;      /* guard port_* access */
 102
 103         struct gserial          *port_usb;
 104
 105         bool                    openclose;      /* open/close in progress */
 106         u8                      port_num;
 107
 108         struct list_head        read_pool;
 109         int read_started;
 110         int read_allocated;
 111         struct list_head        read_queue;
 112         unsigned                n_read;
 113         struct tasklet_struct   push;
 114
 115         struct list_head        write_pool;
 116         int write_started;
 117         int write_allocated;
 118         struct kfifo            port_write_buf;
 119         wait_queue_head_t       drain_wait;     /* wait while writes drain */
 120         bool                    write_busy;
 121         wait_queue_head_t       close_wait;
 122
 123         /* REVISIT this state ... */
 124         struct usb_cdc_line_coding port_line_coding;    /* 8-N-1 etc */
 125 };
 126
 127 static struct portmaster {
 128         struct mutex    lock;                   /* protect open/close */
 129         struct gs_port  *port;
 130 } ports[MAX_U_SERIAL_PORTS];
 131
 132 #define GS_CLOSE_TIMEOUT                15              /* seconds */
 133
 134
 135
 136 #ifdef VERBOSE_DEBUG
 137 #ifndef pr_vdebug
 138 #define pr_vdebug(fmt, arg...) \
 139         pr_debug(fmt, ##arg)
 140 #endif /* pr_vdebug */
 141 #else
 142 #ifndef pr_vdebug
 143 #define pr_vdebug(fmt, arg...) \
 144         ({ if (0) pr_debug(fmt, ##arg); })
 145 #endif /* pr_vdebug */
 146 #endif
 147
 148 /*-------------------------------------------------------------------------*/
 149
 150 /* I/O glue between TTY (upper) and USB function (lower) driver layers */
 151
 152 /*
 153  * gs_alloc_req
 154  *
 155  * Allocate a usb_request and its buffer.  Returns a pointer to the
 156  * usb_request or NULL if there is an error.
 157  */
 158 struct usb_request *
 159 gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
 160 {
 161         struct usb_request *req;
 162
 163         req = usb_ep_alloc_request(ep, kmalloc_flags);
 164
 165         if (req != NULL) {
 166                 req->length = len;
 167                 req->buf = kmalloc(len, kmalloc_flags);
 168                 if (req->buf == NULL) {
 169                         usb_ep_free_request(ep, req);
 170                         return NULL;
 171                 }
 172         }
 173
 174         return req;
 175 }
 176 EXPORT_SYMBOL_GPL(gs_alloc_req);
 177
 178 /*
 179  * gs_free_req
 180  *
 181  * Free a usb_request and its buffer.
 182  */
 183 void gs_free_req(struct usb_ep *ep, struct usb_request *req)
 184 {
 185         kfree(req->buf);
 186         usb_ep_free_request(ep, req);
 187 }
 188 EXPORT_SYMBOL_GPL(gs_free_req);
 189
 190 /*
 191  * gs_send_packet
 192  *
 193  * If there is data to send, a packet is built in the given
 194  * buffer and the size is returned.  If there is no data to
 195  * send, 0 is returned.
 196  *
 197  * Called with port_lock held.
 198  */
 199 static unsigned
 200 gs_send_packet(struct gs_port *port, char *packet, unsigned size)
 201 {
 202         unsigned len;
 203
 204         len = kfifo_len(&port->port_write_buf);
 205         if (len < size)
 206                 size = len;
 207         if (size != 0)
 208                 size = kfifo_out(&port->port_write_buf, packet, size);
 209         return size;
 210 }
 211
 212 /*
 213  * gs_start_tx
 214  *
 215  * This function finds available write requests, calls
 216  * gs_send_packet to fill these packets with data, and
 217  * continues until either there are no more write requests
 218  * available or no more data to send.  This function is
 219  * run whenever data arrives or write requests are available.
 220  *
 221  * Context: caller owns port_lock; port_usb is non-null.
 222  */
 223 static int gs_start_tx(struct gs_port *port)
 224 /*
 225 __releases(&port->port_lock)
 226 __acquires(&port->port_lock)
 227 */
 228 {
 229         struct list_head        *pool = &port->write_pool;
 230         struct usb_ep           *in;
 231         int                     status = 0;
 232         bool                    do_tty_wake = false;
 233
 234         if (!port->port_usb)
 235                 return status;
 236
 237         in = port->port_usb->in;
 238
 239         while (!port->write_busy && !list_empty(pool)) {
 240                 struct usb_request      *req;
 241                 int                     len;
 242
 243                 if (port->write_started >= QUEUE_SIZE)
 244                         break;
 245
 246                 req = list_entry(pool->next, struct usb_request, list);
 247                 len = gs_send_packet(port, req->buf, in->maxpacket);
 248                 if (len == 0) {
 249                         wake_up_interruptible(&port->drain_wait);
 250                         break;
 251                 }
 252                 do_tty_wake = true;
 253
 254                 req->length = len;
 255                 list_del(&req->list);
 256                 req->zero = kfifo_is_empty(&port->port_write_buf);
 257
 258                 pr_vdebug("ttyGS%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
 259                           port->port_num, len, *((u8 *)req->buf),
 260                           *((u8 *)req->buf+1), *((u8 *)req->buf+2));
 261
 262                 /* Drop lock while we call out of driver; completions
 263                  * could be issued while we do so.  Disconnection may
 264                  * happen too; maybe immediately before we queue this!
 265                  *
 266                  * NOTE that we may keep sending data for a while after
 267                  * the TTY closed (dev->ioport->port_tty is NULL).
 268                  */
 269                 port->write_busy = true;
 270                 spin_unlock(&port->port_lock);
 271                 status = usb_ep_queue(in, req, GFP_ATOMIC);
 272                 spin_lock(&port->port_lock);
 273                 port->write_busy = false;
 274
 275                 if (status) {
 276                         pr_debug("%s: %s %s err %d\n",
 277                                         __func__, "queue", in->name, status);
 278                         list_add(&req->list, pool);
 279                         break;
 280                 }
 281
 282                 port->write_started++;
 283
 284                 /* abort immediately after disconnect */
 285                 if (!port->port_usb)
 286                         break;
 287         }
 288
 289         if (do_tty_wake && port->port.tty)
 290                 tty_wakeup(port->port.tty);
 291         return status;
 292 }
 293
 294 /*
 295  * Context: caller owns port_lock, and port_usb is set
 296  */
 297 static unsigned gs_start_rx(struct gs_port *port)
 298 /*
 299 __releases(&port->port_lock)
 300 __acquires(&port->port_lock)
 301 */
 302 {
 303         struct list_head        *pool = &port->read_pool;
 304         struct usb_ep           *out = port->port_usb->out;
 305
 306         while (!list_empty(pool)) {
 307                 struct usb_request      *req;
 308                 int                     status;
 309                 struct tty_struct       *tty;
 310
 311                 /* no more rx if closed */
 312                 tty = port->port.tty;
 313                 if (!tty)
 314                         break;
 315
 316                 if (port->read_started >= QUEUE_SIZE)
 317                         break;
 318
 319                 req = list_entry(pool->next, struct usb_request, list);
 320                 list_del(&req->list);
 321                 req->length = out->maxpacket;
 322
 323                 /* drop lock while we call out; the controller driver
 324                  * may need to call us back (e.g. for disconnect)
 325                  */
 326                 spin_unlock(&port->port_lock);
 327                 status = usb_ep_queue(out, req, GFP_ATOMIC);
 328                 spin_lock(&port->port_lock);
 329
 330                 if (status) {
 331                         pr_debug("%s: %s %s err %d\n",
 332                                         __func__, "queue", out->name, status);
 333                         list_add(&req->list, pool);
 334                         break;
 335                 }
 336                 port->read_started++;
 337
 338                 /* abort immediately after disconnect */
 339                 if (!port->port_usb)
 340                         break;
 341         }
 342         return port->read_started;
 343 }
 344
 345 /*
 346  * RX tasklet takes data out of the RX queue and hands it up to the TTY
 347  * layer until it refuses to take any more data (or is throttled back).
 348  * Then it issues reads for any further data.
 349  *
 350  * If the RX queue becomes full enough that no usb_request is queued,
 351  * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
 352  * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
 353  * can be buffered before the TTY layer's buffers (currently 64 KB).
 354  */
 355 static void gs_rx_push(unsigned long _port)
 356 {
 357         struct gs_port          *port = (void *)_port;
 358         struct tty_struct       *tty;
 359         struct list_head        *queue = &port->read_queue;
 360         bool                    disconnect = false;
 361         bool                    do_push = false;
 362
 363         /* hand any queued data to the tty */
 364         spin_lock_irq(&port->port_lock);
 365         tty = port->port.tty;
 366         while (!list_empty(queue)) {
 367                 struct usb_request      *req;
 368
 369                 req = list_first_entry(queue, struct usb_request, list);
 370
 371                 /* leave data queued if tty was rx throttled */
 372                 if (tty && tty_throttled(tty))
 373                         break;
 374
 375                 switch (req->status) {
 376                 case -ESHUTDOWN:
 377                         disconnect = true;
 378                         pr_vdebug("ttyGS%d: shutdown\n", port->port_num);
 379                         break;
 380
 381                 default:
 382                         /* presumably a transient fault */
 383                         pr_warn("ttyGS%d: unexpected RX status %d\n",
 384                                 port->port_num, req->status);
 385                         /* FALLTHROUGH */
 386                 case 0:
 387                         /* normal completion */
 388                         break;
 389                 }
 390
 391                 /* push data to (open) tty */
 392                 if (req->actual && tty) {
 393                         char            *packet = req->buf;
 394                         unsigned        size = req->actual;
 395                         unsigned        n;
 396                         int             count;
 397
 398                         /* we may have pushed part of this packet already... */
 399                         n = port->n_read;
 400                         if (n) {
 401                                 packet += n;
 402                                 size -= n;
 403                         }
 404
 405                         count = tty_insert_flip_string(&port->port, packet,
 406                                         size);
 407                         if (count)
 408                                 do_push = true;
 409                         if (count != size) {
 410                                 /* stop pushing; TTY layer can't handle more */
 411                                 port->n_read += count;
 412                                 pr_vdebug("ttyGS%d: rx block %d/%d\n",
 413                                           port->port_num, count, req->actual);
 414                                 break;
 415                         }
 416                         port->n_read = 0;
 417                 }
 418
 419                 list_move(&req->list, &port->read_pool);
 420                 port->read_started--;
 421         }
 422
 423         /* Push from tty to ldisc; this is handled by a workqueue,
 424          * so we won't get callbacks and can hold port_lock
 425          */
 426         if (do_push)
 427                 tty_flip_buffer_push(&port->port);
 428
 429
 430         /* We want our data queue to become empty ASAP, keeping data
 431          * in the tty and ldisc (not here).  If we couldn't push any
 432          * this time around, there may be trouble unless there's an
 433          * implicit tty_unthrottle() call on its way...
 434          *
 435          * REVISIT we should probably add a timer to keep the tasklet
 436          * from starving ... but it's not clear that case ever happens.
 437          */
 438         if (!list_empty(queue) && tty) {
 439                 if (!tty_throttled(tty)) {
 440                         if (do_push)
 441                                 tasklet_schedule(&port->push);
 442                         else
 443                                 pr_warn("ttyGS%d: RX not scheduled?\n",
 444                                         port->port_num);
 445                 }
 446         }
 447
 448         /* If we're still connected, refill the USB RX queue. */
 449         if (!disconnect && port->port_usb)
 450                 gs_start_rx(port);
 451
 452         spin_unlock_irq(&port->port_lock);
 453 }
 454
 455 static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
 456 {
 457         struct gs_port  *port = ep->driver_data;
 458
 459         /* Queue all received data until the tty layer is ready for it. */
 460         spin_lock(&port->port_lock);
 461         list_add_tail(&req->list, &port->read_queue);
 462         tasklet_schedule(&port->push);
 463         spin_unlock(&port->port_lock);
 464 }
 465
 466 static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
 467 {
 468         struct gs_port  *port = ep->driver_data;
 469
 470         spin_lock(&port->port_lock);
 471         list_add(&req->list, &port->write_pool);
 472         port->write_started--;
 473
 474         switch (req->status) {
 475         default:
 476                 /* presumably a transient fault */
 477                 pr_warn("%s: unexpected %s status %d\n",
 478                         __func__, ep->name, req->status);
 479                 /* FALL THROUGH */
 480         case 0:
 481                 /* normal completion */
 482                 gs_start_tx(port);
 483                 break;
 484
 485         case -ESHUTDOWN:
 486                 /* disconnect */
 487                 pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
 488                 break;
 489         }
 490
 491         spin_unlock(&port->port_lock);
 492 }
 493
 494 static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
 495                                                          int *allocated)
 496 {
 497         struct usb_request      *req;
 498
 499         while (!list_empty(head)) {
 500                 req = list_entry(head->next, struct usb_request, list);
 501                 list_del(&req->list);
 502                 gs_free_req(ep, req);
 503                 if (allocated)
 504                         (*allocated)--;
 505         }
 506 }
 507
 508 static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
 509                 void (*fn)(struct usb_ep *, struct usb_request *),
 510                 int *allocated)
 511 {
 512         int                     i;
 513         struct usb_request      *req;
 514         int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
 515
 516         /* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
 517          * do quite that many this time, don't fail ... we just won't
 518          * be as speedy as we might otherwise be.
 519          */
 520         for (i = 0; i < n; i++) {
 521                 req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
 522                 if (!req)
 523                         return list_empty(head) ? -ENOMEM : 0;
 524                 req->complete = fn;
 525                 list_add_tail(&req->list, head);
 526                 if (allocated)
 527                         (*allocated)++;
 528         }
 529         return 0;
 530 }
 531
 532 /**
 533  * gs_start_io - start USB I/O streams
 534  * @dev: encapsulates endpoints to use
 535  * Context: holding port_lock; port_tty and port_usb are non-null
 536  *
 537  * We only start I/O when something is connected to both sides of
 538  * this port.  If nothing is listening on the host side, we may
 539  * be pointlessly filling up our TX buffers and FIFO.
 540  */
 541 static int gs_start_io(struct gs_port *port)
 542 {
 543         struct list_head        *head = &port->read_pool;
 544         struct usb_ep           *ep = port->port_usb->out;
 545         int                     status;
 546         unsigned                started;
 547
 548         /* Allocate RX and TX I/O buffers.  We can't easily do this much
 549          * earlier (with GFP_KERNEL) because the requests are coupled to
 550          * endpoints, as are the packet sizes we'll be using.  Different
 551          * configurations may use different endpoints with a given port;
 552          * and high speed vs full speed changes packet sizes too.
 553          */
 554         status = gs_alloc_requests(ep, head, gs_read_complete,
 555                 &port->read_allocated);
 556         if (status)
 557                 return status;
 558
 559         status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
 560                         gs_write_complete, &port->write_allocated);
 561         if (status) {
 562                 gs_free_requests(ep, head, &port->read_allocated);
 563                 return status;
 564         }
 565
 566         /* queue read requests */
 567         port->n_read = 0;
 568         started = gs_start_rx(port);
 569
 570         /* unblock any pending writes into our circular buffer */
 571         if (started) {
 572                 tty_wakeup(port->port.tty);
 573         } else {
 574                 gs_free_requests(ep, head, &port->read_allocated);
 575                 gs_free_requests(port->port_usb->in, &port->write_pool,
 576                         &port->write_allocated);
 577                 status = -EIO;
 578         }
 579
 580         return status;
 581 }
 582
 583 /*-------------------------------------------------------------------------*/
 584
 585 /* TTY Driver */
 586
 587 /*
 588  * gs_open sets up the link between a gs_port and its associated TTY.
 589  * That link is broken *only* by TTY close(), and all driver methods
 590  * know that.
 591  */
 592 static int gs_open(struct tty_struct *tty, struct file *file)
 593 {
 594         int             port_num = tty->index;
 595         struct gs_port  *port;
 596         int             status;
 597
 598         do {
 599                 mutex_lock(&ports[port_num].lock);
 600                 port = ports[port_num].port;
 601                 if (!port)
 602                         status = -ENODEV;
 603                 else {
 604                         spin_lock_irq(&port->port_lock);
 605
 606                         /* already open?  Great. */
 607                         if (port->port.count) {
 608                                 status = 0;
 609                                 port->port.count++;
 610
 611                         /* currently opening/closing? wait ... */
 612                         } else if (port->openclose) {
 613                                 status = -EBUSY;
 614
 615                         /* ... else we do the work */
 616                         } else {
 617                                 status = -EAGAIN;
 618                                 port->openclose = true;
 619                         }
 620                         spin_unlock_irq(&port->port_lock);
 621                 }
 622                 mutex_unlock(&ports[port_num].lock);
 623
 624                 switch (status) {
 625                 default:
 626                         /* fully handled */
 627                         return status;
 628                 case -EAGAIN:
 629                         /* must do the work */
 630                         break;
 631                 case -EBUSY:
 632                         /* wait for EAGAIN task to finish */
 633                         msleep(1);
 634                         /* REVISIT could have a waitchannel here, if
 635                          * concurrent open performance is important
 636                          */
 637                         break;
 638                 }
 639         } while (status != -EAGAIN);
 640
 641         /* Do the "real open" */
 642         spin_lock_irq(&port->port_lock);
 643
 644         /* allocate circular buffer on first open */
 645         if (!kfifo_initialized(&port->port_write_buf)) {
 646
 647                 spin_unlock_irq(&port->port_lock);
 648                 status = kfifo_alloc(&port->port_write_buf,
 649                                      WRITE_BUF_SIZE, GFP_KERNEL);
 650                 spin_lock_irq(&port->port_lock);
 651
 652                 if (status) {
 653                         pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
 654                                 port->port_num, tty, file);
 655                         port->openclose = false;
 656                         goto exit_unlock_port;
 657                 }
 658         }
 659
 660         /* REVISIT if REMOVED (ports[].port NULL), abort the open
 661          * to let rmmod work faster (but this way isn't wrong).
 662          */
 663
 664         /* REVISIT maybe wait for "carrier detect" */
 665
 666         tty->driver_data = port;
 667         port->port.tty = tty;
 668
 669         port->port.count = 1;
 670         port->openclose = false;
 671
 672         /* if connected, start the I/O stream */
 673         if (port->port_usb) {
 674                 struct gserial  *gser = port->port_usb;
 675
 676                 pr_debug("gs_open: start ttyGS%d\n", port->port_num);
 677                 gs_start_io(port);
 678
 679                 if (gser->connect)
 680                         gser->connect(gser);
 681         }
 682
 683         pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
 684
 685         status = 0;
 686
 687 exit_unlock_port:
 688         spin_unlock_irq(&port->port_lock);
 689         return status;
 690 }
 691
 692 static int gs_writes_finished(struct gs_port *p)
 693 {
 694         int cond;
 695
 696         /* return true on disconnect or empty buffer */
 697         spin_lock_irq(&p->port_lock);
 698         cond = (p->port_usb == NULL) || !kfifo_len(&p->port_write_buf);
 699         spin_unlock_irq(&p->port_lock);
 700
 701         return cond;
 702 }
 703
 704 static void gs_close(struct tty_struct *tty, struct file *file)
 705 {
 706         struct gs_port *port = tty->driver_data;
 707         struct gserial  *gser;
 708
 709         spin_lock_irq(&port->port_lock);
 710
 711         if (port->port.count != 1) {
 712                 if (port->port.count == 0)
 713                         WARN_ON(1);
 714                 else
 715                         --port->port.count;
 716                 goto exit;
 717         }
 718
 719         pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
 720
 721         /* mark port as closing but in use; we can drop port lock
 722          * and sleep if necessary
 723          */
 724         port->openclose = true;
 725         port->port.count = 0;
 726
 727         gser = port->port_usb;
 728         if (gser && gser->disconnect)
 729                 gser->disconnect(gser);
 730
 731         /* wait for circular write buffer to drain, disconnect, or at
 732          * most GS_CLOSE_TIMEOUT seconds; then discard the rest
 733          */
 734         if (kfifo_len(&port->port_write_buf) > 0 && gser) {
 735                 spin_unlock_irq(&port->port_lock);
 736                 wait_event_interruptible_timeout(port->drain_wait,
 737                                         gs_writes_finished(port),
 738                                         GS_CLOSE_TIMEOUT * HZ);
 739                 spin_lock_irq(&port->port_lock);
 740                 gser = port->port_usb;
 741         }
 742
 743         /* Iff we're disconnected, there can be no I/O in flight so it's
 744          * ok to free the circular buffer; else just scrub it.  And don't
 745          * let the push tasklet fire again until we're re-opened.
 746          */
 747         if (gser == NULL)
 748                 kfifo_free(&port->port_write_buf);
 749         else
 750                 kfifo_reset(&port->port_write_buf);
 751
 752         port->port.tty = NULL;
 753
 754         port->openclose = false;
 755
 756         pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
 757                         port->port_num, tty, file);
 758
 759         wake_up(&port->close_wait);
 760 exit:
 761         spin_unlock_irq(&port->port_lock);
 762 }
 763
 764 static int gs_write(struct tty_struct *tty, const unsigned char *buf, int count)
 765 {
 766         struct gs_port  *port = tty->driver_data;
 767         unsigned long   flags;
 768
 769         pr_vdebug("gs_write: ttyGS%d (%p) writing %d bytes\n",
 770                         port->port_num, tty, count);
 771
 772         spin_lock_irqsave(&port->port_lock, flags);
 773         if (count)
 774                 count = kfifo_in(&port->port_write_buf, buf, count);
 775         /* treat count == 0 as flush_chars() */
 776         if (port->port_usb)
 777                 gs_start_tx(port);
 778         spin_unlock_irqrestore(&port->port_lock, flags);
 779
 780         return count;
 781 }
 782
 783 static int gs_put_char(struct tty_struct *tty, unsigned char ch)
 784 {
 785         struct gs_port  *port = tty->driver_data;
 786         unsigned long   flags;
 787         int             status;
 788
 789         pr_vdebug("gs_put_char: (%d,%p) char=0x%x, called from %ps\n",
 790                 port->port_num, tty, ch, __builtin_return_address(0));
 791
 792         spin_lock_irqsave(&port->port_lock, flags);
 793         status = kfifo_put(&port->port_write_buf, ch);
 794         spin_unlock_irqrestore(&port->port_lock, flags);
 795
 796         return status;
 797 }
 798
 799 static void gs_flush_chars(struct tty_struct *tty)
 800 {
 801         struct gs_port  *port = tty->driver_data;
 802         unsigned long   flags;
 803
 804         pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
 805
 806         spin_lock_irqsave(&port->port_lock, flags);
 807         if (port->port_usb)
 808                 gs_start_tx(port);
 809         spin_unlock_irqrestore(&port->port_lock, flags);
 810 }
 811
 812 static int gs_write_room(struct tty_struct *tty)
 813 {
 814         struct gs_port  *port = tty->driver_data;
 815         unsigned long   flags;
 816         int             room = 0;
 817
 818         spin_lock_irqsave(&port->port_lock, flags);
 819         if (port->port_usb)
 820                 room = kfifo_avail(&port->port_write_buf);
 821         spin_unlock_irqrestore(&port->port_lock, flags);
 822
 823         pr_vdebug("gs_write_room: (%d,%p) room=%d\n",
 824                 port->port_num, tty, room);
 825
 826         return room;
 827 }
 828
 829 static int gs_chars_in_buffer(struct tty_struct *tty)
 830 {
 831         struct gs_port  *port = tty->driver_data;
 832         unsigned long   flags;
 833         int             chars = 0;
 834
 835         spin_lock_irqsave(&port->port_lock, flags);
 836         chars = kfifo_len(&port->port_write_buf);
 837         spin_unlock_irqrestore(&port->port_lock, flags);
 838
 839         pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%d\n",
 840                 port->port_num, tty, chars);
 841
 842         return chars;
 843 }
 844
 845 /* undo side effects of setting TTY_THROTTLED */
 846 static void gs_unthrottle(struct tty_struct *tty)
 847 {
 848         struct gs_port          *port = tty->driver_data;
 849         unsigned long           flags;
 850
 851         spin_lock_irqsave(&port->port_lock, flags);
 852         if (port->port_usb) {
 853                 /* Kickstart read queue processing.  We don't do xon/xoff,
 854                  * rts/cts, or other handshaking with the host, but if the
 855                  * read queue backs up enough we'll be NAKing OUT packets.
 856                  */
 857                 tasklet_schedule(&port->push);
 858                 pr_vdebug("ttyGS%d: unthrottle\n", port->port_num);
 859         }
 860         spin_unlock_irqrestore(&port->port_lock, flags);
 861 }
 862
 863 static int gs_break_ctl(struct tty_struct *tty, int duration)
 864 {
 865         struct gs_port  *port = tty->driver_data;
 866         int             status = 0;
 867         struct gserial  *gser;
 868
 869         pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
 870                         port->port_num, duration);
 871
 872         spin_lock_irq(&port->port_lock);
 873         gser = port->port_usb;
 874         if (gser && gser->send_break)
 875                 status = gser->send_break(gser, duration);
 876         spin_unlock_irq(&port->port_lock);
 877
 878         return status;
 879 }
 880
 881 static const struct tty_operations gs_tty_ops = {
 882         .open =                 gs_open,
 883         .close =                gs_close,
 884         .write =                gs_write,
 885         .put_char =             gs_put_char,
 886         .flush_chars =          gs_flush_chars,
 887         .write_room =           gs_write_room,
 888         .chars_in_buffer =      gs_chars_in_buffer,
 889         .unthrottle =           gs_unthrottle,
 890         .break_ctl =            gs_break_ctl,
 891 };
 892
 893 /*-------------------------------------------------------------------------*/
 894
 895 static struct tty_driver *gs_tty_driver;
 896
 897 #ifdef CONFIG_U_SERIAL_CONSOLE
 898
 899 static struct gscons_info gscons_info;
 900 static struct console gserial_cons;
 901
 902 static struct usb_request *gs_request_new(struct usb_ep *ep)
 903 {
 904         struct usb_request *req = usb_ep_alloc_request(ep, GFP_ATOMIC);
 905         if (!req)
 906                 return NULL;
 907
 908         req->buf = kmalloc(ep->maxpacket, GFP_ATOMIC);
 909         if (!req->buf) {
 910                 usb_ep_free_request(ep, req);
 911                 return NULL;
 912         }
 913
 914         return req;
 915 }
 916
 917 static void gs_request_free(struct usb_request *req, struct usb_ep *ep)
 918 {
 919         if (!req)
 920                 return;
 921
 922         kfree(req->buf);
 923         usb_ep_free_request(ep, req);
 924 }
 925
 926 static void gs_complete_out(struct usb_ep *ep, struct usb_request *req)
 927 {
 928         struct gscons_info *info = &gscons_info;
 929
 930         switch (req->status) {
 931         default:
 932                 pr_warn("%s: unexpected %s status %d\n",
 933                         __func__, ep->name, req->status);
 934                 /* fall through */
 935         case 0:
 936                 /* normal completion */
 937                 spin_lock(&info->con_lock);
 938                 info->req_busy = 0;
 939                 spin_unlock(&info->con_lock);
 940
 941                 wake_up_process(info->console_thread);
 942                 break;
 943         case -ESHUTDOWN:
 944                 /* disconnect */
 945                 pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
 946                 break;
 947         }
 948 }
 949
 950 static int gs_console_connect(int port_num)
 951 {
 952         struct gscons_info *info = &gscons_info;
 953         struct gs_port *port;
 954         struct usb_ep *ep;
 955
 956         if (port_num != gserial_cons.index) {
 957                 pr_err("%s: port num [%d] is not support console\n",
 958                        __func__, port_num);
 959                 return -ENXIO;
 960         }
 961
 962         port = ports[port_num].port;
 963         ep = port->port_usb->in;
 964         if (!info->console_req) {
 965                 info->console_req = gs_request_new(ep);
 966                 if (!info->console_req)
 967                         return -ENOMEM;
 968                 info->console_req->complete = gs_complete_out;
 969         }
 970
 971         info->port = port;
 972         spin_lock(&info->con_lock);
 973         info->req_busy = 0;
 974         spin_unlock(&info->con_lock);
 975         pr_vdebug("port[%d] console connect!\n", port_num);
 976         return 0;
 977 }
 978
 979 static void gs_console_disconnect(struct usb_ep *ep)
 980 {
 981         struct gscons_info *info = &gscons_info;
 982         struct usb_request *req = info->console_req;
 983
 984         gs_request_free(req, ep);
 985         info->console_req = NULL;
 986 }
 987
 988 static int gs_console_thread(void *data)
 989 {
 990         struct gscons_info *info = &gscons_info;
 991         struct gs_port *port;
 992         struct usb_request *req;
 993         struct usb_ep *ep;
 994         int xfer, ret, count, size;
 995
 996         do {
 997                 port = info->port;
 998                 set_current_state(TASK_INTERRUPTIBLE);
 999                 if (!port || !port->port_usb
1000                     || !port->port_usb->in || !info->console_req)
1001                         goto sched;
1002
1003                 req = info->console_req;
1004                 ep = port->port_usb->in;
1005
1006                 spin_lock_irq(&info->con_lock);
1007                 count = kfifo_len(&info->con_buf);
1008                 size = ep->maxpacket;
1009
1010                 if (count > 0 && !info->req_busy) {
1011                         set_current_state(TASK_RUNNING);
1012                         if (count < size)
1013                                 size = count;
1014
1015                         xfer = kfifo_out(&info->con_buf, req->buf, size);
1016                         req->length = xfer;
1017
1018                         spin_unlock(&info->con_lock);
1019                         ret = usb_ep_queue(ep, req, GFP_ATOMIC);
1020                         spin_lock(&info->con_lock);
1021                         if (ret < 0)
1022                                 info->req_busy = 0;
1023                         else
1024                                 info->req_busy = 1;
1025
1026                         spin_unlock_irq(&info->con_lock);
1027                 } else {
1028                         spin_unlock_irq(&info->con_lock);
1029 sched:
1030                         if (kthread_should_stop()) {
1031                                 set_current_state(TASK_RUNNING);
1032                                 break;
1033                         }
1034                         schedule();
1035                 }
1036         } while (1);
1037
1038         return 0;
1039 }
1040
1041 static int gs_console_setup(struct console *co, char *options)
1042 {
1043         struct gscons_info *info = &gscons_info;
1044         int status;
1045
1046         info->port = NULL;
1047         info->console_req = NULL;
1048         info->req_busy = 0;
1049         spin_lock_init(&info->con_lock);
1050
1051         status = kfifo_alloc(&info->con_buf, GS_CONSOLE_BUF_SIZE, GFP_KERNEL);
1052         if (status) {
1053                 pr_err("%s: allocate console buffer failed\n", __func__);
1054                 return status;
1055         }
1056
1057         info->console_thread = kthread_create(gs_console_thread,
1058                                               co, "gs_console");
1059         if (IS_ERR(info->console_thread)) {
1060                 pr_err("%s: cannot create console thread\n", __func__);
1061                 kfifo_free(&info->con_buf);
1062                 return PTR_ERR(info->console_thread);
1063         }
1064         wake_up_process(info->console_thread);
1065
1066         return 0;
1067 }
1068
1069 static void gs_console_write(struct console *co,
1070                              const char *buf, unsigned count)
1071 {
1072         struct gscons_info *info = &gscons_info;
1073         unsigned long flags;
1074
1075         spin_lock_irqsave(&info->con_lock, flags);
1076         kfifo_in(&info->con_buf, buf, count);
1077         spin_unlock_irqrestore(&info->con_lock, flags);
1078
1079         wake_up_process(info->console_thread);
1080 }
1081
1082 static struct tty_driver *gs_console_device(struct console *co, int *index)
1083 {
1084         struct tty_driver **p = (struct tty_driver **)co->data;
1085
1086         if (!*p)
1087                 return NULL;
1088
1089         *index = co->index;
1090         return *p;
1091 }
1092
1093 static struct console gserial_cons = {
1094         .name =         "ttyGS",
1095         .write =        gs_console_write,
1096         .device =       gs_console_device,
1097         .setup =        gs_console_setup,
1098         .flags =        CON_PRINTBUFFER,
1099         .index =        -1,
1100         .data =         &gs_tty_driver,
1101 };
1102
1103 static void gserial_console_init(void)
1104 {
1105         register_console(&gserial_cons);
1106 }
1107
1108 static void gserial_console_exit(void)
1109 {
1110         struct gscons_info *info = &gscons_info;
1111
1112         unregister_console(&gserial_cons);
1113         if (!IS_ERR_OR_NULL(info->console_thread))
1114                 kthread_stop(info->console_thread);
1115         kfifo_free(&info->con_buf);
1116 }
1117
1118 #else
1119
1120 static int gs_console_connect(int port_num)
1121 {
1122         return 0;
1123 }
1124
1125 static void gs_console_disconnect(struct usb_ep *ep)
1126 {
1127 }
1128
1129 static void gserial_console_init(void)
1130 {
1131 }
1132
1133 static void gserial_console_exit(void)
1134 {
1135 }
1136
1137 #endif
1138
1139 static int
1140 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
1141 {
1142         struct gs_port  *port;
1143         int             ret = 0;
1144
1145         mutex_lock(&ports[port_num].lock);
1146         if (ports[port_num].port) {
1147                 ret = -EBUSY;
1148                 goto out;
1149         }
1150
1151         port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
1152         if (port == NULL) {
1153                 ret = -ENOMEM;
1154                 goto out;
1155         }
1156
1157         tty_port_init(&port->port);
1158         spin_lock_init(&port->port_lock);
1159         init_waitqueue_head(&port->drain_wait);
1160         init_waitqueue_head(&port->close_wait);
1161
1162         tasklet_init(&port->push, gs_rx_push, (unsigned long) port);
1163
1164         INIT_LIST_HEAD(&port->read_pool);
1165         INIT_LIST_HEAD(&port->read_queue);
1166         INIT_LIST_HEAD(&port->write_pool);
1167
1168         port->port_num = port_num;
1169         port->port_line_coding = *coding;
1170
1171         ports[port_num].port = port;
1172 out:
1173         mutex_unlock(&ports[port_num].lock);
1174         return ret;
1175 }
1176
1177 static int gs_closed(struct gs_port *port)
1178 {
1179         int cond;
1180
1181         spin_lock_irq(&port->port_lock);
1182         cond = (port->port.count == 0) && !port->openclose;
1183         spin_unlock_irq(&port->port_lock);
1184         return cond;
1185 }
1186
1187 static void gserial_free_port(struct gs_port *port)
1188 {
1189         tasklet_kill(&port->push);
1190         /* wait for old opens to finish */
1191         wait_event(port->close_wait, gs_closed(port));
1192         WARN_ON(port->port_usb != NULL);
1193         tty_port_destroy(&port->port);
1194         kfree(port);
1195 }
1196
1197 void gserial_free_line(unsigned char port_num)
1198 {
1199         struct gs_port  *port;
1200
1201         mutex_lock(&ports[port_num].lock);
1202         if (WARN_ON(!ports[port_num].port)) {
1203                 mutex_unlock(&ports[port_num].lock);
1204                 return;
1205         }
1206         port = ports[port_num].port;
1207         ports[port_num].port = NULL;
1208         mutex_unlock(&ports[port_num].lock);
1209
1210         gserial_free_port(port);
1211         tty_unregister_device(gs_tty_driver, port_num);
1212         gserial_console_exit();
1213 }
1214 EXPORT_SYMBOL_GPL(gserial_free_line);
1215
1216 int gserial_alloc_line(unsigned char *line_num)
1217 {
1218         struct usb_cdc_line_coding      coding;
1219         struct device                   *tty_dev;
1220         int                             ret;
1221         int                             port_num;
1222
1223         coding.dwDTERate = cpu_to_le32(9600);
1224         coding.bCharFormat = 8;
1225         coding.bParityType = USB_CDC_NO_PARITY;
1226         coding.bDataBits = USB_CDC_1_STOP_BITS;
1227
1228         for (port_num = 0; port_num < MAX_U_SERIAL_PORTS; port_num++) {
1229                 ret = gs_port_alloc(port_num, &coding);
1230                 if (ret == -EBUSY)
1231                         continue;
1232                 if (ret)
1233                         return ret;
1234                 break;
1235         }
1236         if (ret)
1237                 return ret;
1238
1239         /* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
1240
1241         tty_dev = tty_port_register_device(&ports[port_num].port->port,
1242                         gs_tty_driver, port_num, NULL);
1243         if (IS_ERR(tty_dev)) {
1244                 struct gs_port  *port;
1245                 pr_err("%s: failed to register tty for port %d, err %ld\n",
1246                                 __func__, port_num, PTR_ERR(tty_dev));
1247
1248                 ret = PTR_ERR(tty_dev);
1249                 port = ports[port_num].port;
1250                 ports[port_num].port = NULL;
1251                 gserial_free_port(port);
1252                 goto err;
1253         }
1254         *line_num = port_num;
1255         gserial_console_init();
1256 err:
1257         return ret;
1258 }
1259 EXPORT_SYMBOL_GPL(gserial_alloc_line);
1260
1261 /**
1262  * gserial_connect - notify TTY I/O glue that USB link is active
1263  * @gser: the function, set up with endpoints and descriptors
1264  * @port_num: which port is active
1265  * Context: any (usually from irq)
1266  *
1267  * This is called activate endpoints and let the TTY layer know that
1268  * the connection is active ... not unlike "carrier detect".  It won't
1269  * necessarily start I/O queues; unless the TTY is held open by any
1270  * task, there would be no point.  However, the endpoints will be
1271  * activated so the USB host can perform I/O, subject to basic USB
1272  * hardware flow control.
1273  *
1274  * Caller needs to have set up the endpoints and USB function in @dev
1275  * before calling this, as well as the appropriate (speed-specific)
1276  * endpoint descriptors, and also have allocate @port_num by calling
1277  * @gserial_alloc_line().
1278  *
1279  * Returns negative errno or zero.
1280  * On success, ep->driver_data will be overwritten.
1281  */
1282 int gserial_connect(struct gserial *gser, u8 port_num)
1283 {
1284         struct gs_port  *port;
1285         unsigned long   flags;
1286         int             status;
1287
1288         if (port_num >= MAX_U_SERIAL_PORTS)
1289                 return -ENXIO;
1290
1291         port = ports[port_num].port;
1292         if (!port) {
1293                 pr_err("serial line %d not allocated.\n", port_num);
1294                 return -EINVAL;
1295         }
1296         if (port->port_usb) {
1297                 pr_err("serial line %d is in use.\n", port_num);
1298                 return -EBUSY;
1299         }
1300
1301         /* activate the endpoints */
1302         status = usb_ep_enable(gser->in);
1303         if (status < 0)
1304                 return status;
1305         gser->in->driver_data = port;
1306
1307         status = usb_ep_enable(gser->out);
1308         if (status < 0)
1309                 goto fail_out;
1310         gser->out->driver_data = port;
1311
1312         /* then tell the tty glue that I/O can work */
1313         spin_lock_irqsave(&port->port_lock, flags);
1314         gser->ioport = port;
1315         port->port_usb = gser;
1316
1317         /* REVISIT unclear how best to handle this state...
1318          * we don't really couple it with the Linux TTY.
1319          */
1320         gser->port_line_coding = port->port_line_coding;
1321
1322         /* REVISIT if waiting on "carrier detect", signal. */
1323
1324         /* if it's already open, start I/O ... and notify the serial
1325          * protocol about open/close status (connect/disconnect).
1326          */
1327         if (port->port.count) {
1328                 pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
1329                 gs_start_io(port);
1330                 if (gser->connect)
1331                         gser->connect(gser);
1332         } else {
1333                 if (gser->disconnect)
1334                         gser->disconnect(gser);
1335         }
1336
1337         status = gs_console_connect(port_num);
1338         spin_unlock_irqrestore(&port->port_lock, flags);
1339
1340         return status;
1341
1342 fail_out:
1343         usb_ep_disable(gser->in);
1344         return status;
1345 }
1346 EXPORT_SYMBOL_GPL(gserial_connect);
1347 /**
1348  * gserial_disconnect - notify TTY I/O glue that USB link is inactive
1349  * @gser: the function, on which gserial_connect() was called
1350  * Context: any (usually from irq)
1351  *
1352  * This is called to deactivate endpoints and let the TTY layer know
1353  * that the connection went inactive ... not unlike "hangup".
1354  *
1355  * On return, the state is as if gserial_connect() had never been called;
1356  * there is no active USB I/O on these endpoints.
1357  */
1358 void gserial_disconnect(struct gserial *gser)
1359 {
1360         struct gs_port  *port = gser->ioport;
1361         unsigned long   flags;
1362
1363         if (!port)
1364                 return;
1365
1366         /* tell the TTY glue not to do I/O here any more */
1367         spin_lock_irqsave(&port->port_lock, flags);
1368
1369         /* REVISIT as above: how best to track this? */
1370         port->port_line_coding = gser->port_line_coding;
1371
1372         port->port_usb = NULL;
1373         gser->ioport = NULL;
1374         if (port->port.count > 0 || port->openclose) {
1375                 wake_up_interruptible(&port->drain_wait);
1376                 if (port->port.tty)
1377                         tty_hangup(port->port.tty);
1378         }
1379         spin_unlock_irqrestore(&port->port_lock, flags);
1380
1381         /* disable endpoints, aborting down any active I/O */
1382         usb_ep_disable(gser->out);
1383         usb_ep_disable(gser->in);
1384
1385         /* finally, free any unused/unusable I/O buffers */
1386         spin_lock_irqsave(&port->port_lock, flags);
1387         if (port->port.count == 0 && !port->openclose)
1388                 kfifo_free(&port->port_write_buf);
1389         gs_free_requests(gser->out, &port->read_pool, NULL);
1390         gs_free_requests(gser->out, &port->read_queue, NULL);
1391         gs_free_requests(gser->in, &port->write_pool, NULL);
1392
1393         port->read_allocated = port->read_started =
1394                 port->write_allocated = port->write_started = 0;
1395
1396         gs_console_disconnect(gser->in);
1397         spin_unlock_irqrestore(&port->port_lock, flags);
1398 }
1399 EXPORT_SYMBOL_GPL(gserial_disconnect);
1400
1401 static int userial_init(void)
1402 {
1403         unsigned                        i;
1404         int                             status;
1405
1406         gs_tty_driver = alloc_tty_driver(MAX_U_SERIAL_PORTS);
1407         if (!gs_tty_driver)
1408                 return -ENOMEM;
1409
1410         gs_tty_driver->driver_name = "g_serial";
1411         gs_tty_driver->name = "ttyGS";
1412         /* uses dynamically assigned dev_t values */
1413
1414         gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
1415         gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
1416         gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
1417         gs_tty_driver->init_termios = tty_std_termios;
1418
1419         /* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
1420          * MS-Windows.  Otherwise, most of these flags shouldn't affect
1421          * anything unless we were to actually hook up to a serial line.
1422          */
1423         gs_tty_driver->init_termios.c_cflag =
1424                         B9600 | CS8 | CREAD | HUPCL | CLOCAL;
1425         gs_tty_driver->init_termios.c_ispeed = 9600;
1426         gs_tty_driver->init_termios.c_ospeed = 9600;
1427
1428         tty_set_operations(gs_tty_driver, &gs_tty_ops);
1429         for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
1430                 mutex_init(&ports[i].lock);
1431
1432         /* export the driver ... */
1433         status = tty_register_driver(gs_tty_driver);
1434         if (status) {
1435                 pr_err("%s: cannot register, err %d\n",
1436                                 __func__, status);
1437                 goto fail;
1438         }
1439
1440         pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
1441                         MAX_U_SERIAL_PORTS,
1442                         (MAX_U_SERIAL_PORTS == 1) ? "" : "s");
1443
1444         return status;
1445 fail:
1446         put_tty_driver(gs_tty_driver);
1447         gs_tty_driver = NULL;
1448         return status;
1449 }
1450 module_init(userial_init);
1451
1452 static void userial_cleanup(void)
1453 {
1454         tty_unregister_driver(gs_tty_driver);
1455         put_tty_driver(gs_tty_driver);
1456         gs_tty_driver = NULL;
1457 }
1458 module_exit(userial_cleanup);
1459
1460 MODULE_LICENSE("GPL");