drivers/usb/serial/generic.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * USB Serial Converter Generic functions
   4  *
   5  * Copyright (C) 2010 - 2013 Johan Hovold (jhovold@gmail.com)
   6  * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
   7  *
   8  *      This program is free software; you can redistribute it and/or
   9  *      modify it under the terms of the GNU General Public License version
  10  *      2 as published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/sched/signal.h>
  15 #include <linux/errno.h>
  16 #include <linux/slab.h>
  17 #include <linux/sysrq.h>
  18 #include <linux/tty.h>
  19 #include <linux/tty_flip.h>
  20 #include <linux/module.h>
  21 #include <linux/moduleparam.h>
  22 #include <linux/usb.h>
  23 #include <linux/usb/serial.h>
  24 #include <linux/uaccess.h>
  25 #include <linux/kfifo.h>
  26 #include <linux/serial.h>
  27
  28 #ifdef CONFIG_USB_SERIAL_GENERIC
  29
  30 static __u16 vendor  = 0x05f9;
  31 static __u16 product = 0xffff;
  32
  33 module_param(vendor, ushort, 0);
  34 MODULE_PARM_DESC(vendor, "User specified USB idVendor");
  35
  36 module_param(product, ushort, 0);
  37 MODULE_PARM_DESC(product, "User specified USB idProduct");
  38
  39 static struct usb_device_id generic_device_ids[2]; /* Initially all zeroes. */
  40
  41 static int usb_serial_generic_probe(struct usb_serial *serial,
  42                                         const struct usb_device_id *id)
  43 {
  44         struct device *dev = &serial->interface->dev;
  45
  46         dev_info(dev, "The \"generic\" usb-serial driver is only for testing and one-off prototypes.\n");
  47         dev_info(dev, "Tell linux-usb@vger.kernel.org to add your device to a proper driver.\n");
  48
  49         return 0;
  50 }
  51
  52 static int usb_serial_generic_calc_num_ports(struct usb_serial *serial,
  53                                         struct usb_serial_endpoints *epds)
  54 {
  55         struct device *dev = &serial->interface->dev;
  56         int num_ports;
  57
  58         num_ports = max(epds->num_bulk_in, epds->num_bulk_out);
  59
  60         if (num_ports == 0) {
  61                 dev_err(dev, "device has no bulk endpoints\n");
  62                 return -ENODEV;
  63         }
  64
  65         return num_ports;
  66 }
  67
  68 static struct usb_serial_driver usb_serial_generic_device = {
  69         .driver = {
  70                 .owner =        THIS_MODULE,
  71                 .name =         "generic",
  72         },
  73         .id_table =             generic_device_ids,
  74         .probe =                usb_serial_generic_probe,
  75         .calc_num_ports =       usb_serial_generic_calc_num_ports,
  76         .throttle =             usb_serial_generic_throttle,
  77         .unthrottle =           usb_serial_generic_unthrottle,
  78         .resume =               usb_serial_generic_resume,
  79 };
  80
  81 static struct usb_serial_driver * const serial_drivers[] = {
  82         &usb_serial_generic_device, NULL
  83 };
  84
  85 #endif
  86
  87 int usb_serial_generic_register(void)
  88 {
  89         int retval = 0;
  90
  91 #ifdef CONFIG_USB_SERIAL_GENERIC
  92         generic_device_ids[0].idVendor = vendor;
  93         generic_device_ids[0].idProduct = product;
  94         generic_device_ids[0].match_flags =
  95                 USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_PRODUCT;
  96
  97         retval = usb_serial_register_drivers(serial_drivers,
  98                         "usbserial_generic", generic_device_ids);
  99 #endif
 100         return retval;
 101 }
 102
 103 void usb_serial_generic_deregister(void)
 104 {
 105 #ifdef CONFIG_USB_SERIAL_GENERIC
 106         usb_serial_deregister_drivers(serial_drivers);
 107 #endif
 108 }
 109
 110 int usb_serial_generic_open(struct tty_struct *tty, struct usb_serial_port *port)
 111 {
 112         int result = 0;
 113         unsigned long flags;
 114
 115         spin_lock_irqsave(&port->lock, flags);
 116         port->throttled = 0;
 117         port->throttle_req = 0;
 118         spin_unlock_irqrestore(&port->lock, flags);
 119
 120         if (port->bulk_in_size)
 121                 result = usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
 122
 123         return result;
 124 }
 125 EXPORT_SYMBOL_GPL(usb_serial_generic_open);
 126
 127 void usb_serial_generic_close(struct usb_serial_port *port)
 128 {
 129         unsigned long flags;
 130         int i;
 131
 132         if (port->bulk_out_size) {
 133                 for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
 134                         usb_kill_urb(port->write_urbs[i]);
 135
 136                 spin_lock_irqsave(&port->lock, flags);
 137                 kfifo_reset_out(&port->write_fifo);
 138                 spin_unlock_irqrestore(&port->lock, flags);
 139         }
 140         if (port->bulk_in_size) {
 141                 for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i)
 142                         usb_kill_urb(port->read_urbs[i]);
 143         }
 144 }
 145 EXPORT_SYMBOL_GPL(usb_serial_generic_close);
 146
 147 int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
 148                                                 void *dest, size_t size)
 149 {
 150         return kfifo_out_locked(&port->write_fifo, dest, size, &port->lock);
 151 }
 152
 153 /**
 154  * usb_serial_generic_write_start - start writing buffered data
 155  * @port: usb-serial port
 156  * @mem_flags: flags to use for memory allocations
 157  *
 158  * Serialised using USB_SERIAL_WRITE_BUSY flag.
 159  *
 160  * Return: Zero on success or if busy, otherwise a negative errno value.
 161  */
 162 int usb_serial_generic_write_start(struct usb_serial_port *port,
 163                                                         gfp_t mem_flags)
 164 {
 165         struct urb *urb;
 166         int count, result;
 167         unsigned long flags;
 168         int i;
 169
 170         if (test_and_set_bit_lock(USB_SERIAL_WRITE_BUSY, &port->flags))
 171                 return 0;
 172 retry:
 173         spin_lock_irqsave(&port->lock, flags);
 174         if (!port->write_urbs_free || !kfifo_len(&port->write_fifo)) {
 175                 clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);
 176                 spin_unlock_irqrestore(&port->lock, flags);
 177                 return 0;
 178         }
 179         i = (int)find_first_bit(&port->write_urbs_free,
 180                                                 ARRAY_SIZE(port->write_urbs));
 181         spin_unlock_irqrestore(&port->lock, flags);
 182
 183         urb = port->write_urbs[i];
 184         count = port->serial->type->prepare_write_buffer(port,
 185                                                 urb->transfer_buffer,
 186                                                 port->bulk_out_size);
 187         urb->transfer_buffer_length = count;
 188         usb_serial_debug_data(&port->dev, __func__, count, urb->transfer_buffer);
 189         spin_lock_irqsave(&port->lock, flags);
 190         port->tx_bytes += count;
 191         spin_unlock_irqrestore(&port->lock, flags);
 192
 193         clear_bit(i, &port->write_urbs_free);
 194         result = usb_submit_urb(urb, mem_flags);
 195         if (result) {
 196                 dev_err_console(port, "%s - error submitting urb: %d\n",
 197                                                 __func__, result);
 198                 set_bit(i, &port->write_urbs_free);
 199                 spin_lock_irqsave(&port->lock, flags);
 200                 port->tx_bytes -= count;
 201                 spin_unlock_irqrestore(&port->lock, flags);
 202
 203                 clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);
 204                 return result;
 205         }
 206
 207         goto retry;     /* try sending off another urb */
 208 }
 209 EXPORT_SYMBOL_GPL(usb_serial_generic_write_start);
 210
 211 /**
 212  * usb_serial_generic_write - generic write function
 213  * @tty: tty for the port
 214  * @port: usb-serial port
 215  * @buf: data to write
 216  * @count: number of bytes to write
 217  *
 218  * Return: The number of characters buffered, which may be anything from
 219  * zero to @count, or a negative errno value.
 220  */
 221 int usb_serial_generic_write(struct tty_struct *tty,
 222         struct usb_serial_port *port, const unsigned char *buf, int count)
 223 {
 224         int result;
 225
 226         if (!port->bulk_out_size)
 227                 return -ENODEV;
 228
 229         if (!count)
 230                 return 0;
 231
 232         count = kfifo_in_locked(&port->write_fifo, buf, count, &port->lock);
 233         result = usb_serial_generic_write_start(port, GFP_ATOMIC);
 234         if (result)
 235                 return result;
 236
 237         return count;
 238 }
 239 EXPORT_SYMBOL_GPL(usb_serial_generic_write);
 240
 241 int usb_serial_generic_write_room(struct tty_struct *tty)
 242 {
 243         struct usb_serial_port *port = tty->driver_data;
 244         unsigned long flags;
 245         int room;
 246
 247         if (!port->bulk_out_size)
 248                 return 0;
 249
 250         spin_lock_irqsave(&port->lock, flags);
 251         room = kfifo_avail(&port->write_fifo);
 252         spin_unlock_irqrestore(&port->lock, flags);
 253
 254         dev_dbg(&port->dev, "%s - returns %d\n", __func__, room);
 255         return room;
 256 }
 257
 258 int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
 259 {
 260         struct usb_serial_port *port = tty->driver_data;
 261         unsigned long flags;
 262         int chars;
 263
 264         if (!port->bulk_out_size)
 265                 return 0;
 266
 267         spin_lock_irqsave(&port->lock, flags);
 268         chars = kfifo_len(&port->write_fifo) + port->tx_bytes;
 269         spin_unlock_irqrestore(&port->lock, flags);
 270
 271         dev_dbg(&port->dev, "%s - returns %d\n", __func__, chars);
 272         return chars;
 273 }
 274 EXPORT_SYMBOL_GPL(usb_serial_generic_chars_in_buffer);
 275
 276 void usb_serial_generic_wait_until_sent(struct tty_struct *tty, long timeout)
 277 {
 278         struct usb_serial_port *port = tty->driver_data;
 279         unsigned int bps;
 280         unsigned long period;
 281         unsigned long expire;
 282
 283         bps = tty_get_baud_rate(tty);
 284         if (!bps)
 285                 bps = 9600;     /* B0 */
 286         /*
 287          * Use a poll-period of roughly the time it takes to send one
 288          * character or at least one jiffy.
 289          */
 290         period = max_t(unsigned long, (10 * HZ / bps), 1);
 291         if (timeout)
 292                 period = min_t(unsigned long, period, timeout);
 293
 294         dev_dbg(&port->dev, "%s - timeout = %u ms, period = %u ms\n",
 295                                         __func__, jiffies_to_msecs(timeout),
 296                                         jiffies_to_msecs(period));
 297         expire = jiffies + timeout;
 298         while (!port->serial->type->tx_empty(port)) {
 299                 schedule_timeout_interruptible(period);
 300                 if (signal_pending(current))
 301                         break;
 302                 if (timeout && time_after(jiffies, expire))
 303                         break;
 304         }
 305 }
 306 EXPORT_SYMBOL_GPL(usb_serial_generic_wait_until_sent);
 307
 308 static int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
 309                                                 int index, gfp_t mem_flags)
 310 {
 311         int res;
 312
 313         if (!test_and_clear_bit(index, &port->read_urbs_free))
 314                 return 0;
 315
 316         dev_dbg(&port->dev, "%s - urb %d\n", __func__, index);
 317
 318         res = usb_submit_urb(port->read_urbs[index], mem_flags);
 319         if (res) {
 320                 if (res != -EPERM && res != -ENODEV) {
 321                         dev_err(&port->dev,
 322                                         "%s - usb_submit_urb failed: %d\n",
 323                                         __func__, res);
 324                 }
 325                 set_bit(index, &port->read_urbs_free);
 326                 return res;
 327         }
 328
 329         return 0;
 330 }
 331
 332 int usb_serial_generic_submit_read_urbs(struct usb_serial_port *port,
 333                                         gfp_t mem_flags)
 334 {
 335         int res;
 336         int i;
 337
 338         for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
 339                 res = usb_serial_generic_submit_read_urb(port, i, mem_flags);
 340                 if (res)
 341                         goto err;
 342         }
 343
 344         return 0;
 345 err:
 346         for (; i >= 0; --i)
 347                 usb_kill_urb(port->read_urbs[i]);
 348
 349         return res;
 350 }
 351 EXPORT_SYMBOL_GPL(usb_serial_generic_submit_read_urbs);
 352
 353 void usb_serial_generic_process_read_urb(struct urb *urb)
 354 {
 355         struct usb_serial_port *port = urb->context;
 356         char *ch = (char *)urb->transfer_buffer;
 357         int i;
 358
 359         if (!urb->actual_length)
 360                 return;
 361         /*
 362          * The per character mucking around with sysrq path it too slow for
 363          * stuff like 3G modems, so shortcircuit it in the 99.9999999% of
 364          * cases where the USB serial is not a console anyway.
 365          */
 366         if (!port->port.console || !port->sysrq) {
 367                 tty_insert_flip_string(&port->port, ch, urb->actual_length);
 368         } else {
 369                 for (i = 0; i < urb->actual_length; i++, ch++) {
 370                         if (!usb_serial_handle_sysrq_char(port, *ch))
 371                                 tty_insert_flip_char(&port->port, *ch, TTY_NORMAL);
 372                 }
 373         }
 374         tty_flip_buffer_push(&port->port);
 375 }
 376 EXPORT_SYMBOL_GPL(usb_serial_generic_process_read_urb);
 377
 378 void usb_serial_generic_read_bulk_callback(struct urb *urb)
 379 {
 380         struct usb_serial_port *port = urb->context;
 381         unsigned char *data = urb->transfer_buffer;
 382         unsigned long flags;
 383         int status = urb->status;
 384         int i;
 385
 386         for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
 387                 if (urb == port->read_urbs[i])
 388                         break;
 389         }
 390         set_bit(i, &port->read_urbs_free);
 391
 392         dev_dbg(&port->dev, "%s - urb %d, len %d\n", __func__, i,
 393                                                         urb->actual_length);
 394         switch (status) {
 395         case 0:
 396                 break;
 397         case -ENOENT:
 398         case -ECONNRESET:
 399         case -ESHUTDOWN:
 400                 dev_dbg(&port->dev, "%s - urb stopped: %d\n",
 401                                                         __func__, status);
 402                 return;
 403         case -EPIPE:
 404                 dev_err(&port->dev, "%s - urb stopped: %d\n",
 405                                                         __func__, status);
 406                 return;
 407         default:
 408                 dev_dbg(&port->dev, "%s - nonzero urb status: %d\n",
 409                                                         __func__, status);
 410                 goto resubmit;
 411         }
 412
 413         usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);
 414         port->serial->type->process_read_urb(urb);
 415
 416 resubmit:
 417         /* Throttle the device if requested by tty */
 418         spin_lock_irqsave(&port->lock, flags);
 419         port->throttled = port->throttle_req;
 420         if (!port->throttled) {
 421                 spin_unlock_irqrestore(&port->lock, flags);
 422                 usb_serial_generic_submit_read_urb(port, i, GFP_ATOMIC);
 423         } else {
 424                 spin_unlock_irqrestore(&port->lock, flags);
 425         }
 426 }
 427 EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);
 428
 429 void usb_serial_generic_write_bulk_callback(struct urb *urb)
 430 {
 431         unsigned long flags;
 432         struct usb_serial_port *port = urb->context;
 433         int status = urb->status;
 434         int i;
 435
 436         for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i) {
 437                 if (port->write_urbs[i] == urb)
 438                         break;
 439         }
 440         spin_lock_irqsave(&port->lock, flags);
 441         port->tx_bytes -= urb->transfer_buffer_length;
 442         set_bit(i, &port->write_urbs_free);
 443         spin_unlock_irqrestore(&port->lock, flags);
 444
 445         switch (status) {
 446         case 0:
 447                 break;
 448         case -ENOENT:
 449         case -ECONNRESET:
 450         case -ESHUTDOWN:
 451                 dev_dbg(&port->dev, "%s - urb stopped: %d\n",
 452                                                         __func__, status);
 453                 return;
 454         case -EPIPE:
 455                 dev_err_console(port, "%s - urb stopped: %d\n",
 456                                                         __func__, status);
 457                 return;
 458         default:
 459                 dev_err_console(port, "%s - nonzero urb status: %d\n",
 460                                                         __func__, status);
 461                 goto resubmit;
 462         }
 463
 464 resubmit:
 465         usb_serial_generic_write_start(port, GFP_ATOMIC);
 466         usb_serial_port_softint(port);
 467 }
 468 EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback);
 469
 470 void usb_serial_generic_throttle(struct tty_struct *tty)
 471 {
 472         struct usb_serial_port *port = tty->driver_data;
 473         unsigned long flags;
 474
 475         spin_lock_irqsave(&port->lock, flags);
 476         port->throttle_req = 1;
 477         spin_unlock_irqrestore(&port->lock, flags);
 478 }
 479 EXPORT_SYMBOL_GPL(usb_serial_generic_throttle);
 480
 481 void usb_serial_generic_unthrottle(struct tty_struct *tty)
 482 {
 483         struct usb_serial_port *port = tty->driver_data;
 484         int was_throttled;
 485
 486         spin_lock_irq(&port->lock);
 487         was_throttled = port->throttled;
 488         port->throttled = port->throttle_req = 0;
 489         spin_unlock_irq(&port->lock);
 490
 491         if (was_throttled)
 492                 usb_serial_generic_submit_read_urbs(port, GFP_KERNEL);
 493 }
 494 EXPORT_SYMBOL_GPL(usb_serial_generic_unthrottle);
 495
 496 static bool usb_serial_generic_msr_changed(struct tty_struct *tty,
 497                                 unsigned long arg, struct async_icount *cprev)
 498 {
 499         struct usb_serial_port *port = tty->driver_data;
 500         struct async_icount cnow;
 501         unsigned long flags;
 502         bool ret;
 503
 504         /*
 505          * Use tty-port initialised flag to detect all hangups including the
 506          * one generated at USB-device disconnect.
 507          */
 508         if (!tty_port_initialized(&port->port))
 509                 return true;
 510
 511         spin_lock_irqsave(&port->lock, flags);
 512         cnow = port->icount;                            /* atomic copy*/
 513         spin_unlock_irqrestore(&port->lock, flags);
 514
 515         ret =   ((arg & TIOCM_RNG) && (cnow.rng != cprev->rng)) ||
 516                 ((arg & TIOCM_DSR) && (cnow.dsr != cprev->dsr)) ||
 517                 ((arg & TIOCM_CD)  && (cnow.dcd != cprev->dcd)) ||
 518                 ((arg & TIOCM_CTS) && (cnow.cts != cprev->cts));
 519
 520         *cprev = cnow;
 521
 522         return ret;
 523 }
 524
 525 int usb_serial_generic_tiocmiwait(struct tty_struct *tty, unsigned long arg)
 526 {
 527         struct usb_serial_port *port = tty->driver_data;
 528         struct async_icount cnow;
 529         unsigned long flags;
 530         int ret;
 531
 532         spin_lock_irqsave(&port->lock, flags);
 533         cnow = port->icount;                            /* atomic copy */
 534         spin_unlock_irqrestore(&port->lock, flags);
 535
 536         ret = wait_event_interruptible(port->port.delta_msr_wait,
 537                         usb_serial_generic_msr_changed(tty, arg, &cnow));
 538         if (!ret && !tty_port_initialized(&port->port))
 539                 ret = -EIO;
 540
 541         return ret;
 542 }
 543 EXPORT_SYMBOL_GPL(usb_serial_generic_tiocmiwait);
 544
 545 int usb_serial_generic_get_icount(struct tty_struct *tty,
 546                                         struct serial_icounter_struct *icount)
 547 {
 548         struct usb_serial_port *port = tty->driver_data;
 549         struct async_icount cnow;
 550         unsigned long flags;
 551
 552         spin_lock_irqsave(&port->lock, flags);
 553         cnow = port->icount;                            /* atomic copy */
 554         spin_unlock_irqrestore(&port->lock, flags);
 555
 556         icount->cts = cnow.cts;
 557         icount->dsr = cnow.dsr;
 558         icount->rng = cnow.rng;
 559         icount->dcd = cnow.dcd;
 560         icount->tx = cnow.tx;
 561         icount->rx = cnow.rx;
 562         icount->frame = cnow.frame;
 563         icount->parity = cnow.parity;
 564         icount->overrun = cnow.overrun;
 565         icount->brk = cnow.brk;
 566         icount->buf_overrun = cnow.buf_overrun;
 567
 568         return 0;
 569 }
 570 EXPORT_SYMBOL_GPL(usb_serial_generic_get_icount);
 571
 572 #ifdef CONFIG_MAGIC_SYSRQ
 573 int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
 574 {
 575         if (port->sysrq && port->port.console) {
 576                 if (ch && time_before(jiffies, port->sysrq)) {
 577                         handle_sysrq(ch);
 578                         port->sysrq = 0;
 579                         return 1;
 580                 }
 581                 port->sysrq = 0;
 582         }
 583         return 0;
 584 }
 585 #else
 586 int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
 587 {
 588         return 0;
 589 }
 590 #endif
 591 EXPORT_SYMBOL_GPL(usb_serial_handle_sysrq_char);
 592
 593 int usb_serial_handle_break(struct usb_serial_port *port)
 594 {
 595         if (!port->sysrq) {
 596                 port->sysrq = jiffies + HZ*5;
 597                 return 1;
 598         }
 599         port->sysrq = 0;
 600         return 0;
 601 }
 602 EXPORT_SYMBOL_GPL(usb_serial_handle_break);
 603
 604 /**
 605  * usb_serial_handle_dcd_change - handle a change of carrier detect state
 606  * @port: usb-serial port
 607  * @tty: tty for the port
 608  * @status: new carrier detect status, nonzero if active
 609  */
 610 void usb_serial_handle_dcd_change(struct usb_serial_port *usb_port,
 611                                 struct tty_struct *tty, unsigned int status)
 612 {
 613         struct tty_port *port = &usb_port->port;
 614
 615         dev_dbg(&usb_port->dev, "%s - status %d\n", __func__, status);
 616
 617         if (tty) {
 618                 struct tty_ldisc *ld = tty_ldisc_ref(tty);
 619
 620                 if (ld) {
 621                         if (ld->ops->dcd_change)
 622                                 ld->ops->dcd_change(tty, status);
 623                         tty_ldisc_deref(ld);
 624                 }
 625         }
 626
 627         if (status)
 628                 wake_up_interruptible(&port->open_wait);
 629         else if (tty && !C_CLOCAL(tty))
 630                 tty_hangup(tty);
 631 }
 632 EXPORT_SYMBOL_GPL(usb_serial_handle_dcd_change);
 633
 634 int usb_serial_generic_resume(struct usb_serial *serial)
 635 {
 636         struct usb_serial_port *port;
 637         int i, c = 0, r;
 638
 639         for (i = 0; i < serial->num_ports; i++) {
 640                 port = serial->port[i];
 641                 if (!tty_port_initialized(&port->port))
 642                         continue;
 643
 644                 if (port->bulk_in_size) {
 645                         r = usb_serial_generic_submit_read_urbs(port,
 646                                                                 GFP_NOIO);
 647                         if (r < 0)
 648                                 c++;
 649                 }
 650
 651                 if (port->bulk_out_size) {
 652                         r = usb_serial_generic_write_start(port, GFP_NOIO);
 653                         if (r < 0)
 654                                 c++;
 655                 }
 656         }
 657
 658         return c ? -EIO : 0;
 659 }
 660 EXPORT_SYMBOL_GPL(usb_serial_generic_resume);