libusb/os/netbsd_usb.c

   1 /*
   2  * Copyright © 2011 Martin Pieuchot <mpi@openbsd.org>
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #include <config.h>
  20
  21 #include <sys/time.h>
  22 #include <sys/types.h>
  23
  24 #include <errno.h>
  25 #include <fcntl.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <unistd.h>
  30
  31 #include <dev/usb/usb.h>
  32
  33 #include "libusbi.h"
  34
  35 struct device_priv {
  36         char devnode[16];
  37         int fd;
  38
  39         unsigned char *cdesc;                   /* active config descriptor */
  40         usb_device_descriptor_t ddesc;          /* usb device descriptor */
  41 };
  42
  43 struct handle_priv {
  44         int endpoints[USB_MAX_ENDPOINTS];
  45 };
  46
  47 /*
  48  * Backend functions
  49  */
  50 static int netbsd_get_device_list(struct libusb_context *,
  51     struct discovered_devs **);
  52 static int netbsd_open(struct libusb_device_handle *);
  53 static void netbsd_close(struct libusb_device_handle *);
  54
  55 static int netbsd_get_device_descriptor(struct libusb_device *, unsigned char *,
  56     int *);
  57 static int netbsd_get_active_config_descriptor(struct libusb_device *,
  58     unsigned char *, size_t, int *);
  59 static int netbsd_get_config_descriptor(struct libusb_device *, uint8_t,
  60     unsigned char *, size_t, int *);
  61
  62 static int netbsd_get_configuration(struct libusb_device_handle *, int *);
  63 static int netbsd_set_configuration(struct libusb_device_handle *, int);
  64
  65 static int netbsd_claim_interface(struct libusb_device_handle *, int);
  66 static int netbsd_release_interface(struct libusb_device_handle *, int);
  67
  68 static int netbsd_set_interface_altsetting(struct libusb_device_handle *, int,
  69     int);
  70 static int netbsd_clear_halt(struct libusb_device_handle *, unsigned char);
  71 static int netbsd_reset_device(struct libusb_device_handle *);
  72 static void netbsd_destroy_device(struct libusb_device *);
  73
  74 static int netbsd_submit_transfer(struct usbi_transfer *);
  75 static int netbsd_cancel_transfer(struct usbi_transfer *);
  76 static void netbsd_clear_transfer_priv(struct usbi_transfer *);
  77 static int netbsd_handle_transfer_completion(struct usbi_transfer *);
  78 static int netbsd_clock_gettime(int, struct timespec *);
  79
  80 /*
  81  * Private functions
  82  */
  83 static int _errno_to_libusb(int);
  84 static int _cache_active_config_descriptor(struct libusb_device *, int);
  85 static int _sync_control_transfer(struct usbi_transfer *);
  86 static int _sync_gen_transfer(struct usbi_transfer *);
  87 static int _access_endpoint(struct libusb_transfer *);
  88
  89 const struct usbi_os_backend netbsd_backend = {
  90         "Synchronous NetBSD backend",
  91         0,
  92         NULL,                           /* init() */
  93         NULL,                           /* exit() */
  94         netbsd_get_device_list,
  95         NULL,                           /* hotplug_poll */
  96         netbsd_open,
  97         netbsd_close,
  98
  99         netbsd_get_device_descriptor,
 100         netbsd_get_active_config_descriptor,
 101         netbsd_get_config_descriptor,
 102         NULL,                           /* get_config_descriptor_by_value() */
 103
 104         netbsd_get_configuration,
 105         netbsd_set_configuration,
 106
 107         netbsd_claim_interface,
 108         netbsd_release_interface,
 109
 110         netbsd_set_interface_altsetting,
 111         netbsd_clear_halt,
 112         netbsd_reset_device,
 113
 114         NULL,                           /* alloc_streams */
 115         NULL,                           /* free_streams */
 116
 117         NULL,                           /* kernel_driver_active() */
 118         NULL,                           /* detach_kernel_driver() */
 119         NULL,                           /* attach_kernel_driver() */
 120
 121         netbsd_destroy_device,
 122
 123         netbsd_submit_transfer,
 124         netbsd_cancel_transfer,
 125         netbsd_clear_transfer_priv,
 126
 127         NULL,                           /* handle_events() */
 128         netbsd_handle_transfer_completion,
 129
 130         netbsd_clock_gettime,
 131         sizeof(struct device_priv),
 132         sizeof(struct handle_priv),
 133         0,                              /* transfer_priv_size */
 134 };
 135
 136 int
 137 netbsd_get_device_list(struct libusb_context * ctx,
 138         struct discovered_devs **discdevs)
 139 {
 140         struct libusb_device *dev;
 141         struct device_priv *dpriv;
 142         struct usb_device_info di;
 143         unsigned long session_id;
 144         char devnode[16];
 145         int fd, err, i;
 146
 147         usbi_dbg("");
 148
 149         /* Only ugen(4) is supported */
 150         for (i = 0; i < USB_MAX_DEVICES; i++) {
 151                 /* Control endpoint is always .00 */
 152                 snprintf(devnode, sizeof(devnode), "/dev/ugen%d.00", i);
 153
 154                 if ((fd = open(devnode, O_RDONLY)) < 0) {
 155                         if (errno != ENOENT && errno != ENXIO)
 156                                 usbi_err(ctx, "could not open %s", devnode);
 157                         continue;
 158                 }
 159
 160                 if (ioctl(fd, USB_GET_DEVICEINFO, &di) < 0)
 161                         continue;
 162
 163                 session_id = (di.udi_bus << 8 | di.udi_addr);
 164                 dev = usbi_get_device_by_session_id(ctx, session_id);
 165
 166                 if (dev == NULL) {
 167                         dev = usbi_alloc_device(ctx, session_id);
 168                         if (dev == NULL)
 169                                 return (LIBUSB_ERROR_NO_MEM);
 170
 171                         dev->bus_number = di.udi_bus;
 172                         dev->device_address = di.udi_addr;
 173                         dev->speed = di.udi_speed;
 174
 175                         dpriv = (struct device_priv *)dev->os_priv;
 176                         strlcpy(dpriv->devnode, devnode, sizeof(devnode));
 177                         dpriv->fd = -1;
 178
 179                         if (ioctl(fd, USB_GET_DEVICE_DESC, &dpriv->ddesc) < 0) {
 180                                 err = errno;
 181                                 goto error;
 182                         }
 183
 184                         dpriv->cdesc = NULL;
 185                         if (_cache_active_config_descriptor(dev, fd)) {
 186                                 err = errno;
 187                                 goto error;
 188                         }
 189
 190                         if ((err = usbi_sanitize_device(dev)))
 191                                 goto error;
 192                 }
 193                 close(fd);
 194
 195                 if (discovered_devs_append(*discdevs, dev) == NULL)
 196                         return (LIBUSB_ERROR_NO_MEM);
 197
 198                 libusb_unref_device(dev);
 199         }
 200
 201         return (LIBUSB_SUCCESS);
 202
 203 error:
 204         close(fd);
 205         libusb_unref_device(dev);
 206         return _errno_to_libusb(err);
 207 }
 208
 209 int
 210 netbsd_open(struct libusb_device_handle *handle)
 211 {
 212         struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
 213         struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
 214
 215         dpriv->fd = open(dpriv->devnode, O_RDWR);
 216         if (dpriv->fd < 0) {
 217                 dpriv->fd = open(dpriv->devnode, O_RDONLY);
 218                 if (dpriv->fd < 0)
 219                         return _errno_to_libusb(errno);
 220         }
 221
 222         usbi_dbg("open %s: fd %d", dpriv->devnode, dpriv->fd);
 223
 224         return (LIBUSB_SUCCESS);
 225 }
 226
 227 void
 228 netbsd_close(struct libusb_device_handle *handle)
 229 {
 230         struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
 231         struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
 232
 233         usbi_dbg("close: fd %d", dpriv->fd);
 234
 235         close(dpriv->fd);
 236         dpriv->fd = -1;
 237 }
 238
 239 int
 240 netbsd_get_device_descriptor(struct libusb_device *dev, unsigned char *buf,
 241     int *host_endian)
 242 {
 243         struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
 244
 245         usbi_dbg("");
 246
 247         memcpy(buf, &dpriv->ddesc, DEVICE_DESC_LENGTH);
 248
 249         *host_endian = 0;
 250
 251         return (LIBUSB_SUCCESS);
 252 }
 253
 254 int
 255 netbsd_get_active_config_descriptor(struct libusb_device *dev,
 256     unsigned char *buf, size_t len, int *host_endian)
 257 {
 258         struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
 259         usb_config_descriptor_t *ucd;
 260
 261         ucd = (usb_config_descriptor_t *) dpriv->cdesc;
 262         len = MIN(len, UGETW(ucd->wTotalLength));
 263
 264         usbi_dbg("len %d", len);
 265
 266         memcpy(buf, dpriv->cdesc, len);
 267
 268         *host_endian = 0;
 269
 270         return len;
 271 }
 272
 273 int
 274 netbsd_get_config_descriptor(struct libusb_device *dev, uint8_t idx,
 275     unsigned char *buf, size_t len, int *host_endian)
 276 {
 277         struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
 278         struct usb_full_desc ufd;
 279         int fd, err;
 280
 281         usbi_dbg("index %d, len %d", idx, len);
 282
 283         /* A config descriptor may be requested before opening the device */
 284         if (dpriv->fd >= 0) {
 285                 fd = dpriv->fd;
 286         } else {
 287                 fd = open(dpriv->devnode, O_RDONLY);
 288                 if (fd < 0)
 289                         return _errno_to_libusb(errno);
 290         }
 291
 292         ufd.ufd_config_index = idx;
 293         ufd.ufd_size = len;
 294         ufd.ufd_data = buf;
 295
 296         if ((ioctl(fd, USB_GET_FULL_DESC, &ufd)) < 0) {
 297                 err = errno;
 298                 if (dpriv->fd < 0)
 299                         close(fd);
 300                 return _errno_to_libusb(err);
 301         }
 302
 303         if (dpriv->fd < 0)
 304                 close(fd);
 305
 306         *host_endian = 0;
 307
 308         return len;
 309 }
 310
 311 int
 312 netbsd_get_configuration(struct libusb_device_handle *handle, int *config)
 313 {
 314         struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
 315
 316         usbi_dbg("");
 317
 318         if (ioctl(dpriv->fd, USB_GET_CONFIG, config) < 0)
 319                 return _errno_to_libusb(errno);
 320
 321         usbi_dbg("configuration %d", *config);
 322
 323         return (LIBUSB_SUCCESS);
 324 }
 325
 326 int
 327 netbsd_set_configuration(struct libusb_device_handle *handle, int config)
 328 {
 329         struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
 330
 331         usbi_dbg("configuration %d", config);
 332
 333         if (ioctl(dpriv->fd, USB_SET_CONFIG, &config) < 0)
 334                 return _errno_to_libusb(errno);
 335
 336         return _cache_active_config_descriptor(handle->dev, dpriv->fd);
 337 }
 338
 339 int
 340 netbsd_claim_interface(struct libusb_device_handle *handle, int iface)
 341 {
 342         struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
 343         int i;
 344
 345         for (i = 0; i < USB_MAX_ENDPOINTS; i++)
 346                 hpriv->endpoints[i] = -1;
 347
 348         return (LIBUSB_SUCCESS);
 349 }
 350
 351 int
 352 netbsd_release_interface(struct libusb_device_handle *handle, int iface)
 353 {
 354         struct handle_priv *hpriv = (struct handle_priv *)handle->os_priv;
 355         int i;
 356
 357         for (i = 0; i < USB_MAX_ENDPOINTS; i++)
 358                 if (hpriv->endpoints[i] >= 0)
 359                         close(hpriv->endpoints[i]);
 360
 361         return (LIBUSB_SUCCESS);
 362 }
 363
 364 int
 365 netbsd_set_interface_altsetting(struct libusb_device_handle *handle, int iface,
 366     int altsetting)
 367 {
 368         struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
 369         struct usb_alt_interface intf;
 370
 371         usbi_dbg("iface %d, setting %d", iface, altsetting);
 372
 373         memset(&intf, 0, sizeof(intf));
 374
 375         intf.uai_interface_index = iface;
 376         intf.uai_alt_no = altsetting;
 377
 378         if (ioctl(dpriv->fd, USB_SET_ALTINTERFACE, &intf) < 0)
 379                 return _errno_to_libusb(errno);
 380
 381         return (LIBUSB_SUCCESS);
 382 }
 383
 384 int
 385 netbsd_clear_halt(struct libusb_device_handle *handle, unsigned char endpoint)
 386 {
 387         struct device_priv *dpriv = (struct device_priv *)handle->dev->os_priv;
 388         struct usb_ctl_request req;
 389
 390         usbi_dbg("");
 391
 392         req.ucr_request.bmRequestType = UT_WRITE_ENDPOINT;
 393         req.ucr_request.bRequest = UR_CLEAR_FEATURE;
 394         USETW(req.ucr_request.wValue, UF_ENDPOINT_HALT);
 395         USETW(req.ucr_request.wIndex, endpoint);
 396         USETW(req.ucr_request.wLength, 0);
 397
 398         if (ioctl(dpriv->fd, USB_DO_REQUEST, &req) < 0)
 399                 return _errno_to_libusb(errno);
 400
 401         return (LIBUSB_SUCCESS);
 402 }
 403
 404 int
 405 netbsd_reset_device(struct libusb_device_handle *handle)
 406 {
 407         usbi_dbg("");
 408
 409         return (LIBUSB_ERROR_NOT_SUPPORTED);
 410 }
 411
 412 void
 413 netbsd_destroy_device(struct libusb_device *dev)
 414 {
 415         struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
 416
 417         usbi_dbg("");
 418
 419         free(dpriv->cdesc);
 420 }
 421
 422 int
 423 netbsd_submit_transfer(struct usbi_transfer *itransfer)
 424 {
 425         struct libusb_transfer *transfer;
 426         struct handle_priv *hpriv;
 427         int err = 0;
 428
 429         usbi_dbg("");
 430
 431         transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
 432         hpriv = (struct handle_priv *)transfer->dev_handle->os_priv;
 433
 434         switch (transfer->type) {
 435         case LIBUSB_TRANSFER_TYPE_CONTROL:
 436                 err = _sync_control_transfer(itransfer);
 437                 break;
 438         case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
 439                 if (IS_XFEROUT(transfer)) {
 440                         /* Isochronous write is not supported */
 441                         err = LIBUSB_ERROR_NOT_SUPPORTED;
 442                         break;
 443                 }
 444                 err = _sync_gen_transfer(itransfer);
 445                 break;
 446         case LIBUSB_TRANSFER_TYPE_BULK:
 447         case LIBUSB_TRANSFER_TYPE_INTERRUPT:
 448                 if (IS_XFEROUT(transfer) &&
 449                     transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) {
 450                         err = LIBUSB_ERROR_NOT_SUPPORTED;
 451                         break;
 452                 }
 453                 err = _sync_gen_transfer(itransfer);
 454                 break;
 455         case LIBUSB_TRANSFER_TYPE_BULK_STREAM:
 456                 err = LIBUSB_ERROR_NOT_SUPPORTED;
 457                 break;
 458         }
 459
 460         if (err)
 461                 return (err);
 462
 463         usbi_signal_transfer_completion(itransfer);
 464
 465         return (LIBUSB_SUCCESS);
 466 }
 467
 468 int
 469 netbsd_cancel_transfer(struct usbi_transfer *itransfer)
 470 {
 471         usbi_dbg("");
 472
 473         return (LIBUSB_ERROR_NOT_SUPPORTED);
 474 }
 475
 476 void
 477 netbsd_clear_transfer_priv(struct usbi_transfer *itransfer)
 478 {
 479         usbi_dbg("");
 480
 481         /* Nothing to do */
 482 }
 483
 484 int
 485 netbsd_handle_transfer_completion(struct usbi_transfer *itransfer)
 486 {
 487         return usbi_handle_transfer_completion(itransfer, LIBUSB_TRANSFER_COMPLETED);
 488 }
 489
 490 int
 491 netbsd_clock_gettime(int clkid, struct timespec *tp)
 492 {
 493         usbi_dbg("clock %d", clkid);
 494
 495         if (clkid == USBI_CLOCK_REALTIME)
 496                 return clock_gettime(CLOCK_REALTIME, tp);
 497
 498         if (clkid == USBI_CLOCK_MONOTONIC)
 499                 return clock_gettime(CLOCK_MONOTONIC, tp);
 500
 501         return (LIBUSB_ERROR_INVALID_PARAM);
 502 }
 503
 504 int
 505 _errno_to_libusb(int err)
 506 {
 507         switch (err) {
 508         case EIO:
 509                 return (LIBUSB_ERROR_IO);
 510         case EACCES:
 511                 return (LIBUSB_ERROR_ACCESS);
 512         case ENOENT:
 513                 return (LIBUSB_ERROR_NO_DEVICE);
 514         case ENOMEM:
 515                 return (LIBUSB_ERROR_NO_MEM);
 516         }
 517
 518         usbi_dbg("error: %s", strerror(err));
 519
 520         return (LIBUSB_ERROR_OTHER);
 521 }
 522
 523 int
 524 _cache_active_config_descriptor(struct libusb_device *dev, int fd)
 525 {
 526         struct device_priv *dpriv = (struct device_priv *)dev->os_priv;
 527         struct usb_config_desc ucd;
 528         struct usb_full_desc ufd;
 529         unsigned char* buf;
 530         int len;
 531
 532         usbi_dbg("fd %d", fd);
 533
 534         ucd.ucd_config_index = USB_CURRENT_CONFIG_INDEX;
 535
 536         if ((ioctl(fd, USB_GET_CONFIG_DESC, &ucd)) < 0)
 537                 return _errno_to_libusb(errno);
 538
 539         usbi_dbg("active bLength %d", ucd.ucd_desc.bLength);
 540
 541         len = UGETW(ucd.ucd_desc.wTotalLength);
 542         buf = malloc(len);
 543         if (buf == NULL)
 544                 return (LIBUSB_ERROR_NO_MEM);
 545
 546         ufd.ufd_config_index = ucd.ucd_config_index;
 547         ufd.ufd_size = len;
 548         ufd.ufd_data = buf;
 549
 550         usbi_dbg("index %d, len %d", ufd.ufd_config_index, len);
 551
 552         if ((ioctl(fd, USB_GET_FULL_DESC, &ufd)) < 0) {
 553                 free(buf);
 554                 return _errno_to_libusb(errno);
 555         }
 556
 557         if (dpriv->cdesc)
 558                 free(dpriv->cdesc);
 559         dpriv->cdesc = buf;
 560
 561         return (0);
 562 }
 563
 564 int
 565 _sync_control_transfer(struct usbi_transfer *itransfer)
 566 {
 567         struct libusb_transfer *transfer;
 568         struct libusb_control_setup *setup;
 569         struct device_priv *dpriv;
 570         struct usb_ctl_request req;
 571
 572         transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
 573         dpriv = (struct device_priv *)transfer->dev_handle->dev->os_priv;
 574         setup = (struct libusb_control_setup *)transfer->buffer;
 575
 576         usbi_dbg("type %d request %d value %d index %d length %d timeout %d",
 577             setup->bmRequestType, setup->bRequest,
 578             libusb_le16_to_cpu(setup->wValue),
 579             libusb_le16_to_cpu(setup->wIndex),
 580             libusb_le16_to_cpu(setup->wLength), transfer->timeout);
 581
 582         req.ucr_request.bmRequestType = setup->bmRequestType;
 583         req.ucr_request.bRequest = setup->bRequest;
 584         /* Don't use USETW, libusb already deals with the endianness */
 585         (*(uint16_t *)req.ucr_request.wValue) = setup->wValue;
 586         (*(uint16_t *)req.ucr_request.wIndex) = setup->wIndex;
 587         (*(uint16_t *)req.ucr_request.wLength) = setup->wLength;
 588         req.ucr_data = transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
 589
 590         if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
 591                 req.ucr_flags = USBD_SHORT_XFER_OK;
 592
 593         if ((ioctl(dpriv->fd, USB_SET_TIMEOUT, &transfer->timeout)) < 0)
 594                 return _errno_to_libusb(errno);
 595
 596         if ((ioctl(dpriv->fd, USB_DO_REQUEST, &req)) < 0)
 597                 return _errno_to_libusb(errno);
 598
 599         itransfer->transferred = req.ucr_actlen;
 600
 601         usbi_dbg("transferred %d", itransfer->transferred);
 602
 603         return (0);
 604 }
 605
 606 int
 607 _access_endpoint(struct libusb_transfer *transfer)
 608 {
 609         struct handle_priv *hpriv;
 610         struct device_priv *dpriv;
 611         char *s, devnode[16];
 612         int fd, endpt;
 613         mode_t mode;
 614
 615         hpriv = (struct handle_priv *)transfer->dev_handle->os_priv;
 616         dpriv = (struct device_priv *)transfer->dev_handle->dev->os_priv;
 617
 618         endpt = UE_GET_ADDR(transfer->endpoint);
 619         mode = IS_XFERIN(transfer) ? O_RDONLY : O_WRONLY;
 620
 621         usbi_dbg("endpoint %d mode %d", endpt, mode);
 622
 623         if (hpriv->endpoints[endpt] < 0) {
 624                 /* Pick the right node given the control one */
 625                 strlcpy(devnode, dpriv->devnode, sizeof(devnode));
 626                 s = strchr(devnode, '.');
 627                 snprintf(s, 4, ".%02d", endpt);
 628
 629                 /* We may need to read/write to the same endpoint later. */
 630                 if (((fd = open(devnode, O_RDWR)) < 0) && (errno == ENXIO))
 631                         if ((fd = open(devnode, mode)) < 0)
 632                                 return (-1);
 633
 634                 hpriv->endpoints[endpt] = fd;
 635         }
 636
 637         return (hpriv->endpoints[endpt]);
 638 }
 639
 640 int
 641 _sync_gen_transfer(struct usbi_transfer *itransfer)
 642 {
 643         struct libusb_transfer *transfer;
 644         int fd, nr = 1;
 645
 646         transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
 647
 648         /*
 649          * Bulk, Interrupt or Isochronous transfer depends on the
 650          * endpoint and thus the node to open.
 651          */
 652         if ((fd = _access_endpoint(transfer)) < 0)
 653                 return _errno_to_libusb(errno);
 654
 655         if ((ioctl(fd, USB_SET_TIMEOUT, &transfer->timeout)) < 0)
 656                 return _errno_to_libusb(errno);
 657
 658         if (IS_XFERIN(transfer)) {
 659                 if ((transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) == 0)
 660                         if ((ioctl(fd, USB_SET_SHORT_XFER, &nr)) < 0)
 661                                 return _errno_to_libusb(errno);
 662
 663                 nr = read(fd, transfer->buffer, transfer->length);
 664         } else {
 665                 nr = write(fd, transfer->buffer, transfer->length);
 666         }
 667
 668         if (nr < 0)
 669                 return _errno_to_libusb(errno);
 670
 671         itransfer->transferred = nr;
 672
 673         return (0);
 674 }