src/scpi/scpi_usbtmc_libusb.c

   1 /*
   2  * This file is part of the libsigrok project.
   3  *
   4  * Copyright (C) 2014 Aurelien Jacobs <aurel@gnuage.org>
   5  *
   6  * This program is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <config.h>
  21 #include <string.h>
  22 #include <libsigrok/libsigrok.h>
  23 #include "libsigrok-internal.h"
  24 #include "scpi.h"
  25
  26 #define LOG_PREFIX "scpi_usbtmc"
  27
  28 #define MAX_TRANSFER_LENGTH 2048
  29 #define TRANSFER_TIMEOUT 1000
  30
  31 struct scpi_usbtmc_libusb {
  32         struct sr_context *ctx;
  33         struct sr_usb_dev_inst *usb;
  34         int detached_kernel_driver;
  35         uint8_t interface;
  36         uint8_t bulk_in_ep;
  37         uint8_t bulk_out_ep;
  38         uint8_t interrupt_ep;
  39         uint8_t usbtmc_int_cap;
  40         uint8_t usbtmc_dev_cap;
  41         uint8_t usb488_dev_cap;
  42         uint8_t bTag;
  43         uint8_t bulkin_attributes;
  44         uint8_t buffer[MAX_TRANSFER_LENGTH];
  45         int response_length;
  46         int response_bytes_read;
  47         int remaining_length;
  48         int rigol_ds1000;
  49 };
  50
  51 /* Some USBTMC-specific enums, as defined in the USBTMC standard. */
  52 #define SUBCLASS_USBTMC  0x03
  53 #define USBTMC_USB488    0x01
  54
  55 enum {
  56         /* USBTMC control requests */
  57         INITIATE_ABORT_BULK_OUT     =   1,
  58         CHECK_ABORT_BULK_OUT_STATUS =   2,
  59         INITIATE_ABORT_BULK_IN      =   3,
  60         CHECK_ABORT_BULK_IN_STATUS  =   4,
  61         INITIATE_CLEAR              =   5,
  62         CHECK_CLEAR_STATUS          =   6,
  63         GET_CAPABILITIES            =   7,
  64         INDICATOR_PULSE             =  64,
  65
  66         /* USB488 control requests */
  67         READ_STATUS_BYTE            = 128,
  68         REN_CONTROL                 = 160,
  69         GO_TO_LOCAL                 = 161,
  70         LOCAL_LOCKOUT               = 162,
  71 };
  72
  73 /* USBTMC capabilities */
  74 #define USBTMC_INT_CAP_LISTEN_ONLY 0x01
  75 #define USBTMC_INT_CAP_TALK_ONLY   0x02
  76 #define USBTMC_INT_CAP_INDICATOR   0x04
  77
  78 #define USBTMC_DEV_CAP_TERMCHAR    0x01
  79
  80 #define USB488_DEV_CAP_DT1         0x01
  81 #define USB488_DEV_CAP_RL1         0x02
  82 #define USB488_DEV_CAP_SR1         0x04
  83 #define USB488_DEV_CAP_SCPI        0x08
  84
  85 /* Bulk messages constants */
  86 #define USBTMC_BULK_HEADER_SIZE  12
  87
  88 /* Bulk MsgID values */
  89 #define DEV_DEP_MSG_OUT         1
  90 #define REQUEST_DEV_DEP_MSG_IN  2
  91 #define DEV_DEP_MSG_IN          2
  92
  93 /* bmTransferAttributes */
  94 #define EOM                0x01
  95 #define TERM_CHAR_ENABLED  0x02
  96
  97 static GSList *scpi_usbtmc_libusb_scan(struct drv_context *drvc)
  98 {
  99         struct libusb_device **devlist;
 100         struct libusb_device_descriptor des;
 101         struct libusb_config_descriptor *confdes;
 102         const struct libusb_interface_descriptor *intfdes;
 103         GSList *resources = NULL;
 104         int confidx, intfidx, ret, i;
 105         char *res;
 106
 107         ret = libusb_get_device_list(drvc->sr_ctx->libusb_ctx, &devlist);
 108         if (ret < 0) {
 109                 sr_err("Failed to get device list: %s.",
 110                        libusb_error_name(ret));
 111                 return NULL;
 112         }
 113         for (i = 0; devlist[i]; i++) {
 114                 if ((ret = libusb_get_device_descriptor(devlist[i], &des)) < 0) {
 115                         sr_err("Failed to get device descriptor: %s.",
 116                                libusb_error_name(ret));
 117                         continue;
 118                 }
 119
 120                 for (confidx = 0; confidx < des.bNumConfigurations; confidx++) {
 121                         if ((ret = libusb_get_config_descriptor(devlist[i], confidx, &confdes)) < 0) {
 122                                 sr_dbg("Failed to get configuration descriptor: %s, "
 123                                        "ignoring device.", libusb_error_name(ret));
 124                                 break;
 125                         }
 126                         for (intfidx = 0; intfidx < confdes->bNumInterfaces; intfidx++) {
 127                                 intfdes = confdes->interface[intfidx].altsetting;
 128                                 if (intfdes->bInterfaceClass    != LIBUSB_CLASS_APPLICATION ||
 129                                     intfdes->bInterfaceSubClass != SUBCLASS_USBTMC          ||
 130                                     intfdes->bInterfaceProtocol != USBTMC_USB488)
 131                                         continue;
 132                                 sr_dbg("Found USBTMC device (VID:PID = %04x:%04x, "
 133                                        "bus.address = %d.%d).", des.idVendor, des.idProduct,
 134                                        libusb_get_bus_number(devlist[i]),
 135                                        libusb_get_device_address(devlist[i]));
 136                                 res = g_strdup_printf("usbtmc/%d.%d",
 137                                                       libusb_get_bus_number(devlist[i]),
 138                                                       libusb_get_device_address(devlist[i]));
 139                                 resources = g_slist_append(resources, res);
 140                         }
 141                         libusb_free_config_descriptor(confdes);
 142                 }
 143         }
 144         libusb_free_device_list(devlist, 1);
 145
 146         sr_dbg("Found %d device(s).", g_slist_length(resources));
 147
 148         return resources;
 149 }
 150
 151 static int scpi_usbtmc_libusb_dev_inst_new(void *priv, struct drv_context *drvc,
 152                 const char *resource, char **params, const char *serialcomm)
 153 {
 154         struct scpi_usbtmc_libusb *uscpi = priv;
 155         GSList *devices;
 156
 157         (void)resource;
 158         (void)serialcomm;
 159
 160         if (!params || !params[1]) {
 161                 sr_err("Invalid parameters.");
 162                 return SR_ERR;
 163         }
 164
 165         uscpi->ctx = drvc->sr_ctx;
 166         devices = sr_usb_find(uscpi->ctx->libusb_ctx, params[1]);
 167         if (g_slist_length(devices) != 1) {
 168                 sr_err("Failed to find USB device '%s'.", params[1]);
 169                 g_slist_free_full(devices, (GDestroyNotify)sr_usb_dev_inst_free);
 170                 return SR_ERR;
 171         }
 172         uscpi->usb = devices->data;
 173         g_slist_free(devices);
 174
 175         return SR_OK;
 176 }
 177
 178 static int scpi_usbtmc_libusb_open(void *priv)
 179 {
 180         struct scpi_usbtmc_libusb *uscpi = priv;
 181         struct sr_usb_dev_inst *usb = uscpi->usb;
 182         struct libusb_device *dev;
 183         struct libusb_device_descriptor des;
 184         struct libusb_config_descriptor *confdes;
 185         const struct libusb_interface_descriptor *intfdes;
 186         const struct libusb_endpoint_descriptor *ep;
 187         int confidx, intfidx, epidx, config = 0;
 188         uint8_t capabilities[24];
 189         int ret, found = 0;
 190
 191         if (usb->devhdl)
 192                 return SR_OK;
 193
 194         if (sr_usb_open(uscpi->ctx->libusb_ctx, usb) != SR_OK)
 195                 return SR_ERR;
 196
 197         dev = libusb_get_device(usb->devhdl);
 198         if ((ret = libusb_get_device_descriptor(dev, &des)) < 0) {
 199                 sr_err("Failed to get device descriptor: %s.",
 200                        libusb_error_name(ret));
 201                 return SR_ERR;
 202         }
 203
 204         for (confidx = 0; confidx < des.bNumConfigurations; confidx++) {
 205                 if ((ret = libusb_get_config_descriptor(dev, confidx, &confdes)) < 0) {
 206                         sr_dbg("Failed to get configuration descriptor: %s, "
 207                                "ignoring device.", libusb_error_name(ret));
 208                         continue;
 209                 }
 210                 for (intfidx = 0; intfidx < confdes->bNumInterfaces; intfidx++) {
 211                         intfdes = confdes->interface[intfidx].altsetting;
 212                         if (intfdes->bInterfaceClass    != LIBUSB_CLASS_APPLICATION ||
 213                             intfdes->bInterfaceSubClass != SUBCLASS_USBTMC          ||
 214                             intfdes->bInterfaceProtocol != USBTMC_USB488)
 215                                 continue;
 216                         uscpi->interface = intfdes->bInterfaceNumber;
 217                         config = confdes->bConfigurationValue;
 218                         sr_dbg("Interface %d configuration %d.", uscpi->interface, config);
 219                         for (epidx = 0; epidx < intfdes->bNumEndpoints; epidx++) {
 220                                 ep = &intfdes->endpoint[epidx];
 221                                 if (ep->bmAttributes == LIBUSB_TRANSFER_TYPE_BULK &&
 222                                     !(ep->bEndpointAddress & (LIBUSB_ENDPOINT_DIR_MASK))) {
 223                                         uscpi->bulk_out_ep = ep->bEndpointAddress;
 224                                         sr_dbg("Bulk OUT EP %d", uscpi->bulk_out_ep);
 225                                 }
 226                                 if (ep->bmAttributes == LIBUSB_TRANSFER_TYPE_BULK &&
 227                                     ep->bEndpointAddress & (LIBUSB_ENDPOINT_DIR_MASK)) {
 228                                         uscpi->bulk_in_ep = ep->bEndpointAddress;
 229                                         sr_dbg("Bulk IN EP %d", uscpi->bulk_in_ep & 0x7f);
 230                                 }
 231                                 if (ep->bmAttributes == LIBUSB_TRANSFER_TYPE_INTERRUPT &&
 232                                     ep->bEndpointAddress & (LIBUSB_ENDPOINT_DIR_MASK)) {
 233                                         uscpi->interrupt_ep = ep->bEndpointAddress;
 234                                         sr_dbg("Interrupt EP %d", uscpi->interrupt_ep & 0x7f);
 235                                 }
 236                         }
 237                         found = 1;
 238                         uscpi->rigol_ds1000 = des.idVendor  == 0x1ab1 &&
 239                                               des.idProduct == 0x0588;
 240                 }
 241                 libusb_free_config_descriptor(confdes);
 242                 if (found)
 243                         break;
 244         }
 245
 246         if (!found) {
 247                 sr_err("Failed to find USBTMC interface.");
 248                 return SR_ERR;
 249         }
 250
 251         if (libusb_kernel_driver_active(usb->devhdl, uscpi->interface) == 1) {
 252                 if ((ret = libusb_detach_kernel_driver(usb->devhdl,
 253                                                        uscpi->interface)) < 0) {
 254                         sr_err("Failed to detach kernel driver: %s.",
 255                                libusb_error_name(ret));
 256                         return SR_ERR;
 257                 }
 258                 uscpi->detached_kernel_driver = 1;
 259         }
 260
 261         if ((ret = libusb_set_configuration(usb->devhdl, config)) < 0) {
 262                 sr_err("Failed to set configuration: %s.",
 263                        libusb_error_name(ret));
 264                 return SR_ERR;
 265         }
 266
 267         if ((ret = libusb_claim_interface(usb->devhdl, uscpi->interface)) < 0) {
 268                 sr_err("Failed to claim interface: %s.",
 269                        libusb_error_name(ret));
 270                 return SR_ERR;
 271         }
 272
 273         if (!uscpi->rigol_ds1000) {
 274         if ((ret = libusb_clear_halt(usb->devhdl, uscpi->bulk_in_ep)) < 0) {
 275                 sr_err("Failed to clear halt/stall condition for EP %d: %s.",
 276                        uscpi->bulk_in_ep, libusb_error_name(ret));
 277                 return SR_ERR;
 278         }
 279         if ((ret = libusb_clear_halt(usb->devhdl, uscpi->bulk_out_ep)) < 0) {
 280                 sr_err("Failed to clear halt/stall condition for EP %d: %s.",
 281                        uscpi->bulk_out_ep, libusb_error_name(ret));
 282                 return SR_ERR;
 283         }
 284         if ((ret = libusb_clear_halt(usb->devhdl, uscpi->interrupt_ep)) < 0) {
 285                 sr_err("Failed to clear halt/stall condition for EP %d: %s.",
 286                        uscpi->interrupt_ep, libusb_error_name(ret));
 287                 return SR_ERR;
 288         }
 289         }
 290
 291         /* Get capabilities. */
 292         ret = libusb_control_transfer(usb->devhdl,
 293                                       LIBUSB_ENDPOINT_IN         |
 294                                       LIBUSB_REQUEST_TYPE_CLASS  |
 295                                       LIBUSB_RECIPIENT_INTERFACE,
 296                                       GET_CAPABILITIES, 0,
 297                                       uscpi->interface,
 298                                       capabilities, sizeof(capabilities),
 299                                       TRANSFER_TIMEOUT);
 300         if (ret == sizeof(capabilities)) {
 301                 uscpi->usbtmc_int_cap = capabilities[ 4];
 302                 uscpi->usbtmc_dev_cap = capabilities[ 5];
 303                 uscpi->usb488_dev_cap = capabilities[15];
 304         }
 305         sr_dbg("Device capabilities: %s%s%s%s%s, %s, %s",
 306                uscpi->usb488_dev_cap & USB488_DEV_CAP_SCPI       ? "SCPI, "    : "",
 307                uscpi->usbtmc_dev_cap & USBTMC_DEV_CAP_TERMCHAR   ? "TermChar, ": "",
 308                uscpi->usbtmc_int_cap & USBTMC_INT_CAP_LISTEN_ONLY? "L3, " :
 309                uscpi->usbtmc_int_cap & USBTMC_INT_CAP_TALK_ONLY  ? ""     : "L4, ",
 310                uscpi->usbtmc_int_cap & USBTMC_INT_CAP_TALK_ONLY  ? "T5, " :
 311                uscpi->usbtmc_int_cap & USBTMC_INT_CAP_LISTEN_ONLY? ""     : "T6, ",
 312                uscpi->usb488_dev_cap & USB488_DEV_CAP_SR1        ? "SR1"  : "SR0",
 313                uscpi->usb488_dev_cap & USB488_DEV_CAP_RL1        ? "RL1"  : "RL0",
 314                uscpi->usb488_dev_cap & USB488_DEV_CAP_DT1        ? "DT1"  : "DT0");
 315
 316         return SR_OK;
 317 }
 318
 319 static int scpi_usbtmc_libusb_source_add(struct sr_session *session,
 320                 void *priv, int events, int timeout, sr_receive_data_callback cb,
 321                 void *cb_data)
 322 {
 323         struct scpi_usbtmc_libusb *uscpi = priv;
 324         (void)events;
 325         return usb_source_add(session, uscpi->ctx, timeout, cb, cb_data);
 326 }
 327
 328 static int scpi_usbtmc_libusb_source_remove(struct sr_session *session,
 329                 void *priv)
 330 {
 331         struct scpi_usbtmc_libusb *uscpi = priv;
 332         return usb_source_remove(session, uscpi->ctx);
 333 }
 334
 335 static void usbtmc_bulk_out_header_write(void *header, uint8_t MsgID,
 336                                          uint8_t bTag,
 337                                          uint32_t TransferSize,
 338                                          uint8_t bmTransferAttributes,
 339                                          char TermChar)
 340 {
 341           W8(header+ 0, MsgID);
 342           W8(header+ 1, bTag);
 343           W8(header+ 2, ~bTag);
 344           W8(header+ 3, 0);
 345         WL32(header+ 4, TransferSize);
 346           W8(header+ 8, bmTransferAttributes);
 347           W8(header+ 9, TermChar);
 348         WL16(header+10, 0);
 349 }
 350
 351 static int usbtmc_bulk_in_header_read(void *header, uint8_t MsgID,
 352                                       unsigned char bTag,
 353                                       int32_t *TransferSize,
 354                                       uint8_t *bmTransferAttributes)
 355 {
 356         if (R8(header+0) != MsgID ||
 357             R8(header+1) != bTag  ||
 358             R8(header+2) != (unsigned char)~bTag)
 359                 return SR_ERR;
 360         if (TransferSize)
 361                 *TransferSize = RL32(header+4);
 362         if (bmTransferAttributes)
 363                 *bmTransferAttributes = R8(header+8);
 364         return SR_OK;
 365 }
 366
 367 static int scpi_usbtmc_bulkout(struct scpi_usbtmc_libusb *uscpi,
 368                                uint8_t msg_id, const void *data, int32_t size,
 369                                uint8_t transfer_attributes)
 370 {
 371         struct sr_usb_dev_inst *usb = uscpi->usb;
 372         int padded_size, ret, transferred;
 373
 374         if (data && size+USBTMC_BULK_HEADER_SIZE+3 > (int)sizeof(uscpi->buffer)) {
 375                 sr_err("USBTMC bulk out transfer is too big.");
 376                 return SR_ERR;
 377         }
 378
 379         uscpi->bTag++;
 380         uscpi->bTag += !uscpi->bTag;  /* bTag == 0 is invalid so avoid it. */
 381
 382         usbtmc_bulk_out_header_write(uscpi->buffer, msg_id, uscpi->bTag,
 383                                      size, transfer_attributes, 0);
 384         if (data)
 385                 memcpy(uscpi->buffer+USBTMC_BULK_HEADER_SIZE, data, size);
 386         else
 387                 size = 0;
 388         size += USBTMC_BULK_HEADER_SIZE;
 389         padded_size = (size + 3) & ~0x3;
 390         memset(uscpi->buffer+size, 0, padded_size - size);
 391
 392         ret = libusb_bulk_transfer(usb->devhdl, uscpi->bulk_out_ep,
 393                                    uscpi->buffer, padded_size, &transferred,
 394                                    TRANSFER_TIMEOUT);
 395         if (ret < 0) {
 396                 sr_err("USBTMC bulk out transfer error: %s.",
 397                        libusb_error_name(ret));
 398                 return SR_ERR;
 399         }
 400
 401         if (transferred < padded_size) {
 402                 sr_dbg("USBTMC bulk out partial transfer (%d/%d bytes).",
 403                        transferred, padded_size);
 404                 return SR_ERR;
 405         }
 406
 407         return transferred - USBTMC_BULK_HEADER_SIZE;
 408 }
 409
 410 static int scpi_usbtmc_bulkin_start(struct scpi_usbtmc_libusb *uscpi,
 411                                     uint8_t msg_id, void *data, int32_t size,
 412                                     uint8_t *transfer_attributes)
 413 {
 414         struct sr_usb_dev_inst *usb = uscpi->usb;
 415         int ret, transferred, message_size;
 416
 417         ret = libusb_bulk_transfer(usb->devhdl, uscpi->bulk_in_ep, data, size,
 418                                    &transferred, TRANSFER_TIMEOUT);
 419         if (ret < 0) {
 420                 sr_err("USBTMC bulk in transfer error: %s.",
 421                        libusb_error_name(ret));
 422                 return SR_ERR;
 423         }
 424
 425         if (usbtmc_bulk_in_header_read(data, msg_id, uscpi->bTag, &message_size,
 426                                        transfer_attributes) != SR_OK) {
 427                 sr_err("USBTMC invalid bulk in header.");
 428                 return SR_ERR;
 429         }
 430
 431         message_size += USBTMC_BULK_HEADER_SIZE;
 432         uscpi->response_length = MIN(transferred, message_size);
 433         uscpi->response_bytes_read = USBTMC_BULK_HEADER_SIZE;
 434         uscpi->remaining_length = message_size - uscpi->response_length;
 435
 436         return transferred - USBTMC_BULK_HEADER_SIZE;
 437 }
 438
 439 static int scpi_usbtmc_bulkin_continue(struct scpi_usbtmc_libusb *uscpi,
 440                                        void *data, int size)
 441 {
 442         struct sr_usb_dev_inst *usb = uscpi->usb;
 443         int ret, transferred;
 444
 445         ret = libusb_bulk_transfer(usb->devhdl, uscpi->bulk_in_ep, data, size,
 446                                    &transferred, TRANSFER_TIMEOUT);
 447         if (ret < 0) {
 448                 sr_err("USBTMC bulk in transfer error: %s.",
 449                        libusb_error_name(ret));
 450                 return SR_ERR;
 451         }
 452
 453         uscpi->response_length = MIN(transferred, uscpi->remaining_length);
 454         uscpi->response_bytes_read = 0;
 455         uscpi->remaining_length -= uscpi->response_length;
 456
 457         return transferred;
 458 }
 459
 460 static int scpi_usbtmc_libusb_send(void *priv, const char *command)
 461 {
 462         struct scpi_usbtmc_libusb *uscpi = priv;
 463
 464         if (scpi_usbtmc_bulkout(uscpi, DEV_DEP_MSG_OUT,
 465                                 command, strlen(command), EOM) <= 0)
 466                 return SR_ERR;
 467
 468         sr_spew("Successfully sent SCPI command: '%s'.", command);
 469
 470         return SR_OK;
 471 }
 472
 473 static int scpi_usbtmc_libusb_read_begin(void *priv)
 474 {
 475         struct scpi_usbtmc_libusb *uscpi = priv;
 476
 477         uscpi->remaining_length = 0;
 478
 479         if (scpi_usbtmc_bulkout(uscpi, REQUEST_DEV_DEP_MSG_IN,
 480             NULL, INT32_MAX, 0) < 0)
 481                 return SR_ERR;
 482         if (scpi_usbtmc_bulkin_start(uscpi, DEV_DEP_MSG_IN,
 483                                      uscpi->buffer, sizeof(uscpi->buffer),
 484                                      &uscpi->bulkin_attributes) < 0)
 485                 return SR_ERR;
 486
 487         return SR_OK;
 488 }
 489
 490 static int scpi_usbtmc_libusb_read_data(void *priv, char *buf, int maxlen)
 491 {
 492         struct scpi_usbtmc_libusb *uscpi = priv;
 493         int read_length;
 494
 495         if (uscpi->response_bytes_read >= uscpi->response_length) {
 496                 if (uscpi->remaining_length > 0) {
 497                         if (scpi_usbtmc_bulkin_continue(uscpi, uscpi->buffer,
 498                                                         sizeof(uscpi->buffer)) <= 0)
 499                                 return SR_ERR;
 500                 } else {
 501                         if (uscpi->bulkin_attributes & EOM)
 502                                 return SR_ERR;
 503                         if (scpi_usbtmc_libusb_read_begin(uscpi) < 0)
 504                                 return SR_ERR;
 505                 }
 506         }
 507
 508         read_length = MIN(uscpi->response_length - uscpi->response_bytes_read, maxlen);
 509
 510         memcpy(buf, uscpi->buffer + uscpi->response_bytes_read, read_length);
 511
 512         uscpi->response_bytes_read += read_length;
 513
 514         return read_length;
 515 }
 516
 517 static int scpi_usbtmc_libusb_read_complete(void *priv)
 518 {
 519         struct scpi_usbtmc_libusb *uscpi = priv;
 520         return uscpi->response_bytes_read >= uscpi->response_length &&
 521                uscpi->remaining_length <= 0 &&
 522                uscpi->bulkin_attributes & EOM;
 523 }
 524
 525 static int scpi_usbtmc_libusb_close(void *priv)
 526 {
 527         int ret;
 528         struct scpi_usbtmc_libusb *uscpi = priv;
 529         struct sr_usb_dev_inst *usb = uscpi->usb;
 530
 531         if (!usb->devhdl)
 532                 return SR_ERR;
 533
 534         if (!uscpi->rigol_ds1000) {
 535         if ((ret = libusb_clear_halt(usb->devhdl, uscpi->bulk_in_ep)) < 0)
 536                 sr_err("Failed to clear halt/stall condition for EP %d: %s.",
 537                        uscpi->bulk_in_ep, libusb_error_name(ret));
 538         if ((ret = libusb_clear_halt(usb->devhdl, uscpi->bulk_out_ep)) < 0)
 539                 sr_err("Failed to clear halt/stall condition for EP %d: %s.",
 540                        uscpi->bulk_out_ep, libusb_error_name(ret));
 541         if ((ret = libusb_clear_halt(usb->devhdl, uscpi->interrupt_ep)) < 0)
 542                 sr_err("Failed to clear halt/stall condition for EP %d: %s.",
 543                        uscpi->interrupt_ep, libusb_error_name(ret));
 544         }
 545
 546         if ((ret = libusb_release_interface(usb->devhdl, uscpi->interface)) < 0)
 547                 sr_err("Failed to release interface: %s.",
 548                        libusb_error_name(ret));
 549
 550         if (uscpi->detached_kernel_driver) {
 551                 if ((ret = libusb_attach_kernel_driver(usb->devhdl,
 552                                                 uscpi->interface)) < 0)
 553                         sr_err("Failed to re-attach kernel driver: %s.",
 554                                libusb_error_name(ret));
 555
 556                 uscpi->detached_kernel_driver = 0;
 557         }
 558         sr_usb_close(usb);
 559
 560         return SR_OK;
 561 }
 562
 563 static void scpi_usbtmc_libusb_free(void *priv)
 564 {
 565         struct scpi_usbtmc_libusb *uscpi = priv;
 566         sr_usb_dev_inst_free(uscpi->usb);
 567 }
 568
 569 SR_PRIV const struct sr_scpi_dev_inst scpi_usbtmc_libusb_dev = {
 570         .name          = "USBTMC",
 571         .prefix        = "usbtmc",
 572         .priv_size     = sizeof(struct scpi_usbtmc_libusb),
 573         .scan          = scpi_usbtmc_libusb_scan,
 574         .dev_inst_new  = scpi_usbtmc_libusb_dev_inst_new,
 575         .open          = scpi_usbtmc_libusb_open,
 576         .source_add    = scpi_usbtmc_libusb_source_add,
 577         .source_remove = scpi_usbtmc_libusb_source_remove,
 578         .send          = scpi_usbtmc_libusb_send,
 579         .read_begin    = scpi_usbtmc_libusb_read_begin,
 580         .read_data     = scpi_usbtmc_libusb_read_data,
 581         .read_complete = scpi_usbtmc_libusb_read_complete,
 582         .close         = scpi_usbtmc_libusb_close,
 583         .free          = scpi_usbtmc_libusb_free,
 584 };