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