drivers/usb/core/devices.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * devices.c
   4  * (C) Copyright 1999 Randy Dunlap.
   5  * (C) Copyright 1999,2000 Thomas Sailer <[email protected]>.
   6  *     (proc file per device)
   7  * (C) Copyright 1999 Deti Fliegl (new USB architecture)
   8  *
   9  *************************************************************
  10  *
  11  * <mountpoint>/devices contains USB topology, device, config, class,
  12  * interface, & endpoint data.
  13  *
  14  * I considered using /dev/bus/usb/device# for each device
  15  * as it is attached or detached, but I didn't like this for some
  16  * reason -- maybe it's just too deep of a directory structure.
  17  * I also don't like looking in multiple places to gather and view
  18  * the data.  Having only one file for ./devices also prevents race
  19  * conditions that could arise if a program was reading device info
  20  * for devices that are being removed (unplugged).  (That is, the
  21  * program may find a directory for devnum_12 then try to open it,
  22  * but it was just unplugged, so the directory is now deleted.
  23  * But programs would just have to be prepared for situations like
  24  * this in any plug-and-play environment.)
  25  *
  26  * 1999-12-16: Thomas Sailer <[email protected]>
  27  *   Converted the whole proc stuff to real
  28  *   read methods. Now not the whole device list needs to fit
  29  *   into one page, only the device list for one bus.
  30  *   Added a poll method to /sys/kernel/debug/usb/devices, to wake
  31  *   up an eventual usbd
  32  * 2000-01-04: Thomas Sailer <[email protected]>
  33  *   Turned into its own filesystem
  34  * 2000-07-05: Ashley Montanaro <[email protected]>
  35  *   Converted file reading routine to dump to buffer once
  36  *   per device, not per bus
  37  */
  38
  39 #include <linux/fs.h>
  40 #include <linux/mm.h>
  41 #include <linux/gfp.h>
  42 #include <linux/poll.h>
  43 #include <linux/usb.h>
  44 #include <linux/usbdevice_fs.h>
  45 #include <linux/usb/hcd.h>
  46 #include <linux/mutex.h>
  47 #include <linux/uaccess.h>
  48
  49 #include "usb.h"
  50
  51 /* Define ALLOW_SERIAL_NUMBER if you want to see the serial number of devices */
  52 #define ALLOW_SERIAL_NUMBER
  53
  54 static const char format_topo[] =
  55 /* T:  Bus=dd Lev=dd Prnt=dd Port=dd Cnt=dd Dev#=ddd Spd=dddd MxCh=dd */
  56 "\nT:  Bus=%2.2d Lev=%2.2d Prnt=%2.2d Port=%2.2d Cnt=%2.2d Dev#=%3d Spd=%-4s MxCh=%2d\n";
  57
  58 static const char format_string_manufacturer[] =
  59 /* S:  Manufacturer=xxxx */
  60   "S:  Manufacturer=%.100s\n";
  61
  62 static const char format_string_product[] =
  63 /* S:  Product=xxxx */
  64   "S:  Product=%.100s\n";
  65
  66 #ifdef ALLOW_SERIAL_NUMBER
  67 static const char format_string_serialnumber[] =
  68 /* S:  SerialNumber=xxxx */
  69   "S:  SerialNumber=%.100s\n";
  70 #endif
  71
  72 static const char format_bandwidth[] =
  73 /* B:  Alloc=ddd/ddd us (xx%), #Int=ddd, #Iso=ddd */
  74   "B:  Alloc=%3d/%3d us (%2d%%), #Int=%3d, #Iso=%3d\n";
  75
  76 static const char format_device1[] =
  77 /* D:  Ver=xx.xx Cls=xx(sssss) Sub=xx Prot=xx MxPS=dd #Cfgs=dd */
  78   "D:  Ver=%2x.%02x Cls=%02x(%-5s) Sub=%02x Prot=%02x MxPS=%2d #Cfgs=%3d\n";
  79
  80 static const char format_device2[] =
  81 /* P:  Vendor=xxxx ProdID=xxxx Rev=xx.xx */
  82   "P:  Vendor=%04x ProdID=%04x Rev=%2x.%02x\n";
  83
  84 static const char format_config[] =
  85 /* C:  #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA */
  86   "C:%c #Ifs=%2d Cfg#=%2d Atr=%02x MxPwr=%3dmA\n";
  87
  88 static const char format_iad[] =
  89 /* A:  FirstIf#=dd IfCount=dd Cls=xx(sssss) Sub=xx Prot=xx */
  90   "A:  FirstIf#=%2d IfCount=%2d Cls=%02x(%-5s) Sub=%02x Prot=%02x\n";
  91
  92 static const char format_iface[] =
  93 /* I:  If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=xxxx*/
  94   "I:%c If#=%2d Alt=%2d #EPs=%2d Cls=%02x(%-5s) Sub=%02x Prot=%02x Driver=%s\n";
  95
  96 static const char format_endpt[] =
  97 /* E:  Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=D?s */
  98   "E:  Ad=%02x(%c) Atr=%02x(%-4s) MxPS=%4d Ivl=%d%cs\n";
  99
 100 /*
 101  * Wait for an connect/disconnect event to happen. We initialize
 102  * the event counter with an odd number, and each event will increment
 103  * the event counter by two, so it will always _stay_ odd. That means
 104  * that it will never be zero, so "event 0" will never match a current
 105  * event, and thus 'poll' will always trigger as readable for the first
 106  * time it gets called.
 107  */
 108 static struct device_connect_event {
 109         atomic_t count;
 110         wait_queue_head_t wait;
 111 } device_event = {
 112         .count = ATOMIC_INIT(1),
 113         .wait = __WAIT_QUEUE_HEAD_INITIALIZER(device_event.wait)
 114 };
 115
 116 struct class_info {
 117         int class;
 118         char *class_name;
 119 };
 120
 121 static const struct class_info clas_info[] = {
 122         /* max. 5 chars. per name string */
 123         {USB_CLASS_PER_INTERFACE,       ">ifc"},
 124         {USB_CLASS_AUDIO,               "audio"},
 125         {USB_CLASS_COMM,                "comm."},
 126         {USB_CLASS_HID,                 "HID"},
 127         {USB_CLASS_PHYSICAL,            "PID"},
 128         {USB_CLASS_STILL_IMAGE,         "still"},
 129         {USB_CLASS_PRINTER,             "print"},
 130         {USB_CLASS_MASS_STORAGE,        "stor."},
 131         {USB_CLASS_HUB,                 "hub"},
 132         {USB_CLASS_CDC_DATA,            "data"},
 133         {USB_CLASS_CSCID,               "scard"},
 134         {USB_CLASS_CONTENT_SEC,         "c-sec"},
 135         {USB_CLASS_VIDEO,               "video"},
 136         {USB_CLASS_PERSONAL_HEALTHCARE, "perhc"},
 137         {USB_CLASS_AUDIO_VIDEO,         "av"},
 138         {USB_CLASS_BILLBOARD,           "blbrd"},
 139         {USB_CLASS_USB_TYPE_C_BRIDGE,   "bridg"},
 140         {USB_CLASS_WIRELESS_CONTROLLER, "wlcon"},
 141         {USB_CLASS_MISC,                "misc"},
 142         {USB_CLASS_APP_SPEC,            "app."},
 143         {USB_CLASS_VENDOR_SPEC,         "vend."},
 144         {-1,                            "unk."}         /* leave as last */
 145 };
 146
 147 /*****************************************************************/
 148
 149 void usbfs_conn_disc_event(void)
 150 {
 151         atomic_add(2, &device_event.count);
 152         wake_up(&device_event.wait);
 153 }
 154
 155 static const char *class_decode(const int class)
 156 {
 157         int ix;
 158
 159         for (ix = 0; clas_info[ix].class != -1; ix++)
 160                 if (clas_info[ix].class == class)
 161                         break;
 162         return clas_info[ix].class_name;
 163 }
 164
 165 static char *usb_dump_endpoint_descriptor(int speed, char *start, char *end,
 166                                 const struct usb_endpoint_descriptor *desc)
 167 {
 168         char dir, unit, *type;
 169         unsigned interval, bandwidth = 1;
 170
 171         if (start > end)
 172                 return start;
 173
 174         dir = usb_endpoint_dir_in(desc) ? 'I' : 'O';
 175
 176         if (speed == USB_SPEED_HIGH)
 177                 bandwidth = usb_endpoint_maxp_mult(desc);
 178
 179         /* this isn't checking for illegal values */
 180         switch (usb_endpoint_type(desc)) {
 181         case USB_ENDPOINT_XFER_CONTROL:
 182                 type = "Ctrl";
 183                 if (speed == USB_SPEED_HIGH)    /* uframes per NAK */
 184                         interval = desc->bInterval;
 185                 else
 186                         interval = 0;
 187                 dir = 'B';                      /* ctrl is bidirectional */
 188                 break;
 189         case USB_ENDPOINT_XFER_ISOC:
 190                 type = "Isoc";
 191                 interval = 1 << (desc->bInterval - 1);
 192                 break;
 193         case USB_ENDPOINT_XFER_BULK:
 194                 type = "Bulk";
 195                 if (speed == USB_SPEED_HIGH && dir == 'O') /* uframes per NAK */
 196                         interval = desc->bInterval;
 197                 else
 198                         interval = 0;
 199                 break;
 200         case USB_ENDPOINT_XFER_INT:
 201                 type = "Int.";
 202                 if (speed == USB_SPEED_HIGH || speed >= USB_SPEED_SUPER)
 203                         interval = 1 << (desc->bInterval - 1);
 204                 else
 205                         interval = desc->bInterval;
 206                 break;
 207         default:        /* "can't happen" */
 208                 return start;
 209         }
 210         interval *= (speed == USB_SPEED_HIGH ||
 211                      speed >= USB_SPEED_SUPER) ? 125 : 1000;
 212         if (interval % 1000)
 213                 unit = 'u';
 214         else {
 215                 unit = 'm';
 216                 interval /= 1000;
 217         }
 218
 219         start += sprintf(start, format_endpt, desc->bEndpointAddress, dir,
 220                          desc->bmAttributes, type,
 221                          usb_endpoint_maxp(desc) *
 222                          bandwidth,
 223                          interval, unit);
 224         return start;
 225 }
 226
 227 static char *usb_dump_interface_descriptor(char *start, char *end,
 228                                         const struct usb_interface_cache *intfc,
 229                                         const struct usb_interface *iface,
 230                                         int setno)
 231 {
 232         const struct usb_interface_descriptor *desc;
 233         const char *driver_name = "";
 234         int active = 0;
 235
 236         if (start > end)
 237                 return start;
 238         desc = &intfc->altsetting[setno].desc;
 239         if (iface) {
 240                 driver_name = (iface->dev.driver
 241                                 ? iface->dev.driver->name
 242                                 : "(none)");
 243                 active = (desc == &iface->cur_altsetting->desc);
 244         }
 245         start += sprintf(start, format_iface,
 246                          active ? '*' : ' ',    /* mark active altsetting */
 247                          desc->bInterfaceNumber,
 248                          desc->bAlternateSetting,
 249                          desc->bNumEndpoints,
 250                          desc->bInterfaceClass,
 251                          class_decode(desc->bInterfaceClass),
 252                          desc->bInterfaceSubClass,
 253                          desc->bInterfaceProtocol,
 254                          driver_name);
 255         return start;
 256 }
 257
 258 static char *usb_dump_interface(int speed, char *start, char *end,
 259                                 const struct usb_interface_cache *intfc,
 260                                 const struct usb_interface *iface, int setno)
 261 {
 262         const struct usb_host_interface *desc = &intfc->altsetting[setno];
 263         int i;
 264
 265         start = usb_dump_interface_descriptor(start, end, intfc, iface, setno);
 266         for (i = 0; i < desc->desc.bNumEndpoints; i++) {
 267                 if (start > end)
 268                         return start;
 269                 start = usb_dump_endpoint_descriptor(speed,
 270                                 start, end, &desc->endpoint[i].desc);
 271         }
 272         return start;
 273 }
 274
 275 static char *usb_dump_iad_descriptor(char *start, char *end,
 276                         const struct usb_interface_assoc_descriptor *iad)
 277 {
 278         if (start > end)
 279                 return start;
 280         start += sprintf(start, format_iad,
 281                          iad->bFirstInterface,
 282                          iad->bInterfaceCount,
 283                          iad->bFunctionClass,
 284                          class_decode(iad->bFunctionClass),
 285                          iad->bFunctionSubClass,
 286                          iad->bFunctionProtocol);
 287         return start;
 288 }
 289
 290 /* TBD:
 291  * 0. TBDs
 292  * 1. marking active interface altsettings (code lists all, but should mark
 293  *    which ones are active, if any)
 294  */
 295 static char *usb_dump_config_descriptor(char *start, char *end,
 296                                 const struct usb_config_descriptor *desc,
 297                                 int active, int speed)
 298 {
 299         int mul;
 300
 301         if (start > end)
 302                 return start;
 303         if (speed >= USB_SPEED_SUPER)
 304                 mul = 8;
 305         else
 306                 mul = 2;
 307         start += sprintf(start, format_config,
 308                          /* mark active/actual/current cfg. */
 309                          active ? '*' : ' ',
 310                          desc->bNumInterfaces,
 311                          desc->bConfigurationValue,
 312                          desc->bmAttributes,
 313                          desc->bMaxPower * mul);
 314         return start;
 315 }
 316
 317 static char *usb_dump_config(int speed, char *start, char *end,
 318                              const struct usb_host_config *config, int active)
 319 {
 320         int i, j;
 321         struct usb_interface_cache *intfc;
 322         struct usb_interface *interface;
 323
 324         if (start > end)
 325                 return start;
 326         if (!config)
 327                 /* getting these some in 2.3.7; none in 2.3.6 */
 328                 return start + sprintf(start, "(null Cfg. desc.)\n");
 329         start = usb_dump_config_descriptor(start, end, &config->desc, active,
 330                         speed);
 331         for (i = 0; i < USB_MAXIADS; i++) {
 332                 if (config->intf_assoc[i] == NULL)
 333                         break;
 334                 start = usb_dump_iad_descriptor(start, end,
 335                                         config->intf_assoc[i]);
 336         }
 337         for (i = 0; i < config->desc.bNumInterfaces; i++) {
 338                 intfc = config->intf_cache[i];
 339                 interface = config->interface[i];
 340                 for (j = 0; j < intfc->num_altsetting; j++) {
 341                         if (start > end)
 342                                 return start;
 343                         start = usb_dump_interface(speed,
 344                                 start, end, intfc, interface, j);
 345                 }
 346         }
 347         return start;
 348 }
 349
 350 /*
 351  * Dump the different USB descriptors.
 352  */
 353 static char *usb_dump_device_descriptor(char *start, char *end,
 354                                 const struct usb_device_descriptor *desc)
 355 {
 356         u16 bcdUSB = le16_to_cpu(desc->bcdUSB);
 357         u16 bcdDevice = le16_to_cpu(desc->bcdDevice);
 358
 359         if (start > end)
 360                 return start;
 361         start += sprintf(start, format_device1,
 362                           bcdUSB >> 8, bcdUSB & 0xff,
 363                           desc->bDeviceClass,
 364                           class_decode(desc->bDeviceClass),
 365                           desc->bDeviceSubClass,
 366                           desc->bDeviceProtocol,
 367                           desc->bMaxPacketSize0,
 368                           desc->bNumConfigurations);
 369         if (start > end)
 370                 return start;
 371         start += sprintf(start, format_device2,
 372                          le16_to_cpu(desc->idVendor),
 373                          le16_to_cpu(desc->idProduct),
 374                          bcdDevice >> 8, bcdDevice & 0xff);
 375         return start;
 376 }
 377
 378 /*
 379  * Dump the different strings that this device holds.
 380  */
 381 static char *usb_dump_device_strings(char *start, char *end,
 382                                      struct usb_device *dev)
 383 {
 384         if (start > end)
 385                 return start;
 386         if (dev->manufacturer)
 387                 start += sprintf(start, format_string_manufacturer,
 388                                  dev->manufacturer);
 389         if (start > end)
 390                 goto out;
 391         if (dev->product)
 392                 start += sprintf(start, format_string_product, dev->product);
 393         if (start > end)
 394                 goto out;
 395 #ifdef ALLOW_SERIAL_NUMBER
 396         if (dev->serial)
 397                 start += sprintf(start, format_string_serialnumber,
 398                                  dev->serial);
 399 #endif
 400  out:
 401         return start;
 402 }
 403
 404 static char *usb_dump_desc(char *start, char *end, struct usb_device *dev)
 405 {
 406         int i;
 407
 408         if (start > end)
 409                 return start;
 410
 411         start = usb_dump_device_descriptor(start, end, &dev->descriptor);
 412
 413         if (start > end)
 414                 return start;
 415
 416         start = usb_dump_device_strings(start, end, dev);
 417
 418         for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
 419                 if (start > end)
 420                         return start;
 421                 start = usb_dump_config(dev->speed,
 422                                 start, end, dev->config + i,
 423                                 /* active ? */
 424                                 (dev->config + i) == dev->actconfig);
 425         }
 426         return start;
 427 }
 428
 429
 430 #ifdef PROC_EXTRA /* TBD: may want to add this code later */
 431
 432 static char *usb_dump_hub_descriptor(char *start, char *end,
 433                                      const struct usb_hub_descriptor *desc)
 434 {
 435         int leng = USB_DT_HUB_NONVAR_SIZE;
 436         unsigned char *ptr = (unsigned char *)desc;
 437
 438         if (start > end)
 439                 return start;
 440         start += sprintf(start, "Interface:");
 441         while (leng && start <= end) {
 442                 start += sprintf(start, " %02x", *ptr);
 443                 ptr++; leng--;
 444         }
 445         *start++ = '\n';
 446         return start;
 447 }
 448
 449 static char *usb_dump_string(char *start, char *end,
 450                              const struct usb_device *dev, char *id, int index)
 451 {
 452         if (start > end)
 453                 return start;
 454         start += sprintf(start, "Interface:");
 455         if (index <= dev->maxstring && dev->stringindex &&
 456             dev->stringindex[index])
 457                 start += sprintf(start, "%s: %.100s ", id,
 458                                  dev->stringindex[index]);
 459         return start;
 460 }
 461
 462 #endif /* PROC_EXTRA */
 463
 464 /*****************************************************************/
 465
 466 /* This is a recursive function. Parameters:
 467  * buffer - the user-space buffer to write data into
 468  * nbytes - the maximum number of bytes to write
 469  * skip_bytes - the number of bytes to skip before writing anything
 470  * file_offset - the offset into the devices file on completion
 471  * The caller must own the device lock.
 472  */
 473 static ssize_t usb_device_dump(char __user **buffer, size_t *nbytes,
 474                                loff_t *skip_bytes, loff_t *file_offset,
 475                                struct usb_device *usbdev, struct usb_bus *bus,
 476                                int level, int index, int count)
 477 {
 478         int chix;
 479         int ret, cnt = 0;
 480         int parent_devnum = 0;
 481         char *pages_start, *data_end, *speed;
 482         unsigned int length;
 483         ssize_t total_written = 0;
 484         struct usb_device *childdev = NULL;
 485
 486         /* don't bother with anything else if we're not writing any data */
 487         if (*nbytes <= 0)
 488                 return 0;
 489
 490         if (level > MAX_TOPO_LEVEL)
 491                 return 0;
 492         /* allocate 2^1 pages = 8K (on i386);
 493          * should be more than enough for one device */
 494         pages_start = (char *)__get_free_pages(GFP_NOIO, 1);
 495         if (!pages_start)
 496                 return -ENOMEM;
 497
 498         if (usbdev->parent && usbdev->parent->devnum != -1)
 499                 parent_devnum = usbdev->parent->devnum;
 500         /*
 501          * So the root hub's parent is 0 and any device that is
 502          * plugged into the root hub has a parent of 0.
 503          */
 504         switch (usbdev->speed) {
 505         case USB_SPEED_LOW:
 506                 speed = "1.5"; break;
 507         case USB_SPEED_UNKNOWN:         /* usb 1.1 root hub code */
 508         case USB_SPEED_FULL:
 509                 speed = "12"; break;
 510         case USB_SPEED_WIRELESS:        /* Wireless has no real fixed speed */
 511         case USB_SPEED_HIGH:
 512                 speed = "480"; break;
 513         case USB_SPEED_SUPER:
 514                 speed = "5000"; break;
 515         case USB_SPEED_SUPER_PLUS:
 516                 speed = "10000"; break;
 517         default:
 518                 speed = "??";
 519         }
 520         data_end = pages_start + sprintf(pages_start, format_topo,
 521                         bus->busnum, level, parent_devnum,
 522                         index, count, usbdev->devnum,
 523                         speed, usbdev->maxchild);
 524         /*
 525          * level = topology-tier level;
 526          * parent_devnum = parent device number;
 527          * index = parent's connector number;
 528          * count = device count at this level
 529          */
 530         /* If this is the root hub, display the bandwidth information */
 531         if (level == 0) {
 532                 int     max;
 533
 534                 /* super/high speed reserves 80%, full/low reserves 90% */
 535                 if (usbdev->speed == USB_SPEED_HIGH ||
 536                     usbdev->speed >= USB_SPEED_SUPER)
 537                         max = 800;
 538                 else
 539                         max = FRAME_TIME_MAX_USECS_ALLOC;
 540
 541                 /* report "average" periodic allocation over a microsecond.
 542                  * the schedules are actually bursty, HCDs need to deal with
 543                  * that and just compute/report this average.
 544                  */
 545                 data_end += sprintf(data_end, format_bandwidth,
 546                                 bus->bandwidth_allocated, max,
 547                                 (100 * bus->bandwidth_allocated + max / 2)
 548                                         / max,
 549                                 bus->bandwidth_int_reqs,
 550                                 bus->bandwidth_isoc_reqs);
 551
 552         }
 553         data_end = usb_dump_desc(data_end, pages_start + (2 * PAGE_SIZE) - 256,
 554                                  usbdev);
 555
 556         if (data_end > (pages_start + (2 * PAGE_SIZE) - 256))
 557                 data_end += sprintf(data_end, "(truncated)\n");
 558
 559         length = data_end - pages_start;
 560         /* if we can start copying some data to the user */
 561         if (length > *skip_bytes) {
 562                 length -= *skip_bytes;
 563                 if (length > *nbytes)
 564                         length = *nbytes;
 565                 if (copy_to_user(*buffer, pages_start + *skip_bytes, length)) {
 566                         free_pages((unsigned long)pages_start, 1);
 567                         return -EFAULT;
 568                 }
 569                 *nbytes -= length;
 570                 *file_offset += length;
 571                 total_written += length;
 572                 *buffer += length;
 573                 *skip_bytes = 0;
 574         } else
 575                 *skip_bytes -= length;
 576
 577         free_pages((unsigned long)pages_start, 1);
 578
 579         /* Now look at all of this device's children. */
 580         usb_hub_for_each_child(usbdev, chix, childdev) {
 581                 usb_lock_device(childdev);
 582                 ret = usb_device_dump(buffer, nbytes, skip_bytes,
 583                                       file_offset, childdev, bus,
 584                                       level + 1, chix - 1, ++cnt);
 585                 usb_unlock_device(childdev);
 586                 if (ret == -EFAULT)
 587                         return total_written;
 588                 total_written += ret;
 589         }
 590         return total_written;
 591 }
 592
 593 static ssize_t usb_device_read(struct file *file, char __user *buf,
 594                                size_t nbytes, loff_t *ppos)
 595 {
 596         struct usb_bus *bus;
 597         ssize_t ret, total_written = 0;
 598         loff_t skip_bytes = *ppos;
 599         int id;
 600
 601         if (*ppos < 0)
 602                 return -EINVAL;
 603         if (nbytes <= 0)
 604                 return 0;
 605
 606         mutex_lock(&usb_bus_idr_lock);
 607         /* print devices for all busses */
 608         idr_for_each_entry(&usb_bus_idr, bus, id) {
 609                 /* recurse through all children of the root hub */
 610                 if (!bus_to_hcd(bus)->rh_registered)
 611                         continue;
 612                 usb_lock_device(bus->root_hub);
 613                 ret = usb_device_dump(&buf, &nbytes, &skip_bytes, ppos,
 614                                       bus->root_hub, bus, 0, 0, 0);
 615                 usb_unlock_device(bus->root_hub);
 616                 if (ret < 0) {
 617                         mutex_unlock(&usb_bus_idr_lock);
 618                         return ret;
 619                 }
 620                 total_written += ret;
 621         }
 622         mutex_unlock(&usb_bus_idr_lock);
 623         return total_written;
 624 }
 625
 626 /* Kernel lock for "lastev" protection */
 627 static __poll_t usb_device_poll(struct file *file,
 628                                     struct poll_table_struct *wait)
 629 {
 630         unsigned int event_count;
 631
 632         poll_wait(file, &device_event.wait, wait);
 633
 634         event_count = atomic_read(&device_event.count);
 635         if (file->f_version != event_count) {
 636                 file->f_version = event_count;
 637                 return EPOLLIN | EPOLLRDNORM;
 638         }
 639
 640         return 0;
 641 }
 642
 643 const struct file_operations usbfs_devices_fops = {
 644         .llseek =       no_seek_end_llseek,
 645         .read =         usb_device_read,
 646         .poll =         usb_device_poll,
 647 };