drivers/usb/core/devices.c

   1 /*
   2  * devices.c
   3  * (C) Copyright 1999 Randy Dunlap.
   4  * (C) Copyright 1999,2000 Thomas Sailer <sailer@ife.ee.ethz.ch>. (proc file per device)
   5  * (C) Copyright 1999 Deti Fliegl (new USB architecture)
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  *
  21  *************************************************************
  22  *
  23  * <mountpoint>/devices contains USB topology, device, config, class,
  24  * interface, & endpoint data.
  25  *
  26  * I considered using /proc/bus/usb/devices/device# for each device
  27  * as it is attached or detached, but I didn't like this for some
  28  * reason -- maybe it's just too deep of a directory structure.
  29  * I also don't like looking in multiple places to gather and view
  30  * the data.  Having only one file for ./devices also prevents race
  31  * conditions that could arise if a program was reading device info
  32  * for devices that are being removed (unplugged).  (That is, the
  33  * program may find a directory for devnum_12 then try to open it,
  34  * but it was just unplugged, so the directory is now deleted.
  35  * But programs would just have to be prepared for situations like
  36  * this in any plug-and-play environment.)
  37  *
  38  * 1999-12-16: Thomas Sailer <sailer@ife.ee.ethz.ch>
  39  *   Converted the whole proc stuff to real
  40  *   read methods. Now not the whole device list needs to fit
  41  *   into one page, only the device list for one bus.
  42  *   Added a poll method to /proc/bus/usb/devices, to wake
  43  *   up an eventual usbd
  44  * 2000-01-04: Thomas Sailer <sailer@ife.ee.ethz.ch>
  45  *   Turned into its own filesystem
  46  * 2000-07-05: Ashley Montanaro <ashley@compsoc.man.ac.uk>
  47  *   Converted file reading routine to dump to buffer once
  48  *   per device, not per bus
  49  */
  50
  51 #include <linux/fs.h>
  52 #include <linux/mm.h>
  53 #include <linux/slab.h>
  54 #include <linux/poll.h>
  55 #include <linux/usb.h>
  56 #include <linux/smp_lock.h>
  57 #include <linux/usbdevice_fs.h>
  58 #include <linux/mutex.h>
  59 #include <asm/uaccess.h>
  60
  61 #include "usb.h"
  62 #include "hcd.h"
  63
  64 /* Define ALLOW_SERIAL_NUMBER if you want to see the serial number of devices */
  65 #define ALLOW_SERIAL_NUMBER
  66
  67 static const char *format_topo =
  68 /* T:  Bus=dd Lev=dd Prnt=dd Port=dd Cnt=dd Dev#=ddd Spd=ddd MxCh=dd */
  69 "\nT:  Bus=%2.2d Lev=%2.2d Prnt=%2.2d Port=%2.2d Cnt=%2.2d Dev#=%3d Spd=%3s MxCh=%2d\n";
  70
  71 static const char *format_string_manufacturer =
  72 /* S:  Manufacturer=xxxx */
  73   "S:  Manufacturer=%.100s\n";
  74
  75 static const char *format_string_product =
  76 /* S:  Product=xxxx */
  77   "S:  Product=%.100s\n";
  78
  79 #ifdef ALLOW_SERIAL_NUMBER
  80 static const char *format_string_serialnumber =
  81 /* S:  SerialNumber=xxxx */
  82   "S:  SerialNumber=%.100s\n";
  83 #endif
  84
  85 static const char *format_bandwidth =
  86 /* B:  Alloc=ddd/ddd us (xx%), #Int=ddd, #Iso=ddd */
  87   "B:  Alloc=%3d/%3d us (%2d%%), #Int=%3d, #Iso=%3d\n";
  88
  89 static const char *format_device1 =
  90 /* D:  Ver=xx.xx Cls=xx(sssss) Sub=xx Prot=xx MxPS=dd #Cfgs=dd */
  91   "D:  Ver=%2x.%02x Cls=%02x(%-5s) Sub=%02x Prot=%02x MxPS=%2d #Cfgs=%3d\n";
  92
  93 static const char *format_device2 =
  94 /* P:  Vendor=xxxx ProdID=xxxx Rev=xx.xx */
  95   "P:  Vendor=%04x ProdID=%04x Rev=%2x.%02x\n";
  96
  97 static const char *format_config =
  98 /* C:  #Ifs=dd Cfg#=dd Atr=xx MPwr=dddmA */
  99   "C:%c #Ifs=%2d Cfg#=%2d Atr=%02x MxPwr=%3dmA\n";
 100
 101 static const char *format_iad =
 102 /* A:  FirstIf#=dd IfCount=dd Cls=xx(sssss) Sub=xx Prot=xx */
 103   "A:  FirstIf#=%2d IfCount=%2d Cls=%02x(%-5s) Sub=%02x Prot=%02x\n";
 104
 105 static const char *format_iface =
 106 /* I:  If#=dd Alt=dd #EPs=dd Cls=xx(sssss) Sub=xx Prot=xx Driver=xxxx*/
 107   "I:%c If#=%2d Alt=%2d #EPs=%2d Cls=%02x(%-5s) Sub=%02x Prot=%02x Driver=%s\n";
 108
 109 static const char *format_endpt =
 110 /* E:  Ad=xx(s) Atr=xx(ssss) MxPS=dddd Ivl=D?s */
 111   "E:  Ad=%02x(%c) Atr=%02x(%-4s) MxPS=%4d Ivl=%d%cs\n";
 112
 113
 114 /*
 115  * Need access to the driver and USB bus lists.
 116  * extern struct list_head usb_bus_list;
 117  * However, these will come from functions that return ptrs to each of them.
 118  */
 119
 120 static DECLARE_WAIT_QUEUE_HEAD(deviceconndiscwq);
 121 static unsigned int conndiscevcnt;
 122
 123 /* this struct stores the poll state for <mountpoint>/devices pollers */
 124 struct usb_device_status {
 125         unsigned int lastev;
 126 };
 127
 128 struct class_info {
 129         int class;
 130         char *class_name;
 131 };
 132
 133 static const struct class_info clas_info[] =
 134 {                                       /* max. 5 chars. per name string */
 135         {USB_CLASS_PER_INTERFACE,       ">ifc"},
 136         {USB_CLASS_AUDIO,               "audio"},
 137         {USB_CLASS_COMM,                "comm."},
 138         {USB_CLASS_HID,                 "HID"},
 139         {USB_CLASS_HUB,                 "hub"},
 140         {USB_CLASS_PHYSICAL,            "PID"},
 141         {USB_CLASS_PRINTER,             "print"},
 142         {USB_CLASS_MASS_STORAGE,        "stor."},
 143         {USB_CLASS_CDC_DATA,            "data"},
 144         {USB_CLASS_APP_SPEC,            "app."},
 145         {USB_CLASS_VENDOR_SPEC,         "vend."},
 146         {USB_CLASS_STILL_IMAGE,         "still"},
 147         {USB_CLASS_CSCID,               "scard"},
 148         {USB_CLASS_CONTENT_SEC,         "c-sec"},
 149         {USB_CLASS_VIDEO,               "video"},
 150         {-1,                            "unk."}         /* leave as last */
 151 };
 152
 153 /*****************************************************************/
 154
 155 void usbfs_conn_disc_event(void)
 156 {
 157         conndiscevcnt++;
 158         wake_up(&deviceconndiscwq);
 159 }
 160
 161 static const char *class_decode(const int class)
 162 {
 163         int ix;
 164
 165         for (ix = 0; clas_info[ix].class != -1; ix++)
 166                 if (clas_info[ix].class == class)
 167                         break;
 168         return clas_info[ix].class_name;
 169 }
 170
 171 static char *usb_dump_endpoint_descriptor(int speed, char *start, char *end,
 172                                 const struct usb_endpoint_descriptor *desc)
 173 {
 174         char dir, unit, *type;
 175         unsigned interval, bandwidth = 1;
 176
 177         if (start > end)
 178                 return start;
 179
 180         dir = usb_endpoint_dir_in(desc) ? 'I' : 'O';
 181
 182         if (speed == USB_SPEED_HIGH) {
 183                 switch (le16_to_cpu(desc->wMaxPacketSize) & (0x03 << 11)) {
 184                 case 1 << 11:   bandwidth = 2; break;
 185                 case 2 << 11:   bandwidth = 3; break;
 186                 }
 187         }
 188
 189         /* this isn't checking for illegal values */
 190         switch (usb_endpoint_type(desc)) {
 191         case USB_ENDPOINT_XFER_CONTROL:
 192                 type = "Ctrl";
 193                 if (speed == USB_SPEED_HIGH)    /* uframes per NAK */
 194                         interval = desc->bInterval;
 195                 else
 196                         interval = 0;
 197                 dir = 'B';                      /* ctrl is bidirectional */
 198                 break;
 199         case USB_ENDPOINT_XFER_ISOC:
 200                 type = "Isoc";
 201                 interval = 1 << (desc->bInterval - 1);
 202                 break;
 203         case USB_ENDPOINT_XFER_BULK:
 204                 type = "Bulk";
 205                 if (speed == USB_SPEED_HIGH && dir == 'O') /* uframes per NAK */
 206                         interval = desc->bInterval;
 207                 else
 208                         interval = 0;
 209                 break;
 210         case USB_ENDPOINT_XFER_INT:
 211                 type = "Int.";
 212                 if (speed == USB_SPEED_HIGH)
 213                         interval = 1 << (desc->bInterval - 1);
 214                 else
 215                         interval = desc->bInterval;
 216                 break;
 217         default:        /* "can't happen" */
 218                 return start;
 219         }
 220         interval *= (speed == USB_SPEED_HIGH) ? 125 : 1000;
 221         if (interval % 1000)
 222                 unit = 'u';
 223         else {
 224                 unit = 'm';
 225                 interval /= 1000;
 226         }
 227
 228         start += sprintf(start, format_endpt, desc->bEndpointAddress, dir,
 229                          desc->bmAttributes, type,
 230                          (le16_to_cpu(desc->wMaxPacketSize) & 0x07ff) *
 231                          bandwidth,
 232                          interval, unit);
 233         return start;
 234 }
 235
 236 static char *usb_dump_interface_descriptor(char *start, char *end,
 237                                         const struct usb_interface_cache *intfc,
 238                                         const struct usb_interface *iface,
 239                                         int setno)
 240 {
 241         const struct usb_interface_descriptor *desc;
 242         const char *driver_name = "";
 243         int active = 0;
 244
 245         if (start > end)
 246                 return start;
 247         desc = &intfc->altsetting[setno].desc;
 248         if (iface) {
 249                 driver_name = (iface->dev.driver
 250                                 ? iface->dev.driver->name
 251                                 : "(none)");
 252                 active = (desc == &iface->cur_altsetting->desc);
 253         }
 254         start += sprintf(start, format_iface,
 255                          active ? '*' : ' ',    /* mark active altsetting */
 256                          desc->bInterfaceNumber,
 257                          desc->bAlternateSetting,
 258                          desc->bNumEndpoints,
 259                          desc->bInterfaceClass,
 260                          class_decode(desc->bInterfaceClass),
 261                          desc->bInterfaceSubClass,
 262                          desc->bInterfaceProtocol,
 263                          driver_name);
 264         return start;
 265 }
 266
 267 static char *usb_dump_interface(int speed, char *start, char *end,
 268                                 const struct usb_interface_cache *intfc,
 269                                 const struct usb_interface *iface, int setno)
 270 {
 271         const struct usb_host_interface *desc = &intfc->altsetting[setno];
 272         int i;
 273
 274         start = usb_dump_interface_descriptor(start, end, intfc, iface, setno);
 275         for (i = 0; i < desc->desc.bNumEndpoints; i++) {
 276                 if (start > end)
 277                         return start;
 278                 start = usb_dump_endpoint_descriptor(speed,
 279                                 start, end, &desc->endpoint[i].desc);
 280         }
 281         return start;
 282 }
 283
 284 static char *usb_dump_iad_descriptor(char *start, char *end,
 285                         const struct usb_interface_assoc_descriptor *iad)
 286 {
 287         if (start > end)
 288                 return start;
 289         start += sprintf(start, format_iad,
 290                          iad->bFirstInterface,
 291                          iad->bInterfaceCount,
 292                          iad->bFunctionClass,
 293                          class_decode(iad->bFunctionClass),
 294                          iad->bFunctionSubClass,
 295                          iad->bFunctionProtocol);
 296         return start;
 297 }
 298
 299 /* TBD:
 300  * 0. TBDs
 301  * 1. marking active interface altsettings (code lists all, but should mark
 302  *    which ones are active, if any)
 303  */
 304 static char *usb_dump_config_descriptor(char *start, char *end,
 305                                 const struct usb_config_descriptor *desc,
 306                                 int active)
 307 {
 308         if (start > end)
 309                 return start;
 310         start += sprintf(start, format_config,
 311                          /* mark active/actual/current cfg. */
 312                          active ? '*' : ' ',
 313                          desc->bNumInterfaces,
 314                          desc->bConfigurationValue,
 315                          desc->bmAttributes,
 316                          desc->bMaxPower * 2);
 317         return start;
 318 }
 319
 320 static char *usb_dump_config(int speed, char *start, char *end,
 321                              const struct usb_host_config *config, int active)
 322 {
 323         int i, j;
 324         struct usb_interface_cache *intfc;
 325         struct usb_interface *interface;
 326
 327         if (start > end)
 328                 return start;
 329         if (!config)
 330                 /* getting these some in 2.3.7; none in 2.3.6 */
 331                 return start + sprintf(start, "(null Cfg. desc.)\n");
 332         start = usb_dump_config_descriptor(start, end, &config->desc, active);
 333         for (i = 0; i < USB_MAXIADS; i++) {
 334                 if (config->intf_assoc[i] == NULL)
 335                         break;
 336                 start = usb_dump_iad_descriptor(start, end,
 337                                         config->intf_assoc[i]);
 338         }
 339         for (i = 0; i < config->desc.bNumInterfaces; i++) {
 340                 intfc = config->intf_cache[i];
 341                 interface = config->interface[i];
 342                 for (j = 0; j < intfc->num_altsetting; j++) {
 343                         if (start > end)
 344                                 return start;
 345                         start = usb_dump_interface(speed,
 346                                 start, end, intfc, interface, j);
 347                 }
 348         }
 349         return start;
 350 }
 351
 352 /*
 353  * Dump the different USB descriptors.
 354  */
 355 static char *usb_dump_device_descriptor(char *start, char *end,
 356                                 const struct usb_device_descriptor *desc)
 357 {
 358         u16 bcdUSB = le16_to_cpu(desc->bcdUSB);
 359         u16 bcdDevice = le16_to_cpu(desc->bcdDevice);
 360
 361         if (start > end)
 362                 return start;
 363         start += sprintf(start, format_device1,
 364                           bcdUSB >> 8, bcdUSB & 0xff,
 365                           desc->bDeviceClass,
 366                           class_decode(desc->bDeviceClass),
 367                           desc->bDeviceSubClass,
 368                           desc->bDeviceProtocol,
 369                           desc->bMaxPacketSize0,
 370                           desc->bNumConfigurations);
 371         if (start > end)
 372                 return start;
 373         start += sprintf(start, format_device2,
 374                          le16_to_cpu(desc->idVendor),
 375                          le16_to_cpu(desc->idProduct),
 376                          bcdDevice >> 8, bcdDevice & 0xff);
 377         return start;
 378 }
 379
 380 /*
 381  * Dump the different strings that this device holds.
 382  */
 383 static char *usb_dump_device_strings(char *start, char *end,
 384                                      struct usb_device *dev)
 385 {
 386         if (start > end)
 387                 return start;
 388         if (dev->manufacturer)
 389                 start += sprintf(start, format_string_manufacturer,
 390                                  dev->manufacturer);
 391         if (start > end)
 392                 goto out;
 393         if (dev->product)
 394                 start += sprintf(start, format_string_product, dev->product);
 395         if (start > end)
 396                 goto out;
 397 #ifdef ALLOW_SERIAL_NUMBER
 398         if (dev->serial)
 399                 start += sprintf(start, format_string_serialnumber,
 400                                  dev->serial);
 401 #endif
 402  out:
 403         return start;
 404 }
 405
 406 static char *usb_dump_desc(char *start, char *end, struct usb_device *dev)
 407 {
 408         int i;
 409
 410         if (start > end)
 411                 return start;
 412
 413         start = usb_dump_device_descriptor(start, end, &dev->descriptor);
 414
 415         if (start > end)
 416                 return start;
 417
 418         start = usb_dump_device_strings(start, end, dev);
 419
 420         for (i = 0; i < dev->descriptor.bNumConfigurations; i++) {
 421                 if (start > end)
 422                         return start;
 423                 start = usb_dump_config(dev->speed,
 424                                 start, end, dev->config + i,
 425                                 /* active ? */
 426                                 (dev->config + i) == dev->actconfig);
 427         }
 428         return start;
 429 }
 430
 431
 432 #ifdef PROC_EXTRA /* TBD: may want to add this code later */
 433
 434 static char *usb_dump_hub_descriptor(char *start, char *end,
 435                                      const struct usb_hub_descriptor *desc)
 436 {
 437         int leng = USB_DT_HUB_NONVAR_SIZE;
 438         unsigned char *ptr = (unsigned char *)desc;
 439
 440         if (start > end)
 441                 return start;
 442         start += sprintf(start, "Interface:");
 443         while (leng && start <= end) {
 444                 start += sprintf(start, " %02x", *ptr);
 445                 ptr++; leng--;
 446         }
 447         *start++ = '\n';
 448         return start;
 449 }
 450
 451 static char *usb_dump_string(char *start, char *end,
 452                              const struct usb_device *dev, char *id, int index)
 453 {
 454         if (start > end)
 455                 return start;
 456         start += sprintf(start, "Interface:");
 457         if (index <= dev->maxstring && dev->stringindex &&
 458             dev->stringindex[index])
 459                 start += sprintf(start, "%s: %.100s ", id,
 460                                  dev->stringindex[index]);
 461         return start;
 462 }
 463
 464 #endif /* PROC_EXTRA */
 465
 466 /*****************************************************************/
 467
 468 /* This is a recursive function. Parameters:
 469  * buffer - the user-space buffer to write data into
 470  * nbytes - the maximum number of bytes to write
 471  * skip_bytes - the number of bytes to skip before writing anything
 472  * file_offset - the offset into the devices file on completion
 473  * The caller must own the device lock.
 474  */
 475 static ssize_t usb_device_dump(char __user **buffer, size_t *nbytes,
 476                                loff_t *skip_bytes, loff_t *file_offset,
 477                                struct usb_device *usbdev, struct usb_bus *bus,
 478                                int level, int index, int count)
 479 {
 480         int chix;
 481         int ret, cnt = 0;
 482         int parent_devnum = 0;
 483         char *pages_start, *data_end, *speed;
 484         unsigned int length;
 485         ssize_t total_written = 0;
 486
 487         /* don't bother with anything else if we're not writing any data */
 488         if (*nbytes <= 0)
 489                 return 0;
 490
 491         if (level > MAX_TOPO_LEVEL)
 492                 return 0;
 493         /* allocate 2^1 pages = 8K (on i386);
 494          * should be more than enough for one device */
 495         pages_start = (char *)__get_free_pages(GFP_KERNEL, 1);
 496         if (!pages_start)
 497                 return -ENOMEM;
 498
 499         if (usbdev->parent && usbdev->parent->devnum != -1)
 500                 parent_devnum = usbdev->parent->devnum;
 501         /*
 502          * So the root hub's parent is 0 and any device that is
 503          * plugged into the root hub has a parent of 0.
 504          */
 505         switch (usbdev->speed) {
 506         case USB_SPEED_LOW:
 507                 speed = "1.5"; break;
 508         case USB_SPEED_UNKNOWN:         /* usb 1.1 root hub code */
 509         case USB_SPEED_FULL:
 510                 speed = "12 "; break;
 511         case USB_SPEED_HIGH:
 512                 speed = "480"; break;
 513         default:
 514                 speed = "?? ";
 515         }
 516         data_end = pages_start + sprintf(pages_start, format_topo,
 517                         bus->busnum, level, parent_devnum,
 518                         index, count, usbdev->devnum,
 519                         speed, usbdev->maxchild);
 520         /*
 521          * level = topology-tier level;
 522          * parent_devnum = parent device number;
 523          * index = parent's connector number;
 524          * count = device count at this level
 525          */
 526         /* If this is the root hub, display the bandwidth information */
 527         if (level == 0) {
 528                 int     max;
 529
 530                 /* high speed reserves 80%, full/low reserves 90% */
 531                 if (usbdev->speed == USB_SPEED_HIGH)
 532                         max = 800;
 533                 else
 534                         max = FRAME_TIME_MAX_USECS_ALLOC;
 535
 536                 /* report "average" periodic allocation over a microsecond.
 537                  * the schedules are actually bursty, HCDs need to deal with
 538                  * that and just compute/report this average.
 539                  */
 540                 data_end += sprintf(data_end, format_bandwidth,
 541                                 bus->bandwidth_allocated, max,
 542                                 (100 * bus->bandwidth_allocated + max / 2)
 543                                         / max,
 544                                 bus->bandwidth_int_reqs,
 545                                 bus->bandwidth_isoc_reqs);
 546
 547         }
 548         data_end = usb_dump_desc(data_end, pages_start + (2 * PAGE_SIZE) - 256,
 549                                  usbdev);
 550
 551         if (data_end > (pages_start + (2 * PAGE_SIZE) - 256))
 552                 data_end += sprintf(data_end, "(truncated)\n");
 553
 554         length = data_end - pages_start;
 555         /* if we can start copying some data to the user */
 556         if (length > *skip_bytes) {
 557                 length -= *skip_bytes;
 558                 if (length > *nbytes)
 559                         length = *nbytes;
 560                 if (copy_to_user(*buffer, pages_start + *skip_bytes, length)) {
 561                         free_pages((unsigned long)pages_start, 1);
 562                         return -EFAULT;
 563                 }
 564                 *nbytes -= length;
 565                 *file_offset += length;
 566                 total_written += length;
 567                 *buffer += length;
 568                 *skip_bytes = 0;
 569         } else
 570                 *skip_bytes -= length;
 571
 572         free_pages((unsigned long)pages_start, 1);
 573
 574         /* Now look at all of this device's children. */
 575         for (chix = 0; chix < usbdev->maxchild; chix++) {
 576                 struct usb_device *childdev = usbdev->children[chix];
 577
 578                 if (childdev) {
 579                         usb_lock_device(childdev);
 580                         ret = usb_device_dump(buffer, nbytes, skip_bytes,
 581                                               file_offset, childdev, bus,
 582                                               level + 1, chix, ++cnt);
 583                         usb_unlock_device(childdev);
 584                         if (ret == -EFAULT)
 585                                 return total_written;
 586                         total_written += ret;
 587                 }
 588         }
 589         return total_written;
 590 }
 591
 592 static ssize_t usb_device_read(struct file *file, char __user *buf,
 593                                size_t nbytes, loff_t *ppos)
 594 {
 595         struct usb_bus *bus;
 596         ssize_t ret, total_written = 0;
 597         loff_t skip_bytes = *ppos;
 598
 599         if (*ppos < 0)
 600                 return -EINVAL;
 601         if (nbytes <= 0)
 602                 return 0;
 603         if (!access_ok(VERIFY_WRITE, buf, nbytes))
 604                 return -EFAULT;
 605
 606         mutex_lock(&usb_bus_list_lock);
 607         /* print devices for all busses */
 608         list_for_each_entry(bus, &usb_bus_list, bus_list) {
 609                 /* recurse through all children of the root hub */
 610                 if (!bus->root_hub)
 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_list_lock);
 618                         return ret;
 619                 }
 620                 total_written += ret;
 621         }
 622         mutex_unlock(&usb_bus_list_lock);
 623         return total_written;
 624 }
 625
 626 /* Kernel lock for "lastev" protection */
 627 static unsigned int usb_device_poll(struct file *file,
 628                                     struct poll_table_struct *wait)
 629 {
 630         struct usb_device_status *st = file->private_data;
 631         unsigned int mask = 0;
 632
 633         lock_kernel();
 634         if (!st) {
 635                 st = kmalloc(sizeof(struct usb_device_status), GFP_KERNEL);
 636
 637                 /* we may have dropped BKL -
 638                  * need to check for having lost the race */
 639                 if (file->private_data) {
 640                         kfree(st);
 641                         st = file->private_data;
 642                         goto lost_race;
 643                 }
 644                 /* we haven't lost - check for allocation failure now */
 645                 if (!st) {
 646                         unlock_kernel();
 647                         return POLLIN;
 648                 }
 649
 650                 /*
 651                  * need to prevent the module from being unloaded, since
 652                  * proc_unregister does not call the release method and
 653                  * we would have a memory leak
 654                  */
 655                 st->lastev = conndiscevcnt;
 656                 file->private_data = st;
 657                 mask = POLLIN;
 658         }
 659 lost_race:
 660         if (file->f_mode & FMODE_READ)
 661                 poll_wait(file, &deviceconndiscwq, wait);
 662         if (st->lastev != conndiscevcnt)
 663                 mask |= POLLIN;
 664         st->lastev = conndiscevcnt;
 665         unlock_kernel();
 666         return mask;
 667 }
 668
 669 static int usb_device_open(struct inode *inode, struct file *file)
 670 {
 671         file->private_data = NULL;
 672         return 0;
 673 }
 674
 675 static int usb_device_release(struct inode *inode, struct file *file)
 676 {
 677         kfree(file->private_data);
 678         file->private_data = NULL;
 679         return 0;
 680 }
 681
 682 static loff_t usb_device_lseek(struct file *file, loff_t offset, int orig)
 683 {
 684         loff_t ret;
 685
 686         lock_kernel();
 687
 688         switch (orig) {
 689         case 0:
 690                 file->f_pos = offset;
 691                 ret = file->f_pos;
 692                 break;
 693         case 1:
 694                 file->f_pos += offset;
 695                 ret = file->f_pos;
 696                 break;
 697         case 2:
 698         default:
 699                 ret = -EINVAL;
 700         }
 701
 702         unlock_kernel();
 703         return ret;
 704 }
 705
 706 const struct file_operations usbfs_devices_fops = {
 707         .llseek =       usb_device_lseek,
 708         .read =         usb_device_read,
 709         .poll =         usb_device_poll,
 710         .open =         usb_device_open,
 711         .release =      usb_device_release,
 712 };