drivers/hid/hid-core.c

   1 /*
   2  *  HID support for Linux
   3  *
   4  *  Copyright (c) 1999 Andreas Gal
   5  *  Copyright (c) 2000-2005 Vojtech Pavlik <vojtech@suse.cz>
   6  *  Copyright (c) 2005 Michael Haboustak <mike-@cinci.rr.com> for Concept2, Inc
   7  *  Copyright (c) 2006 Jiri Kosina
   8  */
   9
  10 /*
  11  * This program is free software; you can redistribute it and/or modify it
  12  * under the terms of the GNU General Public License as published by the Free
  13  * Software Foundation; either version 2 of the License, or (at your option)
  14  * any later version.
  15  */
  16
  17 #include <linux/module.h>
  18 #include <linux/slab.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/sched.h>
  22 #include <linux/list.h>
  23 #include <linux/mm.h>
  24 #include <linux/smp_lock.h>
  25 #include <linux/spinlock.h>
  26 #include <asm/unaligned.h>
  27 #include <asm/byteorder.h>
  28 #include <linux/input.h>
  29 #include <linux/wait.h>
  30
  31 #undef DEBUG
  32 #undef DEBUG_DATA
  33
  34 #include <linux/hid.h>
  35 #include <linux/hiddev.h>
  36
  37 /*
  38  * Version Information
  39  */
  40
  41 #define DRIVER_VERSION "v2.6"
  42 #define DRIVER_AUTHOR "Andreas Gal, Vojtech Pavlik"
  43 #define DRIVER_DESC "HID core driver"
  44 #define DRIVER_LICENSE "GPL"
  45
  46 /*
  47  * Register a new report for a device.
  48  */
  49
  50 static struct hid_report *hid_register_report(struct hid_device *device, unsigned type, unsigned id)
  51 {
  52         struct hid_report_enum *report_enum = device->report_enum + type;
  53         struct hid_report *report;
  54
  55         if (report_enum->report_id_hash[id])
  56                 return report_enum->report_id_hash[id];
  57
  58         if (!(report = kzalloc(sizeof(struct hid_report), GFP_KERNEL)))
  59                 return NULL;
  60
  61         if (id != 0)
  62                 report_enum->numbered = 1;
  63
  64         report->id = id;
  65         report->type = type;
  66         report->size = 0;
  67         report->device = device;
  68         report_enum->report_id_hash[id] = report;
  69
  70         list_add_tail(&report->list, &report_enum->report_list);
  71
  72         return report;
  73 }
  74
  75 /*
  76  * Register a new field for this report.
  77  */
  78
  79 static struct hid_field *hid_register_field(struct hid_report *report, unsigned usages, unsigned values)
  80 {
  81         struct hid_field *field;
  82
  83         if (report->maxfield == HID_MAX_FIELDS) {
  84                 dbg("too many fields in report");
  85                 return NULL;
  86         }
  87
  88         if (!(field = kzalloc(sizeof(struct hid_field) + usages * sizeof(struct hid_usage)
  89                 + values * sizeof(unsigned), GFP_KERNEL))) return NULL;
  90
  91         field->index = report->maxfield++;
  92         report->field[field->index] = field;
  93         field->usage = (struct hid_usage *)(field + 1);
  94         field->value = (unsigned *)(field->usage + usages);
  95         field->report = report;
  96
  97         return field;
  98 }
  99
 100 /*
 101  * Open a collection. The type/usage is pushed on the stack.
 102  */
 103
 104 static int open_collection(struct hid_parser *parser, unsigned type)
 105 {
 106         struct hid_collection *collection;
 107         unsigned usage;
 108
 109         usage = parser->local.usage[0];
 110
 111         if (parser->collection_stack_ptr == HID_COLLECTION_STACK_SIZE) {
 112                 dbg("collection stack overflow");
 113                 return -1;
 114         }
 115
 116         if (parser->device->maxcollection == parser->device->collection_size) {
 117                 collection = kmalloc(sizeof(struct hid_collection) *
 118                                 parser->device->collection_size * 2, GFP_KERNEL);
 119                 if (collection == NULL) {
 120                         dbg("failed to reallocate collection array");
 121                         return -1;
 122                 }
 123                 memcpy(collection, parser->device->collection,
 124                         sizeof(struct hid_collection) *
 125                         parser->device->collection_size);
 126                 memset(collection + parser->device->collection_size, 0,
 127                         sizeof(struct hid_collection) *
 128                         parser->device->collection_size);
 129                 kfree(parser->device->collection);
 130                 parser->device->collection = collection;
 131                 parser->device->collection_size *= 2;
 132         }
 133
 134         parser->collection_stack[parser->collection_stack_ptr++] =
 135                 parser->device->maxcollection;
 136
 137         collection = parser->device->collection +
 138                 parser->device->maxcollection++;
 139         collection->type = type;
 140         collection->usage = usage;
 141         collection->level = parser->collection_stack_ptr - 1;
 142
 143         if (type == HID_COLLECTION_APPLICATION)
 144                 parser->device->maxapplication++;
 145
 146         return 0;
 147 }
 148
 149 /*
 150  * Close a collection.
 151  */
 152
 153 static int close_collection(struct hid_parser *parser)
 154 {
 155         if (!parser->collection_stack_ptr) {
 156                 dbg("collection stack underflow");
 157                 return -1;
 158         }
 159         parser->collection_stack_ptr--;
 160         return 0;
 161 }
 162
 163 /*
 164  * Climb up the stack, search for the specified collection type
 165  * and return the usage.
 166  */
 167
 168 static unsigned hid_lookup_collection(struct hid_parser *parser, unsigned type)
 169 {
 170         int n;
 171         for (n = parser->collection_stack_ptr - 1; n >= 0; n--)
 172                 if (parser->device->collection[parser->collection_stack[n]].type == type)
 173                         return parser->device->collection[parser->collection_stack[n]].usage;
 174         return 0; /* we know nothing about this usage type */
 175 }
 176
 177 /*
 178  * Add a usage to the temporary parser table.
 179  */
 180
 181 static int hid_add_usage(struct hid_parser *parser, unsigned usage)
 182 {
 183         if (parser->local.usage_index >= HID_MAX_USAGES) {
 184                 dbg("usage index exceeded");
 185                 return -1;
 186         }
 187         parser->local.usage[parser->local.usage_index] = usage;
 188         parser->local.collection_index[parser->local.usage_index] =
 189                 parser->collection_stack_ptr ?
 190                 parser->collection_stack[parser->collection_stack_ptr - 1] : 0;
 191         parser->local.usage_index++;
 192         return 0;
 193 }
 194
 195 /*
 196  * Register a new field for this report.
 197  */
 198
 199 static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsigned flags)
 200 {
 201         struct hid_report *report;
 202         struct hid_field *field;
 203         int usages;
 204         unsigned offset;
 205         int i;
 206
 207         if (!(report = hid_register_report(parser->device, report_type, parser->global.report_id))) {
 208                 dbg("hid_register_report failed");
 209                 return -1;
 210         }
 211
 212         if (parser->global.logical_maximum < parser->global.logical_minimum) {
 213                 dbg("logical range invalid %d %d", parser->global.logical_minimum, parser->global.logical_maximum);
 214                 return -1;
 215         }
 216
 217         offset = report->size;
 218         report->size += parser->global.report_size * parser->global.report_count;
 219
 220         if (!parser->local.usage_index) /* Ignore padding fields */
 221                 return 0;
 222
 223         usages = max_t(int, parser->local.usage_index, parser->global.report_count);
 224
 225         if ((field = hid_register_field(report, usages, parser->global.report_count)) == NULL)
 226                 return 0;
 227
 228         field->physical = hid_lookup_collection(parser, HID_COLLECTION_PHYSICAL);
 229         field->logical = hid_lookup_collection(parser, HID_COLLECTION_LOGICAL);
 230         field->application = hid_lookup_collection(parser, HID_COLLECTION_APPLICATION);
 231
 232         for (i = 0; i < usages; i++) {
 233                 int j = i;
 234                 /* Duplicate the last usage we parsed if we have excess values */
 235                 if (i >= parser->local.usage_index)
 236                         j = parser->local.usage_index - 1;
 237                 field->usage[i].hid = parser->local.usage[j];
 238                 field->usage[i].collection_index =
 239                         parser->local.collection_index[j];
 240         }
 241
 242         field->maxusage = usages;
 243         field->flags = flags;
 244         field->report_offset = offset;
 245         field->report_type = report_type;
 246         field->report_size = parser->global.report_size;
 247         field->report_count = parser->global.report_count;
 248         field->logical_minimum = parser->global.logical_minimum;
 249         field->logical_maximum = parser->global.logical_maximum;
 250         field->physical_minimum = parser->global.physical_minimum;
 251         field->physical_maximum = parser->global.physical_maximum;
 252         field->unit_exponent = parser->global.unit_exponent;
 253         field->unit = parser->global.unit;
 254
 255         return 0;
 256 }
 257
 258 /*
 259  * Read data value from item.
 260  */
 261
 262 static u32 item_udata(struct hid_item *item)
 263 {
 264         switch (item->size) {
 265                 case 1: return item->data.u8;
 266                 case 2: return item->data.u16;
 267                 case 4: return item->data.u32;
 268         }
 269         return 0;
 270 }
 271
 272 static s32 item_sdata(struct hid_item *item)
 273 {
 274         switch (item->size) {
 275                 case 1: return item->data.s8;
 276                 case 2: return item->data.s16;
 277                 case 4: return item->data.s32;
 278         }
 279         return 0;
 280 }
 281
 282 /*
 283  * Process a global item.
 284  */
 285
 286 static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)
 287 {
 288         switch (item->tag) {
 289
 290                 case HID_GLOBAL_ITEM_TAG_PUSH:
 291
 292                         if (parser->global_stack_ptr == HID_GLOBAL_STACK_SIZE) {
 293                                 dbg("global enviroment stack overflow");
 294                                 return -1;
 295                         }
 296
 297                         memcpy(parser->global_stack + parser->global_stack_ptr++,
 298                                 &parser->global, sizeof(struct hid_global));
 299                         return 0;
 300
 301                 case HID_GLOBAL_ITEM_TAG_POP:
 302
 303                         if (!parser->global_stack_ptr) {
 304                                 dbg("global enviroment stack underflow");
 305                                 return -1;
 306                         }
 307
 308                         memcpy(&parser->global, parser->global_stack + --parser->global_stack_ptr,
 309                                 sizeof(struct hid_global));
 310                         return 0;
 311
 312                 case HID_GLOBAL_ITEM_TAG_USAGE_PAGE:
 313                         parser->global.usage_page = item_udata(item);
 314                         return 0;
 315
 316                 case HID_GLOBAL_ITEM_TAG_LOGICAL_MINIMUM:
 317                         parser->global.logical_minimum = item_sdata(item);
 318                         return 0;
 319
 320                 case HID_GLOBAL_ITEM_TAG_LOGICAL_MAXIMUM:
 321                         if (parser->global.logical_minimum < 0)
 322                                 parser->global.logical_maximum = item_sdata(item);
 323                         else
 324                                 parser->global.logical_maximum = item_udata(item);
 325                         return 0;
 326
 327                 case HID_GLOBAL_ITEM_TAG_PHYSICAL_MINIMUM:
 328                         parser->global.physical_minimum = item_sdata(item);
 329                         return 0;
 330
 331                 case HID_GLOBAL_ITEM_TAG_PHYSICAL_MAXIMUM:
 332                         if (parser->global.physical_minimum < 0)
 333                                 parser->global.physical_maximum = item_sdata(item);
 334                         else
 335                                 parser->global.physical_maximum = item_udata(item);
 336                         return 0;
 337
 338                 case HID_GLOBAL_ITEM_TAG_UNIT_EXPONENT:
 339                         parser->global.unit_exponent = item_sdata(item);
 340                         return 0;
 341
 342                 case HID_GLOBAL_ITEM_TAG_UNIT:
 343                         parser->global.unit = item_udata(item);
 344                         return 0;
 345
 346                 case HID_GLOBAL_ITEM_TAG_REPORT_SIZE:
 347                         if ((parser->global.report_size = item_udata(item)) > 32) {
 348                                 dbg("invalid report_size %d", parser->global.report_size);
 349                                 return -1;
 350                         }
 351                         return 0;
 352
 353                 case HID_GLOBAL_ITEM_TAG_REPORT_COUNT:
 354                         if ((parser->global.report_count = item_udata(item)) > HID_MAX_USAGES) {
 355                                 dbg("invalid report_count %d", parser->global.report_count);
 356                                 return -1;
 357                         }
 358                         return 0;
 359
 360                 case HID_GLOBAL_ITEM_TAG_REPORT_ID:
 361                         if ((parser->global.report_id = item_udata(item)) == 0) {
 362                                 dbg("report_id 0 is invalid");
 363                                 return -1;
 364                         }
 365                         return 0;
 366
 367                 default:
 368                         dbg("unknown global tag 0x%x", item->tag);
 369                         return -1;
 370         }
 371 }
 372
 373 /*
 374  * Process a local item.
 375  */
 376
 377 static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)
 378 {
 379         __u32 data;
 380         unsigned n;
 381
 382         if (item->size == 0) {
 383                 dbg("item data expected for local item");
 384                 return -1;
 385         }
 386
 387         data = item_udata(item);
 388
 389         switch (item->tag) {
 390
 391                 case HID_LOCAL_ITEM_TAG_DELIMITER:
 392
 393                         if (data) {
 394                                 /*
 395                                  * We treat items before the first delimiter
 396                                  * as global to all usage sets (branch 0).
 397                                  * In the moment we process only these global
 398                                  * items and the first delimiter set.
 399                                  */
 400                                 if (parser->local.delimiter_depth != 0) {
 401                                         dbg("nested delimiters");
 402                                         return -1;
 403                                 }
 404                                 parser->local.delimiter_depth++;
 405                                 parser->local.delimiter_branch++;
 406                         } else {
 407                                 if (parser->local.delimiter_depth < 1) {
 408                                         dbg("bogus close delimiter");
 409                                         return -1;
 410                                 }
 411                                 parser->local.delimiter_depth--;
 412                         }
 413                         return 1;
 414
 415                 case HID_LOCAL_ITEM_TAG_USAGE:
 416
 417                         if (parser->local.delimiter_branch > 1) {
 418                                 dbg("alternative usage ignored");
 419                                 return 0;
 420                         }
 421
 422                         if (item->size <= 2)
 423                                 data = (parser->global.usage_page << 16) + data;
 424
 425                         return hid_add_usage(parser, data);
 426
 427                 case HID_LOCAL_ITEM_TAG_USAGE_MINIMUM:
 428
 429                         if (parser->local.delimiter_branch > 1) {
 430                                 dbg("alternative usage ignored");
 431                                 return 0;
 432                         }
 433
 434                         if (item->size <= 2)
 435                                 data = (parser->global.usage_page << 16) + data;
 436
 437                         parser->local.usage_minimum = data;
 438                         return 0;
 439
 440                 case HID_LOCAL_ITEM_TAG_USAGE_MAXIMUM:
 441
 442                         if (parser->local.delimiter_branch > 1) {
 443                                 dbg("alternative usage ignored");
 444                                 return 0;
 445                         }
 446
 447                         if (item->size <= 2)
 448                                 data = (parser->global.usage_page << 16) + data;
 449
 450                         for (n = parser->local.usage_minimum; n <= data; n++)
 451                                 if (hid_add_usage(parser, n)) {
 452                                         dbg("hid_add_usage failed\n");
 453                                         return -1;
 454                                 }
 455                         return 0;
 456
 457                 default:
 458
 459                         dbg("unknown local item tag 0x%x", item->tag);
 460                         return 0;
 461         }
 462         return 0;
 463 }
 464
 465 /*
 466  * Process a main item.
 467  */
 468
 469 static int hid_parser_main(struct hid_parser *parser, struct hid_item *item)
 470 {
 471         __u32 data;
 472         int ret;
 473
 474         data = item_udata(item);
 475
 476         switch (item->tag) {
 477                 case HID_MAIN_ITEM_TAG_BEGIN_COLLECTION:
 478                         ret = open_collection(parser, data & 0xff);
 479                         break;
 480                 case HID_MAIN_ITEM_TAG_END_COLLECTION:
 481                         ret = close_collection(parser);
 482                         break;
 483                 case HID_MAIN_ITEM_TAG_INPUT:
 484                         ret = hid_add_field(parser, HID_INPUT_REPORT, data);
 485                         break;
 486                 case HID_MAIN_ITEM_TAG_OUTPUT:
 487                         ret = hid_add_field(parser, HID_OUTPUT_REPORT, data);
 488                         break;
 489                 case HID_MAIN_ITEM_TAG_FEATURE:
 490                         ret = hid_add_field(parser, HID_FEATURE_REPORT, data);
 491                         break;
 492                 default:
 493                         dbg("unknown main item tag 0x%x", item->tag);
 494                         ret = 0;
 495         }
 496
 497         memset(&parser->local, 0, sizeof(parser->local));       /* Reset the local parser environment */
 498
 499         return ret;
 500 }
 501
 502 /*
 503  * Process a reserved item.
 504  */
 505
 506 static int hid_parser_reserved(struct hid_parser *parser, struct hid_item *item)
 507 {
 508         dbg("reserved item type, tag 0x%x", item->tag);
 509         return 0;
 510 }
 511
 512 /*
 513  * Free a report and all registered fields. The field->usage and
 514  * field->value table's are allocated behind the field, so we need
 515  * only to free(field) itself.
 516  */
 517
 518 static void hid_free_report(struct hid_report *report)
 519 {
 520         unsigned n;
 521
 522         for (n = 0; n < report->maxfield; n++)
 523                 kfree(report->field[n]);
 524         kfree(report);
 525 }
 526
 527 /*
 528  * Free a device structure, all reports, and all fields.
 529  */
 530
 531 void hid_free_device(struct hid_device *device)
 532 {
 533         unsigned i,j;
 534
 535         for (i = 0; i < HID_REPORT_TYPES; i++) {
 536                 struct hid_report_enum *report_enum = device->report_enum + i;
 537
 538                 for (j = 0; j < 256; j++) {
 539                         struct hid_report *report = report_enum->report_id_hash[j];
 540                         if (report)
 541                                 hid_free_report(report);
 542                 }
 543         }
 544
 545         kfree(device->rdesc);
 546         kfree(device->collection);
 547         kfree(device);
 548 }
 549 EXPORT_SYMBOL_GPL(hid_free_device);
 550
 551 /*
 552  * Fetch a report description item from the data stream. We support long
 553  * items, though they are not used yet.
 554  */
 555
 556 static u8 *fetch_item(__u8 *start, __u8 *end, struct hid_item *item)
 557 {
 558         u8 b;
 559
 560         if ((end - start) <= 0)
 561                 return NULL;
 562
 563         b = *start++;
 564
 565         item->type = (b >> 2) & 3;
 566         item->tag  = (b >> 4) & 15;
 567
 568         if (item->tag == HID_ITEM_TAG_LONG) {
 569
 570                 item->format = HID_ITEM_FORMAT_LONG;
 571
 572                 if ((end - start) < 2)
 573                         return NULL;
 574
 575                 item->size = *start++;
 576                 item->tag  = *start++;
 577
 578                 if ((end - start) < item->size)
 579                         return NULL;
 580
 581                 item->data.longdata = start;
 582                 start += item->size;
 583                 return start;
 584         }
 585
 586         item->format = HID_ITEM_FORMAT_SHORT;
 587         item->size = b & 3;
 588
 589         switch (item->size) {
 590
 591                 case 0:
 592                         return start;
 593
 594                 case 1:
 595                         if ((end - start) < 1)
 596                                 return NULL;
 597                         item->data.u8 = *start++;
 598                         return start;
 599
 600                 case 2:
 601                         if ((end - start) < 2)
 602                                 return NULL;
 603                         item->data.u16 = le16_to_cpu(get_unaligned((__le16*)start));
 604                         start = (__u8 *)((__le16 *)start + 1);
 605                         return start;
 606
 607                 case 3:
 608                         item->size++;
 609                         if ((end - start) < 4)
 610                                 return NULL;
 611                         item->data.u32 = le32_to_cpu(get_unaligned((__le32*)start));
 612                         start = (__u8 *)((__le32 *)start + 1);
 613                         return start;
 614         }
 615
 616         return NULL;
 617 }
 618
 619 /*
 620  * Parse a report description into a hid_device structure. Reports are
 621  * enumerated, fields are attached to these reports.
 622  */
 623
 624 struct hid_device *hid_parse_report(__u8 *start, unsigned size)
 625 {
 626         struct hid_device *device;
 627         struct hid_parser *parser;
 628         struct hid_item item;
 629         __u8 *end;
 630         unsigned i;
 631         static int (*dispatch_type[])(struct hid_parser *parser,
 632                                       struct hid_item *item) = {
 633                 hid_parser_main,
 634                 hid_parser_global,
 635                 hid_parser_local,
 636                 hid_parser_reserved
 637         };
 638
 639         if (!(device = kzalloc(sizeof(struct hid_device), GFP_KERNEL)))
 640                 return NULL;
 641
 642         if (!(device->collection = kzalloc(sizeof(struct hid_collection) *
 643                                    HID_DEFAULT_NUM_COLLECTIONS, GFP_KERNEL))) {
 644                 kfree(device);
 645                 return NULL;
 646         }
 647         device->collection_size = HID_DEFAULT_NUM_COLLECTIONS;
 648
 649         for (i = 0; i < HID_REPORT_TYPES; i++)
 650                 INIT_LIST_HEAD(&device->report_enum[i].report_list);
 651
 652         if (!(device->rdesc = kmalloc(size, GFP_KERNEL))) {
 653                 kfree(device->collection);
 654                 kfree(device);
 655                 return NULL;
 656         }
 657         memcpy(device->rdesc, start, size);
 658         device->rsize = size;
 659
 660         if (!(parser = kzalloc(sizeof(struct hid_parser), GFP_KERNEL))) {
 661                 kfree(device->rdesc);
 662                 kfree(device->collection);
 663                 kfree(device);
 664                 return NULL;
 665         }
 666         parser->device = device;
 667
 668         end = start + size;
 669         while ((start = fetch_item(start, end, &item)) != NULL) {
 670
 671                 if (item.format != HID_ITEM_FORMAT_SHORT) {
 672                         dbg("unexpected long global item");
 673                         hid_free_device(device);
 674                         kfree(parser);
 675                         return NULL;
 676                 }
 677
 678                 if (dispatch_type[item.type](parser, &item)) {
 679                         dbg("item %u %u %u %u parsing failed\n",
 680                                 item.format, (unsigned)item.size, (unsigned)item.type, (unsigned)item.tag);
 681                         hid_free_device(device);
 682                         kfree(parser);
 683                         return NULL;
 684                 }
 685
 686                 if (start == end) {
 687                         if (parser->collection_stack_ptr) {
 688                                 dbg("unbalanced collection at end of report description");
 689                                 hid_free_device(device);
 690                                 kfree(parser);
 691                                 return NULL;
 692                         }
 693                         if (parser->local.delimiter_depth) {
 694                                 dbg("unbalanced delimiter at end of report description");
 695                                 hid_free_device(device);
 696                                 kfree(parser);
 697                                 return NULL;
 698                         }
 699                         kfree(parser);
 700                         return device;
 701                 }
 702         }
 703
 704         dbg("item fetching failed at offset %d\n", (int)(end - start));
 705         hid_free_device(device);
 706         kfree(parser);
 707         return NULL;
 708 }
 709 EXPORT_SYMBOL_GPL(hid_parse_report);
 710
 711 /*
 712  * Convert a signed n-bit integer to signed 32-bit integer. Common
 713  * cases are done through the compiler, the screwed things has to be
 714  * done by hand.
 715  */
 716
 717 static s32 snto32(__u32 value, unsigned n)
 718 {
 719         switch (n) {
 720                 case 8:  return ((__s8)value);
 721                 case 16: return ((__s16)value);
 722                 case 32: return ((__s32)value);
 723         }
 724         return value & (1 << (n - 1)) ? value | (-1 << n) : value;
 725 }
 726
 727 /*
 728  * Convert a signed 32-bit integer to a signed n-bit integer.
 729  */
 730
 731 static u32 s32ton(__s32 value, unsigned n)
 732 {
 733         s32 a = value >> (n - 1);
 734         if (a && a != -1)
 735                 return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1;
 736         return value & ((1 << n) - 1);
 737 }
 738
 739 /*
 740  * Extract/implement a data field from/to a little endian report (bit array).
 741  *
 742  * Code sort-of follows HID spec:
 743  *     http://www.usb.org/developers/devclass_docs/HID1_11.pdf
 744  *
 745  * While the USB HID spec allows unlimited length bit fields in "report
 746  * descriptors", most devices never use more than 16 bits.
 747  * One model of UPS is claimed to report "LINEV" as a 32-bit field.
 748  * Search linux-kernel and linux-usb-devel archives for "hid-core extract".
 749  */
 750
 751 static __inline__ __u32 extract(__u8 *report, unsigned offset, unsigned n)
 752 {
 753         u64 x;
 754
 755         WARN_ON(n > 32);
 756
 757         report += offset >> 3;  /* adjust byte index */
 758         offset &= 7;            /* now only need bit offset into one byte */
 759         x = get_unaligned((u64 *) report);
 760         x = le64_to_cpu(x);
 761         x = (x >> offset) & ((1ULL << n) - 1);  /* extract bit field */
 762         return (u32) x;
 763 }
 764
 765 /*
 766  * "implement" : set bits in a little endian bit stream.
 767  * Same concepts as "extract" (see comments above).
 768  * The data mangled in the bit stream remains in little endian
 769  * order the whole time. It make more sense to talk about
 770  * endianness of register values by considering a register
 771  * a "cached" copy of the little endiad bit stream.
 772  */
 773 static __inline__ void implement(__u8 *report, unsigned offset, unsigned n, __u32 value)
 774 {
 775         u64 x;
 776         u64 m = (1ULL << n) - 1;
 777
 778         WARN_ON(n > 32);
 779
 780         WARN_ON(value > m);
 781         value &= m;
 782
 783         report += offset >> 3;
 784         offset &= 7;
 785
 786         x = get_unaligned((u64 *)report);
 787         x &= cpu_to_le64(~(m << offset));
 788         x |= cpu_to_le64(((u64) value) << offset);
 789         put_unaligned(x, (u64 *) report);
 790 }
 791
 792 /*
 793  * Search an array for a value.
 794  */
 795
 796 static __inline__ int search(__s32 *array, __s32 value, unsigned n)
 797 {
 798         while (n--) {
 799                 if (*array++ == value)
 800                         return 0;
 801         }
 802         return -1;
 803 }
 804
 805 static void hid_process_event(struct hid_device *hid, struct hid_field *field, struct hid_usage *usage, __s32 value, int interrupt)
 806 {
 807         hid_dump_input(usage, value);
 808         if (hid->claimed & HID_CLAIMED_INPUT)
 809                 hidinput_hid_event(hid, field, usage, value);
 810         if (hid->claimed & HID_CLAIMED_HIDDEV && interrupt && hid->hiddev_hid_event)
 811                 hid->hiddev_hid_event(hid, field, usage, value);
 812 }
 813
 814 /*
 815  * Analyse a received field, and fetch the data from it. The field
 816  * content is stored for next report processing (we do differential
 817  * reporting to the layer).
 818  */
 819
 820 void hid_input_field(struct hid_device *hid, struct hid_field *field, __u8 *data, int interrupt)
 821 {
 822         unsigned n;
 823         unsigned count = field->report_count;
 824         unsigned offset = field->report_offset;
 825         unsigned size = field->report_size;
 826         __s32 min = field->logical_minimum;
 827         __s32 max = field->logical_maximum;
 828         __s32 *value;
 829
 830         if (!(value = kmalloc(sizeof(__s32) * count, GFP_ATOMIC)))
 831                 return;
 832
 833         for (n = 0; n < count; n++) {
 834
 835                         value[n] = min < 0 ? snto32(extract(data, offset + n * size, size), size) :
 836                                                     extract(data, offset + n * size, size);
 837
 838                         if (!(field->flags & HID_MAIN_ITEM_VARIABLE) /* Ignore report if ErrorRollOver */
 839                             && value[n] >= min && value[n] <= max
 840                             && field->usage[value[n] - min].hid == HID_UP_KEYBOARD + 1)
 841                                 goto exit;
 842         }
 843
 844         for (n = 0; n < count; n++) {
 845
 846                 if (HID_MAIN_ITEM_VARIABLE & field->flags) {
 847                         hid_process_event(hid, field, &field->usage[n], value[n], interrupt);
 848                         continue;
 849                 }
 850
 851                 if (field->value[n] >= min && field->value[n] <= max
 852                         && field->usage[field->value[n] - min].hid
 853                         && search(value, field->value[n], count))
 854                                 hid_process_event(hid, field, &field->usage[field->value[n] - min], 0, interrupt);
 855
 856                 if (value[n] >= min && value[n] <= max
 857                         && field->usage[value[n] - min].hid
 858                         && search(field->value, value[n], count))
 859                                 hid_process_event(hid, field, &field->usage[value[n] - min], 1, interrupt);
 860         }
 861
 862         memcpy(field->value, value, count * sizeof(__s32));
 863 exit:
 864         kfree(value);
 865 }
 866 EXPORT_SYMBOL_GPL(hid_input_field);
 867
 868 /*
 869  * Output the field into the report.
 870  */
 871
 872 static void hid_output_field(struct hid_field *field, __u8 *data)
 873 {
 874         unsigned count = field->report_count;
 875         unsigned offset = field->report_offset;
 876         unsigned size = field->report_size;
 877         unsigned n;
 878
 879         for (n = 0; n < count; n++) {
 880                 if (field->logical_minimum < 0) /* signed values */
 881                         implement(data, offset + n * size, size, s32ton(field->value[n], size));
 882                 else                            /* unsigned values */
 883                         implement(data, offset + n * size, size, field->value[n]);
 884         }
 885 }
 886
 887 /*
 888  * Create a report.
 889  */
 890
 891 void hid_output_report(struct hid_report *report, __u8 *data)
 892 {
 893         unsigned n;
 894
 895         if (report->id > 0)
 896                 *data++ = report->id;
 897
 898         for (n = 0; n < report->maxfield; n++)
 899                 hid_output_field(report->field[n], data);
 900 }
 901 EXPORT_SYMBOL_GPL(hid_output_report);
 902
 903 /*
 904  * Set a field value. The report this field belongs to has to be
 905  * created and transferred to the device, to set this value in the
 906  * device.
 907  */
 908
 909 int hid_set_field(struct hid_field *field, unsigned offset, __s32 value)
 910 {
 911         unsigned size = field->report_size;
 912
 913         hid_dump_input(field->usage + offset, value);
 914
 915         if (offset >= field->report_count) {
 916                 dbg("offset (%d) exceeds report_count (%d)", offset, field->report_count);
 917                 hid_dump_field(field, 8);
 918                 return -1;
 919         }
 920         if (field->logical_minimum < 0) {
 921                 if (value != snto32(s32ton(value, size), size)) {
 922                         dbg("value %d is out of range", value);
 923                         return -1;
 924                 }
 925         }
 926         field->value[offset] = value;
 927         return 0;
 928 }
 929 EXPORT_SYMBOL_GPL(hid_set_field);
 930
 931 int hid_input_report(struct hid_device *hid, int type, u8 *data, int size, int interrupt)
 932 {
 933         struct hid_report_enum *report_enum = hid->report_enum + type;
 934         struct hid_report *report;
 935         int n, rsize;
 936
 937         if (!hid)
 938                 return -ENODEV;
 939
 940         if (!size) {
 941                 dbg("empty report");
 942                 return -1;
 943         }
 944
 945 #ifdef DEBUG_DATA
 946         printk(KERN_DEBUG __FILE__ ": report (size %u) (%snumbered)\n", size, report_enum->numbered ? "" : "un");
 947 #endif
 948
 949         n = 0;                          /* Normally report number is 0 */
 950         if (report_enum->numbered) {    /* Device uses numbered reports, data[0] is report number */
 951                 n = *data++;
 952                 size--;
 953         }
 954
 955 #ifdef DEBUG_DATA
 956         {
 957                 int i;
 958                 printk(KERN_DEBUG __FILE__ ": report %d (size %u) = ", n, size);
 959                 for (i = 0; i < size; i++)
 960                         printk(" %02x", data[i]);
 961                 printk("\n");
 962         }
 963 #endif
 964
 965         if (!(report = report_enum->report_id_hash[n])) {
 966                 dbg("undefined report_id %d received", n);
 967                 return -1;
 968         }
 969
 970         rsize = ((report->size - 1) >> 3) + 1;
 971
 972         if (size < rsize) {
 973                 dbg("report %d is too short, (%d < %d)", report->id, size, rsize);
 974                 memset(data + size, 0, rsize - size);
 975         }
 976
 977         if ((hid->claimed & HID_CLAIMED_HIDDEV) && hid->hiddev_report_event)
 978                 hid->hiddev_report_event(hid, report);
 979
 980         for (n = 0; n < report->maxfield; n++)
 981                 hid_input_field(hid, report->field[n], data, interrupt);
 982
 983         if (hid->claimed & HID_CLAIMED_INPUT)
 984                 hidinput_report_event(hid, report);
 985
 986         return 0;
 987 }
 988 EXPORT_SYMBOL_GPL(hid_input_report);
 989
 990 MODULE_LICENSE(DRIVER_LICENSE);
 991