linux/drivers/uwb/neh.c
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   1/*
   2 * WUSB Wire Adapter: Radio Control Interface (WUSB[8])
   3 * Notification and Event Handling
   4 *
   5 * Copyright (C) 2005-2006 Intel Corporation
   6 * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
   7 *
   8 * This program is free software; you can redistribute it and/or
   9 * modify it under the terms of the GNU General Public License version
  10 * 2 as published by the Free Software Foundation.
  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., 51 Franklin Street, Fifth Floor, Boston, MA
  20 * 02110-1301, USA.
  21 *
  22 *
  23 * The RC interface of the Host Wire Adapter (USB dongle) or WHCI PCI
  24 * card delivers a stream of notifications and events to the
  25 * notification end event endpoint or area. This code takes care of
  26 * getting a buffer with that data, breaking it up in separate
  27 * notifications and events and then deliver those.
  28 *
  29 * Events are answers to commands and they carry a context ID that
  30 * associates them to the command. Notifications are that,
  31 * notifications, they come out of the blue and have a context ID of
  32 * zero. Think of the context ID kind of like a handler. The
  33 * uwb_rc_neh_* code deals with managing context IDs.
  34 *
  35 * This is why you require a handle to operate on a UWB host. When you
  36 * open a handle a context ID is assigned to you.
  37 *
  38 * So, as it is done is:
  39 *
  40 * 1. Add an event handler [uwb_rc_neh_add()] (assigns a ctx id)
  41 * 2. Issue command [rc->cmd(rc, ...)]
  42 * 3. Arm the timeout timer [uwb_rc_neh_arm()]
  43 * 4, Release the reference to the neh [uwb_rc_neh_put()]
  44 * 5. Wait for the callback
  45 * 6. Command result (RCEB) is passed to the callback
  46 *
  47 * If (2) fails, you should remove the handle [uwb_rc_neh_rm()]
  48 * instead of arming the timer.
  49 *
  50 * Handles are for using in *serialized* code, single thread.
  51 *
  52 * When the notification/event comes, the IRQ handler/endpoint
  53 * callback passes the data read to uwb_rc_neh_grok() which will break
  54 * it up in a discrete series of events, look up who is listening for
  55 * them and execute the pertinent callbacks.
  56 *
  57 * If the reader detects an error while reading the data stream, call
  58 * uwb_rc_neh_error().
  59 *
  60 * CONSTRAINTS/ASSUMPTIONS:
  61 *
  62 * - Most notifications/events are small (less thank .5k), copying
  63 *   around is ok.
  64 *
  65 * - Notifications/events are ALWAYS smaller than PAGE_SIZE
  66 *
  67 * - Notifications/events always come in a single piece (ie: a buffer
  68 *   will always contain entire notifications/events).
  69 *
  70 * - we cannot know in advance how long each event is (because they
  71 *   lack a length field in their header--smart move by the standards
  72 *   body, btw). So we need a facility to get the event size given the
  73 *   header. This is what the EST code does (notif/Event Size
  74 *   Tables), check nest.c--as well, you can associate the size to
  75 *   the handle [w/ neh->extra_size()].
  76 *
  77 * - Most notifications/events are fixed size; only a few are variable
  78 *   size (NEST takes care of that).
  79 *
  80 * - Listeners of events expect them, so they usually provide a
  81 *   buffer, as they know the size. Listeners to notifications don't,
  82 *   so we allocate their buffers dynamically.
  83 */
  84#include <linux/kernel.h>
  85#include <linux/timer.h>
  86#include <linux/slab.h>
  87#include <linux/err.h>
  88#include <linux/export.h>
  89
  90#include "uwb-internal.h"
  91
  92/*
  93 * UWB Radio Controller Notification/Event Handle
  94 *
  95 * Represents an entity waiting for an event coming from the UWB Radio
  96 * Controller with a given context id (context) and type (evt_type and
  97 * evt). On reception of the notification/event, the callback (cb) is
  98 * called with the event.
  99 *
 100 * If the timer expires before the event is received, the callback is
 101 * called with -ETIMEDOUT as the event size.
 102 */
 103struct uwb_rc_neh {
 104        struct kref kref;
 105
 106        struct uwb_rc *rc;
 107        u8 evt_type;
 108        __le16 evt;
 109        u8 context;
 110        uwb_rc_cmd_cb_f cb;
 111        void *arg;
 112
 113        struct timer_list timer;
 114        struct list_head list_node;
 115};
 116
 117static void uwb_rc_neh_timer(unsigned long arg);
 118
 119static void uwb_rc_neh_release(struct kref *kref)
 120{
 121        struct uwb_rc_neh *neh = container_of(kref, struct uwb_rc_neh, kref);
 122
 123        kfree(neh);
 124}
 125
 126static void uwb_rc_neh_get(struct uwb_rc_neh *neh)
 127{
 128        kref_get(&neh->kref);
 129}
 130
 131/**
 132 * uwb_rc_neh_put - release reference to a neh
 133 * @neh: the neh
 134 */
 135void uwb_rc_neh_put(struct uwb_rc_neh *neh)
 136{
 137        kref_put(&neh->kref, uwb_rc_neh_release);
 138}
 139
 140
 141/**
 142 * Assigns @neh a context id from @rc's pool
 143 *
 144 * @rc:     UWB Radio Controller descriptor; @rc->neh_lock taken
 145 * @neh:    Notification/Event Handle
 146 * @returns 0 if context id was assigned ok; < 0 errno on error (if
 147 *          all the context IDs are taken).
 148 *
 149 * (assumes @wa is locked).
 150 *
 151 * NOTE: WUSB spec reserves context ids 0x00 for notifications and
 152 *       0xff is invalid, so they must not be used. Initialization
 153 *       fills up those two in the bitmap so they are not allocated.
 154 *
 155 * We spread the allocation around to reduce the possibility of two
 156 * consecutive opened @neh's getting the same context ID assigned (to
 157 * avoid surprises with late events that timed out long time ago). So
 158 * first we search from where @rc->ctx_roll is, if not found, we
 159 * search from zero.
 160 */
 161static
 162int __uwb_rc_ctx_get(struct uwb_rc *rc, struct uwb_rc_neh *neh)
 163{
 164        int result;
 165        result = find_next_zero_bit(rc->ctx_bm, UWB_RC_CTX_MAX,
 166                                    rc->ctx_roll++);
 167        if (result < UWB_RC_CTX_MAX)
 168                goto found;
 169        result = find_first_zero_bit(rc->ctx_bm, UWB_RC_CTX_MAX);
 170        if (result < UWB_RC_CTX_MAX)
 171                goto found;
 172        return -ENFILE;
 173found:
 174        set_bit(result, rc->ctx_bm);
 175        neh->context = result;
 176        return 0;
 177}
 178
 179
 180/** Releases @neh's context ID back to @rc (@rc->neh_lock is locked). */
 181static
 182void __uwb_rc_ctx_put(struct uwb_rc *rc, struct uwb_rc_neh *neh)
 183{
 184        struct device *dev = &rc->uwb_dev.dev;
 185        if (neh->context == 0)
 186                return;
 187        if (test_bit(neh->context, rc->ctx_bm) == 0) {
 188                dev_err(dev, "context %u not set in bitmap\n",
 189                        neh->context);
 190                WARN_ON(1);
 191        }
 192        clear_bit(neh->context, rc->ctx_bm);
 193        neh->context = 0;
 194}
 195
 196/**
 197 * uwb_rc_neh_add - add a neh for a radio controller command
 198 * @rc:             the radio controller
 199 * @cmd:            the radio controller command
 200 * @expected_type:  the type of the expected response event
 201 * @expected_event: the expected event ID
 202 * @cb:             callback for when the event is received
 203 * @arg:            argument for the callback
 204 *
 205 * Creates a neh and adds it to the list of those waiting for an
 206 * event.  A context ID will be assigned to the command.
 207 */
 208struct uwb_rc_neh *uwb_rc_neh_add(struct uwb_rc *rc, struct uwb_rccb *cmd,
 209                                  u8 expected_type, u16 expected_event,
 210                                  uwb_rc_cmd_cb_f cb, void *arg)
 211{
 212        int result;
 213        unsigned long flags;
 214        struct device *dev = &rc->uwb_dev.dev;
 215        struct uwb_rc_neh *neh;
 216
 217        neh = kzalloc(sizeof(*neh), GFP_KERNEL);
 218        if (neh == NULL) {
 219                result = -ENOMEM;
 220                goto error_kzalloc;
 221        }
 222
 223        kref_init(&neh->kref);
 224        INIT_LIST_HEAD(&neh->list_node);
 225        init_timer(&neh->timer);
 226        neh->timer.function = uwb_rc_neh_timer;
 227        neh->timer.data     = (unsigned long)neh;
 228
 229        neh->rc = rc;
 230        neh->evt_type = expected_type;
 231        neh->evt = cpu_to_le16(expected_event);
 232        neh->cb = cb;
 233        neh->arg = arg;
 234
 235        spin_lock_irqsave(&rc->neh_lock, flags);
 236        result = __uwb_rc_ctx_get(rc, neh);
 237        if (result >= 0) {
 238                cmd->bCommandContext = neh->context;
 239                list_add_tail(&neh->list_node, &rc->neh_list);
 240                uwb_rc_neh_get(neh);
 241        }
 242        spin_unlock_irqrestore(&rc->neh_lock, flags);
 243        if (result < 0)
 244                goto error_ctx_get;
 245
 246        return neh;
 247
 248error_ctx_get:
 249        kfree(neh);
 250error_kzalloc:
 251        dev_err(dev, "cannot open handle to radio controller: %d\n", result);
 252        return ERR_PTR(result);
 253}
 254
 255static void __uwb_rc_neh_rm(struct uwb_rc *rc, struct uwb_rc_neh *neh)
 256{
 257        __uwb_rc_ctx_put(rc, neh);
 258        list_del(&neh->list_node);
 259}
 260
 261/**
 262 * uwb_rc_neh_rm - remove a neh.
 263 * @rc:  the radio controller
 264 * @neh: the neh to remove
 265 *
 266 * Remove an active neh immediately instead of waiting for the event
 267 * (or a time out).
 268 */
 269void uwb_rc_neh_rm(struct uwb_rc *rc, struct uwb_rc_neh *neh)
 270{
 271        unsigned long flags;
 272
 273        spin_lock_irqsave(&rc->neh_lock, flags);
 274        __uwb_rc_neh_rm(rc, neh);
 275        spin_unlock_irqrestore(&rc->neh_lock, flags);
 276
 277        del_timer_sync(&neh->timer);
 278        uwb_rc_neh_put(neh);
 279}
 280
 281/**
 282 * uwb_rc_neh_arm - arm an event handler timeout timer
 283 *
 284 * @rc:     UWB Radio Controller
 285 * @neh:    Notification/event handler for @rc
 286 *
 287 * The timer is only armed if the neh is active.
 288 */
 289void uwb_rc_neh_arm(struct uwb_rc *rc, struct uwb_rc_neh *neh)
 290{
 291        unsigned long flags;
 292
 293        spin_lock_irqsave(&rc->neh_lock, flags);
 294        if (neh->context)
 295                mod_timer(&neh->timer,
 296                          jiffies + msecs_to_jiffies(UWB_RC_CMD_TIMEOUT_MS));
 297        spin_unlock_irqrestore(&rc->neh_lock, flags);
 298}
 299
 300static void uwb_rc_neh_cb(struct uwb_rc_neh *neh, struct uwb_rceb *rceb, size_t size)
 301{
 302        (*neh->cb)(neh->rc, neh->arg, rceb, size);
 303        uwb_rc_neh_put(neh);
 304}
 305
 306static bool uwb_rc_neh_match(struct uwb_rc_neh *neh, const struct uwb_rceb *rceb)
 307{
 308        return neh->evt_type == rceb->bEventType
 309                && neh->evt == rceb->wEvent
 310                && neh->context == rceb->bEventContext;
 311}
 312
 313/**
 314 * Find the handle waiting for a RC Radio Control Event
 315 *
 316 * @rc:         UWB Radio Controller
 317 * @rceb:       Pointer to the RCEB buffer
 318 * @event_size: Pointer to the size of the RCEB buffer. Might be
 319 *              adjusted to take into account the @neh->extra_size
 320 *              settings.
 321 *
 322 * If the listener has no buffer (NULL buffer), one is allocated for
 323 * the right size (the amount of data received). @neh->ptr will point
 324 * to the event payload, which always starts with a 'struct
 325 * uwb_rceb'. kfree() it when done.
 326 */
 327static
 328struct uwb_rc_neh *uwb_rc_neh_lookup(struct uwb_rc *rc,
 329                                     const struct uwb_rceb *rceb)
 330{
 331        struct uwb_rc_neh *neh = NULL, *h;
 332        unsigned long flags;
 333
 334        spin_lock_irqsave(&rc->neh_lock, flags);
 335
 336        list_for_each_entry(h, &rc->neh_list, list_node) {
 337                if (uwb_rc_neh_match(h, rceb)) {
 338                        neh = h;
 339                        break;
 340                }
 341        }
 342
 343        if (neh)
 344                __uwb_rc_neh_rm(rc, neh);
 345
 346        spin_unlock_irqrestore(&rc->neh_lock, flags);
 347
 348        return neh;
 349}
 350
 351
 352/*
 353 * Process notifications coming from the radio control interface
 354 *
 355 * @rc:    UWB Radio Control Interface descriptor
 356 * @neh:   Notification/Event Handler @neh->ptr points to
 357 *         @uwb_evt->buffer.
 358 *
 359 * This function is called by the event/notif handling subsystem when
 360 * notifications arrive (hwarc_probe() arms a notification/event handle
 361 * that calls back this function for every received notification; this
 362 * function then will rearm itself).
 363 *
 364 * Notification data buffers are dynamically allocated by the NEH
 365 * handling code in neh.c [uwb_rc_neh_lookup()]. What is actually
 366 * allocated is space to contain the notification data.
 367 *
 368 * Buffers are prefixed with a Radio Control Event Block (RCEB) as
 369 * defined by the WUSB Wired-Adapter Radio Control interface. We
 370 * just use it for the notification code.
 371 *
 372 * On each case statement we just transcode endianess of the different
 373 * fields. We declare a pointer to a RCI definition of an event, and
 374 * then to a UWB definition of the same event (which are the same,
 375 * remember). Event if we use different pointers
 376 */
 377static
 378void uwb_rc_notif(struct uwb_rc *rc, struct uwb_rceb *rceb, ssize_t size)
 379{
 380        struct device *dev = &rc->uwb_dev.dev;
 381        struct uwb_event *uwb_evt;
 382
 383        if (size == -ESHUTDOWN)
 384                return;
 385        if (size < 0) {
 386                dev_err(dev, "ignoring event with error code %zu\n",
 387                        size);
 388                return;
 389        }
 390
 391        uwb_evt = kzalloc(sizeof(*uwb_evt), GFP_ATOMIC);
 392        if (unlikely(uwb_evt == NULL)) {
 393                dev_err(dev, "no memory to queue event 0x%02x/%04x/%02x\n",
 394                        rceb->bEventType, le16_to_cpu(rceb->wEvent),
 395                        rceb->bEventContext);
 396                return;
 397        }
 398        uwb_evt->rc = __uwb_rc_get(rc); /* will be put by uwbd's uwbd_event_handle() */
 399        uwb_evt->ts_jiffies = jiffies;
 400        uwb_evt->type = UWB_EVT_TYPE_NOTIF;
 401        uwb_evt->notif.size = size;
 402        uwb_evt->notif.rceb = rceb;
 403
 404        uwbd_event_queue(uwb_evt);
 405}
 406
 407static void uwb_rc_neh_grok_event(struct uwb_rc *rc, struct uwb_rceb *rceb, size_t size)
 408{
 409        struct device *dev = &rc->uwb_dev.dev;
 410        struct uwb_rc_neh *neh;
 411        struct uwb_rceb *notif;
 412
 413        if (rceb->bEventContext == 0) {
 414                notif = kmalloc(size, GFP_ATOMIC);
 415                if (notif) {
 416                        memcpy(notif, rceb, size);
 417                        uwb_rc_notif(rc, notif, size);
 418                } else
 419                        dev_err(dev, "event 0x%02x/%04x/%02x (%zu bytes): no memory\n",
 420                                rceb->bEventType, le16_to_cpu(rceb->wEvent),
 421                                rceb->bEventContext, size);
 422        } else {
 423                neh = uwb_rc_neh_lookup(rc, rceb);
 424                if (neh) {
 425                        del_timer_sync(&neh->timer);
 426                        uwb_rc_neh_cb(neh, rceb, size);
 427                } else
 428                        dev_warn(dev, "event 0x%02x/%04x/%02x (%zu bytes): nobody cared\n",
 429                                 rceb->bEventType, le16_to_cpu(rceb->wEvent),
 430                                 rceb->bEventContext, size);
 431        }
 432}
 433
 434/**
 435 * Given a buffer with one or more UWB RC events/notifications, break
 436 * them up and dispatch them.
 437 *
 438 * @rc:       UWB Radio Controller
 439 * @buf:      Buffer with the stream of notifications/events
 440 * @buf_size: Amount of data in the buffer
 441 *
 442 * Note each notification/event starts always with a 'struct
 443 * uwb_rceb', so the minimum size if 4 bytes.
 444 *
 445 * The device may pass us events formatted differently than expected.
 446 * These are first filtered, potentially creating a new event in a new
 447 * memory location. If a new event is created by the filter it is also
 448 * freed here.
 449 *
 450 * For each notif/event, tries to guess the size looking at the EST
 451 * tables, then looks for a neh that is waiting for that event and if
 452 * found, copies the payload to the neh's buffer and calls it back. If
 453 * not, the data is ignored.
 454 *
 455 * Note that if we can't find a size description in the EST tables, we
 456 * still might find a size in the 'neh' handle in uwb_rc_neh_lookup().
 457 *
 458 * Assumptions:
 459 *
 460 *   @rc->neh_lock is NOT taken
 461 *
 462 * We keep track of various sizes here:
 463 * size:      contains the size of the buffer that is processed for the
 464 *            incoming event. this buffer may contain events that are not
 465 *            formatted as WHCI.
 466 * real_size: the actual space taken by this event in the buffer.
 467 *            We need to keep track of the real size of an event to be able to
 468 *            advance the buffer correctly.
 469 * event_size: the size of the event as expected by the core layer
 470 *            [OR] the size of the event after filtering. if the filtering
 471 *            created a new event in a new memory location then this is
 472 *            effectively the size of a new event buffer
 473 */
 474void uwb_rc_neh_grok(struct uwb_rc *rc, void *buf, size_t buf_size)
 475{
 476        struct device *dev = &rc->uwb_dev.dev;
 477        void *itr;
 478        struct uwb_rceb *rceb;
 479        size_t size, real_size, event_size;
 480        int needtofree;
 481
 482        itr = buf;
 483        size = buf_size;
 484        while (size > 0) {
 485                if (size < sizeof(*rceb)) {
 486                        dev_err(dev, "not enough data in event buffer to "
 487                                "process incoming events (%zu left, minimum is "
 488                                "%zu)\n", size, sizeof(*rceb));
 489                        break;
 490                }
 491
 492                rceb = itr;
 493                if (rc->filter_event) {
 494                        needtofree = rc->filter_event(rc, &rceb, size,
 495                                                      &real_size, &event_size);
 496                        if (needtofree < 0 && needtofree != -ENOANO) {
 497                                dev_err(dev, "BUG: Unable to filter event "
 498                                        "(0x%02x/%04x/%02x) from "
 499                                        "device. \n", rceb->bEventType,
 500                                        le16_to_cpu(rceb->wEvent),
 501                                        rceb->bEventContext);
 502                                break;
 503                        }
 504                } else
 505                        needtofree = -ENOANO;
 506                /* do real processing if there was no filtering or the
 507                 * filtering didn't act */
 508                if (needtofree == -ENOANO) {
 509                        ssize_t ret = uwb_est_find_size(rc, rceb, size);
 510                        if (ret < 0)
 511                                break;
 512                        if (ret > size) {
 513                                dev_err(dev, "BUG: hw sent incomplete event "
 514                                        "0x%02x/%04x/%02x (%zd bytes), only got "
 515                                        "%zu bytes. We don't handle that.\n",
 516                                        rceb->bEventType, le16_to_cpu(rceb->wEvent),
 517                                        rceb->bEventContext, ret, size);
 518                                break;
 519                        }
 520                        real_size = event_size = ret;
 521                }
 522                uwb_rc_neh_grok_event(rc, rceb, event_size);
 523
 524                if (needtofree == 1)
 525                        kfree(rceb);
 526
 527                itr += real_size;
 528                size -= real_size;
 529        }
 530}
 531EXPORT_SYMBOL_GPL(uwb_rc_neh_grok);
 532
 533
 534/**
 535 * The entity that reads from the device notification/event channel has
 536 * detected an error.
 537 *
 538 * @rc:    UWB Radio Controller
 539 * @error: Errno error code
 540 *
 541 */
 542void uwb_rc_neh_error(struct uwb_rc *rc, int error)
 543{
 544        struct uwb_rc_neh *neh;
 545        unsigned long flags;
 546
 547        for (;;) {
 548                spin_lock_irqsave(&rc->neh_lock, flags);
 549                if (list_empty(&rc->neh_list)) {
 550                        spin_unlock_irqrestore(&rc->neh_lock, flags);
 551                        break;
 552                }
 553                neh = list_first_entry(&rc->neh_list, struct uwb_rc_neh, list_node);
 554                __uwb_rc_neh_rm(rc, neh);
 555                spin_unlock_irqrestore(&rc->neh_lock, flags);
 556
 557                del_timer_sync(&neh->timer);
 558                uwb_rc_neh_cb(neh, NULL, error);
 559        }
 560}
 561EXPORT_SYMBOL_GPL(uwb_rc_neh_error);
 562
 563
 564static void uwb_rc_neh_timer(unsigned long arg)
 565{
 566        struct uwb_rc_neh *neh = (struct uwb_rc_neh *)arg;
 567        struct uwb_rc *rc = neh->rc;
 568        unsigned long flags;
 569
 570        spin_lock_irqsave(&rc->neh_lock, flags);
 571        if (neh->context)
 572                __uwb_rc_neh_rm(rc, neh);
 573        else
 574                neh = NULL;
 575        spin_unlock_irqrestore(&rc->neh_lock, flags);
 576
 577        if (neh)
 578                uwb_rc_neh_cb(neh, NULL, -ETIMEDOUT);
 579}
 580
 581/** Initializes the @rc's neh subsystem
 582 */
 583void uwb_rc_neh_create(struct uwb_rc *rc)
 584{
 585        spin_lock_init(&rc->neh_lock);
 586        INIT_LIST_HEAD(&rc->neh_list);
 587        set_bit(0, rc->ctx_bm);         /* 0 is reserved (see [WUSB] table 8-65) */
 588        set_bit(0xff, rc->ctx_bm);      /* and 0xff is invalid */
 589        rc->ctx_roll = 1;
 590}
 591
 592
 593/** Release's the @rc's neh subsystem */
 594void uwb_rc_neh_destroy(struct uwb_rc *rc)
 595{
 596        unsigned long flags;
 597        struct uwb_rc_neh *neh;
 598
 599        for (;;) {
 600                spin_lock_irqsave(&rc->neh_lock, flags);
 601                if (list_empty(&rc->neh_list)) {
 602                        spin_unlock_irqrestore(&rc->neh_lock, flags);
 603                        break;
 604                }
 605                neh = list_first_entry(&rc->neh_list, struct uwb_rc_neh, list_node);
 606                __uwb_rc_neh_rm(rc, neh);
 607                spin_unlock_irqrestore(&rc->neh_lock, flags);
 608
 609                del_timer_sync(&neh->timer);
 610                uwb_rc_neh_put(neh);
 611        }
 612}
 613
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