linux/net/nfc/hci/llc_shdlc.c
<<
>>
Prefs
   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * shdlc Link Layer Control
   4 *
   5 * Copyright (C) 2012  Intel Corporation. All rights reserved.
   6 */
   7
   8#define pr_fmt(fmt) "shdlc: %s: " fmt, __func__
   9
  10#include <linux/types.h>
  11#include <linux/sched.h>
  12#include <linux/wait.h>
  13#include <linux/slab.h>
  14#include <linux/skbuff.h>
  15
  16#include "llc.h"
  17
  18enum shdlc_state {
  19        SHDLC_DISCONNECTED = 0,
  20        SHDLC_CONNECTING = 1,
  21        SHDLC_NEGOTIATING = 2,
  22        SHDLC_HALF_CONNECTED = 3,
  23        SHDLC_CONNECTED = 4
  24};
  25
  26struct llc_shdlc {
  27        struct nfc_hci_dev *hdev;
  28        xmit_to_drv_t xmit_to_drv;
  29        rcv_to_hci_t rcv_to_hci;
  30
  31        struct mutex state_mutex;
  32        enum shdlc_state state;
  33        int hard_fault;
  34
  35        wait_queue_head_t *connect_wq;
  36        int connect_tries;
  37        int connect_result;
  38        struct timer_list connect_timer;/* aka T3 in spec 10.6.1 */
  39
  40        u8 w;                           /* window size */
  41        bool srej_support;
  42
  43        struct timer_list t1_timer;     /* send ack timeout */
  44        bool t1_active;
  45
  46        struct timer_list t2_timer;     /* guard/retransmit timeout */
  47        bool t2_active;
  48
  49        int ns;                         /* next seq num for send */
  50        int nr;                         /* next expected seq num for receive */
  51        int dnr;                        /* oldest sent unacked seq num */
  52
  53        struct sk_buff_head rcv_q;
  54
  55        struct sk_buff_head send_q;
  56        bool rnr;                       /* other side is not ready to receive */
  57
  58        struct sk_buff_head ack_pending_q;
  59
  60        struct work_struct sm_work;
  61
  62        int tx_headroom;
  63        int tx_tailroom;
  64
  65        llc_failure_t llc_failure;
  66};
  67
  68#define SHDLC_LLC_HEAD_ROOM     2
  69
  70#define SHDLC_MAX_WINDOW        4
  71#define SHDLC_SREJ_SUPPORT      false
  72
  73#define SHDLC_CONTROL_HEAD_MASK 0xe0
  74#define SHDLC_CONTROL_HEAD_I    0x80
  75#define SHDLC_CONTROL_HEAD_I2   0xa0
  76#define SHDLC_CONTROL_HEAD_S    0xc0
  77#define SHDLC_CONTROL_HEAD_U    0xe0
  78
  79#define SHDLC_CONTROL_NS_MASK   0x38
  80#define SHDLC_CONTROL_NR_MASK   0x07
  81#define SHDLC_CONTROL_TYPE_MASK 0x18
  82
  83#define SHDLC_CONTROL_M_MASK    0x1f
  84
  85enum sframe_type {
  86        S_FRAME_RR = 0x00,
  87        S_FRAME_REJ = 0x01,
  88        S_FRAME_RNR = 0x02,
  89        S_FRAME_SREJ = 0x03
  90};
  91
  92enum uframe_modifier {
  93        U_FRAME_UA = 0x06,
  94        U_FRAME_RSET = 0x19
  95};
  96
  97#define SHDLC_CONNECT_VALUE_MS  5
  98#define SHDLC_T1_VALUE_MS(w)    ((5 * w) / 4)
  99#define SHDLC_T2_VALUE_MS       300
 100
 101#define SHDLC_DUMP_SKB(info, skb)                                 \
 102do {                                                              \
 103        pr_debug("%s:\n", info);                                  \
 104        print_hex_dump(KERN_DEBUG, "shdlc: ", DUMP_PREFIX_OFFSET, \
 105                       16, 1, skb->data, skb->len, 0);            \
 106} while (0)
 107
 108/* checks x < y <= z modulo 8 */
 109static bool llc_shdlc_x_lt_y_lteq_z(int x, int y, int z)
 110{
 111        if (x < z)
 112                return ((x < y) && (y <= z)) ? true : false;
 113        else
 114                return ((y > x) || (y <= z)) ? true : false;
 115}
 116
 117/* checks x <= y < z modulo 8 */
 118static bool llc_shdlc_x_lteq_y_lt_z(int x, int y, int z)
 119{
 120        if (x <= z)
 121                return ((x <= y) && (y < z)) ? true : false;
 122        else                    /* x > z -> z+8 > x */
 123                return ((y >= x) || (y < z)) ? true : false;
 124}
 125
 126static struct sk_buff *llc_shdlc_alloc_skb(struct llc_shdlc *shdlc,
 127                                           int payload_len)
 128{
 129        struct sk_buff *skb;
 130
 131        skb = alloc_skb(shdlc->tx_headroom + SHDLC_LLC_HEAD_ROOM +
 132                        shdlc->tx_tailroom + payload_len, GFP_KERNEL);
 133        if (skb)
 134                skb_reserve(skb, shdlc->tx_headroom + SHDLC_LLC_HEAD_ROOM);
 135
 136        return skb;
 137}
 138
 139/* immediately sends an S frame. */
 140static int llc_shdlc_send_s_frame(struct llc_shdlc *shdlc,
 141                                  enum sframe_type sframe_type, int nr)
 142{
 143        int r;
 144        struct sk_buff *skb;
 145
 146        pr_debug("sframe_type=%d nr=%d\n", sframe_type, nr);
 147
 148        skb = llc_shdlc_alloc_skb(shdlc, 0);
 149        if (skb == NULL)
 150                return -ENOMEM;
 151
 152        *(u8 *)skb_push(skb, 1) = SHDLC_CONTROL_HEAD_S | (sframe_type << 3) | nr;
 153
 154        r = shdlc->xmit_to_drv(shdlc->hdev, skb);
 155
 156        kfree_skb(skb);
 157
 158        return r;
 159}
 160
 161/* immediately sends an U frame. skb may contain optional payload */
 162static int llc_shdlc_send_u_frame(struct llc_shdlc *shdlc,
 163                                  struct sk_buff *skb,
 164                                  enum uframe_modifier uframe_modifier)
 165{
 166        int r;
 167
 168        pr_debug("uframe_modifier=%d\n", uframe_modifier);
 169
 170        *(u8 *)skb_push(skb, 1) = SHDLC_CONTROL_HEAD_U | uframe_modifier;
 171
 172        r = shdlc->xmit_to_drv(shdlc->hdev, skb);
 173
 174        kfree_skb(skb);
 175
 176        return r;
 177}
 178
 179/*
 180 * Free ack_pending frames until y_nr - 1, and reset t2 according to
 181 * the remaining oldest ack_pending frame sent time
 182 */
 183static void llc_shdlc_reset_t2(struct llc_shdlc *shdlc, int y_nr)
 184{
 185        struct sk_buff *skb;
 186        int dnr = shdlc->dnr;   /* MUST initially be < y_nr */
 187
 188        pr_debug("release ack pending up to frame %d excluded\n", y_nr);
 189
 190        while (dnr != y_nr) {
 191                pr_debug("release ack pending frame %d\n", dnr);
 192
 193                skb = skb_dequeue(&shdlc->ack_pending_q);
 194                kfree_skb(skb);
 195
 196                dnr = (dnr + 1) % 8;
 197        }
 198
 199        if (skb_queue_empty(&shdlc->ack_pending_q)) {
 200                if (shdlc->t2_active) {
 201                        del_timer_sync(&shdlc->t2_timer);
 202                        shdlc->t2_active = false;
 203
 204                        pr_debug
 205                            ("All sent frames acked. Stopped T2(retransmit)\n");
 206                }
 207        } else {
 208                skb = skb_peek(&shdlc->ack_pending_q);
 209
 210                mod_timer(&shdlc->t2_timer, *(unsigned long *)skb->cb +
 211                          msecs_to_jiffies(SHDLC_T2_VALUE_MS));
 212                shdlc->t2_active = true;
 213
 214                pr_debug
 215                    ("Start T2(retransmit) for remaining unacked sent frames\n");
 216        }
 217}
 218
 219/*
 220 * Receive validated frames from lower layer. skb contains HCI payload only.
 221 * Handle according to algorithm at spec:10.8.2
 222 */
 223static void llc_shdlc_rcv_i_frame(struct llc_shdlc *shdlc,
 224                                  struct sk_buff *skb, int ns, int nr)
 225{
 226        int x_ns = ns;
 227        int y_nr = nr;
 228
 229        pr_debug("recvd I-frame %d, remote waiting frame %d\n", ns, nr);
 230
 231        if (shdlc->state != SHDLC_CONNECTED)
 232                goto exit;
 233
 234        if (x_ns != shdlc->nr) {
 235                llc_shdlc_send_s_frame(shdlc, S_FRAME_REJ, shdlc->nr);
 236                goto exit;
 237        }
 238
 239        if (!shdlc->t1_active) {
 240                shdlc->t1_active = true;
 241                mod_timer(&shdlc->t1_timer, jiffies +
 242                          msecs_to_jiffies(SHDLC_T1_VALUE_MS(shdlc->w)));
 243                pr_debug("(re)Start T1(send ack)\n");
 244        }
 245
 246        if (skb->len) {
 247                shdlc->rcv_to_hci(shdlc->hdev, skb);
 248                skb = NULL;
 249        }
 250
 251        shdlc->nr = (shdlc->nr + 1) % 8;
 252
 253        if (llc_shdlc_x_lt_y_lteq_z(shdlc->dnr, y_nr, shdlc->ns)) {
 254                llc_shdlc_reset_t2(shdlc, y_nr);
 255
 256                shdlc->dnr = y_nr;
 257        }
 258
 259exit:
 260        kfree_skb(skb);
 261}
 262
 263static void llc_shdlc_rcv_ack(struct llc_shdlc *shdlc, int y_nr)
 264{
 265        pr_debug("remote acked up to frame %d excluded\n", y_nr);
 266
 267        if (llc_shdlc_x_lt_y_lteq_z(shdlc->dnr, y_nr, shdlc->ns)) {
 268                llc_shdlc_reset_t2(shdlc, y_nr);
 269                shdlc->dnr = y_nr;
 270        }
 271}
 272
 273static void llc_shdlc_requeue_ack_pending(struct llc_shdlc *shdlc)
 274{
 275        struct sk_buff *skb;
 276
 277        pr_debug("ns reset to %d\n", shdlc->dnr);
 278
 279        while ((skb = skb_dequeue_tail(&shdlc->ack_pending_q))) {
 280                skb_pull(skb, 1);       /* remove control field */
 281                skb_queue_head(&shdlc->send_q, skb);
 282        }
 283        shdlc->ns = shdlc->dnr;
 284}
 285
 286static void llc_shdlc_rcv_rej(struct llc_shdlc *shdlc, int y_nr)
 287{
 288        struct sk_buff *skb;
 289
 290        pr_debug("remote asks retransmission from frame %d\n", y_nr);
 291
 292        if (llc_shdlc_x_lteq_y_lt_z(shdlc->dnr, y_nr, shdlc->ns)) {
 293                if (shdlc->t2_active) {
 294                        del_timer_sync(&shdlc->t2_timer);
 295                        shdlc->t2_active = false;
 296                        pr_debug("Stopped T2(retransmit)\n");
 297                }
 298
 299                if (shdlc->dnr != y_nr) {
 300                        while ((shdlc->dnr = ((shdlc->dnr + 1) % 8)) != y_nr) {
 301                                skb = skb_dequeue(&shdlc->ack_pending_q);
 302                                kfree_skb(skb);
 303                        }
 304                }
 305
 306                llc_shdlc_requeue_ack_pending(shdlc);
 307        }
 308}
 309
 310/* See spec RR:10.8.3 REJ:10.8.4 */
 311static void llc_shdlc_rcv_s_frame(struct llc_shdlc *shdlc,
 312                                  enum sframe_type s_frame_type, int nr)
 313{
 314        struct sk_buff *skb;
 315
 316        if (shdlc->state != SHDLC_CONNECTED)
 317                return;
 318
 319        switch (s_frame_type) {
 320        case S_FRAME_RR:
 321                llc_shdlc_rcv_ack(shdlc, nr);
 322                if (shdlc->rnr == true) {       /* see SHDLC 10.7.7 */
 323                        shdlc->rnr = false;
 324                        if (shdlc->send_q.qlen == 0) {
 325                                skb = llc_shdlc_alloc_skb(shdlc, 0);
 326                                if (skb)
 327                                        skb_queue_tail(&shdlc->send_q, skb);
 328                        }
 329                }
 330                break;
 331        case S_FRAME_REJ:
 332                llc_shdlc_rcv_rej(shdlc, nr);
 333                break;
 334        case S_FRAME_RNR:
 335                llc_shdlc_rcv_ack(shdlc, nr);
 336                shdlc->rnr = true;
 337                break;
 338        default:
 339                break;
 340        }
 341}
 342
 343static void llc_shdlc_connect_complete(struct llc_shdlc *shdlc, int r)
 344{
 345        pr_debug("result=%d\n", r);
 346
 347        del_timer_sync(&shdlc->connect_timer);
 348
 349        if (r == 0) {
 350                shdlc->ns = 0;
 351                shdlc->nr = 0;
 352                shdlc->dnr = 0;
 353
 354                shdlc->state = SHDLC_HALF_CONNECTED;
 355        } else {
 356                shdlc->state = SHDLC_DISCONNECTED;
 357        }
 358
 359        shdlc->connect_result = r;
 360
 361        wake_up(shdlc->connect_wq);
 362}
 363
 364static int llc_shdlc_connect_initiate(struct llc_shdlc *shdlc)
 365{
 366        struct sk_buff *skb;
 367
 368        pr_debug("\n");
 369
 370        skb = llc_shdlc_alloc_skb(shdlc, 2);
 371        if (skb == NULL)
 372                return -ENOMEM;
 373
 374        skb_put_u8(skb, SHDLC_MAX_WINDOW);
 375        skb_put_u8(skb, SHDLC_SREJ_SUPPORT ? 1 : 0);
 376
 377        return llc_shdlc_send_u_frame(shdlc, skb, U_FRAME_RSET);
 378}
 379
 380static int llc_shdlc_connect_send_ua(struct llc_shdlc *shdlc)
 381{
 382        struct sk_buff *skb;
 383
 384        pr_debug("\n");
 385
 386        skb = llc_shdlc_alloc_skb(shdlc, 0);
 387        if (skb == NULL)
 388                return -ENOMEM;
 389
 390        return llc_shdlc_send_u_frame(shdlc, skb, U_FRAME_UA);
 391}
 392
 393static void llc_shdlc_rcv_u_frame(struct llc_shdlc *shdlc,
 394                                  struct sk_buff *skb,
 395                                  enum uframe_modifier u_frame_modifier)
 396{
 397        u8 w = SHDLC_MAX_WINDOW;
 398        bool srej_support = SHDLC_SREJ_SUPPORT;
 399        int r;
 400
 401        pr_debug("u_frame_modifier=%d\n", u_frame_modifier);
 402
 403        switch (u_frame_modifier) {
 404        case U_FRAME_RSET:
 405                switch (shdlc->state) {
 406                case SHDLC_NEGOTIATING:
 407                case SHDLC_CONNECTING:
 408                        /*
 409                         * We sent RSET, but chip wants to negotiate or we
 410                         * got RSET before we managed to send out our.
 411                         */
 412                        if (skb->len > 0)
 413                                w = skb->data[0];
 414
 415                        if (skb->len > 1)
 416                                srej_support = skb->data[1] & 0x01 ? true :
 417                                               false;
 418
 419                        if ((w <= SHDLC_MAX_WINDOW) &&
 420                            (SHDLC_SREJ_SUPPORT || (srej_support == false))) {
 421                                shdlc->w = w;
 422                                shdlc->srej_support = srej_support;
 423                                r = llc_shdlc_connect_send_ua(shdlc);
 424                                llc_shdlc_connect_complete(shdlc, r);
 425                        }
 426                        break;
 427                case SHDLC_HALF_CONNECTED:
 428                        /*
 429                         * Chip resent RSET due to its timeout - Ignote it
 430                         * as we already sent UA.
 431                         */
 432                        break;
 433                case SHDLC_CONNECTED:
 434                        /*
 435                         * Chip wants to reset link. This is unexpected and
 436                         * unsupported.
 437                         */
 438                        shdlc->hard_fault = -ECONNRESET;
 439                        break;
 440                default:
 441                        break;
 442                }
 443                break;
 444        case U_FRAME_UA:
 445                if ((shdlc->state == SHDLC_CONNECTING &&
 446                     shdlc->connect_tries > 0) ||
 447                    (shdlc->state == SHDLC_NEGOTIATING)) {
 448                        llc_shdlc_connect_complete(shdlc, 0);
 449                        shdlc->state = SHDLC_CONNECTED;
 450                }
 451                break;
 452        default:
 453                break;
 454        }
 455
 456        kfree_skb(skb);
 457}
 458
 459static void llc_shdlc_handle_rcv_queue(struct llc_shdlc *shdlc)
 460{
 461        struct sk_buff *skb;
 462        u8 control;
 463        int nr;
 464        int ns;
 465        enum sframe_type s_frame_type;
 466        enum uframe_modifier u_frame_modifier;
 467
 468        if (shdlc->rcv_q.qlen)
 469                pr_debug("rcvQlen=%d\n", shdlc->rcv_q.qlen);
 470
 471        while ((skb = skb_dequeue(&shdlc->rcv_q)) != NULL) {
 472                control = skb->data[0];
 473                skb_pull(skb, 1);
 474                switch (control & SHDLC_CONTROL_HEAD_MASK) {
 475                case SHDLC_CONTROL_HEAD_I:
 476                case SHDLC_CONTROL_HEAD_I2:
 477                        if (shdlc->state == SHDLC_HALF_CONNECTED)
 478                                shdlc->state = SHDLC_CONNECTED;
 479
 480                        ns = (control & SHDLC_CONTROL_NS_MASK) >> 3;
 481                        nr = control & SHDLC_CONTROL_NR_MASK;
 482                        llc_shdlc_rcv_i_frame(shdlc, skb, ns, nr);
 483                        break;
 484                case SHDLC_CONTROL_HEAD_S:
 485                        if (shdlc->state == SHDLC_HALF_CONNECTED)
 486                                shdlc->state = SHDLC_CONNECTED;
 487
 488                        s_frame_type = (control & SHDLC_CONTROL_TYPE_MASK) >> 3;
 489                        nr = control & SHDLC_CONTROL_NR_MASK;
 490                        llc_shdlc_rcv_s_frame(shdlc, s_frame_type, nr);
 491                        kfree_skb(skb);
 492                        break;
 493                case SHDLC_CONTROL_HEAD_U:
 494                        u_frame_modifier = control & SHDLC_CONTROL_M_MASK;
 495                        llc_shdlc_rcv_u_frame(shdlc, skb, u_frame_modifier);
 496                        break;
 497                default:
 498                        pr_err("UNKNOWN Control=%d\n", control);
 499                        kfree_skb(skb);
 500                        break;
 501                }
 502        }
 503}
 504
 505static int llc_shdlc_w_used(int ns, int dnr)
 506{
 507        int unack_count;
 508
 509        if (dnr <= ns)
 510                unack_count = ns - dnr;
 511        else
 512                unack_count = 8 - dnr + ns;
 513
 514        return unack_count;
 515}
 516
 517/* Send frames according to algorithm at spec:10.8.1 */
 518static void llc_shdlc_handle_send_queue(struct llc_shdlc *shdlc)
 519{
 520        struct sk_buff *skb;
 521        int r;
 522        unsigned long time_sent;
 523
 524        if (shdlc->send_q.qlen)
 525                pr_debug
 526                    ("sendQlen=%d ns=%d dnr=%d rnr=%s w_room=%d unackQlen=%d\n",
 527                     shdlc->send_q.qlen, shdlc->ns, shdlc->dnr,
 528                     shdlc->rnr == false ? "false" : "true",
 529                     shdlc->w - llc_shdlc_w_used(shdlc->ns, shdlc->dnr),
 530                     shdlc->ack_pending_q.qlen);
 531
 532        while (shdlc->send_q.qlen && shdlc->ack_pending_q.qlen < shdlc->w &&
 533               (shdlc->rnr == false)) {
 534
 535                if (shdlc->t1_active) {
 536                        del_timer_sync(&shdlc->t1_timer);
 537                        shdlc->t1_active = false;
 538                        pr_debug("Stopped T1(send ack)\n");
 539                }
 540
 541                skb = skb_dequeue(&shdlc->send_q);
 542
 543                *(u8 *)skb_push(skb, 1) = SHDLC_CONTROL_HEAD_I | (shdlc->ns << 3) |
 544                                        shdlc->nr;
 545
 546                pr_debug("Sending I-Frame %d, waiting to rcv %d\n", shdlc->ns,
 547                         shdlc->nr);
 548                SHDLC_DUMP_SKB("shdlc frame written", skb);
 549
 550                r = shdlc->xmit_to_drv(shdlc->hdev, skb);
 551                if (r < 0) {
 552                        shdlc->hard_fault = r;
 553                        break;
 554                }
 555
 556                shdlc->ns = (shdlc->ns + 1) % 8;
 557
 558                time_sent = jiffies;
 559                *(unsigned long *)skb->cb = time_sent;
 560
 561                skb_queue_tail(&shdlc->ack_pending_q, skb);
 562
 563                if (shdlc->t2_active == false) {
 564                        shdlc->t2_active = true;
 565                        mod_timer(&shdlc->t2_timer, time_sent +
 566                                  msecs_to_jiffies(SHDLC_T2_VALUE_MS));
 567                        pr_debug("Started T2 (retransmit)\n");
 568                }
 569        }
 570}
 571
 572static void llc_shdlc_connect_timeout(struct timer_list *t)
 573{
 574        struct llc_shdlc *shdlc = from_timer(shdlc, t, connect_timer);
 575
 576        pr_debug("\n");
 577
 578        schedule_work(&shdlc->sm_work);
 579}
 580
 581static void llc_shdlc_t1_timeout(struct timer_list *t)
 582{
 583        struct llc_shdlc *shdlc = from_timer(shdlc, t, t1_timer);
 584
 585        pr_debug("SoftIRQ: need to send ack\n");
 586
 587        schedule_work(&shdlc->sm_work);
 588}
 589
 590static void llc_shdlc_t2_timeout(struct timer_list *t)
 591{
 592        struct llc_shdlc *shdlc = from_timer(shdlc, t, t2_timer);
 593
 594        pr_debug("SoftIRQ: need to retransmit\n");
 595
 596        schedule_work(&shdlc->sm_work);
 597}
 598
 599static void llc_shdlc_sm_work(struct work_struct *work)
 600{
 601        struct llc_shdlc *shdlc = container_of(work, struct llc_shdlc, sm_work);
 602        int r;
 603
 604        pr_debug("\n");
 605
 606        mutex_lock(&shdlc->state_mutex);
 607
 608        switch (shdlc->state) {
 609        case SHDLC_DISCONNECTED:
 610                skb_queue_purge(&shdlc->rcv_q);
 611                skb_queue_purge(&shdlc->send_q);
 612                skb_queue_purge(&shdlc->ack_pending_q);
 613                break;
 614        case SHDLC_CONNECTING:
 615                if (shdlc->hard_fault) {
 616                        llc_shdlc_connect_complete(shdlc, shdlc->hard_fault);
 617                        break;
 618                }
 619
 620                if (shdlc->connect_tries++ < 5)
 621                        r = llc_shdlc_connect_initiate(shdlc);
 622                else
 623                        r = -ETIME;
 624                if (r < 0) {
 625                        llc_shdlc_connect_complete(shdlc, r);
 626                } else {
 627                        mod_timer(&shdlc->connect_timer, jiffies +
 628                                  msecs_to_jiffies(SHDLC_CONNECT_VALUE_MS));
 629
 630                        shdlc->state = SHDLC_NEGOTIATING;
 631                }
 632                break;
 633        case SHDLC_NEGOTIATING:
 634                if (timer_pending(&shdlc->connect_timer) == 0) {
 635                        shdlc->state = SHDLC_CONNECTING;
 636                        schedule_work(&shdlc->sm_work);
 637                }
 638
 639                llc_shdlc_handle_rcv_queue(shdlc);
 640
 641                if (shdlc->hard_fault) {
 642                        llc_shdlc_connect_complete(shdlc, shdlc->hard_fault);
 643                        break;
 644                }
 645                break;
 646        case SHDLC_HALF_CONNECTED:
 647        case SHDLC_CONNECTED:
 648                llc_shdlc_handle_rcv_queue(shdlc);
 649                llc_shdlc_handle_send_queue(shdlc);
 650
 651                if (shdlc->t1_active && timer_pending(&shdlc->t1_timer) == 0) {
 652                        pr_debug
 653                            ("Handle T1(send ack) elapsed (T1 now inactive)\n");
 654
 655                        shdlc->t1_active = false;
 656                        r = llc_shdlc_send_s_frame(shdlc, S_FRAME_RR,
 657                                                   shdlc->nr);
 658                        if (r < 0)
 659                                shdlc->hard_fault = r;
 660                }
 661
 662                if (shdlc->t2_active && timer_pending(&shdlc->t2_timer) == 0) {
 663                        pr_debug
 664                            ("Handle T2(retransmit) elapsed (T2 inactive)\n");
 665
 666                        shdlc->t2_active = false;
 667
 668                        llc_shdlc_requeue_ack_pending(shdlc);
 669                        llc_shdlc_handle_send_queue(shdlc);
 670                }
 671
 672                if (shdlc->hard_fault)
 673                        shdlc->llc_failure(shdlc->hdev, shdlc->hard_fault);
 674                break;
 675        default:
 676                break;
 677        }
 678        mutex_unlock(&shdlc->state_mutex);
 679}
 680
 681/*
 682 * Called from syscall context to establish shdlc link. Sleeps until
 683 * link is ready or failure.
 684 */
 685static int llc_shdlc_connect(struct llc_shdlc *shdlc)
 686{
 687        DECLARE_WAIT_QUEUE_HEAD_ONSTACK(connect_wq);
 688
 689        pr_debug("\n");
 690
 691        mutex_lock(&shdlc->state_mutex);
 692
 693        shdlc->state = SHDLC_CONNECTING;
 694        shdlc->connect_wq = &connect_wq;
 695        shdlc->connect_tries = 0;
 696        shdlc->connect_result = 1;
 697
 698        mutex_unlock(&shdlc->state_mutex);
 699
 700        schedule_work(&shdlc->sm_work);
 701
 702        wait_event(connect_wq, shdlc->connect_result != 1);
 703
 704        return shdlc->connect_result;
 705}
 706
 707static void llc_shdlc_disconnect(struct llc_shdlc *shdlc)
 708{
 709        pr_debug("\n");
 710
 711        mutex_lock(&shdlc->state_mutex);
 712
 713        shdlc->state = SHDLC_DISCONNECTED;
 714
 715        mutex_unlock(&shdlc->state_mutex);
 716
 717        schedule_work(&shdlc->sm_work);
 718}
 719
 720/*
 721 * Receive an incoming shdlc frame. Frame has already been crc-validated.
 722 * skb contains only LLC header and payload.
 723 * If skb == NULL, it is a notification that the link below is dead.
 724 */
 725static void llc_shdlc_recv_frame(struct llc_shdlc *shdlc, struct sk_buff *skb)
 726{
 727        if (skb == NULL) {
 728                pr_err("NULL Frame -> link is dead\n");
 729                shdlc->hard_fault = -EREMOTEIO;
 730        } else {
 731                SHDLC_DUMP_SKB("incoming frame", skb);
 732                skb_queue_tail(&shdlc->rcv_q, skb);
 733        }
 734
 735        schedule_work(&shdlc->sm_work);
 736}
 737
 738static void *llc_shdlc_init(struct nfc_hci_dev *hdev, xmit_to_drv_t xmit_to_drv,
 739                            rcv_to_hci_t rcv_to_hci, int tx_headroom,
 740                            int tx_tailroom, int *rx_headroom, int *rx_tailroom,
 741                            llc_failure_t llc_failure)
 742{
 743        struct llc_shdlc *shdlc;
 744
 745        *rx_headroom = SHDLC_LLC_HEAD_ROOM;
 746        *rx_tailroom = 0;
 747
 748        shdlc = kzalloc(sizeof(struct llc_shdlc), GFP_KERNEL);
 749        if (shdlc == NULL)
 750                return NULL;
 751
 752        mutex_init(&shdlc->state_mutex);
 753        shdlc->state = SHDLC_DISCONNECTED;
 754
 755        timer_setup(&shdlc->connect_timer, llc_shdlc_connect_timeout, 0);
 756        timer_setup(&shdlc->t1_timer, llc_shdlc_t1_timeout, 0);
 757        timer_setup(&shdlc->t2_timer, llc_shdlc_t2_timeout, 0);
 758
 759        shdlc->w = SHDLC_MAX_WINDOW;
 760        shdlc->srej_support = SHDLC_SREJ_SUPPORT;
 761
 762        skb_queue_head_init(&shdlc->rcv_q);
 763        skb_queue_head_init(&shdlc->send_q);
 764        skb_queue_head_init(&shdlc->ack_pending_q);
 765
 766        INIT_WORK(&shdlc->sm_work, llc_shdlc_sm_work);
 767
 768        shdlc->hdev = hdev;
 769        shdlc->xmit_to_drv = xmit_to_drv;
 770        shdlc->rcv_to_hci = rcv_to_hci;
 771        shdlc->tx_headroom = tx_headroom;
 772        shdlc->tx_tailroom = tx_tailroom;
 773        shdlc->llc_failure = llc_failure;
 774
 775        return shdlc;
 776}
 777
 778static void llc_shdlc_deinit(struct nfc_llc *llc)
 779{
 780        struct llc_shdlc *shdlc = nfc_llc_get_data(llc);
 781
 782        skb_queue_purge(&shdlc->rcv_q);
 783        skb_queue_purge(&shdlc->send_q);
 784        skb_queue_purge(&shdlc->ack_pending_q);
 785
 786        kfree(shdlc);
 787}
 788
 789static int llc_shdlc_start(struct nfc_llc *llc)
 790{
 791        struct llc_shdlc *shdlc = nfc_llc_get_data(llc);
 792
 793        return llc_shdlc_connect(shdlc);
 794}
 795
 796static int llc_shdlc_stop(struct nfc_llc *llc)
 797{
 798        struct llc_shdlc *shdlc = nfc_llc_get_data(llc);
 799
 800        llc_shdlc_disconnect(shdlc);
 801
 802        return 0;
 803}
 804
 805static void llc_shdlc_rcv_from_drv(struct nfc_llc *llc, struct sk_buff *skb)
 806{
 807        struct llc_shdlc *shdlc = nfc_llc_get_data(llc);
 808
 809        llc_shdlc_recv_frame(shdlc, skb);
 810}
 811
 812static int llc_shdlc_xmit_from_hci(struct nfc_llc *llc, struct sk_buff *skb)
 813{
 814        struct llc_shdlc *shdlc = nfc_llc_get_data(llc);
 815
 816        skb_queue_tail(&shdlc->send_q, skb);
 817
 818        schedule_work(&shdlc->sm_work);
 819
 820        return 0;
 821}
 822
 823static struct nfc_llc_ops llc_shdlc_ops = {
 824        .init = llc_shdlc_init,
 825        .deinit = llc_shdlc_deinit,
 826        .start = llc_shdlc_start,
 827        .stop = llc_shdlc_stop,
 828        .rcv_from_drv = llc_shdlc_rcv_from_drv,
 829        .xmit_from_hci = llc_shdlc_xmit_from_hci,
 830};
 831
 832int nfc_llc_shdlc_register(void)
 833{
 834        return nfc_llc_register(LLC_SHDLC_NAME, &llc_shdlc_ops);
 835}
 836