drivers/staging/gdm724x/gdm_mux.c

   1 /*
   2  * Copyright (c) 2012 GCT Semiconductor, Inc. All rights reserved.
   3  *
   4  * This software is licensed under the terms of the GNU General Public
   5  * License version 2, as published by the Free Software Foundation, and
   6  * may be copied, distributed, and modified under those terms.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16 #include <linux/module.h>
  17 #include <linux/kernel.h>
  18 #include <linux/usb.h>
  19 #include <linux/errno.h>
  20 #include <linux/init.h>
  21 #include <linux/tty.h>
  22 #include <linux/tty_driver.h>
  23 #include <linux/tty_flip.h>
  24 #include <linux/slab.h>
  25 #include <linux/usb/cdc.h>
  26
  27 #include "gdm_mux.h"
  28
  29 struct workqueue_struct *mux_rx_wq;
  30
  31 static u16 packet_type[TTY_MAX_COUNT] = {0xF011, 0xF010};
  32
  33 #define USB_DEVICE_CDC_DATA(vid, pid) \
  34         .match_flags = \
  35                 USB_DEVICE_ID_MATCH_DEVICE |\
  36                 USB_DEVICE_ID_MATCH_INT_CLASS |\
  37                 USB_DEVICE_ID_MATCH_INT_SUBCLASS,\
  38         .idVendor = vid,\
  39         .idProduct = pid,\
  40         .bInterfaceClass = USB_CLASS_COMM,\
  41         .bInterfaceSubClass = USB_CDC_SUBCLASS_ACM
  42
  43 static const struct usb_device_id id_table[] = {
  44         { USB_DEVICE_CDC_DATA(0x1076, 0x8000) }, /* GCT GDM7240 */
  45         { USB_DEVICE_CDC_DATA(0x1076, 0x8f00) }, /* GCT GDM7243 */
  46         { USB_DEVICE_CDC_DATA(0x1076, 0x9000) }, /* GCT GDM7243 */
  47         { USB_DEVICE_CDC_DATA(0x1d74, 0x2300) }, /* LGIT Phoenix */
  48         {}
  49 };
  50
  51
  52 MODULE_DEVICE_TABLE(usb, id_table);
  53
  54 int packet_type_to_index(u16 packetType)
  55 {
  56         int i;
  57
  58         for (i = 0; i < TTY_MAX_COUNT; i++) {
  59                 if (packet_type[i] == packetType)
  60                         return i;
  61         }
  62
  63         return -1;
  64 }
  65
  66 static struct mux_tx *alloc_mux_tx(int len)
  67 {
  68         struct mux_tx *t = NULL;
  69
  70         t = kzalloc(sizeof(struct mux_tx), GFP_ATOMIC);
  71         if (!t)
  72                 return NULL;
  73
  74         t->urb = usb_alloc_urb(0, GFP_ATOMIC);
  75         t->buf = kmalloc(MUX_TX_MAX_SIZE, GFP_ATOMIC);
  76         if (!t->urb || !t->buf) {
  77                 usb_free_urb(t->urb);
  78                 kfree(t->buf);
  79                 kfree(t);
  80                 return NULL;
  81         }
  82
  83         return t;
  84 }
  85
  86 static void free_mux_tx(struct mux_tx *t)
  87 {
  88         if (t) {
  89                 usb_free_urb(t->urb);
  90                 kfree(t->buf);
  91                 kfree(t);
  92         }
  93 }
  94
  95 static struct mux_rx *alloc_mux_rx(void)
  96 {
  97         struct mux_rx *r = NULL;
  98
  99         r = kzalloc(sizeof(struct mux_rx), GFP_ATOMIC);
 100         if (!r)
 101                 return NULL;
 102
 103         r->urb = usb_alloc_urb(0, GFP_ATOMIC);
 104         r->buf = kmalloc(MUX_RX_MAX_SIZE, GFP_ATOMIC);
 105         if (!r->urb || !r->buf) {
 106                 usb_free_urb(r->urb);
 107                 kfree(r->buf);
 108                 kfree(r);
 109                 return NULL;
 110         }
 111
 112         return r;
 113 }
 114
 115 static void free_mux_rx(struct mux_rx *r)
 116 {
 117         if (r) {
 118                 usb_free_urb(r->urb);
 119                 kfree(r->buf);
 120                 kfree(r);
 121         }
 122 }
 123
 124 static struct mux_rx *get_rx_struct(struct rx_cxt *rx)
 125 {
 126         struct mux_rx *r;
 127         unsigned long flags;
 128
 129         spin_lock_irqsave(&rx->free_list_lock, flags);
 130
 131         if (list_empty(&rx->rx_free_list)) {
 132                 spin_unlock_irqrestore(&rx->free_list_lock, flags);
 133                 return NULL;
 134         }
 135
 136         r = list_entry(rx->rx_free_list.prev, struct mux_rx, free_list);
 137         list_del(&r->free_list);
 138
 139         spin_unlock_irqrestore(&rx->free_list_lock, flags);
 140
 141         return r;
 142 }
 143
 144 static void put_rx_struct(struct rx_cxt *rx, struct mux_rx *r)
 145 {
 146         unsigned long flags;
 147
 148         spin_lock_irqsave(&rx->free_list_lock, flags);
 149         list_add_tail(&r->free_list, &rx->rx_free_list);
 150         spin_unlock_irqrestore(&rx->free_list_lock, flags);
 151 }
 152
 153
 154 static int up_to_host(struct mux_rx *r)
 155 {
 156         struct mux_dev *mux_dev = (struct mux_dev *)r->mux_dev;
 157         struct mux_pkt_header *mux_header;
 158         unsigned int start_flag;
 159         unsigned int payload_size;
 160         unsigned short packet_type;
 161         int remain;
 162         int dummy_cnt;
 163         u32 packet_size_sum = r->offset;
 164         int index;
 165         int ret = TO_HOST_INVALID_PACKET;
 166         int len = r->len;
 167
 168         while (1) {
 169                 mux_header = (struct mux_pkt_header *)(r->buf + packet_size_sum);
 170                 start_flag = __le32_to_cpu(mux_header->start_flag);
 171                 payload_size = __le32_to_cpu(mux_header->payload_size);
 172                 packet_type = __le16_to_cpu(mux_header->packet_type);
 173
 174                 if (start_flag != START_FLAG) {
 175                         pr_err("invalid START_FLAG %x\n", start_flag);
 176                         break;
 177                 }
 178
 179                 remain = (MUX_HEADER_SIZE + payload_size) % 4;
 180                 dummy_cnt = remain ? (4-remain) : 0;
 181
 182                 if (len - packet_size_sum <
 183                         MUX_HEADER_SIZE + payload_size + dummy_cnt) {
 184                         pr_err("invalid payload : %d %d %04x\n",
 185                                payload_size, len, packet_type);
 186                         break;
 187                 }
 188
 189                 index = packet_type_to_index(packet_type);
 190                 if (index < 0) {
 191                         pr_err("invalid index %d\n", index);
 192                         break;
 193                 }
 194
 195                 ret = r->callback(mux_header->data,
 196                                 payload_size,
 197                                 index,
 198                                 mux_dev->tty_dev,
 199                                 RECV_PACKET_PROCESS_CONTINUE
 200                                 );
 201                 if (ret == TO_HOST_BUFFER_REQUEST_FAIL) {
 202                         r->offset += packet_size_sum;
 203                         break;
 204                 }
 205
 206                 packet_size_sum += MUX_HEADER_SIZE + payload_size + dummy_cnt;
 207                 if (len - packet_size_sum <= MUX_HEADER_SIZE + 2) {
 208                         ret = r->callback(NULL,
 209                                         0,
 210                                         index,
 211                                         mux_dev->tty_dev,
 212                                         RECV_PACKET_PROCESS_COMPLETE
 213                                         );
 214                         break;
 215                 }
 216         }
 217
 218         return ret;
 219 }
 220
 221 static void do_rx(struct work_struct *work)
 222 {
 223         struct mux_dev *mux_dev =
 224                 container_of(work, struct mux_dev , work_rx.work);
 225         struct mux_rx *r;
 226         struct rx_cxt *rx = (struct rx_cxt *)&mux_dev->rx;
 227         unsigned long flags;
 228         int ret = 0;
 229
 230         while (1) {
 231                 spin_lock_irqsave(&rx->to_host_lock, flags);
 232                 if (list_empty(&rx->to_host_list)) {
 233                         spin_unlock_irqrestore(&rx->to_host_lock, flags);
 234                         break;
 235                 }
 236                 r = list_entry(rx->to_host_list.next, struct mux_rx, to_host_list);
 237                 list_del(&r->to_host_list);
 238                 spin_unlock_irqrestore(&rx->to_host_lock, flags);
 239
 240                 ret = up_to_host(r);
 241                 if (ret == TO_HOST_BUFFER_REQUEST_FAIL)
 242                         pr_err("failed to send mux data to host\n");
 243                 else
 244                         put_rx_struct(rx, r);
 245         }
 246 }
 247
 248 static void remove_rx_submit_list(struct mux_rx *r, struct rx_cxt *rx)
 249 {
 250         unsigned long flags;
 251         struct mux_rx   *r_remove, *r_remove_next;
 252
 253         spin_lock_irqsave(&rx->submit_list_lock, flags);
 254         list_for_each_entry_safe(r_remove, r_remove_next, &rx->rx_submit_list, rx_submit_list) {
 255                 if (r == r_remove)
 256                         list_del(&r->rx_submit_list);
 257         }
 258         spin_unlock_irqrestore(&rx->submit_list_lock, flags);
 259 }
 260
 261 static void gdm_mux_rcv_complete(struct urb *urb)
 262 {
 263         struct mux_rx *r = urb->context;
 264         struct mux_dev *mux_dev = (struct mux_dev *)r->mux_dev;
 265         struct rx_cxt *rx = &mux_dev->rx;
 266         unsigned long flags;
 267
 268         remove_rx_submit_list(r, rx);
 269
 270         if (urb->status) {
 271                 if (mux_dev->usb_state == PM_NORMAL)
 272                         pr_err("%s: urb status error %d\n",
 273                                __func__, urb->status);
 274                 put_rx_struct(rx, r);
 275         } else {
 276                 r->len = r->urb->actual_length;
 277                 spin_lock_irqsave(&rx->to_host_lock, flags);
 278                 list_add_tail(&r->to_host_list, &rx->to_host_list);
 279                 queue_work(mux_rx_wq, &mux_dev->work_rx.work);
 280                 spin_unlock_irqrestore(&rx->to_host_lock, flags);
 281         }
 282 }
 283
 284 static int gdm_mux_recv(void *priv_dev,
 285                         int (*cb)(void *data, int len, int tty_index, struct tty_dev *tty_dev, int complete)
 286                         )
 287 {
 288         struct mux_dev *mux_dev = priv_dev;
 289         struct usb_device *usbdev = mux_dev->usbdev;
 290         struct mux_rx *r;
 291         struct rx_cxt *rx = &mux_dev->rx;
 292         unsigned long flags;
 293         int ret;
 294
 295         if (!usbdev) {
 296                 pr_err("device is disconnected\n");
 297                 return -ENODEV;
 298         }
 299
 300         r = get_rx_struct(rx);
 301         if (!r) {
 302                 pr_err("get_rx_struct fail\n");
 303                 return -ENOMEM;
 304         }
 305
 306         r->offset = 0;
 307         r->mux_dev = (void *)mux_dev;
 308         r->callback = cb;
 309         mux_dev->rx_cb = cb;
 310
 311         usb_fill_bulk_urb(r->urb,
 312                           usbdev,
 313                           usb_rcvbulkpipe(usbdev, 0x86),
 314                           r->buf,
 315                           MUX_RX_MAX_SIZE,
 316                           gdm_mux_rcv_complete,
 317                           r);
 318
 319         spin_lock_irqsave(&rx->submit_list_lock, flags);
 320         list_add_tail(&r->rx_submit_list, &rx->rx_submit_list);
 321         spin_unlock_irqrestore(&rx->submit_list_lock, flags);
 322
 323         ret = usb_submit_urb(r->urb, GFP_KERNEL);
 324
 325         if (ret) {
 326                 spin_lock_irqsave(&rx->submit_list_lock, flags);
 327                 list_del(&r->rx_submit_list);
 328                 spin_unlock_irqrestore(&rx->submit_list_lock, flags);
 329
 330                 put_rx_struct(rx, r);
 331
 332                 pr_err("usb_submit_urb ret=%d\n", ret);
 333         }
 334
 335         usb_mark_last_busy(usbdev);
 336
 337         return ret;
 338 }
 339
 340 static void gdm_mux_send_complete(struct urb *urb)
 341 {
 342         struct mux_tx *t = urb->context;
 343
 344         if (urb->status == -ECONNRESET) {
 345                 pr_info("CONNRESET\n");
 346                 free_mux_tx(t);
 347                 return;
 348         }
 349
 350         if (t->callback)
 351                 t->callback(t->cb_data);
 352
 353         free_mux_tx(t);
 354 }
 355
 356 static int gdm_mux_send(void *priv_dev, void *data, int len, int tty_index,
 357                         void (*cb)(void *data), void *cb_data)
 358 {
 359         struct mux_dev *mux_dev = priv_dev;
 360         struct usb_device *usbdev = mux_dev->usbdev;
 361         struct mux_pkt_header *mux_header;
 362         struct mux_tx *t = NULL;
 363         static u32 seq_num = 1;
 364         int remain;
 365         int dummy_cnt;
 366         int total_len;
 367         int ret;
 368         unsigned long flags;
 369
 370         if (mux_dev->usb_state == PM_SUSPEND) {
 371                 ret = usb_autopm_get_interface(mux_dev->intf);
 372                 if (!ret)
 373                         usb_autopm_put_interface(mux_dev->intf);
 374         }
 375
 376         spin_lock_irqsave(&mux_dev->write_lock, flags);
 377
 378         remain = (MUX_HEADER_SIZE + len) % 4;
 379         dummy_cnt = remain ? (4 - remain) : 0;
 380
 381         total_len = len + MUX_HEADER_SIZE + dummy_cnt;
 382
 383         t = alloc_mux_tx(total_len);
 384         if (!t) {
 385                 pr_err("alloc_mux_tx fail\n");
 386                 spin_unlock_irqrestore(&mux_dev->write_lock, flags);
 387                 return -ENOMEM;
 388         }
 389
 390         mux_header = (struct mux_pkt_header *)t->buf;
 391         mux_header->start_flag = __cpu_to_le32(START_FLAG);
 392         mux_header->seq_num = __cpu_to_le32(seq_num++);
 393         mux_header->payload_size = __cpu_to_le32((u32)len);
 394         mux_header->packet_type = __cpu_to_le16(packet_type[tty_index]);
 395
 396         memcpy(t->buf+MUX_HEADER_SIZE, data, len);
 397         memset(t->buf+MUX_HEADER_SIZE+len, 0, dummy_cnt);
 398
 399         t->len = total_len;
 400         t->callback = cb;
 401         t->cb_data = cb_data;
 402
 403         usb_fill_bulk_urb(t->urb,
 404                           usbdev,
 405                           usb_sndbulkpipe(usbdev, 5),
 406                           t->buf,
 407                           total_len,
 408                           gdm_mux_send_complete,
 409                           t);
 410
 411         ret = usb_submit_urb(t->urb, GFP_ATOMIC);
 412
 413         spin_unlock_irqrestore(&mux_dev->write_lock, flags);
 414
 415         if (ret)
 416                 pr_err("usb_submit_urb Error: %d\n", ret);
 417
 418         usb_mark_last_busy(usbdev);
 419
 420         return ret;
 421 }
 422
 423 static int gdm_mux_send_control(void *priv_dev, int request, int value, void *buf, int len)
 424 {
 425         struct mux_dev *mux_dev = priv_dev;
 426         struct usb_device *usbdev = mux_dev->usbdev;
 427         int ret;
 428
 429         ret = usb_control_msg(usbdev,
 430                               usb_sndctrlpipe(usbdev, 0),
 431                               request,
 432                               USB_RT_ACM,
 433                               value,
 434                               2,
 435                               buf,
 436                               len,
 437                               5000
 438                              );
 439
 440         if (ret < 0)
 441                 pr_err("usb_control_msg error: %d\n", ret);
 442
 443         return ret < 0 ? ret : 0;
 444 }
 445
 446 static void release_usb(struct mux_dev *mux_dev)
 447 {
 448         struct rx_cxt           *rx = &mux_dev->rx;
 449         struct mux_rx           *r, *r_next;
 450         unsigned long           flags;
 451
 452         cancel_delayed_work(&mux_dev->work_rx);
 453
 454         spin_lock_irqsave(&rx->submit_list_lock, flags);
 455         list_for_each_entry_safe(r, r_next, &rx->rx_submit_list, rx_submit_list) {
 456                 spin_unlock_irqrestore(&rx->submit_list_lock, flags);
 457                 usb_kill_urb(r->urb);
 458                 spin_lock_irqsave(&rx->submit_list_lock, flags);
 459         }
 460         spin_unlock_irqrestore(&rx->submit_list_lock, flags);
 461
 462         spin_lock_irqsave(&rx->free_list_lock, flags);
 463         list_for_each_entry_safe(r, r_next, &rx->rx_free_list, free_list) {
 464                 list_del(&r->free_list);
 465                 free_mux_rx(r);
 466         }
 467         spin_unlock_irqrestore(&rx->free_list_lock, flags);
 468
 469         spin_lock_irqsave(&rx->to_host_lock, flags);
 470         list_for_each_entry_safe(r, r_next, &rx->to_host_list, to_host_list) {
 471                 if (r->mux_dev == (void *)mux_dev) {
 472                         list_del(&r->to_host_list);
 473                         free_mux_rx(r);
 474                 }
 475         }
 476         spin_unlock_irqrestore(&rx->to_host_lock, flags);
 477 }
 478
 479
 480 static int init_usb(struct mux_dev *mux_dev)
 481 {
 482         struct mux_rx *r;
 483         struct rx_cxt *rx = &mux_dev->rx;
 484         int ret = 0;
 485         int i;
 486
 487         spin_lock_init(&mux_dev->write_lock);
 488         INIT_LIST_HEAD(&rx->to_host_list);
 489         INIT_LIST_HEAD(&rx->rx_submit_list);
 490         INIT_LIST_HEAD(&rx->rx_free_list);
 491         spin_lock_init(&rx->to_host_lock);
 492         spin_lock_init(&rx->submit_list_lock);
 493         spin_lock_init(&rx->free_list_lock);
 494
 495         for (i = 0; i < MAX_ISSUE_NUM * 2; i++) {
 496                 r = alloc_mux_rx();
 497                 if (r == NULL) {
 498                         ret = -ENOMEM;
 499                         break;
 500                 }
 501
 502                 list_add(&r->free_list, &rx->rx_free_list);
 503         }
 504
 505         INIT_DELAYED_WORK(&mux_dev->work_rx, do_rx);
 506
 507         return ret;
 508 }
 509
 510 static int gdm_mux_probe(struct usb_interface *intf, const struct usb_device_id *id)
 511 {
 512         struct mux_dev *mux_dev;
 513         struct tty_dev *tty_dev;
 514         u16 idVendor, idProduct;
 515         int bInterfaceNumber;
 516         int ret;
 517         int i;
 518         struct usb_device *usbdev = interface_to_usbdev(intf);
 519         bInterfaceNumber = intf->cur_altsetting->desc.bInterfaceNumber;
 520
 521         idVendor = __le16_to_cpu(usbdev->descriptor.idVendor);
 522         idProduct = __le16_to_cpu(usbdev->descriptor.idProduct);
 523
 524         pr_info("mux vid = 0x%04x pid = 0x%04x\n", idVendor, idProduct);
 525
 526         if (bInterfaceNumber != 2)
 527                 return -ENODEV;
 528
 529         mux_dev = kzalloc(sizeof(struct mux_dev), GFP_KERNEL);
 530         if (!mux_dev)
 531                 return -ENOMEM;
 532
 533         tty_dev = kzalloc(sizeof(struct tty_dev), GFP_KERNEL);
 534         if (!tty_dev) {
 535                 ret = -ENOMEM;
 536                 goto err_free_mux;
 537         }
 538
 539         mux_dev->usbdev = usbdev;
 540         mux_dev->control_intf = intf;
 541
 542         ret = init_usb(mux_dev);
 543         if (ret)
 544                 goto err_free_tty;
 545
 546         tty_dev->priv_dev = (void *)mux_dev;
 547         tty_dev->send_func = gdm_mux_send;
 548         tty_dev->recv_func = gdm_mux_recv;
 549         tty_dev->send_control = gdm_mux_send_control;
 550
 551         ret = register_lte_tty_device(tty_dev, &intf->dev);
 552         if (ret)
 553                 goto err_unregister_tty;
 554
 555         for (i = 0; i < TTY_MAX_COUNT; i++)
 556                 mux_dev->tty_dev = tty_dev;
 557
 558         mux_dev->intf = intf;
 559         mux_dev->usb_state = PM_NORMAL;
 560
 561         usb_get_dev(usbdev);
 562         usb_set_intfdata(intf, tty_dev);
 563
 564         return 0;
 565
 566 err_unregister_tty:
 567         unregister_lte_tty_device(tty_dev);
 568         release_usb(mux_dev);
 569 err_free_tty:
 570         kfree(tty_dev);
 571 err_free_mux:
 572         kfree(mux_dev);
 573
 574         return ret;
 575 }
 576
 577 static void gdm_mux_disconnect(struct usb_interface *intf)
 578 {
 579         struct tty_dev *tty_dev;
 580         struct mux_dev *mux_dev;
 581         struct usb_device *usbdev = interface_to_usbdev(intf);
 582
 583         tty_dev = usb_get_intfdata(intf);
 584
 585         mux_dev = tty_dev->priv_dev;
 586
 587         release_usb(mux_dev);
 588         unregister_lte_tty_device(tty_dev);
 589
 590         kfree(mux_dev);
 591         kfree(tty_dev);
 592
 593         usb_put_dev(usbdev);
 594 }
 595
 596 static int gdm_mux_suspend(struct usb_interface *intf, pm_message_t pm_msg)
 597 {
 598         struct tty_dev *tty_dev;
 599         struct mux_dev *mux_dev;
 600         struct rx_cxt *rx;
 601         struct mux_rx *r, *r_next;
 602         unsigned long flags;
 603
 604         tty_dev = usb_get_intfdata(intf);
 605         mux_dev = tty_dev->priv_dev;
 606         rx = &mux_dev->rx;
 607
 608         if (mux_dev->usb_state != PM_NORMAL) {
 609                 pr_err("usb suspend - invalid state\n");
 610                 return -1;
 611         }
 612
 613         mux_dev->usb_state = PM_SUSPEND;
 614
 615
 616         spin_lock_irqsave(&rx->submit_list_lock, flags);
 617         list_for_each_entry_safe(r, r_next, &rx->rx_submit_list, rx_submit_list) {
 618                 spin_unlock_irqrestore(&rx->submit_list_lock, flags);
 619                 usb_kill_urb(r->urb);
 620                 spin_lock_irqsave(&rx->submit_list_lock, flags);
 621         }
 622         spin_unlock_irqrestore(&rx->submit_list_lock, flags);
 623
 624         return 0;
 625 }
 626
 627 static int gdm_mux_resume(struct usb_interface *intf)
 628 {
 629         struct tty_dev *tty_dev;
 630         struct mux_dev *mux_dev;
 631         u8 i;
 632
 633         tty_dev = usb_get_intfdata(intf);
 634         mux_dev = tty_dev->priv_dev;
 635
 636         if (mux_dev->usb_state != PM_SUSPEND) {
 637                 pr_err("usb resume - invalid state\n");
 638                 return -1;
 639         }
 640
 641         mux_dev->usb_state = PM_NORMAL;
 642
 643         for (i = 0; i < MAX_ISSUE_NUM; i++)
 644                 gdm_mux_recv(mux_dev, mux_dev->rx_cb);
 645
 646         return 0;
 647 }
 648
 649 static struct usb_driver gdm_mux_driver = {
 650         .name = "gdm_mux",
 651         .probe = gdm_mux_probe,
 652         .disconnect = gdm_mux_disconnect,
 653         .id_table = id_table,
 654         .supports_autosuspend = 1,
 655         .suspend = gdm_mux_suspend,
 656         .resume = gdm_mux_resume,
 657         .reset_resume = gdm_mux_resume,
 658 };
 659
 660 static int __init gdm_usb_mux_init(void)
 661 {
 662
 663         mux_rx_wq = create_workqueue("mux_rx_wq");
 664         if (mux_rx_wq == NULL) {
 665                 pr_err("work queue create fail\n");
 666                 return -1;
 667         }
 668
 669         register_lte_tty_driver();
 670
 671         return usb_register(&gdm_mux_driver);
 672 }
 673
 674 static void __exit gdm_usb_mux_exit(void)
 675 {
 676         unregister_lte_tty_driver();
 677
 678         if (mux_rx_wq) {
 679                 flush_workqueue(mux_rx_wq);
 680                 destroy_workqueue(mux_rx_wq);
 681         }
 682
 683         usb_deregister(&gdm_mux_driver);
 684 }
 685
 686 module_init(gdm_usb_mux_init);
 687 module_exit(gdm_usb_mux_exit);
 688
 689 MODULE_DESCRIPTION("GCT LTE TTY Device Driver");
 690 MODULE_LICENSE("GPL");