drivers/usb/gadget/function/f_eem.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * f_eem.c -- USB CDC Ethernet (EEM) link function driver
   4  *
   5  * Copyright (C) 2003-2005,2008 David Brownell
   6  * Copyright (C) 2008 Nokia Corporation
   7  * Copyright (C) 2009 EF Johnson Technologies
   8  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/module.h>
  12 #include <linux/device.h>
  13 #include <linux/etherdevice.h>
  14 #include <linux/crc32.h>
  15 #include <linux/slab.h>
  16
  17 #include "u_ether.h"
  18 #include "u_ether_configfs.h"
  19 #include "u_eem.h"
  20
  21 #define EEM_HLEN 2
  22
  23 /*
  24  * This function is a "CDC Ethernet Emulation Model" (CDC EEM)
  25  * Ethernet link.
  26  */
  27
  28 struct f_eem {
  29         struct gether                   port;
  30         u8                              ctrl_id;
  31 };
  32
  33 static inline struct f_eem *func_to_eem(struct usb_function *f)
  34 {
  35         return container_of(f, struct f_eem, port.func);
  36 }
  37
  38 /*-------------------------------------------------------------------------*/
  39
  40 /* interface descriptor: */
  41
  42 static struct usb_interface_descriptor eem_intf = {
  43         .bLength =              sizeof eem_intf,
  44         .bDescriptorType =      USB_DT_INTERFACE,
  45
  46         /* .bInterfaceNumber = DYNAMIC */
  47         .bNumEndpoints =        2,
  48         .bInterfaceClass =      USB_CLASS_COMM,
  49         .bInterfaceSubClass =   USB_CDC_SUBCLASS_EEM,
  50         .bInterfaceProtocol =   USB_CDC_PROTO_EEM,
  51         /* .iInterface = DYNAMIC */
  52 };
  53
  54 /* full speed support: */
  55
  56 static struct usb_endpoint_descriptor eem_fs_in_desc = {
  57         .bLength =              USB_DT_ENDPOINT_SIZE,
  58         .bDescriptorType =      USB_DT_ENDPOINT,
  59
  60         .bEndpointAddress =     USB_DIR_IN,
  61         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
  62 };
  63
  64 static struct usb_endpoint_descriptor eem_fs_out_desc = {
  65         .bLength =              USB_DT_ENDPOINT_SIZE,
  66         .bDescriptorType =      USB_DT_ENDPOINT,
  67
  68         .bEndpointAddress =     USB_DIR_OUT,
  69         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
  70 };
  71
  72 static struct usb_descriptor_header *eem_fs_function[] = {
  73         /* CDC EEM control descriptors */
  74         (struct usb_descriptor_header *) &eem_intf,
  75         (struct usb_descriptor_header *) &eem_fs_in_desc,
  76         (struct usb_descriptor_header *) &eem_fs_out_desc,
  77         NULL,
  78 };
  79
  80 /* high speed support: */
  81
  82 static struct usb_endpoint_descriptor eem_hs_in_desc = {
  83         .bLength =              USB_DT_ENDPOINT_SIZE,
  84         .bDescriptorType =      USB_DT_ENDPOINT,
  85
  86         .bEndpointAddress =     USB_DIR_IN,
  87         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
  88         .wMaxPacketSize =       cpu_to_le16(512),
  89 };
  90
  91 static struct usb_endpoint_descriptor eem_hs_out_desc = {
  92         .bLength =              USB_DT_ENDPOINT_SIZE,
  93         .bDescriptorType =      USB_DT_ENDPOINT,
  94
  95         .bEndpointAddress =     USB_DIR_OUT,
  96         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
  97         .wMaxPacketSize =       cpu_to_le16(512),
  98 };
  99
 100 static struct usb_descriptor_header *eem_hs_function[] = {
 101         /* CDC EEM control descriptors */
 102         (struct usb_descriptor_header *) &eem_intf,
 103         (struct usb_descriptor_header *) &eem_hs_in_desc,
 104         (struct usb_descriptor_header *) &eem_hs_out_desc,
 105         NULL,
 106 };
 107
 108 /* super speed support: */
 109
 110 static struct usb_endpoint_descriptor eem_ss_in_desc = {
 111         .bLength =              USB_DT_ENDPOINT_SIZE,
 112         .bDescriptorType =      USB_DT_ENDPOINT,
 113
 114         .bEndpointAddress =     USB_DIR_IN,
 115         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 116         .wMaxPacketSize =       cpu_to_le16(1024),
 117 };
 118
 119 static struct usb_endpoint_descriptor eem_ss_out_desc = {
 120         .bLength =              USB_DT_ENDPOINT_SIZE,
 121         .bDescriptorType =      USB_DT_ENDPOINT,
 122
 123         .bEndpointAddress =     USB_DIR_OUT,
 124         .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 125         .wMaxPacketSize =       cpu_to_le16(1024),
 126 };
 127
 128 static struct usb_ss_ep_comp_descriptor eem_ss_bulk_comp_desc = {
 129         .bLength =              sizeof eem_ss_bulk_comp_desc,
 130         .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
 131
 132         /* the following 2 values can be tweaked if necessary */
 133         /* .bMaxBurst =         0, */
 134         /* .bmAttributes =      0, */
 135 };
 136
 137 static struct usb_descriptor_header *eem_ss_function[] = {
 138         /* CDC EEM control descriptors */
 139         (struct usb_descriptor_header *) &eem_intf,
 140         (struct usb_descriptor_header *) &eem_ss_in_desc,
 141         (struct usb_descriptor_header *) &eem_ss_bulk_comp_desc,
 142         (struct usb_descriptor_header *) &eem_ss_out_desc,
 143         (struct usb_descriptor_header *) &eem_ss_bulk_comp_desc,
 144         NULL,
 145 };
 146
 147 /* string descriptors: */
 148
 149 static struct usb_string eem_string_defs[] = {
 150         [0].s = "CDC Ethernet Emulation Model (EEM)",
 151         {  } /* end of list */
 152 };
 153
 154 static struct usb_gadget_strings eem_string_table = {
 155         .language =             0x0409, /* en-us */
 156         .strings =              eem_string_defs,
 157 };
 158
 159 static struct usb_gadget_strings *eem_strings[] = {
 160         &eem_string_table,
 161         NULL,
 162 };
 163
 164 /*-------------------------------------------------------------------------*/
 165
 166 static int eem_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 167 {
 168         struct usb_composite_dev *cdev = f->config->cdev;
 169         u16                     w_index = le16_to_cpu(ctrl->wIndex);
 170         u16                     w_value = le16_to_cpu(ctrl->wValue);
 171         u16                     w_length = le16_to_cpu(ctrl->wLength);
 172
 173         DBG(cdev, "invalid control req%02x.%02x v%04x i%04x l%d\n",
 174                 ctrl->bRequestType, ctrl->bRequest,
 175                 w_value, w_index, w_length);
 176
 177         /* device either stalls (value < 0) or reports success */
 178         return -EOPNOTSUPP;
 179 }
 180
 181
 182 static int eem_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 183 {
 184         struct f_eem            *eem = func_to_eem(f);
 185         struct usb_composite_dev *cdev = f->config->cdev;
 186         struct net_device       *net;
 187
 188         /* we know alt == 0, so this is an activation or a reset */
 189         if (alt != 0)
 190                 goto fail;
 191
 192         if (intf == eem->ctrl_id) {
 193                 DBG(cdev, "reset eem\n");
 194                 gether_disconnect(&eem->port);
 195
 196                 if (!eem->port.in_ep->desc || !eem->port.out_ep->desc) {
 197                         DBG(cdev, "init eem\n");
 198                         if (config_ep_by_speed(cdev->gadget, f,
 199                                                eem->port.in_ep) ||
 200                             config_ep_by_speed(cdev->gadget, f,
 201                                                eem->port.out_ep)) {
 202                                 eem->port.in_ep->desc = NULL;
 203                                 eem->port.out_ep->desc = NULL;
 204                                 goto fail;
 205                         }
 206                 }
 207
 208                 /* zlps should not occur because zero-length EEM packets
 209                  * will be inserted in those cases where they would occur
 210                  */
 211                 eem->port.is_zlp_ok = 1;
 212                 eem->port.cdc_filter = DEFAULT_FILTER;
 213                 DBG(cdev, "activate eem\n");
 214                 net = gether_connect(&eem->port);
 215                 if (IS_ERR(net))
 216                         return PTR_ERR(net);
 217         } else
 218                 goto fail;
 219
 220         return 0;
 221 fail:
 222         return -EINVAL;
 223 }
 224
 225 static void eem_disable(struct usb_function *f)
 226 {
 227         struct f_eem            *eem = func_to_eem(f);
 228         struct usb_composite_dev *cdev = f->config->cdev;
 229
 230         DBG(cdev, "eem deactivated\n");
 231
 232         if (eem->port.in_ep->enabled)
 233                 gether_disconnect(&eem->port);
 234 }
 235
 236 /*-------------------------------------------------------------------------*/
 237
 238 /* EEM function driver setup/binding */
 239
 240 static int eem_bind(struct usb_configuration *c, struct usb_function *f)
 241 {
 242         struct usb_composite_dev *cdev = c->cdev;
 243         struct f_eem            *eem = func_to_eem(f);
 244         struct usb_string       *us;
 245         int                     status;
 246         struct usb_ep           *ep;
 247
 248         struct f_eem_opts       *eem_opts;
 249
 250         eem_opts = container_of(f->fi, struct f_eem_opts, func_inst);
 251         /*
 252          * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
 253          * configurations are bound in sequence with list_for_each_entry,
 254          * in each configuration its functions are bound in sequence
 255          * with list_for_each_entry, so we assume no race condition
 256          * with regard to eem_opts->bound access
 257          */
 258         if (!eem_opts->bound) {
 259                 mutex_lock(&eem_opts->lock);
 260                 gether_set_gadget(eem_opts->net, cdev->gadget);
 261                 status = gether_register_netdev(eem_opts->net);
 262                 mutex_unlock(&eem_opts->lock);
 263                 if (status)
 264                         return status;
 265                 eem_opts->bound = true;
 266         }
 267
 268         us = usb_gstrings_attach(cdev, eem_strings,
 269                                  ARRAY_SIZE(eem_string_defs));
 270         if (IS_ERR(us))
 271                 return PTR_ERR(us);
 272         eem_intf.iInterface = us[0].id;
 273
 274         /* allocate instance-specific interface IDs */
 275         status = usb_interface_id(c, f);
 276         if (status < 0)
 277                 goto fail;
 278         eem->ctrl_id = status;
 279         eem_intf.bInterfaceNumber = status;
 280
 281         status = -ENODEV;
 282
 283         /* allocate instance-specific endpoints */
 284         ep = usb_ep_autoconfig(cdev->gadget, &eem_fs_in_desc);
 285         if (!ep)
 286                 goto fail;
 287         eem->port.in_ep = ep;
 288
 289         ep = usb_ep_autoconfig(cdev->gadget, &eem_fs_out_desc);
 290         if (!ep)
 291                 goto fail;
 292         eem->port.out_ep = ep;
 293
 294         status = -ENOMEM;
 295
 296         /* support all relevant hardware speeds... we expect that when
 297          * hardware is dual speed, all bulk-capable endpoints work at
 298          * both speeds
 299          */
 300         eem_hs_in_desc.bEndpointAddress = eem_fs_in_desc.bEndpointAddress;
 301         eem_hs_out_desc.bEndpointAddress = eem_fs_out_desc.bEndpointAddress;
 302
 303         eem_ss_in_desc.bEndpointAddress = eem_fs_in_desc.bEndpointAddress;
 304         eem_ss_out_desc.bEndpointAddress = eem_fs_out_desc.bEndpointAddress;
 305
 306         status = usb_assign_descriptors(f, eem_fs_function, eem_hs_function,
 307                         eem_ss_function, NULL);
 308         if (status)
 309                 goto fail;
 310
 311         DBG(cdev, "CDC Ethernet (EEM): %s speed IN/%s OUT/%s\n",
 312                         gadget_is_superspeed(c->cdev->gadget) ? "super" :
 313                         gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
 314                         eem->port.in_ep->name, eem->port.out_ep->name);
 315         return 0;
 316
 317 fail:
 318         ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
 319
 320         return status;
 321 }
 322
 323 static void eem_cmd_complete(struct usb_ep *ep, struct usb_request *req)
 324 {
 325         struct sk_buff *skb = (struct sk_buff *)req->context;
 326
 327         dev_kfree_skb_any(skb);
 328 }
 329
 330 /*
 331  * Add the EEM header and ethernet checksum.
 332  * We currently do not attempt to put multiple ethernet frames
 333  * into a single USB transfer
 334  */
 335 static struct sk_buff *eem_wrap(struct gether *port, struct sk_buff *skb)
 336 {
 337         struct sk_buff  *skb2 = NULL;
 338         struct usb_ep   *in = port->in_ep;
 339         int             headroom, tailroom, padlen = 0;
 340         u16             len;
 341
 342         if (!skb)
 343                 return NULL;
 344
 345         len = skb->len;
 346         headroom = skb_headroom(skb);
 347         tailroom = skb_tailroom(skb);
 348
 349         /* When (len + EEM_HLEN + ETH_FCS_LEN) % in->maxpacket) is 0,
 350          * stick two bytes of zero-length EEM packet on the end.
 351          */
 352         if (((len + EEM_HLEN + ETH_FCS_LEN) % in->maxpacket) == 0)
 353                 padlen += 2;
 354
 355         if ((tailroom >= (ETH_FCS_LEN + padlen)) &&
 356                         (headroom >= EEM_HLEN) && !skb_cloned(skb))
 357                 goto done;
 358
 359         skb2 = skb_copy_expand(skb, EEM_HLEN, ETH_FCS_LEN + padlen, GFP_ATOMIC);
 360         dev_kfree_skb_any(skb);
 361         skb = skb2;
 362         if (!skb)
 363                 return skb;
 364
 365 done:
 366         /* use the "no CRC" option */
 367         put_unaligned_be32(0xdeadbeef, skb_put(skb, 4));
 368
 369         /* EEM packet header format:
 370          * b0..13:      length of ethernet frame
 371          * b14:         bmCRC (0 == sentinel CRC)
 372          * b15:         bmType (0 == data)
 373          */
 374         len = skb->len;
 375         put_unaligned_le16(len & 0x3FFF, skb_push(skb, 2));
 376
 377         /* add a zero-length EEM packet, if needed */
 378         if (padlen)
 379                 put_unaligned_le16(0, skb_put(skb, 2));
 380
 381         return skb;
 382 }
 383
 384 /*
 385  * Remove the EEM header.  Note that there can be many EEM packets in a single
 386  * USB transfer, so we need to break them out and handle them independently.
 387  */
 388 static int eem_unwrap(struct gether *port,
 389                         struct sk_buff *skb,
 390                         struct sk_buff_head *list)
 391 {
 392         struct usb_composite_dev        *cdev = port->func.config->cdev;
 393         int                             status = 0;
 394
 395         do {
 396                 struct sk_buff  *skb2;
 397                 u16             header;
 398                 u16             len = 0;
 399
 400                 if (skb->len < EEM_HLEN) {
 401                         status = -EINVAL;
 402                         DBG(cdev, "invalid EEM header\n");
 403                         goto error;
 404                 }
 405
 406                 /* remove the EEM header */
 407                 header = get_unaligned_le16(skb->data);
 408                 skb_pull(skb, EEM_HLEN);
 409
 410                 /* EEM packet header format:
 411                  * b0..14:      EEM type dependent (data or command)
 412                  * b15:         bmType (0 == data, 1 == command)
 413                  */
 414                 if (header & BIT(15)) {
 415                         struct usb_request      *req = cdev->req;
 416                         u16                     bmEEMCmd;
 417
 418                         /* EEM command packet format:
 419                          * b0..10:      bmEEMCmdParam
 420                          * b11..13:     bmEEMCmd
 421                          * b14:         reserved (must be zero)
 422                          * b15:         bmType (1 == command)
 423                          */
 424                         if (header & BIT(14))
 425                                 continue;
 426
 427                         bmEEMCmd = (header >> 11) & 0x7;
 428                         switch (bmEEMCmd) {
 429                         case 0: /* echo */
 430                                 len = header & 0x7FF;
 431                                 if (skb->len < len) {
 432                                         status = -EOVERFLOW;
 433                                         goto error;
 434                                 }
 435
 436                                 skb2 = skb_clone(skb, GFP_ATOMIC);
 437                                 if (unlikely(!skb2)) {
 438                                         DBG(cdev, "EEM echo response error\n");
 439                                         goto next;
 440                                 }
 441                                 skb_trim(skb2, len);
 442                                 put_unaligned_le16(BIT(15) | BIT(11) | len,
 443                                                         skb_push(skb2, 2));
 444                                 skb_copy_bits(skb2, 0, req->buf, skb2->len);
 445                                 req->length = skb2->len;
 446                                 req->complete = eem_cmd_complete;
 447                                 req->zero = 1;
 448                                 req->context = skb2;
 449                                 if (usb_ep_queue(port->in_ep, req, GFP_ATOMIC))
 450                                         DBG(cdev, "echo response queue fail\n");
 451                                 break;
 452
 453                         case 1:  /* echo response */
 454                         case 2:  /* suspend hint */
 455                         case 3:  /* response hint */
 456                         case 4:  /* response complete hint */
 457                         case 5:  /* tickle */
 458                         default: /* reserved */
 459                                 continue;
 460                         }
 461                 } else {
 462                         u32             crc, crc2;
 463                         struct sk_buff  *skb3;
 464
 465                         /* check for zero-length EEM packet */
 466                         if (header == 0)
 467                                 continue;
 468
 469                         /* EEM data packet format:
 470                          * b0..13:      length of ethernet frame
 471                          * b14:         bmCRC (0 == sentinel, 1 == calculated)
 472                          * b15:         bmType (0 == data)
 473                          */
 474                         len = header & 0x3FFF;
 475                         if ((skb->len < len)
 476                                         || (len < (ETH_HLEN + ETH_FCS_LEN))) {
 477                                 status = -EINVAL;
 478                                 goto error;
 479                         }
 480
 481                         /* validate CRC */
 482                         if (header & BIT(14)) {
 483                                 crc = get_unaligned_le32(skb->data + len
 484                                                         - ETH_FCS_LEN);
 485                                 crc2 = ~crc32_le(~0,
 486                                                 skb->data, len - ETH_FCS_LEN);
 487                         } else {
 488                                 crc = get_unaligned_be32(skb->data + len
 489                                                         - ETH_FCS_LEN);
 490                                 crc2 = 0xdeadbeef;
 491                         }
 492                         if (crc != crc2) {
 493                                 DBG(cdev, "invalid EEM CRC\n");
 494                                 goto next;
 495                         }
 496
 497                         skb2 = skb_clone(skb, GFP_ATOMIC);
 498                         if (unlikely(!skb2)) {
 499                                 DBG(cdev, "unable to unframe EEM packet\n");
 500                                 continue;
 501                         }
 502                         skb_trim(skb2, len - ETH_FCS_LEN);
 503
 504                         skb3 = skb_copy_expand(skb2,
 505                                                 NET_IP_ALIGN,
 506                                                 0,
 507                                                 GFP_ATOMIC);
 508                         if (unlikely(!skb3)) {
 509                                 dev_kfree_skb_any(skb2);
 510                                 continue;
 511                         }
 512                         dev_kfree_skb_any(skb2);
 513                         skb_queue_tail(list, skb3);
 514                 }
 515 next:
 516                 skb_pull(skb, len);
 517         } while (skb->len);
 518
 519 error:
 520         dev_kfree_skb_any(skb);
 521         return status;
 522 }
 523
 524 static inline struct f_eem_opts *to_f_eem_opts(struct config_item *item)
 525 {
 526         return container_of(to_config_group(item), struct f_eem_opts,
 527                             func_inst.group);
 528 }
 529
 530 /* f_eem_item_ops */
 531 USB_ETHERNET_CONFIGFS_ITEM(eem);
 532
 533 /* f_eem_opts_dev_addr */
 534 USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(eem);
 535
 536 /* f_eem_opts_host_addr */
 537 USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(eem);
 538
 539 /* f_eem_opts_qmult */
 540 USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(eem);
 541
 542 /* f_eem_opts_ifname */
 543 USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(eem);
 544
 545 static struct configfs_attribute *eem_attrs[] = {
 546         &eem_opts_attr_dev_addr,
 547         &eem_opts_attr_host_addr,
 548         &eem_opts_attr_qmult,
 549         &eem_opts_attr_ifname,
 550         NULL,
 551 };
 552
 553 static const struct config_item_type eem_func_type = {
 554         .ct_item_ops    = &eem_item_ops,
 555         .ct_attrs       = eem_attrs,
 556         .ct_owner       = THIS_MODULE,
 557 };
 558
 559 static void eem_free_inst(struct usb_function_instance *f)
 560 {
 561         struct f_eem_opts *opts;
 562
 563         opts = container_of(f, struct f_eem_opts, func_inst);
 564         if (opts->bound)
 565                 gether_cleanup(netdev_priv(opts->net));
 566         else
 567                 free_netdev(opts->net);
 568         kfree(opts);
 569 }
 570
 571 static struct usb_function_instance *eem_alloc_inst(void)
 572 {
 573         struct f_eem_opts *opts;
 574
 575         opts = kzalloc(sizeof(*opts), GFP_KERNEL);
 576         if (!opts)
 577                 return ERR_PTR(-ENOMEM);
 578         mutex_init(&opts->lock);
 579         opts->func_inst.free_func_inst = eem_free_inst;
 580         opts->net = gether_setup_default();
 581         if (IS_ERR(opts->net)) {
 582                 struct net_device *net = opts->net;
 583                 kfree(opts);
 584                 return ERR_CAST(net);
 585         }
 586
 587         config_group_init_type_name(&opts->func_inst.group, "", &eem_func_type);
 588
 589         return &opts->func_inst;
 590 }
 591
 592 static void eem_free(struct usb_function *f)
 593 {
 594         struct f_eem *eem;
 595         struct f_eem_opts *opts;
 596
 597         eem = func_to_eem(f);
 598         opts = container_of(f->fi, struct f_eem_opts, func_inst);
 599         kfree(eem);
 600         mutex_lock(&opts->lock);
 601         opts->refcnt--;
 602         mutex_unlock(&opts->lock);
 603 }
 604
 605 static void eem_unbind(struct usb_configuration *c, struct usb_function *f)
 606 {
 607         DBG(c->cdev, "eem unbind\n");
 608
 609         usb_free_all_descriptors(f);
 610 }
 611
 612 static struct usb_function *eem_alloc(struct usb_function_instance *fi)
 613 {
 614         struct f_eem    *eem;
 615         struct f_eem_opts *opts;
 616
 617         /* allocate and initialize one new instance */
 618         eem = kzalloc(sizeof(*eem), GFP_KERNEL);
 619         if (!eem)
 620                 return ERR_PTR(-ENOMEM);
 621
 622         opts = container_of(fi, struct f_eem_opts, func_inst);
 623         mutex_lock(&opts->lock);
 624         opts->refcnt++;
 625
 626         eem->port.ioport = netdev_priv(opts->net);
 627         mutex_unlock(&opts->lock);
 628         eem->port.cdc_filter = DEFAULT_FILTER;
 629
 630         eem->port.func.name = "cdc_eem";
 631         /* descriptors are per-instance copies */
 632         eem->port.func.bind = eem_bind;
 633         eem->port.func.unbind = eem_unbind;
 634         eem->port.func.set_alt = eem_set_alt;
 635         eem->port.func.setup = eem_setup;
 636         eem->port.func.disable = eem_disable;
 637         eem->port.func.free_func = eem_free;
 638         eem->port.wrap = eem_wrap;
 639         eem->port.unwrap = eem_unwrap;
 640         eem->port.header_len = EEM_HLEN;
 641
 642         return &eem->port.func;
 643 }
 644
 645 DECLARE_USB_FUNCTION_INIT(eem, eem_alloc_inst, eem_alloc);
 646 MODULE_LICENSE("GPL");
 647 MODULE_AUTHOR("David Brownell");