linux/drivers/usb/gadget/function/f_subset.c
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   1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * f_subset.c -- "CDC Subset" Ethernet link function driver
   4 *
   5 * Copyright (C) 2003-2005,2008 David Brownell
   6 * Copyright (C) 2008 Nokia Corporation
   7 */
   8
   9#include <linux/slab.h>
  10#include <linux/kernel.h>
  11#include <linux/module.h>
  12#include <linux/device.h>
  13#include <linux/etherdevice.h>
  14
  15#include "u_ether.h"
  16#include "u_ether_configfs.h"
  17#include "u_gether.h"
  18
  19/*
  20 * This function packages a simple "CDC Subset" Ethernet port with no real
  21 * control mechanisms; just raw data transfer over two bulk endpoints.
  22 * The data transfer model is exactly that of CDC Ethernet, which is
  23 * why we call it the "CDC Subset".
  24 *
  25 * Because it's not standardized, this has some interoperability issues.
  26 * They mostly relate to driver binding, since the data transfer model is
  27 * so simple (CDC Ethernet).  The original versions of this protocol used
  28 * specific product/vendor IDs:  byteswapped IDs for Digital Equipment's
  29 * SA-1100 "Itsy" board, which could run Linux 2.4 kernels and supported
  30 * daughtercards with USB peripheral connectors.  (It was used more often
  31 * with other boards, using the Itsy identifiers.)  Linux hosts recognized
  32 * this with CONFIG_USB_ARMLINUX; these devices have only one configuration
  33 * and one interface.
  34 *
  35 * At some point, MCCI defined a (nonconformant) CDC MDLM variant called
  36 * "SAFE", which happens to have a mode which is identical to the "CDC
  37 * Subset" in terms of data transfer and lack of control model.  This was
  38 * adopted by later Sharp Zaurus models, and by some other software which
  39 * Linux hosts recognize with CONFIG_USB_NET_ZAURUS.
  40 *
  41 * Because Microsoft's RNDIS drivers are far from robust, we added a few
  42 * descriptors to the CDC Subset code, making this code look like a SAFE
  43 * implementation.  This lets you use MCCI's host side MS-Windows drivers
  44 * if you get fed up with RNDIS.  It also makes it easier for composite
  45 * drivers to work, since they can use class based binding instead of
  46 * caring about specific product and vendor IDs.
  47 */
  48
  49struct f_gether {
  50        struct gether                   port;
  51
  52        char                            ethaddr[14];
  53};
  54
  55static inline struct f_gether *func_to_geth(struct usb_function *f)
  56{
  57        return container_of(f, struct f_gether, port.func);
  58}
  59
  60/*-------------------------------------------------------------------------*/
  61
  62/*
  63 * "Simple" CDC-subset option is a simple vendor-neutral model that most
  64 * full speed controllers can handle:  one interface, two bulk endpoints.
  65 * To assist host side drivers, we fancy it up a bit, and add descriptors so
  66 * some host side drivers will understand it as a "SAFE" variant.
  67 *
  68 * "SAFE" loosely follows CDC WMC MDLM, violating the spec in various ways.
  69 * Data endpoints live in the control interface, there's no data interface.
  70 * And it's not used to talk to a cell phone radio.
  71 */
  72
  73/* interface descriptor: */
  74
  75static struct usb_interface_descriptor subset_data_intf = {
  76        .bLength =              sizeof subset_data_intf,
  77        .bDescriptorType =      USB_DT_INTERFACE,
  78
  79        /* .bInterfaceNumber = DYNAMIC */
  80        .bAlternateSetting =    0,
  81        .bNumEndpoints =        2,
  82        .bInterfaceClass =      USB_CLASS_COMM,
  83        .bInterfaceSubClass =   USB_CDC_SUBCLASS_MDLM,
  84        .bInterfaceProtocol =   0,
  85        /* .iInterface = DYNAMIC */
  86};
  87
  88static struct usb_cdc_header_desc mdlm_header_desc = {
  89        .bLength =              sizeof mdlm_header_desc,
  90        .bDescriptorType =      USB_DT_CS_INTERFACE,
  91        .bDescriptorSubType =   USB_CDC_HEADER_TYPE,
  92
  93        .bcdCDC =               cpu_to_le16(0x0110),
  94};
  95
  96static struct usb_cdc_mdlm_desc mdlm_desc = {
  97        .bLength =              sizeof mdlm_desc,
  98        .bDescriptorType =      USB_DT_CS_INTERFACE,
  99        .bDescriptorSubType =   USB_CDC_MDLM_TYPE,
 100
 101        .bcdVersion =           cpu_to_le16(0x0100),
 102        .bGUID = {
 103                0x5d, 0x34, 0xcf, 0x66, 0x11, 0x18, 0x11, 0xd6,
 104                0xa2, 0x1a, 0x00, 0x01, 0x02, 0xca, 0x9a, 0x7f,
 105        },
 106};
 107
 108/* since "usb_cdc_mdlm_detail_desc" is a variable length structure, we
 109 * can't really use its struct.  All we do here is say that we're using
 110 * the submode of "SAFE" which directly matches the CDC Subset.
 111 */
 112static u8 mdlm_detail_desc[] = {
 113        6,
 114        USB_DT_CS_INTERFACE,
 115        USB_CDC_MDLM_DETAIL_TYPE,
 116
 117        0,      /* "SAFE" */
 118        0,      /* network control capabilities (none) */
 119        0,      /* network data capabilities ("raw" encapsulation) */
 120};
 121
 122static struct usb_cdc_ether_desc ether_desc = {
 123        .bLength =              sizeof ether_desc,
 124        .bDescriptorType =      USB_DT_CS_INTERFACE,
 125        .bDescriptorSubType =   USB_CDC_ETHERNET_TYPE,
 126
 127        /* this descriptor actually adds value, surprise! */
 128        /* .iMACAddress = DYNAMIC */
 129        .bmEthernetStatistics = cpu_to_le32(0), /* no statistics */
 130        .wMaxSegmentSize =      cpu_to_le16(ETH_FRAME_LEN),
 131        .wNumberMCFilters =     cpu_to_le16(0),
 132        .bNumberPowerFilters =  0,
 133};
 134
 135/* full speed support: */
 136
 137static struct usb_endpoint_descriptor fs_subset_in_desc = {
 138        .bLength =              USB_DT_ENDPOINT_SIZE,
 139        .bDescriptorType =      USB_DT_ENDPOINT,
 140
 141        .bEndpointAddress =     USB_DIR_IN,
 142        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 143};
 144
 145static struct usb_endpoint_descriptor fs_subset_out_desc = {
 146        .bLength =              USB_DT_ENDPOINT_SIZE,
 147        .bDescriptorType =      USB_DT_ENDPOINT,
 148
 149        .bEndpointAddress =     USB_DIR_OUT,
 150        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 151};
 152
 153static struct usb_descriptor_header *fs_eth_function[] = {
 154        (struct usb_descriptor_header *) &subset_data_intf,
 155        (struct usb_descriptor_header *) &mdlm_header_desc,
 156        (struct usb_descriptor_header *) &mdlm_desc,
 157        (struct usb_descriptor_header *) &mdlm_detail_desc,
 158        (struct usb_descriptor_header *) &ether_desc,
 159        (struct usb_descriptor_header *) &fs_subset_in_desc,
 160        (struct usb_descriptor_header *) &fs_subset_out_desc,
 161        NULL,
 162};
 163
 164/* high speed support: */
 165
 166static struct usb_endpoint_descriptor hs_subset_in_desc = {
 167        .bLength =              USB_DT_ENDPOINT_SIZE,
 168        .bDescriptorType =      USB_DT_ENDPOINT,
 169
 170        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 171        .wMaxPacketSize =       cpu_to_le16(512),
 172};
 173
 174static struct usb_endpoint_descriptor hs_subset_out_desc = {
 175        .bLength =              USB_DT_ENDPOINT_SIZE,
 176        .bDescriptorType =      USB_DT_ENDPOINT,
 177
 178        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 179        .wMaxPacketSize =       cpu_to_le16(512),
 180};
 181
 182static struct usb_descriptor_header *hs_eth_function[] = {
 183        (struct usb_descriptor_header *) &subset_data_intf,
 184        (struct usb_descriptor_header *) &mdlm_header_desc,
 185        (struct usb_descriptor_header *) &mdlm_desc,
 186        (struct usb_descriptor_header *) &mdlm_detail_desc,
 187        (struct usb_descriptor_header *) &ether_desc,
 188        (struct usb_descriptor_header *) &hs_subset_in_desc,
 189        (struct usb_descriptor_header *) &hs_subset_out_desc,
 190        NULL,
 191};
 192
 193/* super speed support: */
 194
 195static struct usb_endpoint_descriptor ss_subset_in_desc = {
 196        .bLength =              USB_DT_ENDPOINT_SIZE,
 197        .bDescriptorType =      USB_DT_ENDPOINT,
 198
 199        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 200        .wMaxPacketSize =       cpu_to_le16(1024),
 201};
 202
 203static struct usb_endpoint_descriptor ss_subset_out_desc = {
 204        .bLength =              USB_DT_ENDPOINT_SIZE,
 205        .bDescriptorType =      USB_DT_ENDPOINT,
 206
 207        .bmAttributes =         USB_ENDPOINT_XFER_BULK,
 208        .wMaxPacketSize =       cpu_to_le16(1024),
 209};
 210
 211static struct usb_ss_ep_comp_descriptor ss_subset_bulk_comp_desc = {
 212        .bLength =              sizeof ss_subset_bulk_comp_desc,
 213        .bDescriptorType =      USB_DT_SS_ENDPOINT_COMP,
 214
 215        /* the following 2 values can be tweaked if necessary */
 216        /* .bMaxBurst =         0, */
 217        /* .bmAttributes =      0, */
 218};
 219
 220static struct usb_descriptor_header *ss_eth_function[] = {
 221        (struct usb_descriptor_header *) &subset_data_intf,
 222        (struct usb_descriptor_header *) &mdlm_header_desc,
 223        (struct usb_descriptor_header *) &mdlm_desc,
 224        (struct usb_descriptor_header *) &mdlm_detail_desc,
 225        (struct usb_descriptor_header *) &ether_desc,
 226        (struct usb_descriptor_header *) &ss_subset_in_desc,
 227        (struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
 228        (struct usb_descriptor_header *) &ss_subset_out_desc,
 229        (struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
 230        NULL,
 231};
 232
 233/* string descriptors: */
 234
 235static struct usb_string geth_string_defs[] = {
 236        [0].s = "CDC Ethernet Subset/SAFE",
 237        [1].s = "",
 238        {  } /* end of list */
 239};
 240
 241static struct usb_gadget_strings geth_string_table = {
 242        .language =             0x0409, /* en-us */
 243        .strings =              geth_string_defs,
 244};
 245
 246static struct usb_gadget_strings *geth_strings[] = {
 247        &geth_string_table,
 248        NULL,
 249};
 250
 251/*-------------------------------------------------------------------------*/
 252
 253static int geth_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 254{
 255        struct f_gether         *geth = func_to_geth(f);
 256        struct usb_composite_dev *cdev = f->config->cdev;
 257        struct net_device       *net;
 258
 259        /* we know alt == 0, so this is an activation or a reset */
 260
 261        if (geth->port.in_ep->enabled) {
 262                DBG(cdev, "reset cdc subset\n");
 263                gether_disconnect(&geth->port);
 264        }
 265
 266        DBG(cdev, "init + activate cdc subset\n");
 267        if (config_ep_by_speed(cdev->gadget, f, geth->port.in_ep) ||
 268            config_ep_by_speed(cdev->gadget, f, geth->port.out_ep)) {
 269                geth->port.in_ep->desc = NULL;
 270                geth->port.out_ep->desc = NULL;
 271                return -EINVAL;
 272        }
 273
 274        net = gether_connect(&geth->port);
 275        return PTR_ERR_OR_ZERO(net);
 276}
 277
 278static void geth_disable(struct usb_function *f)
 279{
 280        struct f_gether *geth = func_to_geth(f);
 281        struct usb_composite_dev *cdev = f->config->cdev;
 282
 283        DBG(cdev, "net deactivated\n");
 284        gether_disconnect(&geth->port);
 285}
 286
 287/*-------------------------------------------------------------------------*/
 288
 289/* serial function driver setup/binding */
 290
 291static int
 292geth_bind(struct usb_configuration *c, struct usb_function *f)
 293{
 294        struct usb_composite_dev *cdev = c->cdev;
 295        struct f_gether         *geth = func_to_geth(f);
 296        struct usb_string       *us;
 297        int                     status;
 298        struct usb_ep           *ep;
 299
 300        struct f_gether_opts    *gether_opts;
 301
 302        gether_opts = container_of(f->fi, struct f_gether_opts, func_inst);
 303
 304        /*
 305         * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
 306         * configurations are bound in sequence with list_for_each_entry,
 307         * in each configuration its functions are bound in sequence
 308         * with list_for_each_entry, so we assume no race condition
 309         * with regard to gether_opts->bound access
 310         */
 311        if (!gether_opts->bound) {
 312                mutex_lock(&gether_opts->lock);
 313                gether_set_gadget(gether_opts->net, cdev->gadget);
 314                status = gether_register_netdev(gether_opts->net);
 315                mutex_unlock(&gether_opts->lock);
 316                if (status)
 317                        return status;
 318                gether_opts->bound = true;
 319        }
 320
 321        us = usb_gstrings_attach(cdev, geth_strings,
 322                                 ARRAY_SIZE(geth_string_defs));
 323        if (IS_ERR(us))
 324                return PTR_ERR(us);
 325
 326        subset_data_intf.iInterface = us[0].id;
 327        ether_desc.iMACAddress = us[1].id;
 328
 329        /* allocate instance-specific interface IDs */
 330        status = usb_interface_id(c, f);
 331        if (status < 0)
 332                goto fail;
 333        subset_data_intf.bInterfaceNumber = status;
 334
 335        status = -ENODEV;
 336
 337        /* allocate instance-specific endpoints */
 338        ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_in_desc);
 339        if (!ep)
 340                goto fail;
 341        geth->port.in_ep = ep;
 342
 343        ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_out_desc);
 344        if (!ep)
 345                goto fail;
 346        geth->port.out_ep = ep;
 347
 348        /* support all relevant hardware speeds... we expect that when
 349         * hardware is dual speed, all bulk-capable endpoints work at
 350         * both speeds
 351         */
 352        hs_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
 353        hs_subset_out_desc.bEndpointAddress =
 354                fs_subset_out_desc.bEndpointAddress;
 355
 356        ss_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
 357        ss_subset_out_desc.bEndpointAddress =
 358                fs_subset_out_desc.bEndpointAddress;
 359
 360        status = usb_assign_descriptors(f, fs_eth_function, hs_eth_function,
 361                        ss_eth_function, ss_eth_function);
 362        if (status)
 363                goto fail;
 364
 365        /* NOTE:  all that is done without knowing or caring about
 366         * the network link ... which is unavailable to this code
 367         * until we're activated via set_alt().
 368         */
 369
 370        DBG(cdev, "CDC Subset: %s speed IN/%s OUT/%s\n",
 371                        gadget_is_superspeed(c->cdev->gadget) ? "super" :
 372                        gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
 373                        geth->port.in_ep->name, geth->port.out_ep->name);
 374        return 0;
 375
 376fail:
 377        ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
 378
 379        return status;
 380}
 381
 382static inline struct f_gether_opts *to_f_gether_opts(struct config_item *item)
 383{
 384        return container_of(to_config_group(item), struct f_gether_opts,
 385                            func_inst.group);
 386}
 387
 388/* f_gether_item_ops */
 389USB_ETHERNET_CONFIGFS_ITEM(gether);
 390
 391/* f_gether_opts_dev_addr */
 392USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(gether);
 393
 394/* f_gether_opts_host_addr */
 395USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(gether);
 396
 397/* f_gether_opts_qmult */
 398USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(gether);
 399
 400/* f_gether_opts_ifname */
 401USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(gether);
 402
 403static struct configfs_attribute *gether_attrs[] = {
 404        &gether_opts_attr_dev_addr,
 405        &gether_opts_attr_host_addr,
 406        &gether_opts_attr_qmult,
 407        &gether_opts_attr_ifname,
 408        NULL,
 409};
 410
 411static const struct config_item_type gether_func_type = {
 412        .ct_item_ops    = &gether_item_ops,
 413        .ct_attrs       = gether_attrs,
 414        .ct_owner       = THIS_MODULE,
 415};
 416
 417static void geth_free_inst(struct usb_function_instance *f)
 418{
 419        struct f_gether_opts *opts;
 420
 421        opts = container_of(f, struct f_gether_opts, func_inst);
 422        if (opts->bound)
 423                gether_cleanup(netdev_priv(opts->net));
 424        else
 425                free_netdev(opts->net);
 426        kfree(opts);
 427}
 428
 429static struct usb_function_instance *geth_alloc_inst(void)
 430{
 431        struct f_gether_opts *opts;
 432
 433        opts = kzalloc(sizeof(*opts), GFP_KERNEL);
 434        if (!opts)
 435                return ERR_PTR(-ENOMEM);
 436        mutex_init(&opts->lock);
 437        opts->func_inst.free_func_inst = geth_free_inst;
 438        opts->net = gether_setup_default();
 439        if (IS_ERR(opts->net)) {
 440                struct net_device *net = opts->net;
 441                kfree(opts);
 442                return ERR_CAST(net);
 443        }
 444
 445        config_group_init_type_name(&opts->func_inst.group, "",
 446                                    &gether_func_type);
 447
 448        return &opts->func_inst;
 449}
 450
 451static void geth_free(struct usb_function *f)
 452{
 453        struct f_gether *eth;
 454
 455        eth = func_to_geth(f);
 456        kfree(eth);
 457}
 458
 459static void geth_unbind(struct usb_configuration *c, struct usb_function *f)
 460{
 461        geth_string_defs[0].id = 0;
 462        usb_free_all_descriptors(f);
 463}
 464
 465static struct usb_function *geth_alloc(struct usb_function_instance *fi)
 466{
 467        struct f_gether *geth;
 468        struct f_gether_opts *opts;
 469        int status;
 470
 471        /* allocate and initialize one new instance */
 472        geth = kzalloc(sizeof(*geth), GFP_KERNEL);
 473        if (!geth)
 474                return ERR_PTR(-ENOMEM);
 475
 476        opts = container_of(fi, struct f_gether_opts, func_inst);
 477
 478        mutex_lock(&opts->lock);
 479        opts->refcnt++;
 480        /* export host's Ethernet address in CDC format */
 481        status = gether_get_host_addr_cdc(opts->net, geth->ethaddr,
 482                                          sizeof(geth->ethaddr));
 483        if (status < 12) {
 484                kfree(geth);
 485                mutex_unlock(&opts->lock);
 486                return ERR_PTR(-EINVAL);
 487        }
 488        geth_string_defs[1].s = geth->ethaddr;
 489
 490        geth->port.ioport = netdev_priv(opts->net);
 491        mutex_unlock(&opts->lock);
 492        geth->port.cdc_filter = DEFAULT_FILTER;
 493
 494        geth->port.func.name = "cdc_subset";
 495        geth->port.func.bind = geth_bind;
 496        geth->port.func.unbind = geth_unbind;
 497        geth->port.func.set_alt = geth_set_alt;
 498        geth->port.func.disable = geth_disable;
 499        geth->port.func.free_func = geth_free;
 500
 501        return &geth->port.func;
 502}
 503
 504DECLARE_USB_FUNCTION_INIT(geth, geth_alloc_inst, geth_alloc);
 505MODULE_LICENSE("GPL");
 506MODULE_AUTHOR("David Brownell");
 507