net/dsa/dsa2.c

   1 /*
   2  * net/dsa/dsa2.c - Hardware switch handling, binding version 2
   3  * Copyright (c) 2008-2009 Marvell Semiconductor
   4  * Copyright (c) 2013 Florian Fainelli <florian@openwrt.org>
   5  * Copyright (c) 2016 Andrew Lunn <andrew@lunn.ch>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  */
  12
  13 #include <linux/device.h>
  14 #include <linux/err.h>
  15 #include <linux/list.h>
  16 #include <linux/netdevice.h>
  17 #include <linux/slab.h>
  18 #include <linux/rtnetlink.h>
  19 #include <linux/of.h>
  20 #include <linux/of_net.h>
  21
  22 #include "dsa_priv.h"
  23
  24 static LIST_HEAD(dsa_tree_list);
  25 static DEFINE_MUTEX(dsa2_mutex);
  26
  27 static const struct devlink_ops dsa_devlink_ops = {
  28 };
  29
  30 static struct dsa_switch_tree *dsa_tree_find(int index)
  31 {
  32         struct dsa_switch_tree *dst;
  33
  34         list_for_each_entry(dst, &dsa_tree_list, list)
  35                 if (dst->index == index)
  36                         return dst;
  37
  38         return NULL;
  39 }
  40
  41 static struct dsa_switch_tree *dsa_tree_alloc(int index)
  42 {
  43         struct dsa_switch_tree *dst;
  44
  45         dst = kzalloc(sizeof(*dst), GFP_KERNEL);
  46         if (!dst)
  47                 return NULL;
  48
  49         dst->index = index;
  50
  51         INIT_LIST_HEAD(&dst->list);
  52         list_add_tail(&dsa_tree_list, &dst->list);
  53
  54         kref_init(&dst->refcount);
  55
  56         return dst;
  57 }
  58
  59 static void dsa_tree_free(struct dsa_switch_tree *dst)
  60 {
  61         list_del(&dst->list);
  62         kfree(dst);
  63 }
  64
  65 static struct dsa_switch_tree *dsa_tree_get(struct dsa_switch_tree *dst)
  66 {
  67         if (dst)
  68                 kref_get(&dst->refcount);
  69
  70         return dst;
  71 }
  72
  73 static struct dsa_switch_tree *dsa_tree_touch(int index)
  74 {
  75         struct dsa_switch_tree *dst;
  76
  77         dst = dsa_tree_find(index);
  78         if (dst)
  79                 return dsa_tree_get(dst);
  80         else
  81                 return dsa_tree_alloc(index);
  82 }
  83
  84 static void dsa_tree_release(struct kref *ref)
  85 {
  86         struct dsa_switch_tree *dst;
  87
  88         dst = container_of(ref, struct dsa_switch_tree, refcount);
  89
  90         dsa_tree_free(dst);
  91 }
  92
  93 static void dsa_tree_put(struct dsa_switch_tree *dst)
  94 {
  95         if (dst)
  96                 kref_put(&dst->refcount, dsa_tree_release);
  97 }
  98
  99 static bool dsa_port_is_dsa(struct dsa_port *port)
 100 {
 101         return port->type == DSA_PORT_TYPE_DSA;
 102 }
 103
 104 static bool dsa_port_is_cpu(struct dsa_port *port)
 105 {
 106         return port->type == DSA_PORT_TYPE_CPU;
 107 }
 108
 109 static bool dsa_port_is_user(struct dsa_port *dp)
 110 {
 111         return dp->type == DSA_PORT_TYPE_USER;
 112 }
 113
 114 static struct dsa_port *dsa_tree_find_port_by_node(struct dsa_switch_tree *dst,
 115                                                    struct device_node *dn)
 116 {
 117         struct dsa_switch *ds;
 118         struct dsa_port *dp;
 119         int device, port;
 120
 121         for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 122                 ds = dst->ds[device];
 123                 if (!ds)
 124                         continue;
 125
 126                 for (port = 0; port < ds->num_ports; port++) {
 127                         dp = &ds->ports[port];
 128
 129                         if (dp->dn == dn)
 130                                 return dp;
 131                 }
 132         }
 133
 134         return NULL;
 135 }
 136
 137 static bool dsa_port_setup_routing_table(struct dsa_port *dp)
 138 {
 139         struct dsa_switch *ds = dp->ds;
 140         struct dsa_switch_tree *dst = ds->dst;
 141         struct device_node *dn = dp->dn;
 142         struct of_phandle_iterator it;
 143         struct dsa_port *link_dp;
 144         int err;
 145
 146         of_for_each_phandle(&it, err, dn, "link", NULL, 0) {
 147                 link_dp = dsa_tree_find_port_by_node(dst, it.node);
 148                 if (!link_dp) {
 149                         of_node_put(it.node);
 150                         return false;
 151                 }
 152
 153                 ds->rtable[link_dp->ds->index] = dp->index;
 154         }
 155
 156         return true;
 157 }
 158
 159 static bool dsa_switch_setup_routing_table(struct dsa_switch *ds)
 160 {
 161         bool complete = true;
 162         struct dsa_port *dp;
 163         int i;
 164
 165         for (i = 0; i < DSA_MAX_SWITCHES; i++)
 166                 ds->rtable[i] = DSA_RTABLE_NONE;
 167
 168         for (i = 0; i < ds->num_ports; i++) {
 169                 dp = &ds->ports[i];
 170
 171                 if (dsa_port_is_dsa(dp)) {
 172                         complete = dsa_port_setup_routing_table(dp);
 173                         if (!complete)
 174                                 break;
 175                 }
 176         }
 177
 178         return complete;
 179 }
 180
 181 static bool dsa_tree_setup_routing_table(struct dsa_switch_tree *dst)
 182 {
 183         struct dsa_switch *ds;
 184         bool complete = true;
 185         int device;
 186
 187         for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 188                 ds = dst->ds[device];
 189                 if (!ds)
 190                         continue;
 191
 192                 complete = dsa_switch_setup_routing_table(ds);
 193                 if (!complete)
 194                         break;
 195         }
 196
 197         return complete;
 198 }
 199
 200 static struct dsa_port *dsa_tree_find_first_cpu(struct dsa_switch_tree *dst)
 201 {
 202         struct dsa_switch *ds;
 203         struct dsa_port *dp;
 204         int device, port;
 205
 206         for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 207                 ds = dst->ds[device];
 208                 if (!ds)
 209                         continue;
 210
 211                 for (port = 0; port < ds->num_ports; port++) {
 212                         dp = &ds->ports[port];
 213
 214                         if (dsa_port_is_cpu(dp))
 215                                 return dp;
 216                 }
 217         }
 218
 219         return NULL;
 220 }
 221
 222 static int dsa_tree_setup_default_cpu(struct dsa_switch_tree *dst)
 223 {
 224         struct dsa_switch *ds;
 225         struct dsa_port *dp;
 226         int device, port;
 227
 228         /* DSA currently only supports a single CPU port */
 229         dst->cpu_dp = dsa_tree_find_first_cpu(dst);
 230         if (!dst->cpu_dp) {
 231                 pr_warn("Tree has no master device\n");
 232                 return -EINVAL;
 233         }
 234
 235         /* Assign the default CPU port to all ports of the fabric */
 236         for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 237                 ds = dst->ds[device];
 238                 if (!ds)
 239                         continue;
 240
 241                 for (port = 0; port < ds->num_ports; port++) {
 242                         dp = &ds->ports[port];
 243
 244                         if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp))
 245                                 dp->cpu_dp = dst->cpu_dp;
 246                 }
 247         }
 248
 249         return 0;
 250 }
 251
 252 static void dsa_tree_teardown_default_cpu(struct dsa_switch_tree *dst)
 253 {
 254         /* DSA currently only supports a single CPU port */
 255         dst->cpu_dp = NULL;
 256 }
 257
 258 static int dsa_port_setup(struct dsa_port *dp)
 259 {
 260         struct dsa_switch *ds = dp->ds;
 261         int err;
 262
 263         memset(&dp->devlink_port, 0, sizeof(dp->devlink_port));
 264
 265         err = devlink_port_register(ds->devlink, &dp->devlink_port, dp->index);
 266         if (err)
 267                 return err;
 268
 269         switch (dp->type) {
 270         case DSA_PORT_TYPE_UNUSED:
 271                 break;
 272         case DSA_PORT_TYPE_CPU:
 273         case DSA_PORT_TYPE_DSA:
 274                 err = dsa_port_link_register_of(dp);
 275                 if (err) {
 276                         dev_err(ds->dev, "failed to setup link for port %d.%d\n",
 277                                 ds->index, dp->index);
 278                         return err;
 279                 }
 280                 break;
 281         case DSA_PORT_TYPE_USER:
 282                 err = dsa_slave_create(dp);
 283                 if (err)
 284                         dev_err(ds->dev, "failed to create slave for port %d.%d\n",
 285                                 ds->index, dp->index);
 286                 else
 287                         devlink_port_type_eth_set(&dp->devlink_port, dp->slave);
 288                 break;
 289         }
 290
 291         return 0;
 292 }
 293
 294 static void dsa_port_teardown(struct dsa_port *dp)
 295 {
 296         devlink_port_unregister(&dp->devlink_port);
 297
 298         switch (dp->type) {
 299         case DSA_PORT_TYPE_UNUSED:
 300                 break;
 301         case DSA_PORT_TYPE_CPU:
 302         case DSA_PORT_TYPE_DSA:
 303                 dsa_port_link_unregister_of(dp);
 304                 break;
 305         case DSA_PORT_TYPE_USER:
 306                 if (dp->slave) {
 307                         dsa_slave_destroy(dp->slave);
 308                         dp->slave = NULL;
 309                 }
 310                 break;
 311         }
 312 }
 313
 314 static int dsa_switch_setup(struct dsa_switch *ds)
 315 {
 316         int err;
 317
 318         /* Initialize ds->phys_mii_mask before registering the slave MDIO bus
 319          * driver and before ops->setup() has run, since the switch drivers and
 320          * the slave MDIO bus driver rely on these values for probing PHY
 321          * devices or not
 322          */
 323         ds->phys_mii_mask |= dsa_user_ports(ds);
 324
 325         /* Add the switch to devlink before calling setup, so that setup can
 326          * add dpipe tables
 327          */
 328         ds->devlink = devlink_alloc(&dsa_devlink_ops, 0);
 329         if (!ds->devlink)
 330                 return -ENOMEM;
 331
 332         err = devlink_register(ds->devlink, ds->dev);
 333         if (err)
 334                 return err;
 335
 336         err = ds->ops->setup(ds);
 337         if (err < 0)
 338                 return err;
 339
 340         err = dsa_switch_register_notifier(ds);
 341         if (err)
 342                 return err;
 343
 344         if (!ds->slave_mii_bus && ds->ops->phy_read) {
 345                 ds->slave_mii_bus = devm_mdiobus_alloc(ds->dev);
 346                 if (!ds->slave_mii_bus)
 347                         return -ENOMEM;
 348
 349                 dsa_slave_mii_bus_init(ds);
 350
 351                 err = mdiobus_register(ds->slave_mii_bus);
 352                 if (err < 0)
 353                         return err;
 354         }
 355
 356         return 0;
 357 }
 358
 359 static void dsa_switch_teardown(struct dsa_switch *ds)
 360 {
 361         if (ds->slave_mii_bus && ds->ops->phy_read)
 362                 mdiobus_unregister(ds->slave_mii_bus);
 363
 364         dsa_switch_unregister_notifier(ds);
 365
 366         if (ds->devlink) {
 367                 devlink_unregister(ds->devlink);
 368                 devlink_free(ds->devlink);
 369                 ds->devlink = NULL;
 370         }
 371
 372 }
 373
 374 static int dsa_tree_setup_switches(struct dsa_switch_tree *dst)
 375 {
 376         struct dsa_switch *ds;
 377         struct dsa_port *dp;
 378         int device, port;
 379         int err;
 380
 381         for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 382                 ds = dst->ds[device];
 383                 if (!ds)
 384                         continue;
 385
 386                 err = dsa_switch_setup(ds);
 387                 if (err)
 388                         return err;
 389
 390                 for (port = 0; port < ds->num_ports; port++) {
 391                         dp = &ds->ports[port];
 392
 393                         err = dsa_port_setup(dp);
 394                         if (err)
 395                                 return err;
 396                 }
 397         }
 398
 399         return 0;
 400 }
 401
 402 static void dsa_tree_teardown_switches(struct dsa_switch_tree *dst)
 403 {
 404         struct dsa_switch *ds;
 405         struct dsa_port *dp;
 406         int device, port;
 407
 408         for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 409                 ds = dst->ds[device];
 410                 if (!ds)
 411                         continue;
 412
 413                 for (port = 0; port < ds->num_ports; port++) {
 414                         dp = &ds->ports[port];
 415
 416                         dsa_port_teardown(dp);
 417                 }
 418
 419                 dsa_switch_teardown(ds);
 420         }
 421 }
 422
 423 static int dsa_tree_setup_master(struct dsa_switch_tree *dst)
 424 {
 425         struct dsa_port *cpu_dp = dst->cpu_dp;
 426         struct net_device *master = cpu_dp->master;
 427
 428         /* DSA currently supports a single pair of CPU port and master device */
 429         return dsa_master_setup(master, cpu_dp);
 430 }
 431
 432 static void dsa_tree_teardown_master(struct dsa_switch_tree *dst)
 433 {
 434         struct dsa_port *cpu_dp = dst->cpu_dp;
 435         struct net_device *master = cpu_dp->master;
 436
 437         return dsa_master_teardown(master);
 438 }
 439
 440 static int dsa_tree_setup(struct dsa_switch_tree *dst)
 441 {
 442         bool complete;
 443         int err;
 444
 445         if (dst->setup) {
 446                 pr_err("DSA: tree %d already setup! Disjoint trees?\n",
 447                        dst->index);
 448                 return -EEXIST;
 449         }
 450
 451         complete = dsa_tree_setup_routing_table(dst);
 452         if (!complete)
 453                 return 0;
 454
 455         err = dsa_tree_setup_default_cpu(dst);
 456         if (err)
 457                 return err;
 458
 459         err = dsa_tree_setup_switches(dst);
 460         if (err)
 461                 return err;
 462
 463         err = dsa_tree_setup_master(dst);
 464         if (err)
 465                 return err;
 466
 467         dst->setup = true;
 468
 469         pr_info("DSA: tree %d setup\n", dst->index);
 470
 471         return 0;
 472 }
 473
 474 static void dsa_tree_teardown(struct dsa_switch_tree *dst)
 475 {
 476         if (!dst->setup)
 477                 return;
 478
 479         dsa_tree_teardown_master(dst);
 480
 481         dsa_tree_teardown_switches(dst);
 482
 483         dsa_tree_teardown_default_cpu(dst);
 484
 485         pr_info("DSA: tree %d torn down\n", dst->index);
 486
 487         dst->setup = false;
 488 }
 489
 490 static void dsa_tree_remove_switch(struct dsa_switch_tree *dst,
 491                                    unsigned int index)
 492 {
 493         dsa_tree_teardown(dst);
 494
 495         dst->ds[index] = NULL;
 496         dsa_tree_put(dst);
 497 }
 498
 499 static int dsa_tree_add_switch(struct dsa_switch_tree *dst,
 500                                struct dsa_switch *ds)
 501 {
 502         unsigned int index = ds->index;
 503         int err;
 504
 505         if (dst->ds[index])
 506                 return -EBUSY;
 507
 508         dsa_tree_get(dst);
 509         dst->ds[index] = ds;
 510
 511         err = dsa_tree_setup(dst);
 512         if (err)
 513                 dsa_tree_remove_switch(dst, index);
 514
 515         return err;
 516 }
 517
 518 static int dsa_port_parse_user(struct dsa_port *dp, const char *name)
 519 {
 520         if (!name)
 521                 name = "eth%d";
 522
 523         dp->type = DSA_PORT_TYPE_USER;
 524         dp->name = name;
 525
 526         return 0;
 527 }
 528
 529 static int dsa_port_parse_dsa(struct dsa_port *dp)
 530 {
 531         dp->type = DSA_PORT_TYPE_DSA;
 532
 533         return 0;
 534 }
 535
 536 static int dsa_port_parse_cpu(struct dsa_port *dp, struct net_device *master)
 537 {
 538         struct dsa_switch *ds = dp->ds;
 539         struct dsa_switch_tree *dst = ds->dst;
 540         const struct dsa_device_ops *tag_ops;
 541         enum dsa_tag_protocol tag_protocol;
 542
 543         tag_protocol = ds->ops->get_tag_protocol(ds, dp->index);
 544         tag_ops = dsa_resolve_tag_protocol(tag_protocol);
 545         if (IS_ERR(tag_ops)) {
 546                 dev_warn(ds->dev, "No tagger for this switch\n");
 547                 return PTR_ERR(tag_ops);
 548         }
 549
 550         dp->type = DSA_PORT_TYPE_CPU;
 551         dp->rcv = tag_ops->rcv;
 552         dp->tag_ops = tag_ops;
 553         dp->master = master;
 554         dp->dst = dst;
 555
 556         return 0;
 557 }
 558
 559 static int dsa_port_parse_of(struct dsa_port *dp, struct device_node *dn)
 560 {
 561         struct device_node *ethernet = of_parse_phandle(dn, "ethernet", 0);
 562         const char *name = of_get_property(dn, "label", NULL);
 563         bool link = of_property_read_bool(dn, "link");
 564
 565         dp->dn = dn;
 566
 567         if (ethernet) {
 568                 struct net_device *master;
 569
 570                 master = of_find_net_device_by_node(ethernet);
 571                 if (!master)
 572                         return -EPROBE_DEFER;
 573
 574                 return dsa_port_parse_cpu(dp, master);
 575         }
 576
 577         if (link)
 578                 return dsa_port_parse_dsa(dp);
 579
 580         return dsa_port_parse_user(dp, name);
 581 }
 582
 583 static int dsa_switch_parse_ports_of(struct dsa_switch *ds,
 584                                      struct device_node *dn)
 585 {
 586         struct device_node *ports, *port;
 587         struct dsa_port *dp;
 588         u32 reg;
 589         int err;
 590
 591         ports = of_get_child_by_name(dn, "ports");
 592         if (!ports) {
 593                 dev_err(ds->dev, "no ports child node found\n");
 594                 return -EINVAL;
 595         }
 596
 597         for_each_available_child_of_node(ports, port) {
 598                 err = of_property_read_u32(port, "reg", &reg);
 599                 if (err)
 600                         return err;
 601
 602                 if (reg >= ds->num_ports)
 603                         return -EINVAL;
 604
 605                 dp = &ds->ports[reg];
 606
 607                 err = dsa_port_parse_of(dp, port);
 608                 if (err)
 609                         return err;
 610         }
 611
 612         return 0;
 613 }
 614
 615 static int dsa_switch_parse_member_of(struct dsa_switch *ds,
 616                                       struct device_node *dn)
 617 {
 618         u32 m[2] = { 0, 0 };
 619         int sz;
 620
 621         /* Don't error out if this optional property isn't found */
 622         sz = of_property_read_variable_u32_array(dn, "dsa,member", m, 2, 2);
 623         if (sz < 0 && sz != -EINVAL)
 624                 return sz;
 625
 626         ds->index = m[1];
 627         if (ds->index >= DSA_MAX_SWITCHES)
 628                 return -EINVAL;
 629
 630         ds->dst = dsa_tree_touch(m[0]);
 631         if (!ds->dst)
 632                 return -ENOMEM;
 633
 634         return 0;
 635 }
 636
 637 static int dsa_switch_parse_of(struct dsa_switch *ds, struct device_node *dn)
 638 {
 639         int err;
 640
 641         err = dsa_switch_parse_member_of(ds, dn);
 642         if (err)
 643                 return err;
 644
 645         return dsa_switch_parse_ports_of(ds, dn);
 646 }
 647
 648 static int dsa_port_parse(struct dsa_port *dp, const char *name,
 649                           struct device *dev)
 650 {
 651         if (!strcmp(name, "cpu")) {
 652                 struct net_device *master;
 653
 654                 master = dsa_dev_to_net_device(dev);
 655                 if (!master)
 656                         return -EPROBE_DEFER;
 657
 658                 dev_put(master);
 659
 660                 return dsa_port_parse_cpu(dp, master);
 661         }
 662
 663         if (!strcmp(name, "dsa"))
 664                 return dsa_port_parse_dsa(dp);
 665
 666         return dsa_port_parse_user(dp, name);
 667 }
 668
 669 static int dsa_switch_parse_ports(struct dsa_switch *ds,
 670                                   struct dsa_chip_data *cd)
 671 {
 672         bool valid_name_found = false;
 673         struct dsa_port *dp;
 674         struct device *dev;
 675         const char *name;
 676         unsigned int i;
 677         int err;
 678
 679         for (i = 0; i < DSA_MAX_PORTS; i++) {
 680                 name = cd->port_names[i];
 681                 dev = cd->netdev[i];
 682                 dp = &ds->ports[i];
 683
 684                 if (!name)
 685                         continue;
 686
 687                 err = dsa_port_parse(dp, name, dev);
 688                 if (err)
 689                         return err;
 690
 691                 valid_name_found = true;
 692         }
 693
 694         if (!valid_name_found && i == DSA_MAX_PORTS)
 695                 return -EINVAL;
 696
 697         return 0;
 698 }
 699
 700 static int dsa_switch_parse(struct dsa_switch *ds, struct dsa_chip_data *cd)
 701 {
 702         ds->cd = cd;
 703
 704         /* We don't support interconnected switches nor multiple trees via
 705          * platform data, so this is the unique switch of the tree.
 706          */
 707         ds->index = 0;
 708         ds->dst = dsa_tree_touch(0);
 709         if (!ds->dst)
 710                 return -ENOMEM;
 711
 712         return dsa_switch_parse_ports(ds, cd);
 713 }
 714
 715 static int dsa_switch_add(struct dsa_switch *ds)
 716 {
 717         struct dsa_switch_tree *dst = ds->dst;
 718
 719         return dsa_tree_add_switch(dst, ds);
 720 }
 721
 722 static int dsa_switch_probe(struct dsa_switch *ds)
 723 {
 724         struct dsa_chip_data *pdata = ds->dev->platform_data;
 725         struct device_node *np = ds->dev->of_node;
 726         int err;
 727
 728         if (np)
 729                 err = dsa_switch_parse_of(ds, np);
 730         else if (pdata)
 731                 err = dsa_switch_parse(ds, pdata);
 732         else
 733                 err = -ENODEV;
 734
 735         if (err)
 736                 return err;
 737
 738         return dsa_switch_add(ds);
 739 }
 740
 741 struct dsa_switch *dsa_switch_alloc(struct device *dev, size_t n)
 742 {
 743         size_t size = sizeof(struct dsa_switch) + n * sizeof(struct dsa_port);
 744         struct dsa_switch *ds;
 745         int i;
 746
 747         ds = devm_kzalloc(dev, size, GFP_KERNEL);
 748         if (!ds)
 749                 return NULL;
 750
 751         ds->dev = dev;
 752         ds->num_ports = n;
 753
 754         for (i = 0; i < ds->num_ports; ++i) {
 755                 ds->ports[i].index = i;
 756                 ds->ports[i].ds = ds;
 757         }
 758
 759         return ds;
 760 }
 761 EXPORT_SYMBOL_GPL(dsa_switch_alloc);
 762
 763 int dsa_register_switch(struct dsa_switch *ds)
 764 {
 765         int err;
 766
 767         mutex_lock(&dsa2_mutex);
 768         err = dsa_switch_probe(ds);
 769         dsa_tree_put(ds->dst);
 770         mutex_unlock(&dsa2_mutex);
 771
 772         return err;
 773 }
 774 EXPORT_SYMBOL_GPL(dsa_register_switch);
 775
 776 static void dsa_switch_remove(struct dsa_switch *ds)
 777 {
 778         struct dsa_switch_tree *dst = ds->dst;
 779         unsigned int index = ds->index;
 780
 781         dsa_tree_remove_switch(dst, index);
 782 }
 783
 784 void dsa_unregister_switch(struct dsa_switch *ds)
 785 {
 786         mutex_lock(&dsa2_mutex);
 787         dsa_switch_remove(ds);
 788         mutex_unlock(&dsa2_mutex);
 789 }
 790 EXPORT_SYMBOL_GPL(dsa_unregister_switch);