drivers/base/component.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Componentized device handling.
   4  */
   5 #include <linux/component.h>
   6 #include <linux/device.h>
   7 #include <linux/list.h>
   8 #include <linux/mutex.h>
   9 #include <linux/of.h>
  10 #include <linux/slab.h>
  11 #include <linux/debugfs.h>
  12
  13 /**
  14  * DOC: overview
  15  *
  16  * The component helper allows drivers to collect a pile of sub-devices,
  17  * including their bound drivers, into an aggregate driver. Various subsystems
  18  * already provide functions to get hold of such components, e.g.
  19  * of_clk_get_by_name(). The component helper can be used when such a
  20  * subsystem-specific way to find a device is not available: The component
  21  * helper fills the niche of aggregate drivers for specific hardware, where
  22  * further standardization into a subsystem would not be practical. The common
  23  * example is when a logical device (e.g. a DRM display driver) is spread around
  24  * the SoC on various components (scanout engines, blending blocks, transcoders
  25  * for various outputs and so on).
  26  *
  27  * The component helper also doesn't solve runtime dependencies, e.g. for system
  28  * suspend and resume operations. See also :ref:`device links<device_link>`.
  29  *
  30  * Components are registered using component_add() and unregistered with
  31  * component_del(), usually from the driver's probe and disconnect functions.
  32  *
  33  * Aggregate drivers first assemble a component match list of what they need
  34  * using component_match_add(). This is then registered as an aggregate driver
  35  * using component_master_add_with_match(), and unregistered using
  36  * component_master_del().
  37  */
  38
  39 struct component;
  40
  41 struct component_match_array {
  42         void *data;
  43         int (*compare)(struct device *, void *);
  44         int (*compare_typed)(struct device *, int, void *);
  45         void (*release)(struct device *, void *);
  46         struct component *component;
  47         bool duplicate;
  48 };
  49
  50 struct component_match {
  51         size_t alloc;
  52         size_t num;
  53         struct component_match_array *compare;
  54 };
  55
  56 struct aggregate_device {
  57         struct list_head node;
  58         bool bound;
  59
  60         const struct component_master_ops *ops;
  61         struct device *parent;
  62         struct component_match *match;
  63 };
  64
  65 struct component {
  66         struct list_head node;
  67         struct aggregate_device *adev;
  68         bool bound;
  69
  70         const struct component_ops *ops;
  71         int subcomponent;
  72         struct device *dev;
  73 };
  74
  75 static DEFINE_MUTEX(component_mutex);
  76 static LIST_HEAD(component_list);
  77 static LIST_HEAD(aggregate_devices);
  78
  79 #ifdef CONFIG_DEBUG_FS
  80
  81 static struct dentry *component_debugfs_dir;
  82
  83 static int component_devices_show(struct seq_file *s, void *data)
  84 {
  85         struct aggregate_device *m = s->private;
  86         struct component_match *match = m->match;
  87         size_t i;
  88
  89         mutex_lock(&component_mutex);
  90         seq_printf(s, "%-40s %20s\n", "aggregate_device name", "status");
  91         seq_puts(s, "-------------------------------------------------------------\n");
  92         seq_printf(s, "%-40s %20s\n\n",
  93                    dev_name(m->parent), m->bound ? "bound" : "not bound");
  94
  95         seq_printf(s, "%-40s %20s\n", "device name", "status");
  96         seq_puts(s, "-------------------------------------------------------------\n");
  97         for (i = 0; i < match->num; i++) {
  98                 struct component *component = match->compare[i].component;
  99
 100                 seq_printf(s, "%-40s %20s\n",
 101                            component ? dev_name(component->dev) : "(unknown)",
 102                            component ? (component->bound ? "bound" : "not bound") : "not registered");
 103         }
 104         mutex_unlock(&component_mutex);
 105
 106         return 0;
 107 }
 108
 109 DEFINE_SHOW_ATTRIBUTE(component_devices);
 110
 111 static int __init component_debug_init(void)
 112 {
 113         component_debugfs_dir = debugfs_create_dir("device_component", NULL);
 114
 115         return 0;
 116 }
 117
 118 core_initcall(component_debug_init);
 119
 120 static void component_debugfs_add(struct aggregate_device *m)
 121 {
 122         debugfs_create_file(dev_name(m->parent), 0444, component_debugfs_dir, m,
 123                             &component_devices_fops);
 124 }
 125
 126 static void component_debugfs_del(struct aggregate_device *m)
 127 {
 128         debugfs_lookup_and_remove(dev_name(m->parent), component_debugfs_dir);
 129 }
 130
 131 #else
 132
 133 static void component_debugfs_add(struct aggregate_device *m)
 134 { }
 135
 136 static void component_debugfs_del(struct aggregate_device *m)
 137 { }
 138
 139 #endif
 140
 141 static struct aggregate_device *__aggregate_find(struct device *parent,
 142         const struct component_master_ops *ops)
 143 {
 144         struct aggregate_device *m;
 145
 146         list_for_each_entry(m, &aggregate_devices, node)
 147                 if (m->parent == parent && (!ops || m->ops == ops))
 148                         return m;
 149
 150         return NULL;
 151 }
 152
 153 static struct component *find_component(struct aggregate_device *adev,
 154         struct component_match_array *mc)
 155 {
 156         struct component *c;
 157
 158         list_for_each_entry(c, &component_list, node) {
 159                 if (c->adev && c->adev != adev)
 160                         continue;
 161
 162                 if (mc->compare && mc->compare(c->dev, mc->data))
 163                         return c;
 164
 165                 if (mc->compare_typed &&
 166                     mc->compare_typed(c->dev, c->subcomponent, mc->data))
 167                         return c;
 168         }
 169
 170         return NULL;
 171 }
 172
 173 static int find_components(struct aggregate_device *adev)
 174 {
 175         struct component_match *match = adev->match;
 176         size_t i;
 177         int ret = 0;
 178
 179         /*
 180          * Scan the array of match functions and attach
 181          * any components which are found to this adev.
 182          */
 183         for (i = 0; i < match->num; i++) {
 184                 struct component_match_array *mc = &match->compare[i];
 185                 struct component *c;
 186
 187                 dev_dbg(adev->parent, "Looking for component %zu\n", i);
 188
 189                 if (match->compare[i].component)
 190                         continue;
 191
 192                 c = find_component(adev, mc);
 193                 if (!c) {
 194                         ret = -ENXIO;
 195                         break;
 196                 }
 197
 198                 dev_dbg(adev->parent, "found component %s, duplicate %u\n",
 199                         dev_name(c->dev), !!c->adev);
 200
 201                 /* Attach this component to the adev */
 202                 match->compare[i].duplicate = !!c->adev;
 203                 match->compare[i].component = c;
 204                 c->adev = adev;
 205         }
 206         return ret;
 207 }
 208
 209 /* Detach component from associated aggregate_device */
 210 static void remove_component(struct aggregate_device *adev, struct component *c)
 211 {
 212         size_t i;
 213
 214         /* Detach the component from this adev. */
 215         for (i = 0; i < adev->match->num; i++)
 216                 if (adev->match->compare[i].component == c)
 217                         adev->match->compare[i].component = NULL;
 218 }
 219
 220 /*
 221  * Try to bring up an aggregate device.  If component is NULL, we're interested
 222  * in this aggregate device, otherwise it's a component which must be present
 223  * to try and bring up the aggregate device.
 224  *
 225  * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
 226  */
 227 static int try_to_bring_up_aggregate_device(struct aggregate_device *adev,
 228         struct component *component)
 229 {
 230         int ret;
 231
 232         dev_dbg(adev->parent, "trying to bring up adev\n");
 233
 234         if (find_components(adev)) {
 235                 dev_dbg(adev->parent, "master has incomplete components\n");
 236                 return 0;
 237         }
 238
 239         if (component && component->adev != adev) {
 240                 dev_dbg(adev->parent, "master is not for this component (%s)\n",
 241                         dev_name(component->dev));
 242                 return 0;
 243         }
 244
 245         if (!devres_open_group(adev->parent, adev, GFP_KERNEL))
 246                 return -ENOMEM;
 247
 248         /* Found all components */
 249         ret = adev->ops->bind(adev->parent);
 250         if (ret < 0) {
 251                 devres_release_group(adev->parent, NULL);
 252                 if (ret != -EPROBE_DEFER)
 253                         dev_info(adev->parent, "adev bind failed: %d\n", ret);
 254                 return ret;
 255         }
 256
 257         devres_close_group(adev->parent, NULL);
 258         adev->bound = true;
 259         return 1;
 260 }
 261
 262 static int try_to_bring_up_masters(struct component *component)
 263 {
 264         struct aggregate_device *adev;
 265         int ret = 0;
 266
 267         list_for_each_entry(adev, &aggregate_devices, node) {
 268                 if (!adev->bound) {
 269                         ret = try_to_bring_up_aggregate_device(adev, component);
 270                         if (ret != 0)
 271                                 break;
 272                 }
 273         }
 274
 275         return ret;
 276 }
 277
 278 static void take_down_aggregate_device(struct aggregate_device *adev)
 279 {
 280         if (adev->bound) {
 281                 adev->ops->unbind(adev->parent);
 282                 devres_release_group(adev->parent, adev);
 283                 adev->bound = false;
 284         }
 285 }
 286
 287 /**
 288  * component_compare_of - A common component compare function for of_node
 289  * @dev: component device
 290  * @data: @compare_data from component_match_add_release()
 291  *
 292  * A common compare function when compare_data is device of_node. e.g.
 293  * component_match_add_release(masterdev, &match, component_release_of,
 294  * component_compare_of, component_dev_of_node)
 295  */
 296 int component_compare_of(struct device *dev, void *data)
 297 {
 298         return device_match_of_node(dev, data);
 299 }
 300 EXPORT_SYMBOL_GPL(component_compare_of);
 301
 302 /**
 303  * component_release_of - A common component release function for of_node
 304  * @dev: component device
 305  * @data: @compare_data from component_match_add_release()
 306  *
 307  * About the example, Please see component_compare_of().
 308  */
 309 void component_release_of(struct device *dev, void *data)
 310 {
 311         of_node_put(data);
 312 }
 313 EXPORT_SYMBOL_GPL(component_release_of);
 314
 315 /**
 316  * component_compare_dev - A common component compare function for dev
 317  * @dev: component device
 318  * @data: @compare_data from component_match_add_release()
 319  *
 320  * A common compare function when compare_data is struce device. e.g.
 321  * component_match_add(masterdev, &match, component_compare_dev, component_dev)
 322  */
 323 int component_compare_dev(struct device *dev, void *data)
 324 {
 325         return dev == data;
 326 }
 327 EXPORT_SYMBOL_GPL(component_compare_dev);
 328
 329 /**
 330  * component_compare_dev_name - A common component compare function for device name
 331  * @dev: component device
 332  * @data: @compare_data from component_match_add_release()
 333  *
 334  * A common compare function when compare_data is device name string. e.g.
 335  * component_match_add(masterdev, &match, component_compare_dev_name,
 336  * "component_dev_name")
 337  */
 338 int component_compare_dev_name(struct device *dev, void *data)
 339 {
 340         return device_match_name(dev, data);
 341 }
 342 EXPORT_SYMBOL_GPL(component_compare_dev_name);
 343
 344 static void devm_component_match_release(struct device *parent, void *res)
 345 {
 346         struct component_match *match = res;
 347         unsigned int i;
 348
 349         for (i = 0; i < match->num; i++) {
 350                 struct component_match_array *mc = &match->compare[i];
 351
 352                 if (mc->release)
 353                         mc->release(parent, mc->data);
 354         }
 355
 356         kfree(match->compare);
 357 }
 358
 359 static int component_match_realloc(struct component_match *match, size_t num)
 360 {
 361         struct component_match_array *new;
 362
 363         if (match->alloc == num)
 364                 return 0;
 365
 366         new = kmalloc_array(num, sizeof(*new), GFP_KERNEL);
 367         if (!new)
 368                 return -ENOMEM;
 369
 370         if (match->compare) {
 371                 memcpy(new, match->compare, sizeof(*new) *
 372                                             min(match->num, num));
 373                 kfree(match->compare);
 374         }
 375         match->compare = new;
 376         match->alloc = num;
 377
 378         return 0;
 379 }
 380
 381 static void __component_match_add(struct device *parent,
 382         struct component_match **matchptr,
 383         void (*release)(struct device *, void *),
 384         int (*compare)(struct device *, void *),
 385         int (*compare_typed)(struct device *, int, void *),
 386         void *compare_data)
 387 {
 388         struct component_match *match = *matchptr;
 389
 390         if (IS_ERR(match))
 391                 return;
 392
 393         if (!match) {
 394                 match = devres_alloc(devm_component_match_release,
 395                                      sizeof(*match), GFP_KERNEL);
 396                 if (!match) {
 397                         *matchptr = ERR_PTR(-ENOMEM);
 398                         return;
 399                 }
 400
 401                 devres_add(parent, match);
 402
 403                 *matchptr = match;
 404         }
 405
 406         if (match->num == match->alloc) {
 407                 size_t new_size = match->alloc + 16;
 408                 int ret;
 409
 410                 ret = component_match_realloc(match, new_size);
 411                 if (ret) {
 412                         *matchptr = ERR_PTR(ret);
 413                         return;
 414                 }
 415         }
 416
 417         match->compare[match->num].compare = compare;
 418         match->compare[match->num].compare_typed = compare_typed;
 419         match->compare[match->num].release = release;
 420         match->compare[match->num].data = compare_data;
 421         match->compare[match->num].component = NULL;
 422         match->num++;
 423 }
 424
 425 /**
 426  * component_match_add_release - add a component match entry with release callback
 427  * @parent: parent device of the aggregate driver
 428  * @matchptr: pointer to the list of component matches
 429  * @release: release function for @compare_data
 430  * @compare: compare function to match against all components
 431  * @compare_data: opaque pointer passed to the @compare function
 432  *
 433  * Adds a new component match to the list stored in @matchptr, which the
 434  * aggregate driver needs to function. The list of component matches pointed to
 435  * by @matchptr must be initialized to NULL before adding the first match. This
 436  * only matches against components added with component_add().
 437  *
 438  * The allocated match list in @matchptr is automatically released using devm
 439  * actions, where upon @release will be called to free any references held by
 440  * @compare_data, e.g. when @compare_data is a &device_node that must be
 441  * released with of_node_put().
 442  *
 443  * See also component_match_add() and component_match_add_typed().
 444  */
 445 void component_match_add_release(struct device *parent,
 446         struct component_match **matchptr,
 447         void (*release)(struct device *, void *),
 448         int (*compare)(struct device *, void *), void *compare_data)
 449 {
 450         __component_match_add(parent, matchptr, release, compare, NULL,
 451                               compare_data);
 452 }
 453 EXPORT_SYMBOL(component_match_add_release);
 454
 455 /**
 456  * component_match_add_typed - add a component match entry for a typed component
 457  * @parent: parent device of the aggregate driver
 458  * @matchptr: pointer to the list of component matches
 459  * @compare_typed: compare function to match against all typed components
 460  * @compare_data: opaque pointer passed to the @compare function
 461  *
 462  * Adds a new component match to the list stored in @matchptr, which the
 463  * aggregate driver needs to function. The list of component matches pointed to
 464  * by @matchptr must be initialized to NULL before adding the first match. This
 465  * only matches against components added with component_add_typed().
 466  *
 467  * The allocated match list in @matchptr is automatically released using devm
 468  * actions.
 469  *
 470  * See also component_match_add_release() and component_match_add_typed().
 471  */
 472 void component_match_add_typed(struct device *parent,
 473         struct component_match **matchptr,
 474         int (*compare_typed)(struct device *, int, void *), void *compare_data)
 475 {
 476         __component_match_add(parent, matchptr, NULL, NULL, compare_typed,
 477                               compare_data);
 478 }
 479 EXPORT_SYMBOL(component_match_add_typed);
 480
 481 static void free_aggregate_device(struct aggregate_device *adev)
 482 {
 483         struct component_match *match = adev->match;
 484         int i;
 485
 486         component_debugfs_del(adev);
 487         list_del(&adev->node);
 488
 489         if (match) {
 490                 for (i = 0; i < match->num; i++) {
 491                         struct component *c = match->compare[i].component;
 492                         if (c)
 493                                 c->adev = NULL;
 494                 }
 495         }
 496
 497         kfree(adev);
 498 }
 499
 500 /**
 501  * component_master_add_with_match - register an aggregate driver
 502  * @parent: parent device of the aggregate driver
 503  * @ops: callbacks for the aggregate driver
 504  * @match: component match list for the aggregate driver
 505  *
 506  * Registers a new aggregate driver consisting of the components added to @match
 507  * by calling one of the component_match_add() functions. Once all components in
 508  * @match are available, it will be assembled by calling
 509  * &component_master_ops.bind from @ops. Must be unregistered by calling
 510  * component_master_del().
 511  */
 512 int component_master_add_with_match(struct device *parent,
 513         const struct component_master_ops *ops,
 514         struct component_match *match)
 515 {
 516         struct aggregate_device *adev;
 517         int ret;
 518
 519         /* Reallocate the match array for its true size */
 520         ret = component_match_realloc(match, match->num);
 521         if (ret)
 522                 return ret;
 523
 524         adev = kzalloc(sizeof(*adev), GFP_KERNEL);
 525         if (!adev)
 526                 return -ENOMEM;
 527
 528         adev->parent = parent;
 529         adev->ops = ops;
 530         adev->match = match;
 531
 532         component_debugfs_add(adev);
 533         /* Add to the list of available aggregate devices. */
 534         mutex_lock(&component_mutex);
 535         list_add(&adev->node, &aggregate_devices);
 536
 537         ret = try_to_bring_up_aggregate_device(adev, NULL);
 538
 539         if (ret < 0)
 540                 free_aggregate_device(adev);
 541
 542         mutex_unlock(&component_mutex);
 543
 544         return ret < 0 ? ret : 0;
 545 }
 546 EXPORT_SYMBOL_GPL(component_master_add_with_match);
 547
 548 /**
 549  * component_master_del - unregister an aggregate driver
 550  * @parent: parent device of the aggregate driver
 551  * @ops: callbacks for the aggregate driver
 552  *
 553  * Unregisters an aggregate driver registered with
 554  * component_master_add_with_match(). If necessary the aggregate driver is first
 555  * disassembled by calling &component_master_ops.unbind from @ops.
 556  */
 557 void component_master_del(struct device *parent,
 558         const struct component_master_ops *ops)
 559 {
 560         struct aggregate_device *adev;
 561
 562         mutex_lock(&component_mutex);
 563         adev = __aggregate_find(parent, ops);
 564         if (adev) {
 565                 take_down_aggregate_device(adev);
 566                 free_aggregate_device(adev);
 567         }
 568         mutex_unlock(&component_mutex);
 569 }
 570 EXPORT_SYMBOL_GPL(component_master_del);
 571
 572 static void component_unbind(struct component *component,
 573         struct aggregate_device *adev, void *data)
 574 {
 575         WARN_ON(!component->bound);
 576
 577         if (component->ops && component->ops->unbind)
 578                 component->ops->unbind(component->dev, adev->parent, data);
 579         component->bound = false;
 580
 581         /* Release all resources claimed in the binding of this component */
 582         devres_release_group(component->dev, component);
 583 }
 584
 585 /**
 586  * component_unbind_all - unbind all components of an aggregate driver
 587  * @parent: parent device of the aggregate driver
 588  * @data: opaque pointer, passed to all components
 589  *
 590  * Unbinds all components of the aggregate device by passing @data to their
 591  * &component_ops.unbind functions. Should be called from
 592  * &component_master_ops.unbind.
 593  */
 594 void component_unbind_all(struct device *parent, void *data)
 595 {
 596         struct aggregate_device *adev;
 597         struct component *c;
 598         size_t i;
 599
 600         WARN_ON(!mutex_is_locked(&component_mutex));
 601
 602         adev = __aggregate_find(parent, NULL);
 603         if (!adev)
 604                 return;
 605
 606         /* Unbind components in reverse order */
 607         for (i = adev->match->num; i--; )
 608                 if (!adev->match->compare[i].duplicate) {
 609                         c = adev->match->compare[i].component;
 610                         component_unbind(c, adev, data);
 611                 }
 612 }
 613 EXPORT_SYMBOL_GPL(component_unbind_all);
 614
 615 static int component_bind(struct component *component, struct aggregate_device *adev,
 616         void *data)
 617 {
 618         int ret;
 619
 620         /*
 621          * Each component initialises inside its own devres group.
 622          * This allows us to roll-back a failed component without
 623          * affecting anything else.
 624          */
 625         if (!devres_open_group(adev->parent, NULL, GFP_KERNEL))
 626                 return -ENOMEM;
 627
 628         /*
 629          * Also open a group for the device itself: this allows us
 630          * to release the resources claimed against the sub-device
 631          * at the appropriate moment.
 632          */
 633         if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
 634                 devres_release_group(adev->parent, NULL);
 635                 return -ENOMEM;
 636         }
 637
 638         dev_dbg(adev->parent, "binding %s (ops %ps)\n",
 639                 dev_name(component->dev), component->ops);
 640
 641         ret = component->ops->bind(component->dev, adev->parent, data);
 642         if (!ret) {
 643                 component->bound = true;
 644
 645                 /*
 646                  * Close the component device's group so that resources
 647                  * allocated in the binding are encapsulated for removal
 648                  * at unbind.  Remove the group on the DRM device as we
 649                  * can clean those resources up independently.
 650                  */
 651                 devres_close_group(component->dev, NULL);
 652                 devres_remove_group(adev->parent, NULL);
 653
 654                 dev_info(adev->parent, "bound %s (ops %ps)\n",
 655                          dev_name(component->dev), component->ops);
 656         } else {
 657                 devres_release_group(component->dev, NULL);
 658                 devres_release_group(adev->parent, NULL);
 659
 660                 if (ret != -EPROBE_DEFER)
 661                         dev_err(adev->parent, "failed to bind %s (ops %ps): %d\n",
 662                                 dev_name(component->dev), component->ops, ret);
 663         }
 664
 665         return ret;
 666 }
 667
 668 /**
 669  * component_bind_all - bind all components of an aggregate driver
 670  * @parent: parent device of the aggregate driver
 671  * @data: opaque pointer, passed to all components
 672  *
 673  * Binds all components of the aggregate @dev by passing @data to their
 674  * &component_ops.bind functions. Should be called from
 675  * &component_master_ops.bind.
 676  */
 677 int component_bind_all(struct device *parent, void *data)
 678 {
 679         struct aggregate_device *adev;
 680         struct component *c;
 681         size_t i;
 682         int ret = 0;
 683
 684         WARN_ON(!mutex_is_locked(&component_mutex));
 685
 686         adev = __aggregate_find(parent, NULL);
 687         if (!adev)
 688                 return -EINVAL;
 689
 690         /* Bind components in match order */
 691         for (i = 0; i < adev->match->num; i++)
 692                 if (!adev->match->compare[i].duplicate) {
 693                         c = adev->match->compare[i].component;
 694                         ret = component_bind(c, adev, data);
 695                         if (ret)
 696                                 break;
 697                 }
 698
 699         if (ret != 0) {
 700                 for (; i > 0; i--)
 701                         if (!adev->match->compare[i - 1].duplicate) {
 702                                 c = adev->match->compare[i - 1].component;
 703                                 component_unbind(c, adev, data);
 704                         }
 705         }
 706
 707         return ret;
 708 }
 709 EXPORT_SYMBOL_GPL(component_bind_all);
 710
 711 static int __component_add(struct device *dev, const struct component_ops *ops,
 712         int subcomponent)
 713 {
 714         struct component *component;
 715         int ret;
 716
 717         component = kzalloc(sizeof(*component), GFP_KERNEL);
 718         if (!component)
 719                 return -ENOMEM;
 720
 721         component->ops = ops;
 722         component->dev = dev;
 723         component->subcomponent = subcomponent;
 724
 725         dev_dbg(dev, "adding component (ops %ps)\n", ops);
 726
 727         mutex_lock(&component_mutex);
 728         list_add_tail(&component->node, &component_list);
 729
 730         ret = try_to_bring_up_masters(component);
 731         if (ret < 0) {
 732                 if (component->adev)
 733                         remove_component(component->adev, component);
 734                 list_del(&component->node);
 735
 736                 kfree(component);
 737         }
 738         mutex_unlock(&component_mutex);
 739
 740         return ret < 0 ? ret : 0;
 741 }
 742
 743 /**
 744  * component_add_typed - register a component
 745  * @dev: component device
 746  * @ops: component callbacks
 747  * @subcomponent: nonzero identifier for subcomponents
 748  *
 749  * Register a new component for @dev. Functions in @ops will be call when the
 750  * aggregate driver is ready to bind the overall driver by calling
 751  * component_bind_all(). See also &struct component_ops.
 752  *
 753  * @subcomponent must be nonzero and is used to differentiate between multiple
 754  * components registered on the same device @dev. These components are match
 755  * using component_match_add_typed().
 756  *
 757  * The component needs to be unregistered at driver unload/disconnect by
 758  * calling component_del().
 759  *
 760  * See also component_add().
 761  */
 762 int component_add_typed(struct device *dev, const struct component_ops *ops,
 763         int subcomponent)
 764 {
 765         if (WARN_ON(subcomponent == 0))
 766                 return -EINVAL;
 767
 768         return __component_add(dev, ops, subcomponent);
 769 }
 770 EXPORT_SYMBOL_GPL(component_add_typed);
 771
 772 /**
 773  * component_add - register a component
 774  * @dev: component device
 775  * @ops: component callbacks
 776  *
 777  * Register a new component for @dev. Functions in @ops will be called when the
 778  * aggregate driver is ready to bind the overall driver by calling
 779  * component_bind_all(). See also &struct component_ops.
 780  *
 781  * The component needs to be unregistered at driver unload/disconnect by
 782  * calling component_del().
 783  *
 784  * See also component_add_typed() for a variant that allows multiple different
 785  * components on the same device.
 786  */
 787 int component_add(struct device *dev, const struct component_ops *ops)
 788 {
 789         return __component_add(dev, ops, 0);
 790 }
 791 EXPORT_SYMBOL_GPL(component_add);
 792
 793 /**
 794  * component_del - unregister a component
 795  * @dev: component device
 796  * @ops: component callbacks
 797  *
 798  * Unregister a component added with component_add(). If the component is bound
 799  * into an aggregate driver, this will force the entire aggregate driver, including
 800  * all its components, to be unbound.
 801  */
 802 void component_del(struct device *dev, const struct component_ops *ops)
 803 {
 804         struct component *c, *component = NULL;
 805
 806         mutex_lock(&component_mutex);
 807         list_for_each_entry(c, &component_list, node)
 808                 if (c->dev == dev && c->ops == ops) {
 809                         list_del(&c->node);
 810                         component = c;
 811                         break;
 812                 }
 813
 814         if (component && component->adev) {
 815                 take_down_aggregate_device(component->adev);
 816                 remove_component(component->adev, component);
 817         }
 818
 819         mutex_unlock(&component_mutex);
 820
 821         WARN_ON(!component);
 822         kfree(component);
 823 }
 824 EXPORT_SYMBOL_GPL(component_del);