drivers/base/component.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Componentized device handling.
   4  *
   5  * This is work in progress.  We gather up the component devices into a list,
   6  * and bind them when instructed.  At the moment, we're specific to the DRM
   7  * subsystem, and only handles one master device, but this doesn't have to be
   8  * the case.
   9  */
  10 #include <linux/component.h>
  11 #include <linux/device.h>
  12 #include <linux/kref.h>
  13 #include <linux/list.h>
  14 #include <linux/module.h>
  15 #include <linux/mutex.h>
  16 #include <linux/slab.h>
  17 #include <linux/debugfs.h>
  18
  19 struct component;
  20
  21 struct component_match_array {
  22         void *data;
  23         int (*compare)(struct device *, void *);
  24         void (*release)(struct device *, void *);
  25         struct component *component;
  26         bool duplicate;
  27 };
  28
  29 struct component_match {
  30         size_t alloc;
  31         size_t num;
  32         struct component_match_array *compare;
  33 };
  34
  35 struct master {
  36         struct list_head node;
  37         bool bound;
  38
  39         const struct component_master_ops *ops;
  40         struct device *dev;
  41         struct component_match *match;
  42         struct dentry *dentry;
  43 };
  44
  45 struct component {
  46         struct list_head node;
  47         struct master *master;
  48         bool bound;
  49
  50         const struct component_ops *ops;
  51         struct device *dev;
  52 };
  53
  54 static DEFINE_MUTEX(component_mutex);
  55 static LIST_HEAD(component_list);
  56 static LIST_HEAD(masters);
  57
  58 #ifdef CONFIG_DEBUG_FS
  59
  60 static struct dentry *component_debugfs_dir;
  61
  62 static int component_devices_show(struct seq_file *s, void *data)
  63 {
  64         struct master *m = s->private;
  65         struct component_match *match = m->match;
  66         size_t i;
  67
  68         mutex_lock(&component_mutex);
  69         seq_printf(s, "%-40s %20s\n", "master name", "status");
  70         seq_puts(s, "-------------------------------------------------------------\n");
  71         seq_printf(s, "%-40s %20s\n\n",
  72                    dev_name(m->dev), m->bound ? "bound" : "not bound");
  73
  74         seq_printf(s, "%-40s %20s\n", "device name", "status");
  75         seq_puts(s, "-------------------------------------------------------------\n");
  76         for (i = 0; i < match->num; i++) {
  77                 struct component *component = match->compare[i].component;
  78
  79                 seq_printf(s, "%-40s %20s\n",
  80                            component ? dev_name(component->dev) : "(unknown)",
  81                            component ? (component->bound ? "bound" : "not bound") : "not registered");
  82         }
  83         mutex_unlock(&component_mutex);
  84
  85         return 0;
  86 }
  87
  88 static int component_devices_open(struct inode *inode, struct file *file)
  89 {
  90         return single_open(file, component_devices_show, inode->i_private);
  91 }
  92
  93 static const struct file_operations component_devices_fops = {
  94         .open = component_devices_open,
  95         .read = seq_read,
  96         .llseek = seq_lseek,
  97         .release = single_release,
  98 };
  99
 100 static int __init component_debug_init(void)
 101 {
 102         component_debugfs_dir = debugfs_create_dir("device_component", NULL);
 103
 104         return 0;
 105 }
 106
 107 core_initcall(component_debug_init);
 108
 109 static void component_master_debugfs_add(struct master *m)
 110 {
 111         m->dentry = debugfs_create_file(dev_name(m->dev), 0444,
 112                                         component_debugfs_dir,
 113                                         m, &component_devices_fops);
 114 }
 115
 116 static void component_master_debugfs_del(struct master *m)
 117 {
 118         debugfs_remove(m->dentry);
 119         m->dentry = NULL;
 120 }
 121
 122 #else
 123
 124 static void component_master_debugfs_add(struct master *m)
 125 { }
 126
 127 static void component_master_debugfs_del(struct master *m)
 128 { }
 129
 130 #endif
 131
 132 static struct master *__master_find(struct device *dev,
 133         const struct component_master_ops *ops)
 134 {
 135         struct master *m;
 136
 137         list_for_each_entry(m, &masters, node)
 138                 if (m->dev == dev && (!ops || m->ops == ops))
 139                         return m;
 140
 141         return NULL;
 142 }
 143
 144 static struct component *find_component(struct master *master,
 145         int (*compare)(struct device *, void *), void *compare_data)
 146 {
 147         struct component *c;
 148
 149         list_for_each_entry(c, &component_list, node) {
 150                 if (c->master && c->master != master)
 151                         continue;
 152
 153                 if (compare(c->dev, compare_data))
 154                         return c;
 155         }
 156
 157         return NULL;
 158 }
 159
 160 static int find_components(struct master *master)
 161 {
 162         struct component_match *match = master->match;
 163         size_t i;
 164         int ret = 0;
 165
 166         /*
 167          * Scan the array of match functions and attach
 168          * any components which are found to this master.
 169          */
 170         for (i = 0; i < match->num; i++) {
 171                 struct component_match_array *mc = &match->compare[i];
 172                 struct component *c;
 173
 174                 dev_dbg(master->dev, "Looking for component %zu\n", i);
 175
 176                 if (match->compare[i].component)
 177                         continue;
 178
 179                 c = find_component(master, mc->compare, mc->data);
 180                 if (!c) {
 181                         ret = -ENXIO;
 182                         break;
 183                 }
 184
 185                 dev_dbg(master->dev, "found component %s, duplicate %u\n", dev_name(c->dev), !!c->master);
 186
 187                 /* Attach this component to the master */
 188                 match->compare[i].duplicate = !!c->master;
 189                 match->compare[i].component = c;
 190                 c->master = master;
 191         }
 192         return ret;
 193 }
 194
 195 /* Detach component from associated master */
 196 static void remove_component(struct master *master, struct component *c)
 197 {
 198         size_t i;
 199
 200         /* Detach the component from this master. */
 201         for (i = 0; i < master->match->num; i++)
 202                 if (master->match->compare[i].component == c)
 203                         master->match->compare[i].component = NULL;
 204 }
 205
 206 /*
 207  * Try to bring up a master.  If component is NULL, we're interested in
 208  * this master, otherwise it's a component which must be present to try
 209  * and bring up the master.
 210  *
 211  * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
 212  */
 213 static int try_to_bring_up_master(struct master *master,
 214         struct component *component)
 215 {
 216         int ret;
 217
 218         dev_dbg(master->dev, "trying to bring up master\n");
 219
 220         if (find_components(master)) {
 221                 dev_dbg(master->dev, "master has incomplete components\n");
 222                 return 0;
 223         }
 224
 225         if (component && component->master != master) {
 226                 dev_dbg(master->dev, "master is not for this component (%s)\n",
 227                         dev_name(component->dev));
 228                 return 0;
 229         }
 230
 231         if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 232                 return -ENOMEM;
 233
 234         /* Found all components */
 235         ret = master->ops->bind(master->dev);
 236         if (ret < 0) {
 237                 devres_release_group(master->dev, NULL);
 238                 if (ret != -EPROBE_DEFER)
 239                         dev_info(master->dev, "master bind failed: %d\n", ret);
 240                 return ret;
 241         }
 242
 243         master->bound = true;
 244         return 1;
 245 }
 246
 247 static int try_to_bring_up_masters(struct component *component)
 248 {
 249         struct master *m;
 250         int ret = 0;
 251
 252         list_for_each_entry(m, &masters, node) {
 253                 if (!m->bound) {
 254                         ret = try_to_bring_up_master(m, component);
 255                         if (ret != 0)
 256                                 break;
 257                 }
 258         }
 259
 260         return ret;
 261 }
 262
 263 static void take_down_master(struct master *master)
 264 {
 265         if (master->bound) {
 266                 master->ops->unbind(master->dev);
 267                 devres_release_group(master->dev, NULL);
 268                 master->bound = false;
 269         }
 270 }
 271
 272 static void component_match_release(struct device *master,
 273         struct component_match *match)
 274 {
 275         unsigned int i;
 276
 277         for (i = 0; i < match->num; i++) {
 278                 struct component_match_array *mc = &match->compare[i];
 279
 280                 if (mc->release)
 281                         mc->release(master, mc->data);
 282         }
 283
 284         kfree(match->compare);
 285 }
 286
 287 static void devm_component_match_release(struct device *dev, void *res)
 288 {
 289         component_match_release(dev, res);
 290 }
 291
 292 static int component_match_realloc(struct device *dev,
 293         struct component_match *match, size_t num)
 294 {
 295         struct component_match_array *new;
 296
 297         if (match->alloc == num)
 298                 return 0;
 299
 300         new = kmalloc_array(num, sizeof(*new), GFP_KERNEL);
 301         if (!new)
 302                 return -ENOMEM;
 303
 304         if (match->compare) {
 305                 memcpy(new, match->compare, sizeof(*new) *
 306                                             min(match->num, num));
 307                 kfree(match->compare);
 308         }
 309         match->compare = new;
 310         match->alloc = num;
 311
 312         return 0;
 313 }
 314
 315 /*
 316  * Add a component to be matched, with a release function.
 317  *
 318  * The match array is first created or extended if necessary.
 319  */
 320 void component_match_add_release(struct device *master,
 321         struct component_match **matchptr,
 322         void (*release)(struct device *, void *),
 323         int (*compare)(struct device *, void *), void *compare_data)
 324 {
 325         struct component_match *match = *matchptr;
 326
 327         if (IS_ERR(match))
 328                 return;
 329
 330         if (!match) {
 331                 match = devres_alloc(devm_component_match_release,
 332                                      sizeof(*match), GFP_KERNEL);
 333                 if (!match) {
 334                         *matchptr = ERR_PTR(-ENOMEM);
 335                         return;
 336                 }
 337
 338                 devres_add(master, match);
 339
 340                 *matchptr = match;
 341         }
 342
 343         if (match->num == match->alloc) {
 344                 size_t new_size = match->alloc + 16;
 345                 int ret;
 346
 347                 ret = component_match_realloc(master, match, new_size);
 348                 if (ret) {
 349                         *matchptr = ERR_PTR(ret);
 350                         return;
 351                 }
 352         }
 353
 354         match->compare[match->num].compare = compare;
 355         match->compare[match->num].release = release;
 356         match->compare[match->num].data = compare_data;
 357         match->compare[match->num].component = NULL;
 358         match->num++;
 359 }
 360 EXPORT_SYMBOL(component_match_add_release);
 361
 362 static void free_master(struct master *master)
 363 {
 364         struct component_match *match = master->match;
 365         int i;
 366
 367         component_master_debugfs_del(master);
 368         list_del(&master->node);
 369
 370         if (match) {
 371                 for (i = 0; i < match->num; i++) {
 372                         struct component *c = match->compare[i].component;
 373                         if (c)
 374                                 c->master = NULL;
 375                 }
 376         }
 377
 378         kfree(master);
 379 }
 380
 381 int component_master_add_with_match(struct device *dev,
 382         const struct component_master_ops *ops,
 383         struct component_match *match)
 384 {
 385         struct master *master;
 386         int ret;
 387
 388         /* Reallocate the match array for its true size */
 389         ret = component_match_realloc(dev, match, match->num);
 390         if (ret)
 391                 return ret;
 392
 393         master = kzalloc(sizeof(*master), GFP_KERNEL);
 394         if (!master)
 395                 return -ENOMEM;
 396
 397         master->dev = dev;
 398         master->ops = ops;
 399         master->match = match;
 400
 401         component_master_debugfs_add(master);
 402         /* Add to the list of available masters. */
 403         mutex_lock(&component_mutex);
 404         list_add(&master->node, &masters);
 405
 406         ret = try_to_bring_up_master(master, NULL);
 407
 408         if (ret < 0)
 409                 free_master(master);
 410
 411         mutex_unlock(&component_mutex);
 412
 413         return ret < 0 ? ret : 0;
 414 }
 415 EXPORT_SYMBOL_GPL(component_master_add_with_match);
 416
 417 void component_master_del(struct device *dev,
 418         const struct component_master_ops *ops)
 419 {
 420         struct master *master;
 421
 422         mutex_lock(&component_mutex);
 423         master = __master_find(dev, ops);
 424         if (master) {
 425                 take_down_master(master);
 426                 free_master(master);
 427         }
 428         mutex_unlock(&component_mutex);
 429 }
 430 EXPORT_SYMBOL_GPL(component_master_del);
 431
 432 static void component_unbind(struct component *component,
 433         struct master *master, void *data)
 434 {
 435         WARN_ON(!component->bound);
 436
 437         component->ops->unbind(component->dev, master->dev, data);
 438         component->bound = false;
 439
 440         /* Release all resources claimed in the binding of this component */
 441         devres_release_group(component->dev, component);
 442 }
 443
 444 void component_unbind_all(struct device *master_dev, void *data)
 445 {
 446         struct master *master;
 447         struct component *c;
 448         size_t i;
 449
 450         WARN_ON(!mutex_is_locked(&component_mutex));
 451
 452         master = __master_find(master_dev, NULL);
 453         if (!master)
 454                 return;
 455
 456         /* Unbind components in reverse order */
 457         for (i = master->match->num; i--; )
 458                 if (!master->match->compare[i].duplicate) {
 459                         c = master->match->compare[i].component;
 460                         component_unbind(c, master, data);
 461                 }
 462 }
 463 EXPORT_SYMBOL_GPL(component_unbind_all);
 464
 465 static int component_bind(struct component *component, struct master *master,
 466         void *data)
 467 {
 468         int ret;
 469
 470         /*
 471          * Each component initialises inside its own devres group.
 472          * This allows us to roll-back a failed component without
 473          * affecting anything else.
 474          */
 475         if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 476                 return -ENOMEM;
 477
 478         /*
 479          * Also open a group for the device itself: this allows us
 480          * to release the resources claimed against the sub-device
 481          * at the appropriate moment.
 482          */
 483         if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
 484                 devres_release_group(master->dev, NULL);
 485                 return -ENOMEM;
 486         }
 487
 488         dev_dbg(master->dev, "binding %s (ops %ps)\n",
 489                 dev_name(component->dev), component->ops);
 490
 491         ret = component->ops->bind(component->dev, master->dev, data);
 492         if (!ret) {
 493                 component->bound = true;
 494
 495                 /*
 496                  * Close the component device's group so that resources
 497                  * allocated in the binding are encapsulated for removal
 498                  * at unbind.  Remove the group on the DRM device as we
 499                  * can clean those resources up independently.
 500                  */
 501                 devres_close_group(component->dev, NULL);
 502                 devres_remove_group(master->dev, NULL);
 503
 504                 dev_info(master->dev, "bound %s (ops %ps)\n",
 505                          dev_name(component->dev), component->ops);
 506         } else {
 507                 devres_release_group(component->dev, NULL);
 508                 devres_release_group(master->dev, NULL);
 509
 510                 if (ret != -EPROBE_DEFER)
 511                         dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
 512                                 dev_name(component->dev), component->ops, ret);
 513         }
 514
 515         return ret;
 516 }
 517
 518 int component_bind_all(struct device *master_dev, void *data)
 519 {
 520         struct master *master;
 521         struct component *c;
 522         size_t i;
 523         int ret = 0;
 524
 525         WARN_ON(!mutex_is_locked(&component_mutex));
 526
 527         master = __master_find(master_dev, NULL);
 528         if (!master)
 529                 return -EINVAL;
 530
 531         /* Bind components in match order */
 532         for (i = 0; i < master->match->num; i++)
 533                 if (!master->match->compare[i].duplicate) {
 534                         c = master->match->compare[i].component;
 535                         ret = component_bind(c, master, data);
 536                         if (ret)
 537                                 break;
 538                 }
 539
 540         if (ret != 0) {
 541                 for (; i > 0; i--)
 542                         if (!master->match->compare[i - 1].duplicate) {
 543                                 c = master->match->compare[i - 1].component;
 544                                 component_unbind(c, master, data);
 545                         }
 546         }
 547
 548         return ret;
 549 }
 550 EXPORT_SYMBOL_GPL(component_bind_all);
 551
 552 int component_add(struct device *dev, const struct component_ops *ops)
 553 {
 554         struct component *component;
 555         int ret;
 556
 557         component = kzalloc(sizeof(*component), GFP_KERNEL);
 558         if (!component)
 559                 return -ENOMEM;
 560
 561         component->ops = ops;
 562         component->dev = dev;
 563
 564         dev_dbg(dev, "adding component (ops %ps)\n", ops);
 565
 566         mutex_lock(&component_mutex);
 567         list_add_tail(&component->node, &component_list);
 568
 569         ret = try_to_bring_up_masters(component);
 570         if (ret < 0) {
 571                 if (component->master)
 572                         remove_component(component->master, component);
 573                 list_del(&component->node);
 574
 575                 kfree(component);
 576         }
 577         mutex_unlock(&component_mutex);
 578
 579         return ret < 0 ? ret : 0;
 580 }
 581 EXPORT_SYMBOL_GPL(component_add);
 582
 583 void component_del(struct device *dev, const struct component_ops *ops)
 584 {
 585         struct component *c, *component = NULL;
 586
 587         mutex_lock(&component_mutex);
 588         list_for_each_entry(c, &component_list, node)
 589                 if (c->dev == dev && c->ops == ops) {
 590                         list_del(&c->node);
 591                         component = c;
 592                         break;
 593                 }
 594
 595         if (component && component->master) {
 596                 take_down_master(component->master);
 597                 remove_component(component->master, component);
 598         }
 599
 600         mutex_unlock(&component_mutex);
 601
 602         WARN_ON(!component);
 603         kfree(component);
 604 }
 605 EXPORT_SYMBOL_GPL(component_del);
 606
 607 MODULE_LICENSE("GPL v2");