drivers/base/component.c

   1 /*
   2  * Componentized device handling.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * This is work in progress.  We gather up the component devices into a list,
   9  * and bind them when instructed.  At the moment, we're specific to the DRM
  10  * subsystem, and only handles one master device, but this doesn't have to be
  11  * the case.
  12  */
  13 #include <linux/component.h>
  14 #include <linux/device.h>
  15 #include <linux/kref.h>
  16 #include <linux/list.h>
  17 #include <linux/module.h>
  18 #include <linux/mutex.h>
  19 #include <linux/slab.h>
  20
  21 struct component_match {
  22         size_t alloc;
  23         size_t num;
  24         struct {
  25                 void *data;
  26                 int (*fn)(struct device *, void *);
  27         } compare[0];
  28 };
  29
  30 struct master {
  31         struct list_head node;
  32         struct list_head components;
  33         bool bound;
  34
  35         const struct component_master_ops *ops;
  36         struct device *dev;
  37         struct component_match *match;
  38 };
  39
  40 struct component {
  41         struct list_head node;
  42         struct list_head master_node;
  43         struct master *master;
  44         bool bound;
  45
  46         const struct component_ops *ops;
  47         struct device *dev;
  48 };
  49
  50 static DEFINE_MUTEX(component_mutex);
  51 static LIST_HEAD(component_list);
  52 static LIST_HEAD(masters);
  53
  54 static struct master *__master_find(struct device *dev,
  55         const struct component_master_ops *ops)
  56 {
  57         struct master *m;
  58
  59         list_for_each_entry(m, &masters, node)
  60                 if (m->dev == dev && (!ops || m->ops == ops))
  61                         return m;
  62
  63         return NULL;
  64 }
  65
  66 /* Attach an unattached component to a master. */
  67 static void component_attach_master(struct master *master, struct component *c)
  68 {
  69         c->master = master;
  70
  71         list_add_tail(&c->master_node, &master->components);
  72 }
  73
  74 /* Detach a component from a master. */
  75 static void component_detach_master(struct master *master, struct component *c)
  76 {
  77         list_del(&c->master_node);
  78
  79         c->master = NULL;
  80 }
  81
  82 /*
  83  * Add a component to a master, finding the component via the compare
  84  * function and compare data.  This is safe to call for duplicate matches
  85  * and will not result in the same component being added multiple times.
  86  */
  87 int component_master_add_child(struct master *master,
  88         int (*compare)(struct device *, void *), void *compare_data)
  89 {
  90         struct component *c;
  91         int ret = -ENXIO;
  92
  93         list_for_each_entry(c, &component_list, node) {
  94                 if (c->master && c->master != master)
  95                         continue;
  96
  97                 if (compare(c->dev, compare_data)) {
  98                         if (!c->master)
  99                                 component_attach_master(master, c);
 100                         ret = 0;
 101                         break;
 102                 }
 103         }
 104
 105         return ret;
 106 }
 107 EXPORT_SYMBOL_GPL(component_master_add_child);
 108
 109 static int find_components(struct master *master)
 110 {
 111         struct component_match *match = master->match;
 112         size_t i;
 113         int ret = 0;
 114
 115         if (!match) {
 116                 /*
 117                  * Search the list of components, looking for components that
 118                  * belong to this master, and attach them to the master.
 119                  */
 120                 return master->ops->add_components(master->dev, master);
 121         }
 122
 123         /*
 124          * Scan the array of match functions and attach
 125          * any components which are found to this master.
 126          */
 127         for (i = 0; i < match->num; i++) {
 128                 ret = component_master_add_child(master,
 129                                                  match->compare[i].fn,
 130                                                  match->compare[i].data);
 131                 if (ret)
 132                         break;
 133         }
 134         return ret;
 135 }
 136
 137 /* Detach all attached components from this master */
 138 static void master_remove_components(struct master *master)
 139 {
 140         while (!list_empty(&master->components)) {
 141                 struct component *c = list_first_entry(&master->components,
 142                                         struct component, master_node);
 143
 144                 WARN_ON(c->master != master);
 145
 146                 component_detach_master(master, c);
 147         }
 148 }
 149
 150 /*
 151  * Try to bring up a master.  If component is NULL, we're interested in
 152  * this master, otherwise it's a component which must be present to try
 153  * and bring up the master.
 154  *
 155  * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
 156  */
 157 static int try_to_bring_up_master(struct master *master,
 158         struct component *component)
 159 {
 160         int ret;
 161
 162         if (master->bound)
 163                 return 0;
 164
 165         /*
 166          * Search the list of components, looking for components that
 167          * belong to this master, and attach them to the master.
 168          */
 169         if (find_components(master)) {
 170                 /* Failed to find all components */
 171                 ret = 0;
 172                 goto out;
 173         }
 174
 175         if (component && component->master != master) {
 176                 ret = 0;
 177                 goto out;
 178         }
 179
 180         if (!devres_open_group(master->dev, NULL, GFP_KERNEL)) {
 181                 ret = -ENOMEM;
 182                 goto out;
 183         }
 184
 185         /* Found all components */
 186         ret = master->ops->bind(master->dev);
 187         if (ret < 0) {
 188                 devres_release_group(master->dev, NULL);
 189                 dev_info(master->dev, "master bind failed: %d\n", ret);
 190                 goto out;
 191         }
 192
 193         master->bound = true;
 194         return 1;
 195
 196 out:
 197         master_remove_components(master);
 198
 199         return ret;
 200 }
 201
 202 static int try_to_bring_up_masters(struct component *component)
 203 {
 204         struct master *m;
 205         int ret = 0;
 206
 207         list_for_each_entry(m, &masters, node) {
 208                 ret = try_to_bring_up_master(m, component);
 209                 if (ret != 0)
 210                         break;
 211         }
 212
 213         return ret;
 214 }
 215
 216 static void take_down_master(struct master *master)
 217 {
 218         if (master->bound) {
 219                 master->ops->unbind(master->dev);
 220                 devres_release_group(master->dev, NULL);
 221                 master->bound = false;
 222         }
 223
 224         master_remove_components(master);
 225 }
 226
 227 static size_t component_match_size(size_t num)
 228 {
 229         return offsetof(struct component_match, compare[num]);
 230 }
 231
 232 static struct component_match *component_match_realloc(struct device *dev,
 233         struct component_match *match, size_t num)
 234 {
 235         struct component_match *new;
 236
 237         if (match && match->alloc == num)
 238                 return match;
 239
 240         new = devm_kmalloc(dev, component_match_size(num), GFP_KERNEL);
 241         if (!new)
 242                 return ERR_PTR(-ENOMEM);
 243
 244         if (match) {
 245                 memcpy(new, match, component_match_size(min(match->num, num)));
 246                 devm_kfree(dev, match);
 247         } else {
 248                 new->num = 0;
 249         }
 250
 251         new->alloc = num;
 252
 253         return new;
 254 }
 255
 256 /*
 257  * Add a component to be matched.
 258  *
 259  * The match array is first created or extended if necessary.
 260  */
 261 void component_match_add(struct device *dev, struct component_match **matchptr,
 262         int (*compare)(struct device *, void *), void *compare_data)
 263 {
 264         struct component_match *match = *matchptr;
 265
 266         if (IS_ERR(match))
 267                 return;
 268
 269         if (!match || match->num == match->alloc) {
 270                 size_t new_size = match ? match->alloc + 16 : 15;
 271
 272                 match = component_match_realloc(dev, match, new_size);
 273
 274                 *matchptr = match;
 275
 276                 if (IS_ERR(match))
 277                         return;
 278         }
 279
 280         match->compare[match->num].fn = compare;
 281         match->compare[match->num].data = compare_data;
 282         match->num++;
 283 }
 284 EXPORT_SYMBOL(component_match_add);
 285
 286 int component_master_add_with_match(struct device *dev,
 287         const struct component_master_ops *ops,
 288         struct component_match *match)
 289 {
 290         struct master *master;
 291         int ret;
 292
 293         if (ops->add_components && match)
 294                 return -EINVAL;
 295
 296         /* Reallocate the match array for its true size */
 297         match = component_match_realloc(dev, match, match->num);
 298         if (IS_ERR(match))
 299                 return PTR_ERR(match);
 300
 301         master = kzalloc(sizeof(*master), GFP_KERNEL);
 302         if (!master)
 303                 return -ENOMEM;
 304
 305         master->dev = dev;
 306         master->ops = ops;
 307         master->match = match;
 308         INIT_LIST_HEAD(&master->components);
 309
 310         /* Add to the list of available masters. */
 311         mutex_lock(&component_mutex);
 312         list_add(&master->node, &masters);
 313
 314         ret = try_to_bring_up_master(master, NULL);
 315
 316         if (ret < 0) {
 317                 /* Delete off the list if we weren't successful */
 318                 list_del(&master->node);
 319                 kfree(master);
 320         }
 321         mutex_unlock(&component_mutex);
 322
 323         return ret < 0 ? ret : 0;
 324 }
 325 EXPORT_SYMBOL_GPL(component_master_add_with_match);
 326
 327 int component_master_add(struct device *dev,
 328         const struct component_master_ops *ops)
 329 {
 330         return component_master_add_with_match(dev, ops, NULL);
 331 }
 332 EXPORT_SYMBOL_GPL(component_master_add);
 333
 334 void component_master_del(struct device *dev,
 335         const struct component_master_ops *ops)
 336 {
 337         struct master *master;
 338
 339         mutex_lock(&component_mutex);
 340         master = __master_find(dev, ops);
 341         if (master) {
 342                 take_down_master(master);
 343
 344                 list_del(&master->node);
 345                 kfree(master);
 346         }
 347         mutex_unlock(&component_mutex);
 348 }
 349 EXPORT_SYMBOL_GPL(component_master_del);
 350
 351 static void component_unbind(struct component *component,
 352         struct master *master, void *data)
 353 {
 354         WARN_ON(!component->bound);
 355
 356         component->ops->unbind(component->dev, master->dev, data);
 357         component->bound = false;
 358
 359         /* Release all resources claimed in the binding of this component */
 360         devres_release_group(component->dev, component);
 361 }
 362
 363 void component_unbind_all(struct device *master_dev, void *data)
 364 {
 365         struct master *master;
 366         struct component *c;
 367
 368         WARN_ON(!mutex_is_locked(&component_mutex));
 369
 370         master = __master_find(master_dev, NULL);
 371         if (!master)
 372                 return;
 373
 374         list_for_each_entry_reverse(c, &master->components, master_node)
 375                 component_unbind(c, master, data);
 376 }
 377 EXPORT_SYMBOL_GPL(component_unbind_all);
 378
 379 static int component_bind(struct component *component, struct master *master,
 380         void *data)
 381 {
 382         int ret;
 383
 384         /*
 385          * Each component initialises inside its own devres group.
 386          * This allows us to roll-back a failed component without
 387          * affecting anything else.
 388          */
 389         if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 390                 return -ENOMEM;
 391
 392         /*
 393          * Also open a group for the device itself: this allows us
 394          * to release the resources claimed against the sub-device
 395          * at the appropriate moment.
 396          */
 397         if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
 398                 devres_release_group(master->dev, NULL);
 399                 return -ENOMEM;
 400         }
 401
 402         dev_dbg(master->dev, "binding %s (ops %ps)\n",
 403                 dev_name(component->dev), component->ops);
 404
 405         ret = component->ops->bind(component->dev, master->dev, data);
 406         if (!ret) {
 407                 component->bound = true;
 408
 409                 /*
 410                  * Close the component device's group so that resources
 411                  * allocated in the binding are encapsulated for removal
 412                  * at unbind.  Remove the group on the DRM device as we
 413                  * can clean those resources up independently.
 414                  */
 415                 devres_close_group(component->dev, NULL);
 416                 devres_remove_group(master->dev, NULL);
 417
 418                 dev_info(master->dev, "bound %s (ops %ps)\n",
 419                          dev_name(component->dev), component->ops);
 420         } else {
 421                 devres_release_group(component->dev, NULL);
 422                 devres_release_group(master->dev, NULL);
 423
 424                 dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
 425                         dev_name(component->dev), component->ops, ret);
 426         }
 427
 428         return ret;
 429 }
 430
 431 int component_bind_all(struct device *master_dev, void *data)
 432 {
 433         struct master *master;
 434         struct component *c;
 435         int ret = 0;
 436
 437         WARN_ON(!mutex_is_locked(&component_mutex));
 438
 439         master = __master_find(master_dev, NULL);
 440         if (!master)
 441                 return -EINVAL;
 442
 443         list_for_each_entry(c, &master->components, master_node) {
 444                 ret = component_bind(c, master, data);
 445                 if (ret)
 446                         break;
 447         }
 448
 449         if (ret != 0) {
 450                 list_for_each_entry_continue_reverse(c, &master->components,
 451                                                      master_node)
 452                         component_unbind(c, master, data);
 453         }
 454
 455         return ret;
 456 }
 457 EXPORT_SYMBOL_GPL(component_bind_all);
 458
 459 int component_add(struct device *dev, const struct component_ops *ops)
 460 {
 461         struct component *component;
 462         int ret;
 463
 464         component = kzalloc(sizeof(*component), GFP_KERNEL);
 465         if (!component)
 466                 return -ENOMEM;
 467
 468         component->ops = ops;
 469         component->dev = dev;
 470
 471         dev_dbg(dev, "adding component (ops %ps)\n", ops);
 472
 473         mutex_lock(&component_mutex);
 474         list_add_tail(&component->node, &component_list);
 475
 476         ret = try_to_bring_up_masters(component);
 477         if (ret < 0) {
 478                 list_del(&component->node);
 479
 480                 kfree(component);
 481         }
 482         mutex_unlock(&component_mutex);
 483
 484         return ret < 0 ? ret : 0;
 485 }
 486 EXPORT_SYMBOL_GPL(component_add);
 487
 488 void component_del(struct device *dev, const struct component_ops *ops)
 489 {
 490         struct component *c, *component = NULL;
 491
 492         mutex_lock(&component_mutex);
 493         list_for_each_entry(c, &component_list, node)
 494                 if (c->dev == dev && c->ops == ops) {
 495                         list_del(&c->node);
 496                         component = c;
 497                         break;
 498                 }
 499
 500         if (component && component->master)
 501                 take_down_master(component->master);
 502
 503         mutex_unlock(&component_mutex);
 504
 505         WARN_ON(!component);
 506         kfree(component);
 507 }
 508 EXPORT_SYMBOL_GPL(component_del);
 509
 510 MODULE_LICENSE("GPL v2");