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 static 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
 108 static int find_components(struct master *master)
 109 {
 110         struct component_match *match = master->match;
 111         size_t i;
 112         int ret = 0;
 113
 114         /*
 115          * Scan the array of match functions and attach
 116          * any components which are found to this master.
 117          */
 118         for (i = 0; i < match->num; i++) {
 119                 ret = component_master_add_child(master,
 120                                                  match->compare[i].fn,
 121                                                  match->compare[i].data);
 122                 if (ret)
 123                         break;
 124         }
 125         return ret;
 126 }
 127
 128 /* Detach all attached components from this master */
 129 static void master_remove_components(struct master *master)
 130 {
 131         while (!list_empty(&master->components)) {
 132                 struct component *c = list_first_entry(&master->components,
 133                                         struct component, master_node);
 134
 135                 WARN_ON(c->master != master);
 136
 137                 component_detach_master(master, c);
 138         }
 139 }
 140
 141 /*
 142  * Try to bring up a master.  If component is NULL, we're interested in
 143  * this master, otherwise it's a component which must be present to try
 144  * and bring up the master.
 145  *
 146  * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
 147  */
 148 static int try_to_bring_up_master(struct master *master,
 149         struct component *component)
 150 {
 151         int ret;
 152
 153         if (find_components(master)) {
 154                 /* Failed to find all components */
 155                 ret = 0;
 156                 goto out;
 157         }
 158
 159         if (component && component->master != master) {
 160                 ret = 0;
 161                 goto out;
 162         }
 163
 164         if (!devres_open_group(master->dev, NULL, GFP_KERNEL)) {
 165                 ret = -ENOMEM;
 166                 goto out;
 167         }
 168
 169         /* Found all components */
 170         ret = master->ops->bind(master->dev);
 171         if (ret < 0) {
 172                 devres_release_group(master->dev, NULL);
 173                 dev_info(master->dev, "master bind failed: %d\n", ret);
 174                 goto out;
 175         }
 176
 177         master->bound = true;
 178         return 1;
 179
 180 out:
 181         master_remove_components(master);
 182
 183         return ret;
 184 }
 185
 186 static int try_to_bring_up_masters(struct component *component)
 187 {
 188         struct master *m;
 189         int ret = 0;
 190
 191         list_for_each_entry(m, &masters, node) {
 192                 if (!m->bound) {
 193                         ret = try_to_bring_up_master(m, component);
 194                         if (ret != 0)
 195                                 break;
 196                 }
 197         }
 198
 199         return ret;
 200 }
 201
 202 static void take_down_master(struct master *master)
 203 {
 204         if (master->bound) {
 205                 master->ops->unbind(master->dev);
 206                 devres_release_group(master->dev, NULL);
 207                 master->bound = false;
 208         }
 209
 210         master_remove_components(master);
 211 }
 212
 213 static size_t component_match_size(size_t num)
 214 {
 215         return offsetof(struct component_match, compare[num]);
 216 }
 217
 218 static struct component_match *component_match_realloc(struct device *dev,
 219         struct component_match *match, size_t num)
 220 {
 221         struct component_match *new;
 222
 223         if (match && match->alloc == num)
 224                 return match;
 225
 226         new = devm_kmalloc(dev, component_match_size(num), GFP_KERNEL);
 227         if (!new)
 228                 return ERR_PTR(-ENOMEM);
 229
 230         if (match) {
 231                 memcpy(new, match, component_match_size(min(match->num, num)));
 232                 devm_kfree(dev, match);
 233         } else {
 234                 new->num = 0;
 235         }
 236
 237         new->alloc = num;
 238
 239         return new;
 240 }
 241
 242 /*
 243  * Add a component to be matched.
 244  *
 245  * The match array is first created or extended if necessary.
 246  */
 247 void component_match_add(struct device *dev, struct component_match **matchptr,
 248         int (*compare)(struct device *, void *), void *compare_data)
 249 {
 250         struct component_match *match = *matchptr;
 251
 252         if (IS_ERR(match))
 253                 return;
 254
 255         if (!match || match->num == match->alloc) {
 256                 size_t new_size = match ? match->alloc + 16 : 15;
 257
 258                 match = component_match_realloc(dev, match, new_size);
 259
 260                 *matchptr = match;
 261
 262                 if (IS_ERR(match))
 263                         return;
 264         }
 265
 266         match->compare[match->num].fn = compare;
 267         match->compare[match->num].data = compare_data;
 268         match->num++;
 269 }
 270 EXPORT_SYMBOL(component_match_add);
 271
 272 int component_master_add_with_match(struct device *dev,
 273         const struct component_master_ops *ops,
 274         struct component_match *match)
 275 {
 276         struct master *master;
 277         int ret;
 278
 279         /* Reallocate the match array for its true size */
 280         match = component_match_realloc(dev, match, match->num);
 281         if (IS_ERR(match))
 282                 return PTR_ERR(match);
 283
 284         master = kzalloc(sizeof(*master), GFP_KERNEL);
 285         if (!master)
 286                 return -ENOMEM;
 287
 288         master->dev = dev;
 289         master->ops = ops;
 290         master->match = match;
 291         INIT_LIST_HEAD(&master->components);
 292
 293         /* Add to the list of available masters. */
 294         mutex_lock(&component_mutex);
 295         list_add(&master->node, &masters);
 296
 297         ret = try_to_bring_up_master(master, NULL);
 298
 299         if (ret < 0) {
 300                 /* Delete off the list if we weren't successful */
 301                 list_del(&master->node);
 302                 kfree(master);
 303         }
 304         mutex_unlock(&component_mutex);
 305
 306         return ret < 0 ? ret : 0;
 307 }
 308 EXPORT_SYMBOL_GPL(component_master_add_with_match);
 309
 310 void component_master_del(struct device *dev,
 311         const struct component_master_ops *ops)
 312 {
 313         struct master *master;
 314
 315         mutex_lock(&component_mutex);
 316         master = __master_find(dev, ops);
 317         if (master) {
 318                 take_down_master(master);
 319
 320                 list_del(&master->node);
 321                 kfree(master);
 322         }
 323         mutex_unlock(&component_mutex);
 324 }
 325 EXPORT_SYMBOL_GPL(component_master_del);
 326
 327 static void component_unbind(struct component *component,
 328         struct master *master, void *data)
 329 {
 330         WARN_ON(!component->bound);
 331
 332         component->ops->unbind(component->dev, master->dev, data);
 333         component->bound = false;
 334
 335         /* Release all resources claimed in the binding of this component */
 336         devres_release_group(component->dev, component);
 337 }
 338
 339 void component_unbind_all(struct device *master_dev, void *data)
 340 {
 341         struct master *master;
 342         struct component *c;
 343
 344         WARN_ON(!mutex_is_locked(&component_mutex));
 345
 346         master = __master_find(master_dev, NULL);
 347         if (!master)
 348                 return;
 349
 350         list_for_each_entry_reverse(c, &master->components, master_node)
 351                 component_unbind(c, master, data);
 352 }
 353 EXPORT_SYMBOL_GPL(component_unbind_all);
 354
 355 static int component_bind(struct component *component, struct master *master,
 356         void *data)
 357 {
 358         int ret;
 359
 360         /*
 361          * Each component initialises inside its own devres group.
 362          * This allows us to roll-back a failed component without
 363          * affecting anything else.
 364          */
 365         if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 366                 return -ENOMEM;
 367
 368         /*
 369          * Also open a group for the device itself: this allows us
 370          * to release the resources claimed against the sub-device
 371          * at the appropriate moment.
 372          */
 373         if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
 374                 devres_release_group(master->dev, NULL);
 375                 return -ENOMEM;
 376         }
 377
 378         dev_dbg(master->dev, "binding %s (ops %ps)\n",
 379                 dev_name(component->dev), component->ops);
 380
 381         ret = component->ops->bind(component->dev, master->dev, data);
 382         if (!ret) {
 383                 component->bound = true;
 384
 385                 /*
 386                  * Close the component device's group so that resources
 387                  * allocated in the binding are encapsulated for removal
 388                  * at unbind.  Remove the group on the DRM device as we
 389                  * can clean those resources up independently.
 390                  */
 391                 devres_close_group(component->dev, NULL);
 392                 devres_remove_group(master->dev, NULL);
 393
 394                 dev_info(master->dev, "bound %s (ops %ps)\n",
 395                          dev_name(component->dev), component->ops);
 396         } else {
 397                 devres_release_group(component->dev, NULL);
 398                 devres_release_group(master->dev, NULL);
 399
 400                 dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
 401                         dev_name(component->dev), component->ops, ret);
 402         }
 403
 404         return ret;
 405 }
 406
 407 int component_bind_all(struct device *master_dev, void *data)
 408 {
 409         struct master *master;
 410         struct component *c;
 411         int ret = 0;
 412
 413         WARN_ON(!mutex_is_locked(&component_mutex));
 414
 415         master = __master_find(master_dev, NULL);
 416         if (!master)
 417                 return -EINVAL;
 418
 419         list_for_each_entry(c, &master->components, master_node) {
 420                 ret = component_bind(c, master, data);
 421                 if (ret)
 422                         break;
 423         }
 424
 425         if (ret != 0) {
 426                 list_for_each_entry_continue_reverse(c, &master->components,
 427                                                      master_node)
 428                         component_unbind(c, master, data);
 429         }
 430
 431         return ret;
 432 }
 433 EXPORT_SYMBOL_GPL(component_bind_all);
 434
 435 int component_add(struct device *dev, const struct component_ops *ops)
 436 {
 437         struct component *component;
 438         int ret;
 439
 440         component = kzalloc(sizeof(*component), GFP_KERNEL);
 441         if (!component)
 442                 return -ENOMEM;
 443
 444         component->ops = ops;
 445         component->dev = dev;
 446
 447         dev_dbg(dev, "adding component (ops %ps)\n", ops);
 448
 449         mutex_lock(&component_mutex);
 450         list_add_tail(&component->node, &component_list);
 451
 452         ret = try_to_bring_up_masters(component);
 453         if (ret < 0) {
 454                 list_del(&component->node);
 455
 456                 kfree(component);
 457         }
 458         mutex_unlock(&component_mutex);
 459
 460         return ret < 0 ? ret : 0;
 461 }
 462 EXPORT_SYMBOL_GPL(component_add);
 463
 464 void component_del(struct device *dev, const struct component_ops *ops)
 465 {
 466         struct component *c, *component = NULL;
 467
 468         mutex_lock(&component_mutex);
 469         list_for_each_entry(c, &component_list, node)
 470                 if (c->dev == dev && c->ops == ops) {
 471                         list_del(&c->node);
 472                         component = c;
 473                         break;
 474                 }
 475
 476         if (component && component->master)
 477                 take_down_master(component->master);
 478
 479         mutex_unlock(&component_mutex);
 480
 481         WARN_ON(!component);
 482         kfree(component);
 483 }
 484 EXPORT_SYMBOL_GPL(component_del);
 485
 486 MODULE_LICENSE("GPL v2");