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 master {
  22         struct list_head node;
  23         struct list_head components;
  24         bool bound;
  25
  26         const struct component_master_ops *ops;
  27         struct device *dev;
  28 };
  29
  30 struct component {
  31         struct list_head node;
  32         struct list_head master_node;
  33         struct master *master;
  34         bool bound;
  35
  36         const struct component_ops *ops;
  37         struct device *dev;
  38 };
  39
  40 static DEFINE_MUTEX(component_mutex);
  41 static LIST_HEAD(component_list);
  42 static LIST_HEAD(masters);
  43
  44 static struct master *__master_find(struct device *dev,
  45         const struct component_master_ops *ops)
  46 {
  47         struct master *m;
  48
  49         list_for_each_entry(m, &masters, node)
  50                 if (m->dev == dev && (!ops || m->ops == ops))
  51                         return m;
  52
  53         return NULL;
  54 }
  55
  56 /* Attach an unattached component to a master. */
  57 static void component_attach_master(struct master *master, struct component *c)
  58 {
  59         c->master = master;
  60
  61         list_add_tail(&c->master_node, &master->components);
  62 }
  63
  64 /* Detach a component from a master. */
  65 static void component_detach_master(struct master *master, struct component *c)
  66 {
  67         list_del(&c->master_node);
  68
  69         c->master = NULL;
  70 }
  71
  72 int component_master_add_child(struct master *master,
  73         int (*compare)(struct device *, void *), void *compare_data)
  74 {
  75         struct component *c;
  76         int ret = -ENXIO;
  77
  78         list_for_each_entry(c, &component_list, node) {
  79                 if (c->master)
  80                         continue;
  81
  82                 if (compare(c->dev, compare_data)) {
  83                         component_attach_master(master, c);
  84                         ret = 0;
  85                         break;
  86                 }
  87         }
  88
  89         return ret;
  90 }
  91 EXPORT_SYMBOL_GPL(component_master_add_child);
  92
  93 /* Detach all attached components from this master */
  94 static void master_remove_components(struct master *master)
  95 {
  96         while (!list_empty(&master->components)) {
  97                 struct component *c = list_first_entry(&master->components,
  98                                         struct component, master_node);
  99
 100                 WARN_ON(c->master != master);
 101
 102                 component_detach_master(master, c);
 103         }
 104 }
 105
 106 /*
 107  * Try to bring up a master.  If component is NULL, we're interested in
 108  * this master, otherwise it's a component which must be present to try
 109  * and bring up the master.
 110  *
 111  * Returns 1 for successful bringup, 0 if not ready, or -ve errno.
 112  */
 113 static int try_to_bring_up_master(struct master *master,
 114         struct component *component)
 115 {
 116         int ret = 0;
 117
 118         if (!master->bound) {
 119                 /*
 120                  * Search the list of components, looking for components that
 121                  * belong to this master, and attach them to the master.
 122                  */
 123                 if (master->ops->add_components(master->dev, master)) {
 124                         /* Failed to find all components */
 125                         master_remove_components(master);
 126                         ret = 0;
 127                         goto out;
 128                 }
 129
 130                 if (component && component->master != master) {
 131                         master_remove_components(master);
 132                         ret = 0;
 133                         goto out;
 134                 }
 135
 136                 if (!devres_open_group(master->dev, NULL, GFP_KERNEL)) {
 137                         ret = -ENOMEM;
 138                         goto out;
 139                 }
 140
 141                 /* Found all components */
 142                 ret = master->ops->bind(master->dev);
 143                 if (ret < 0) {
 144                         devres_release_group(master->dev, NULL);
 145                         dev_info(master->dev, "master bind failed: %d\n", ret);
 146                         master_remove_components(master);
 147                         goto out;
 148                 }
 149
 150                 master->bound = true;
 151                 ret = 1;
 152         }
 153 out:
 154
 155         return ret;
 156 }
 157
 158 static int try_to_bring_up_masters(struct component *component)
 159 {
 160         struct master *m;
 161         int ret = 0;
 162
 163         list_for_each_entry(m, &masters, node) {
 164                 ret = try_to_bring_up_master(m, component);
 165                 if (ret != 0)
 166                         break;
 167         }
 168
 169         return ret;
 170 }
 171
 172 static void take_down_master(struct master *master)
 173 {
 174         if (master->bound) {
 175                 master->ops->unbind(master->dev);
 176                 devres_release_group(master->dev, NULL);
 177                 master->bound = false;
 178         }
 179
 180         master_remove_components(master);
 181 }
 182
 183 int component_master_add(struct device *dev,
 184         const struct component_master_ops *ops)
 185 {
 186         struct master *master;
 187         int ret;
 188
 189         master = kzalloc(sizeof(*master), GFP_KERNEL);
 190         if (!master)
 191                 return -ENOMEM;
 192
 193         master->dev = dev;
 194         master->ops = ops;
 195         INIT_LIST_HEAD(&master->components);
 196
 197         /* Add to the list of available masters. */
 198         mutex_lock(&component_mutex);
 199         list_add(&master->node, &masters);
 200
 201         ret = try_to_bring_up_master(master, NULL);
 202
 203         if (ret < 0) {
 204                 /* Delete off the list if we weren't successful */
 205                 list_del(&master->node);
 206                 kfree(master);
 207         }
 208         mutex_unlock(&component_mutex);
 209
 210         return ret < 0 ? ret : 0;
 211 }
 212 EXPORT_SYMBOL_GPL(component_master_add);
 213
 214 void component_master_del(struct device *dev,
 215         const struct component_master_ops *ops)
 216 {
 217         struct master *master;
 218
 219         mutex_lock(&component_mutex);
 220         master = __master_find(dev, ops);
 221         if (master) {
 222                 take_down_master(master);
 223
 224                 list_del(&master->node);
 225                 kfree(master);
 226         }
 227         mutex_unlock(&component_mutex);
 228 }
 229 EXPORT_SYMBOL_GPL(component_master_del);
 230
 231 static void component_unbind(struct component *component,
 232         struct master *master, void *data)
 233 {
 234         WARN_ON(!component->bound);
 235
 236         component->ops->unbind(component->dev, master->dev, data);
 237         component->bound = false;
 238
 239         /* Release all resources claimed in the binding of this component */
 240         devres_release_group(component->dev, component);
 241 }
 242
 243 void component_unbind_all(struct device *master_dev, void *data)
 244 {
 245         struct master *master;
 246         struct component *c;
 247
 248         WARN_ON(!mutex_is_locked(&component_mutex));
 249
 250         master = __master_find(master_dev, NULL);
 251         if (!master)
 252                 return;
 253
 254         list_for_each_entry_reverse(c, &master->components, master_node)
 255                 component_unbind(c, master, data);
 256 }
 257 EXPORT_SYMBOL_GPL(component_unbind_all);
 258
 259 static int component_bind(struct component *component, struct master *master,
 260         void *data)
 261 {
 262         int ret;
 263
 264         /*
 265          * Each component initialises inside its own devres group.
 266          * This allows us to roll-back a failed component without
 267          * affecting anything else.
 268          */
 269         if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 270                 return -ENOMEM;
 271
 272         /*
 273          * Also open a group for the device itself: this allows us
 274          * to release the resources claimed against the sub-device
 275          * at the appropriate moment.
 276          */
 277         if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
 278                 devres_release_group(master->dev, NULL);
 279                 return -ENOMEM;
 280         }
 281
 282         dev_dbg(master->dev, "binding %s (ops %ps)\n",
 283                 dev_name(component->dev), component->ops);
 284
 285         ret = component->ops->bind(component->dev, master->dev, data);
 286         if (!ret) {
 287                 component->bound = true;
 288
 289                 /*
 290                  * Close the component device's group so that resources
 291                  * allocated in the binding are encapsulated for removal
 292                  * at unbind.  Remove the group on the DRM device as we
 293                  * can clean those resources up independently.
 294                  */
 295                 devres_close_group(component->dev, NULL);
 296                 devres_remove_group(master->dev, NULL);
 297
 298                 dev_info(master->dev, "bound %s (ops %ps)\n",
 299                          dev_name(component->dev), component->ops);
 300         } else {
 301                 devres_release_group(component->dev, NULL);
 302                 devres_release_group(master->dev, NULL);
 303
 304                 dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
 305                         dev_name(component->dev), component->ops, ret);
 306         }
 307
 308         return ret;
 309 }
 310
 311 int component_bind_all(struct device *master_dev, void *data)
 312 {
 313         struct master *master;
 314         struct component *c;
 315         int ret = 0;
 316
 317         WARN_ON(!mutex_is_locked(&component_mutex));
 318
 319         master = __master_find(master_dev, NULL);
 320         if (!master)
 321                 return -EINVAL;
 322
 323         list_for_each_entry(c, &master->components, master_node) {
 324                 ret = component_bind(c, master, data);
 325                 if (ret)
 326                         break;
 327         }
 328
 329         if (ret != 0) {
 330                 list_for_each_entry_continue_reverse(c, &master->components,
 331                                                      master_node)
 332                         component_unbind(c, master, data);
 333         }
 334
 335         return ret;
 336 }
 337 EXPORT_SYMBOL_GPL(component_bind_all);
 338
 339 int component_add(struct device *dev, const struct component_ops *ops)
 340 {
 341         struct component *component;
 342         int ret;
 343
 344         component = kzalloc(sizeof(*component), GFP_KERNEL);
 345         if (!component)
 346                 return -ENOMEM;
 347
 348         component->ops = ops;
 349         component->dev = dev;
 350
 351         dev_dbg(dev, "adding component (ops %ps)\n", ops);
 352
 353         mutex_lock(&component_mutex);
 354         list_add_tail(&component->node, &component_list);
 355
 356         ret = try_to_bring_up_masters(component);
 357         if (ret < 0) {
 358                 list_del(&component->node);
 359
 360                 kfree(component);
 361         }
 362         mutex_unlock(&component_mutex);
 363
 364         return ret < 0 ? ret : 0;
 365 }
 366 EXPORT_SYMBOL_GPL(component_add);
 367
 368 void component_del(struct device *dev, const struct component_ops *ops)
 369 {
 370         struct component *c, *component = NULL;
 371
 372         mutex_lock(&component_mutex);
 373         list_for_each_entry(c, &component_list, node)
 374                 if (c->dev == dev && c->ops == ops) {
 375                         list_del(&c->node);
 376                         component = c;
 377                         break;
 378                 }
 379
 380         if (component && component->master)
 381                 take_down_master(component->master);
 382
 383         mutex_unlock(&component_mutex);
 384
 385         WARN_ON(!component);
 386         kfree(component);
 387 }
 388 EXPORT_SYMBOL_GPL(component_del);
 389
 390 MODULE_LICENSE("GPL v2");