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                 /* Found all components */
 137                 ret = master->ops->bind(master->dev);
 138                 if (ret < 0) {
 139                         master_remove_components(master);
 140                         goto out;
 141                 }
 142
 143                 master->bound = true;
 144                 ret = 1;
 145         }
 146 out:
 147
 148         return ret;
 149 }
 150
 151 static int try_to_bring_up_masters(struct component *component)
 152 {
 153         struct master *m;
 154         int ret = 0;
 155
 156         list_for_each_entry(m, &masters, node) {
 157                 ret = try_to_bring_up_master(m, component);
 158                 if (ret != 0)
 159                         break;
 160         }
 161
 162         return ret;
 163 }
 164
 165 static void take_down_master(struct master *master)
 166 {
 167         if (master->bound) {
 168                 master->ops->unbind(master->dev);
 169                 master->bound = false;
 170         }
 171
 172         master_remove_components(master);
 173 }
 174
 175 int component_master_add(struct device *dev,
 176         const struct component_master_ops *ops)
 177 {
 178         struct master *master;
 179         int ret;
 180
 181         master = kzalloc(sizeof(*master), GFP_KERNEL);
 182         if (!master)
 183                 return -ENOMEM;
 184
 185         master->dev = dev;
 186         master->ops = ops;
 187         INIT_LIST_HEAD(&master->components);
 188
 189         /* Add to the list of available masters. */
 190         mutex_lock(&component_mutex);
 191         list_add(&master->node, &masters);
 192
 193         ret = try_to_bring_up_master(master, NULL);
 194
 195         if (ret < 0) {
 196                 /* Delete off the list if we weren't successful */
 197                 list_del(&master->node);
 198                 kfree(master);
 199         }
 200         mutex_unlock(&component_mutex);
 201
 202         return ret < 0 ? ret : 0;
 203 }
 204 EXPORT_SYMBOL_GPL(component_master_add);
 205
 206 void component_master_del(struct device *dev,
 207         const struct component_master_ops *ops)
 208 {
 209         struct master *master;
 210
 211         mutex_lock(&component_mutex);
 212         master = __master_find(dev, ops);
 213         if (master) {
 214                 take_down_master(master);
 215
 216                 list_del(&master->node);
 217                 kfree(master);
 218         }
 219         mutex_unlock(&component_mutex);
 220 }
 221 EXPORT_SYMBOL_GPL(component_master_del);
 222
 223 static void component_unbind(struct component *component,
 224         struct master *master, void *data)
 225 {
 226         WARN_ON(!component->bound);
 227
 228         component->ops->unbind(component->dev, master->dev, data);
 229         component->bound = false;
 230
 231         /* Release all resources claimed in the binding of this component */
 232         devres_release_group(component->dev, component);
 233 }
 234
 235 void component_unbind_all(struct device *master_dev, void *data)
 236 {
 237         struct master *master;
 238         struct component *c;
 239
 240         WARN_ON(!mutex_is_locked(&component_mutex));
 241
 242         master = __master_find(master_dev, NULL);
 243         if (!master)
 244                 return;
 245
 246         list_for_each_entry_reverse(c, &master->components, master_node)
 247                 component_unbind(c, master, data);
 248 }
 249 EXPORT_SYMBOL_GPL(component_unbind_all);
 250
 251 static int component_bind(struct component *component, struct master *master,
 252         void *data)
 253 {
 254         int ret;
 255
 256         /*
 257          * Each component initialises inside its own devres group.
 258          * This allows us to roll-back a failed component without
 259          * affecting anything else.
 260          */
 261         if (!devres_open_group(master->dev, NULL, GFP_KERNEL))
 262                 return -ENOMEM;
 263
 264         /*
 265          * Also open a group for the device itself: this allows us
 266          * to release the resources claimed against the sub-device
 267          * at the appropriate moment.
 268          */
 269         if (!devres_open_group(component->dev, component, GFP_KERNEL)) {
 270                 devres_release_group(master->dev, NULL);
 271                 return -ENOMEM;
 272         }
 273
 274         dev_dbg(master->dev, "binding %s (ops %ps)\n",
 275                 dev_name(component->dev), component->ops);
 276
 277         ret = component->ops->bind(component->dev, master->dev, data);
 278         if (!ret) {
 279                 component->bound = true;
 280
 281                 /*
 282                  * Close the component device's group so that resources
 283                  * allocated in the binding are encapsulated for removal
 284                  * at unbind.  Remove the group on the DRM device as we
 285                  * can clean those resources up independently.
 286                  */
 287                 devres_close_group(component->dev, NULL);
 288                 devres_remove_group(master->dev, NULL);
 289
 290                 dev_info(master->dev, "bound %s (ops %ps)\n",
 291                          dev_name(component->dev), component->ops);
 292         } else {
 293                 devres_release_group(component->dev, NULL);
 294                 devres_release_group(master->dev, NULL);
 295
 296                 dev_err(master->dev, "failed to bind %s (ops %ps): %d\n",
 297                         dev_name(component->dev), component->ops, ret);
 298         }
 299
 300         return ret;
 301 }
 302
 303 int component_bind_all(struct device *master_dev, void *data)
 304 {
 305         struct master *master;
 306         struct component *c;
 307         int ret = 0;
 308
 309         WARN_ON(!mutex_is_locked(&component_mutex));
 310
 311         master = __master_find(master_dev, NULL);
 312         if (!master)
 313                 return -EINVAL;
 314
 315         list_for_each_entry(c, &master->components, master_node) {
 316                 ret = component_bind(c, master, data);
 317                 if (ret)
 318                         break;
 319         }
 320
 321         if (ret != 0) {
 322                 list_for_each_entry_continue_reverse(c, &master->components,
 323                                                      master_node)
 324                         component_unbind(c, master, data);
 325         }
 326
 327         return ret;
 328 }
 329 EXPORT_SYMBOL_GPL(component_bind_all);
 330
 331 int component_add(struct device *dev, const struct component_ops *ops)
 332 {
 333         struct component *component;
 334         int ret;
 335
 336         component = kzalloc(sizeof(*component), GFP_KERNEL);
 337         if (!component)
 338                 return -ENOMEM;
 339
 340         component->ops = ops;
 341         component->dev = dev;
 342
 343         dev_dbg(dev, "adding component (ops %ps)\n", ops);
 344
 345         mutex_lock(&component_mutex);
 346         list_add_tail(&component->node, &component_list);
 347
 348         ret = try_to_bring_up_masters(component);
 349         if (ret < 0) {
 350                 list_del(&component->node);
 351
 352                 kfree(component);
 353         }
 354         mutex_unlock(&component_mutex);
 355
 356         return ret < 0 ? ret : 0;
 357 }
 358 EXPORT_SYMBOL_GPL(component_add);
 359
 360 void component_del(struct device *dev, const struct component_ops *ops)
 361 {
 362         struct component *c, *component = NULL;
 363
 364         mutex_lock(&component_mutex);
 365         list_for_each_entry(c, &component_list, node)
 366                 if (c->dev == dev && c->ops == ops) {
 367                         list_del(&c->node);
 368                         component = c;
 369                         break;
 370                 }
 371
 372         if (component && component->master)
 373                 take_down_master(component->master);
 374
 375         mutex_unlock(&component_mutex);
 376
 377         WARN_ON(!component);
 378         kfree(component);
 379 }
 380 EXPORT_SYMBOL_GPL(component_del);
 381
 382 MODULE_LICENSE("GPL v2");