root/drivers/video/backlight/backlight.c

DEFINITIONS

1. fb_notifier_callback
2. backlight_register_fb
3. backlight_unregister_fb
4. backlight_register_fb
5. backlight_unregister_fb
6. backlight_generate_event
7. bl_power_show
8. bl_power_store
9. brightness_show
10. backlight_device_set_brightness
11. brightness_store
12. type_show
13. max_brightness_show
14. actual_brightness_show
15. scale_show
16. backlight_suspend
17. backlight_resume
18. bl_device_release
19. backlight_force_update
20. backlight_device_register
21. backlight_device_get_by_type
22. backlight_device_unregister
23. devm_backlight_device_release
24. devm_backlight_device_match
25. backlight_register_notifier
26. backlight_unregister_notifier
27. devm_backlight_device_register
28. devm_backlight_device_unregister
29. of_parent_match
30. of_find_backlight_by_node
31. of_find_backlight
32. devm_backlight_release
33. devm_of_find_backlight
34. backlight_class_exit
35. backlight_class_init

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Backlight Lowlevel Control Abstraction
   4  *
   5  * Copyright (C) 2003,2004 Hewlett-Packard Company
   6  *
   7  */
   8 
   9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10 
  11 #include <linux/module.h>
  12 #include <linux/init.h>
  13 #include <linux/device.h>
  14 #include <linux/backlight.h>
  15 #include <linux/notifier.h>
  16 #include <linux/ctype.h>
  17 #include <linux/err.h>
  18 #include <linux/fb.h>
  19 #include <linux/slab.h>
  20 
  21 #ifdef CONFIG_PMAC_BACKLIGHT
  22 #include <asm/backlight.h>
  23 #endif
  24 
  25 static struct list_head backlight_dev_list;
  26 static struct mutex backlight_dev_list_mutex;
  27 static struct blocking_notifier_head backlight_notifier;
  28 
  29 static const char *const backlight_types[] = {
  30         [BACKLIGHT_RAW] = "raw",
  31         [BACKLIGHT_PLATFORM] = "platform",
  32         [BACKLIGHT_FIRMWARE] = "firmware",
  33 };
  34 
  35 static const char *const backlight_scale_types[] = {
  36         [BACKLIGHT_SCALE_UNKNOWN]       = "unknown",
  37         [BACKLIGHT_SCALE_LINEAR]        = "linear",
  38         [BACKLIGHT_SCALE_NON_LINEAR]    = "non-linear",
  39 };
  40 
  41 #if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
  42                            defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
  43 /* This callback gets called when something important happens inside a
  44  * framebuffer driver. We're looking if that important event is blanking,
  45  * and if it is and necessary, we're switching backlight power as well ...
  46  */
  47 static int fb_notifier_callback(struct notifier_block *self,
  48                                 unsigned long event, void *data)
  49 {
  50         struct backlight_device *bd;
  51         struct fb_event *evdata = data;
  52         int node = evdata->info->node;
  53         int fb_blank = 0;
  54 
  55         /* If we aren't interested in this event, skip it immediately ... */
  56         if (event != FB_EVENT_BLANK)
  57                 return 0;
  58 
  59         bd = container_of(self, struct backlight_device, fb_notif);
  60         mutex_lock(&bd->ops_lock);
  61         if (bd->ops)
  62                 if (!bd->ops->check_fb ||
  63                     bd->ops->check_fb(bd, evdata->info)) {
  64                         fb_blank = *(int *)evdata->data;
  65                         if (fb_blank == FB_BLANK_UNBLANK &&
  66                             !bd->fb_bl_on[node]) {
  67                                 bd->fb_bl_on[node] = true;
  68                                 if (!bd->use_count++) {
  69                                         bd->props.state &= ~BL_CORE_FBBLANK;
  70                                         bd->props.fb_blank = FB_BLANK_UNBLANK;
  71                                         backlight_update_status(bd);
  72                                 }
  73                         } else if (fb_blank != FB_BLANK_UNBLANK &&
  74                                    bd->fb_bl_on[node]) {
  75                                 bd->fb_bl_on[node] = false;
  76                                 if (!(--bd->use_count)) {
  77                                         bd->props.state |= BL_CORE_FBBLANK;
  78                                         bd->props.fb_blank = fb_blank;
  79                                         backlight_update_status(bd);
  80                                 }
  81                         }
  82                 }
  83         mutex_unlock(&bd->ops_lock);
  84         return 0;
  85 }
  86 
  87 static int backlight_register_fb(struct backlight_device *bd)
  88 {
  89         memset(&bd->fb_notif, 0, sizeof(bd->fb_notif));
  90         bd->fb_notif.notifier_call = fb_notifier_callback;
  91 
  92         return fb_register_client(&bd->fb_notif);
  93 }
  94 
  95 static void backlight_unregister_fb(struct backlight_device *bd)
  96 {
  97         fb_unregister_client(&bd->fb_notif);
  98 }
  99 #else
 100 static inline int backlight_register_fb(struct backlight_device *bd)
 101 {
 102         return 0;
 103 }
 104 
 105 static inline void backlight_unregister_fb(struct backlight_device *bd)
 106 {
 107 }
 108 #endif /* CONFIG_FB */
 109 
 110 static void backlight_generate_event(struct backlight_device *bd,
 111                                      enum backlight_update_reason reason)
 112 {
 113         char *envp[2];
 114 
 115         switch (reason) {
 116         case BACKLIGHT_UPDATE_SYSFS:
 117                 envp[0] = "SOURCE=sysfs";
 118                 break;
 119         case BACKLIGHT_UPDATE_HOTKEY:
 120                 envp[0] = "SOURCE=hotkey";
 121                 break;
 122         default:
 123                 envp[0] = "SOURCE=unknown";
 124                 break;
 125         }
 126         envp[1] = NULL;
 127         kobject_uevent_env(&bd->dev.kobj, KOBJ_CHANGE, envp);
 128         sysfs_notify(&bd->dev.kobj, NULL, "actual_brightness");
 129 }
 130 
 131 static ssize_t bl_power_show(struct device *dev, struct device_attribute *attr,
 132                 char *buf)
 133 {
 134         struct backlight_device *bd = to_backlight_device(dev);
 135 
 136         return sprintf(buf, "%d\n", bd->props.power);
 137 }
 138 
 139 static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr,
 140                 const char *buf, size_t count)
 141 {
 142         int rc;
 143         struct backlight_device *bd = to_backlight_device(dev);
 144         unsigned long power, old_power;
 145 
 146         rc = kstrtoul(buf, 0, &power);
 147         if (rc)
 148                 return rc;
 149 
 150         rc = -ENXIO;
 151         mutex_lock(&bd->ops_lock);
 152         if (bd->ops) {
 153                 pr_debug("set power to %lu\n", power);
 154                 if (bd->props.power != power) {
 155                         old_power = bd->props.power;
 156                         bd->props.power = power;
 157                         rc = backlight_update_status(bd);
 158                         if (rc)
 159                                 bd->props.power = old_power;
 160                         else
 161                                 rc = count;
 162                 } else {
 163                         rc = count;
 164                 }
 165         }
 166         mutex_unlock(&bd->ops_lock);
 167 
 168         return rc;
 169 }
 170 static DEVICE_ATTR_RW(bl_power);
 171 
 172 static ssize_t brightness_show(struct device *dev,
 173                 struct device_attribute *attr, char *buf)
 174 {
 175         struct backlight_device *bd = to_backlight_device(dev);
 176 
 177         return sprintf(buf, "%d\n", bd->props.brightness);
 178 }
 179 
 180 int backlight_device_set_brightness(struct backlight_device *bd,
 181                                     unsigned long brightness)
 182 {
 183         int rc = -ENXIO;
 184 
 185         mutex_lock(&bd->ops_lock);
 186         if (bd->ops) {
 187                 if (brightness > bd->props.max_brightness)
 188                         rc = -EINVAL;
 189                 else {
 190                         pr_debug("set brightness to %lu\n", brightness);
 191                         bd->props.brightness = brightness;
 192                         rc = backlight_update_status(bd);
 193                 }
 194         }
 195         mutex_unlock(&bd->ops_lock);
 196 
 197         backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);
 198 
 199         return rc;
 200 }
 201 EXPORT_SYMBOL(backlight_device_set_brightness);
 202 
 203 static ssize_t brightness_store(struct device *dev,
 204                 struct device_attribute *attr, const char *buf, size_t count)
 205 {
 206         int rc;
 207         struct backlight_device *bd = to_backlight_device(dev);
 208         unsigned long brightness;
 209 
 210         rc = kstrtoul(buf, 0, &brightness);
 211         if (rc)
 212                 return rc;
 213 
 214         rc = backlight_device_set_brightness(bd, brightness);
 215 
 216         return rc ? rc : count;
 217 }
 218 static DEVICE_ATTR_RW(brightness);
 219 
 220 static ssize_t type_show(struct device *dev, struct device_attribute *attr,
 221                 char *buf)
 222 {
 223         struct backlight_device *bd = to_backlight_device(dev);
 224 
 225         return sprintf(buf, "%s\n", backlight_types[bd->props.type]);
 226 }
 227 static DEVICE_ATTR_RO(type);
 228 
 229 static ssize_t max_brightness_show(struct device *dev,
 230                 struct device_attribute *attr, char *buf)
 231 {
 232         struct backlight_device *bd = to_backlight_device(dev);
 233 
 234         return sprintf(buf, "%d\n", bd->props.max_brightness);
 235 }
 236 static DEVICE_ATTR_RO(max_brightness);
 237 
 238 static ssize_t actual_brightness_show(struct device *dev,
 239                 struct device_attribute *attr, char *buf)
 240 {
 241         int rc = -ENXIO;
 242         struct backlight_device *bd = to_backlight_device(dev);
 243 
 244         mutex_lock(&bd->ops_lock);
 245         if (bd->ops && bd->ops->get_brightness)
 246                 rc = sprintf(buf, "%d\n", bd->ops->get_brightness(bd));
 247         else
 248                 rc = sprintf(buf, "%d\n", bd->props.brightness);
 249         mutex_unlock(&bd->ops_lock);
 250 
 251         return rc;
 252 }
 253 static DEVICE_ATTR_RO(actual_brightness);
 254 
 255 static ssize_t scale_show(struct device *dev,
 256                 struct device_attribute *attr, char *buf)
 257 {
 258         struct backlight_device *bd = to_backlight_device(dev);
 259 
 260         if (WARN_ON(bd->props.scale > BACKLIGHT_SCALE_NON_LINEAR))
 261                 return sprintf(buf, "unknown\n");
 262 
 263         return sprintf(buf, "%s\n", backlight_scale_types[bd->props.scale]);
 264 }
 265 static DEVICE_ATTR_RO(scale);
 266 
 267 static struct class *backlight_class;
 268 
 269 #ifdef CONFIG_PM_SLEEP
 270 static int backlight_suspend(struct device *dev)
 271 {
 272         struct backlight_device *bd = to_backlight_device(dev);
 273 
 274         mutex_lock(&bd->ops_lock);
 275         if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
 276                 bd->props.state |= BL_CORE_SUSPENDED;
 277                 backlight_update_status(bd);
 278         }
 279         mutex_unlock(&bd->ops_lock);
 280 
 281         return 0;
 282 }
 283 
 284 static int backlight_resume(struct device *dev)
 285 {
 286         struct backlight_device *bd = to_backlight_device(dev);
 287 
 288         mutex_lock(&bd->ops_lock);
 289         if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
 290                 bd->props.state &= ~BL_CORE_SUSPENDED;
 291                 backlight_update_status(bd);
 292         }
 293         mutex_unlock(&bd->ops_lock);
 294 
 295         return 0;
 296 }
 297 #endif
 298 
 299 static SIMPLE_DEV_PM_OPS(backlight_class_dev_pm_ops, backlight_suspend,
 300                          backlight_resume);
 301 
 302 static void bl_device_release(struct device *dev)
 303 {
 304         struct backlight_device *bd = to_backlight_device(dev);
 305         kfree(bd);
 306 }
 307 
 308 static struct attribute *bl_device_attrs[] = {
 309         &dev_attr_bl_power.attr,
 310         &dev_attr_brightness.attr,
 311         &dev_attr_actual_brightness.attr,
 312         &dev_attr_max_brightness.attr,
 313         &dev_attr_scale.attr,
 314         &dev_attr_type.attr,
 315         NULL,
 316 };
 317 ATTRIBUTE_GROUPS(bl_device);
 318 
 319 /**
 320  * backlight_force_update - tell the backlight subsystem that hardware state
 321  *   has changed
 322  * @bd: the backlight device to update
 323  *
 324  * Updates the internal state of the backlight in response to a hardware event,
 325  * and generate a uevent to notify userspace
 326  */
 327 void backlight_force_update(struct backlight_device *bd,
 328                             enum backlight_update_reason reason)
 329 {
 330         mutex_lock(&bd->ops_lock);
 331         if (bd->ops && bd->ops->get_brightness)
 332                 bd->props.brightness = bd->ops->get_brightness(bd);
 333         mutex_unlock(&bd->ops_lock);
 334         backlight_generate_event(bd, reason);
 335 }
 336 EXPORT_SYMBOL(backlight_force_update);
 337 
 338 /**
 339  * backlight_device_register - create and register a new object of
 340  *   backlight_device class.
 341  * @name: the name of the new object(must be the same as the name of the
 342  *   respective framebuffer device).
 343  * @parent: a pointer to the parent device
 344  * @devdata: an optional pointer to be stored for private driver use. The
 345  *   methods may retrieve it by using bl_get_data(bd).
 346  * @ops: the backlight operations structure.
 347  *
 348  * Creates and registers new backlight device. Returns either an
 349  * ERR_PTR() or a pointer to the newly allocated device.
 350  */
 351 struct backlight_device *backlight_device_register(const char *name,
 352         struct device *parent, void *devdata, const struct backlight_ops *ops,
 353         const struct backlight_properties *props)
 354 {
 355         struct backlight_device *new_bd;
 356         int rc;
 357 
 358         pr_debug("backlight_device_register: name=%s\n", name);
 359 
 360         new_bd = kzalloc(sizeof(struct backlight_device), GFP_KERNEL);
 361         if (!new_bd)
 362                 return ERR_PTR(-ENOMEM);
 363 
 364         mutex_init(&new_bd->update_lock);
 365         mutex_init(&new_bd->ops_lock);
 366 
 367         new_bd->dev.class = backlight_class;
 368         new_bd->dev.parent = parent;
 369         new_bd->dev.release = bl_device_release;
 370         dev_set_name(&new_bd->dev, "%s", name);
 371         dev_set_drvdata(&new_bd->dev, devdata);
 372 
 373         /* Set default properties */
 374         if (props) {
 375                 memcpy(&new_bd->props, props,
 376                        sizeof(struct backlight_properties));
 377                 if (props->type <= 0 || props->type >= BACKLIGHT_TYPE_MAX) {
 378                         WARN(1, "%s: invalid backlight type", name);
 379                         new_bd->props.type = BACKLIGHT_RAW;
 380                 }
 381         } else {
 382                 new_bd->props.type = BACKLIGHT_RAW;
 383         }
 384 
 385         rc = device_register(&new_bd->dev);
 386         if (rc) {
 387                 put_device(&new_bd->dev);
 388                 return ERR_PTR(rc);
 389         }
 390 
 391         rc = backlight_register_fb(new_bd);
 392         if (rc) {
 393                 device_unregister(&new_bd->dev);
 394                 return ERR_PTR(rc);
 395         }
 396 
 397         new_bd->ops = ops;
 398 
 399 #ifdef CONFIG_PMAC_BACKLIGHT
 400         mutex_lock(&pmac_backlight_mutex);
 401         if (!pmac_backlight)
 402                 pmac_backlight = new_bd;
 403         mutex_unlock(&pmac_backlight_mutex);
 404 #endif
 405 
 406         mutex_lock(&backlight_dev_list_mutex);
 407         list_add(&new_bd->entry, &backlight_dev_list);
 408         mutex_unlock(&backlight_dev_list_mutex);
 409 
 410         blocking_notifier_call_chain(&backlight_notifier,
 411                                      BACKLIGHT_REGISTERED, new_bd);
 412 
 413         return new_bd;
 414 }
 415 EXPORT_SYMBOL(backlight_device_register);
 416 
 417 struct backlight_device *backlight_device_get_by_type(enum backlight_type type)
 418 {
 419         bool found = false;
 420         struct backlight_device *bd;
 421 
 422         mutex_lock(&backlight_dev_list_mutex);
 423         list_for_each_entry(bd, &backlight_dev_list, entry) {
 424                 if (bd->props.type == type) {
 425                         found = true;
 426                         break;
 427                 }
 428         }
 429         mutex_unlock(&backlight_dev_list_mutex);
 430 
 431         return found ? bd : NULL;
 432 }
 433 EXPORT_SYMBOL(backlight_device_get_by_type);
 434 
 435 /**
 436  * backlight_device_unregister - unregisters a backlight device object.
 437  * @bd: the backlight device object to be unregistered and freed.
 438  *
 439  * Unregisters a previously registered via backlight_device_register object.
 440  */
 441 void backlight_device_unregister(struct backlight_device *bd)
 442 {
 443         if (!bd)
 444                 return;
 445 
 446         mutex_lock(&backlight_dev_list_mutex);
 447         list_del(&bd->entry);
 448         mutex_unlock(&backlight_dev_list_mutex);
 449 
 450 #ifdef CONFIG_PMAC_BACKLIGHT
 451         mutex_lock(&pmac_backlight_mutex);
 452         if (pmac_backlight == bd)
 453                 pmac_backlight = NULL;
 454         mutex_unlock(&pmac_backlight_mutex);
 455 #endif
 456 
 457         blocking_notifier_call_chain(&backlight_notifier,
 458                                      BACKLIGHT_UNREGISTERED, bd);
 459 
 460         mutex_lock(&bd->ops_lock);
 461         bd->ops = NULL;
 462         mutex_unlock(&bd->ops_lock);
 463 
 464         backlight_unregister_fb(bd);
 465         device_unregister(&bd->dev);
 466 }
 467 EXPORT_SYMBOL(backlight_device_unregister);
 468 
 469 static void devm_backlight_device_release(struct device *dev, void *res)
 470 {
 471         struct backlight_device *backlight = *(struct backlight_device **)res;
 472 
 473         backlight_device_unregister(backlight);
 474 }
 475 
 476 static int devm_backlight_device_match(struct device *dev, void *res,
 477                                         void *data)
 478 {
 479         struct backlight_device **r = res;
 480 
 481         return *r == data;
 482 }
 483 
 484 /**
 485  * backlight_register_notifier - get notified of backlight (un)registration
 486  * @nb: notifier block with the notifier to call on backlight (un)registration
 487  *
 488  * @return 0 on success, otherwise a negative error code
 489  *
 490  * Register a notifier to get notified when backlight devices get registered
 491  * or unregistered.
 492  */
 493 int backlight_register_notifier(struct notifier_block *nb)
 494 {
 495         return blocking_notifier_chain_register(&backlight_notifier, nb);
 496 }
 497 EXPORT_SYMBOL(backlight_register_notifier);
 498 
 499 /**
 500  * backlight_unregister_notifier - unregister a backlight notifier
 501  * @nb: notifier block to unregister
 502  *
 503  * @return 0 on success, otherwise a negative error code
 504  *
 505  * Register a notifier to get notified when backlight devices get registered
 506  * or unregistered.
 507  */
 508 int backlight_unregister_notifier(struct notifier_block *nb)
 509 {
 510         return blocking_notifier_chain_unregister(&backlight_notifier, nb);
 511 }
 512 EXPORT_SYMBOL(backlight_unregister_notifier);
 513 
 514 /**
 515  * devm_backlight_device_register - resource managed backlight_device_register()
 516  * @dev: the device to register
 517  * @name: the name of the device
 518  * @parent: a pointer to the parent device
 519  * @devdata: an optional pointer to be stored for private driver use
 520  * @ops: the backlight operations structure
 521  * @props: the backlight properties
 522  *
 523  * @return a struct backlight on success, or an ERR_PTR on error
 524  *
 525  * Managed backlight_device_register(). The backlight_device returned
 526  * from this function are automatically freed on driver detach.
 527  * See backlight_device_register() for more information.
 528  */
 529 struct backlight_device *devm_backlight_device_register(struct device *dev,
 530         const char *name, struct device *parent, void *devdata,
 531         const struct backlight_ops *ops,
 532         const struct backlight_properties *props)
 533 {
 534         struct backlight_device **ptr, *backlight;
 535 
 536         ptr = devres_alloc(devm_backlight_device_release, sizeof(*ptr),
 537                         GFP_KERNEL);
 538         if (!ptr)
 539                 return ERR_PTR(-ENOMEM);
 540 
 541         backlight = backlight_device_register(name, parent, devdata, ops,
 542                                                 props);
 543         if (!IS_ERR(backlight)) {
 544                 *ptr = backlight;
 545                 devres_add(dev, ptr);
 546         } else {
 547                 devres_free(ptr);
 548         }
 549 
 550         return backlight;
 551 }
 552 EXPORT_SYMBOL(devm_backlight_device_register);
 553 
 554 /**
 555  * devm_backlight_device_unregister - resource managed backlight_device_unregister()
 556  * @dev: the device to unregister
 557  * @bd: the backlight device to unregister
 558  *
 559  * Deallocated a backlight allocated with devm_backlight_device_register().
 560  * Normally this function will not need to be called and the resource management
 561  * code will ensure that the resource is freed.
 562  */
 563 void devm_backlight_device_unregister(struct device *dev,
 564                                 struct backlight_device *bd)
 565 {
 566         int rc;
 567 
 568         rc = devres_release(dev, devm_backlight_device_release,
 569                                 devm_backlight_device_match, bd);
 570         WARN_ON(rc);
 571 }
 572 EXPORT_SYMBOL(devm_backlight_device_unregister);
 573 
 574 #ifdef CONFIG_OF
 575 static int of_parent_match(struct device *dev, const void *data)
 576 {
 577         return dev->parent && dev->parent->of_node == data;
 578 }
 579 
 580 /**
 581  * of_find_backlight_by_node() - find backlight device by device-tree node
 582  * @node: device-tree node of the backlight device
 583  *
 584  * Returns a pointer to the backlight device corresponding to the given DT
 585  * node or NULL if no such backlight device exists or if the device hasn't
 586  * been probed yet.
 587  *
 588  * This function obtains a reference on the backlight device and it is the
 589  * caller's responsibility to drop the reference by calling put_device() on
 590  * the backlight device's .dev field.
 591  */
 592 struct backlight_device *of_find_backlight_by_node(struct device_node *node)
 593 {
 594         struct device *dev;
 595 
 596         dev = class_find_device(backlight_class, NULL, node, of_parent_match);
 597 
 598         return dev ? to_backlight_device(dev) : NULL;
 599 }
 600 EXPORT_SYMBOL(of_find_backlight_by_node);
 601 #endif
 602 
 603 /**
 604  * of_find_backlight - Get backlight device
 605  * @dev: Device
 606  *
 607  * This function looks for a property named 'backlight' on the DT node
 608  * connected to @dev and looks up the backlight device.
 609  *
 610  * Call backlight_put() to drop the reference on the backlight device.
 611  *
 612  * Returns:
 613  * A pointer to the backlight device if found.
 614  * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
 615  * device is found.
 616  * NULL if there's no backlight property.
 617  */
 618 struct backlight_device *of_find_backlight(struct device *dev)
 619 {
 620         struct backlight_device *bd = NULL;
 621         struct device_node *np;
 622 
 623         if (!dev)
 624                 return NULL;
 625 
 626         if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
 627                 np = of_parse_phandle(dev->of_node, "backlight", 0);
 628                 if (np) {
 629                         bd = of_find_backlight_by_node(np);
 630                         of_node_put(np);
 631                         if (!bd)
 632                                 return ERR_PTR(-EPROBE_DEFER);
 633                         /*
 634                          * Note: gpio_backlight uses brightness as
 635                          * power state during probe
 636                          */
 637                         if (!bd->props.brightness)
 638                                 bd->props.brightness = bd->props.max_brightness;
 639                 }
 640         }
 641 
 642         return bd;
 643 }
 644 EXPORT_SYMBOL(of_find_backlight);
 645 
 646 static void devm_backlight_release(void *data)
 647 {
 648         backlight_put(data);
 649 }
 650 
 651 /**
 652  * devm_of_find_backlight - Resource-managed of_find_backlight()
 653  * @dev: Device
 654  *
 655  * Device managed version of of_find_backlight().
 656  * The reference on the backlight device is automatically
 657  * dropped on driver detach.
 658  */
 659 struct backlight_device *devm_of_find_backlight(struct device *dev)
 660 {
 661         struct backlight_device *bd;
 662         int ret;
 663 
 664         bd = of_find_backlight(dev);
 665         if (IS_ERR_OR_NULL(bd))
 666                 return bd;
 667         ret = devm_add_action(dev, devm_backlight_release, bd);
 668         if (ret) {
 669                 backlight_put(bd);
 670                 return ERR_PTR(ret);
 671         }
 672         return bd;
 673 }
 674 EXPORT_SYMBOL(devm_of_find_backlight);
 675 
 676 static void __exit backlight_class_exit(void)
 677 {
 678         class_destroy(backlight_class);
 679 }
 680 
 681 static int __init backlight_class_init(void)
 682 {
 683         backlight_class = class_create(THIS_MODULE, "backlight");
 684         if (IS_ERR(backlight_class)) {
 685                 pr_warn("Unable to create backlight class; errno = %ld\n",
 686                         PTR_ERR(backlight_class));
 687                 return PTR_ERR(backlight_class);
 688         }
 689 
 690         backlight_class->dev_groups = bl_device_groups;
 691         backlight_class->pm = &backlight_class_dev_pm_ops;
 692         INIT_LIST_HEAD(&backlight_dev_list);
 693         mutex_init(&backlight_dev_list_mutex);
 694         BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);
 695 
 696         return 0;
 697 }
 698 
 699 /*
 700  * if this is compiled into the kernel, we need to ensure that the
 701  * class is registered before users of the class try to register lcd's
 702  */
 703 postcore_initcall(backlight_class_init);
 704 module_exit(backlight_class_exit);
 705 
 706 MODULE_LICENSE("GPL");
 707 MODULE_AUTHOR("Jamey Hicks <jamey.hicks@hp.com>, Andrew Zabolotny <zap@homelink.ru>");
 708 MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");