summaryrefslogtreecommitdiff
path: root/drivers/video/backlight/backlight.c
blob: cac3e35d763087e9f4e1167df921f6ad1ed25b94 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Backlight Lowlevel Control Abstraction
 *
 * Copyright (C) 2003,2004 Hewlett-Packard Company
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/backlight.h>
#include <linux/notifier.h>
#include <linux/ctype.h>
#include <linux/err.h>
#include <linux/fb.h>
#include <linux/slab.h>

#ifdef CONFIG_PMAC_BACKLIGHT
#include <asm/backlight.h>
#endif

static struct list_head backlight_dev_list;
static struct mutex backlight_dev_list_mutex;
static struct blocking_notifier_head backlight_notifier;

static const char *const backlight_types[] = {
	[BACKLIGHT_RAW] = "raw",
	[BACKLIGHT_PLATFORM] = "platform",
	[BACKLIGHT_FIRMWARE] = "firmware",
};

static const char *const backlight_scale_types[] = {
	[BACKLIGHT_SCALE_UNKNOWN]	= "unknown",
	[BACKLIGHT_SCALE_LINEAR]	= "linear",
	[BACKLIGHT_SCALE_NON_LINEAR]	= "non-linear",
};

#if defined(CONFIG_FB) || (defined(CONFIG_FB_MODULE) && \
			   defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
/* This callback gets called when something important happens inside a
 * framebuffer driver. We're looking if that important event is blanking,
 * and if it is and necessary, we're switching backlight power as well ...
 */
static int fb_notifier_callback(struct notifier_block *self,
				unsigned long event, void *data)
{
	struct backlight_device *bd;
	struct fb_event *evdata = data;
	int node = evdata->info->node;
	int fb_blank = 0;

	/* If we aren't interested in this event, skip it immediately ... */
	if (event != FB_EVENT_BLANK)
		return 0;

	bd = container_of(self, struct backlight_device, fb_notif);
	mutex_lock(&bd->ops_lock);
	if (bd->ops)
		if (!bd->ops->check_fb ||
		    bd->ops->check_fb(bd, evdata->info)) {
			fb_blank = *(int *)evdata->data;
			if (fb_blank == FB_BLANK_UNBLANK &&
			    !bd->fb_bl_on[node]) {
				bd->fb_bl_on[node] = true;
				if (!bd->use_count++) {
					bd->props.state &= ~BL_CORE_FBBLANK;
					bd->props.fb_blank = FB_BLANK_UNBLANK;
					backlight_update_status(bd);
				}
			} else if (fb_blank != FB_BLANK_UNBLANK &&
				   bd->fb_bl_on[node]) {
				bd->fb_bl_on[node] = false;
				if (!(--bd->use_count)) {
					bd->props.state |= BL_CORE_FBBLANK;
					bd->props.fb_blank = fb_blank;
					backlight_update_status(bd);
				}
			}
		}
	mutex_unlock(&bd->ops_lock);
	return 0;
}

static int backlight_register_fb(struct backlight_device *bd)
{
	memset(&bd->fb_notif, 0, sizeof(bd->fb_notif));
	bd->fb_notif.notifier_call = fb_notifier_callback;

	return fb_register_client(&bd->fb_notif);
}

static void backlight_unregister_fb(struct backlight_device *bd)
{
	fb_unregister_client(&bd->fb_notif);
}
#else
static inline int backlight_register_fb(struct backlight_device *bd)
{
	return 0;
}

static inline void backlight_unregister_fb(struct backlight_device *bd)
{
}
#endif /* CONFIG_FB */

static void backlight_generate_event(struct backlight_device *bd,
				     enum backlight_update_reason reason)
{
	char *envp[2];

	switch (reason) {
	case BACKLIGHT_UPDATE_SYSFS:
		envp[0] = "SOURCE=sysfs";
		break;
	case BACKLIGHT_UPDATE_HOTKEY:
		envp[0] = "SOURCE=hotkey";
		break;
	default:
		envp[0] = "SOURCE=unknown";
		break;
	}
	envp[1] = NULL;
	kobject_uevent_env(&bd->dev.kobj, KOBJ_CHANGE, envp);
	sysfs_notify(&bd->dev.kobj, NULL, "actual_brightness");
}

static ssize_t bl_power_show(struct device *dev, struct device_attribute *attr,
		char *buf)
{
	struct backlight_device *bd = to_backlight_device(dev);

	return sprintf(buf, "%d\n", bd->props.power);
}

static ssize_t bl_power_store(struct device *dev, struct device_attribute *attr,
		const char *buf, size_t count)
{
	int rc;
	struct backlight_device *bd = to_backlight_device(dev);
	unsigned long power, old_power;

	rc = kstrtoul(buf, 0, &power);
	if (rc)
		return rc;

	rc = -ENXIO;
	mutex_lock(&bd->ops_lock);
	if (bd->ops) {
		pr_debug("set power to %lu\n", power);
		if (bd->props.power != power) {
			old_power = bd->props.power;
			bd->props.power = power;
			rc = backlight_update_status(bd);
			if (rc)
				bd->props.power = old_power;
			else
				rc = count;
		} else {
			rc = count;
		}
	}
	mutex_unlock(&bd->ops_lock);

	return rc;
}
static DEVICE_ATTR_RW(bl_power);

static ssize_t brightness_show(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	struct backlight_device *bd = to_backlight_device(dev);

	return sprintf(buf, "%d\n", bd->props.brightness);
}

int backlight_device_set_brightness(struct backlight_device *bd,
				    unsigned long brightness)
{
	int rc = -ENXIO;

	mutex_lock(&bd->ops_lock);
	if (bd->ops) {
		if (brightness > bd->props.max_brightness)
			rc = -EINVAL;
		else {
			pr_debug("set brightness to %lu\n", brightness);
			bd->props.brightness = brightness;
			rc = backlight_update_status(bd);
		}
	}
	mutex_unlock(&bd->ops_lock);

	backlight_generate_event(bd, BACKLIGHT_UPDATE_SYSFS);

	return rc;
}
EXPORT_SYMBOL(backlight_device_set_brightness);

static ssize_t brightness_store(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t count)
{
	int rc;
	struct backlight_device *bd = to_backlight_device(dev);
	unsigned long brightness;

	rc = kstrtoul(buf, 0, &brightness);
	if (rc)
		return rc;

	rc = backlight_device_set_brightness(bd, brightness);

	return rc ? rc : count;
}
static DEVICE_ATTR_RW(brightness);

static ssize_t type_show(struct device *dev, struct device_attribute *attr,
		char *buf)
{
	struct backlight_device *bd = to_backlight_device(dev);

	return sprintf(buf, "%s\n", backlight_types[bd->props.type]);
}
static DEVICE_ATTR_RO(type);

static ssize_t max_brightness_show(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	struct backlight_device *bd = to_backlight_device(dev);

	return sprintf(buf, "%d\n", bd->props.max_brightness);
}
static DEVICE_ATTR_RO(max_brightness);

static ssize_t actual_brightness_show(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	int rc = -ENXIO;
	struct backlight_device *bd = to_backlight_device(dev);

	mutex_lock(&bd->ops_lock);
	if (bd->ops && bd->ops->get_brightness)
		rc = sprintf(buf, "%d\n", bd->ops->get_brightness(bd));
	else
		rc = sprintf(buf, "%d\n", bd->props.brightness);
	mutex_unlock(&bd->ops_lock);

	return rc;
}
static DEVICE_ATTR_RO(actual_brightness);

static ssize_t scale_show(struct device *dev,
		struct device_attribute *attr, char *buf)
{
	struct backlight_device *bd = to_backlight_device(dev);

	if (WARN_ON(bd->props.scale > BACKLIGHT_SCALE_NON_LINEAR))
		return sprintf(buf, "unknown\n");

	return sprintf(buf, "%s\n", backlight_scale_types[bd->props.scale]);
}
static DEVICE_ATTR_RO(scale);

static struct class *backlight_class;

#ifdef CONFIG_PM_SLEEP
static int backlight_suspend(struct device *dev)
{
	struct backlight_device *bd = to_backlight_device(dev);

	mutex_lock(&bd->ops_lock);
	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
		bd->props.state |= BL_CORE_SUSPENDED;
		backlight_update_status(bd);
	}
	mutex_unlock(&bd->ops_lock);

	return 0;
}

static int backlight_resume(struct device *dev)
{
	struct backlight_device *bd = to_backlight_device(dev);

	mutex_lock(&bd->ops_lock);
	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
		bd->props.state &= ~BL_CORE_SUSPENDED;
		backlight_update_status(bd);
	}
	mutex_unlock(&bd->ops_lock);

	return 0;
}
#endif

static SIMPLE_DEV_PM_OPS(backlight_class_dev_pm_ops, backlight_suspend,
			 backlight_resume);

static void bl_device_release(struct device *dev)
{
	struct backlight_device *bd = to_backlight_device(dev);
	kfree(bd);
}

static struct attribute *bl_device_attrs[] = {
	&dev_attr_bl_power.attr,
	&dev_attr_brightness.attr,
	&dev_attr_actual_brightness.attr,
	&dev_attr_max_brightness.attr,
	&dev_attr_scale.attr,
	&dev_attr_type.attr,
	NULL,
};
ATTRIBUTE_GROUPS(bl_device);

/**
 * backlight_force_update - tell the backlight subsystem that hardware state
 *   has changed
 * @bd: the backlight device to update
 *
 * Updates the internal state of the backlight in response to a hardware event,
 * and generate a uevent to notify userspace
 */
void backlight_force_update(struct backlight_device *bd,
			    enum backlight_update_reason reason)
{
	mutex_lock(&bd->ops_lock);
	if (bd->ops && bd->ops->get_brightness)
		bd->props.brightness = bd->ops->get_brightness(bd);
	mutex_unlock(&bd->ops_lock);
	backlight_generate_event(bd, reason);
}
EXPORT_SYMBOL(backlight_force_update);

/**
 * backlight_device_register - create and register a new object of
 *   backlight_device class.
 * @name: the name of the new object(must be the same as the name of the
 *   respective framebuffer device).
 * @parent: a pointer to the parent device
 * @devdata: an optional pointer to be stored for private driver use. The
 *   methods may retrieve it by using bl_get_data(bd).
 * @ops: the backlight operations structure.
 *
 * Creates and registers new backlight device. Returns either an
 * ERR_PTR() or a pointer to the newly allocated device.
 */
struct backlight_device *backlight_device_register(const char *name,
	struct device *parent, void *devdata, const struct backlight_ops *ops,
	const struct backlight_properties *props)
{
	struct backlight_device *new_bd;
	int rc;

	pr_debug("backlight_device_register: name=%s\n", name);

	new_bd = kzalloc(sizeof(struct backlight_device), GFP_KERNEL);
	if (!new_bd)
		return ERR_PTR(-ENOMEM);

	mutex_init(&new_bd->update_lock);
	mutex_init(&new_bd->ops_lock);

	new_bd->dev.class = backlight_class;
	new_bd->dev.parent = parent;
	new_bd->dev.release = bl_device_release;
	dev_set_name(&new_bd->dev, "%s", name);
	dev_set_drvdata(&new_bd->dev, devdata);

	/* Set default properties */
	if (props) {
		memcpy(&new_bd->props, props,
		       sizeof(struct backlight_properties));
		if (props->type <= 0 || props->type >= BACKLIGHT_TYPE_MAX) {
			WARN(1, "%s: invalid backlight type", name);
			new_bd->props.type = BACKLIGHT_RAW;
		}
	} else {
		new_bd->props.type = BACKLIGHT_RAW;
	}

	rc = device_register(&new_bd->dev);
	if (rc) {
		put_device(&new_bd->dev);
		return ERR_PTR(rc);
	}

	rc = backlight_register_fb(new_bd);
	if (rc) {
		device_unregister(&new_bd->dev);
		return ERR_PTR(rc);
	}

	new_bd->ops = ops;

#ifdef CONFIG_PMAC_BACKLIGHT
	mutex_lock(&pmac_backlight_mutex);
	if (!pmac_backlight)
		pmac_backlight = new_bd;
	mutex_unlock(&pmac_backlight_mutex);
#endif

	mutex_lock(&backlight_dev_list_mutex);
	list_add(&new_bd->entry, &backlight_dev_list);
	mutex_unlock(&backlight_dev_list_mutex);

	blocking_notifier_call_chain(&backlight_notifier,
				     BACKLIGHT_REGISTERED, new_bd);

	return new_bd;
}
EXPORT_SYMBOL(backlight_device_register);

struct backlight_device *backlight_device_get_by_type(enum backlight_type type)
{
	bool found = false;
	struct backlight_device *bd;

	mutex_lock(&backlight_dev_list_mutex);
	list_for_each_entry(bd, &backlight_dev_list, entry) {
		if (bd->props.type == type) {
			found = true;
			break;
		}
	}
	mutex_unlock(&backlight_dev_list_mutex);

	return found ? bd : NULL;
}
EXPORT_SYMBOL(backlight_device_get_by_type);

/**
 * backlight_device_unregister - unregisters a backlight device object.
 * @bd: the backlight device object to be unregistered and freed.
 *
 * Unregisters a previously registered via backlight_device_register object.
 */
void backlight_device_unregister(struct backlight_device *bd)
{
	if (!bd)
		return;

	mutex_lock(&backlight_dev_list_mutex);
	list_del(&bd->entry);
	mutex_unlock(&backlight_dev_list_mutex);

#ifdef CONFIG_PMAC_BACKLIGHT
	mutex_lock(&pmac_backlight_mutex);
	if (pmac_backlight == bd)
		pmac_backlight = NULL;
	mutex_unlock(&pmac_backlight_mutex);
#endif

	blocking_notifier_call_chain(&backlight_notifier,
				     BACKLIGHT_UNREGISTERED, bd);

	mutex_lock(&bd->ops_lock);
	bd->ops = NULL;
	mutex_unlock(&bd->ops_lock);

	backlight_unregister_fb(bd);
	device_unregister(&bd->dev);
}
EXPORT_SYMBOL(backlight_device_unregister);

static void devm_backlight_device_release(struct device *dev, void *res)
{
	struct backlight_device *backlight = *(struct backlight_device **)res;

	backlight_device_unregister(backlight);
}

static int devm_backlight_device_match(struct device *dev, void *res,
					void *data)
{
	struct backlight_device **r = res;

	return *r == data;
}

/**
 * backlight_register_notifier - get notified of backlight (un)registration
 * @nb: notifier block with the notifier to call on backlight (un)registration
 *
 * @return 0 on success, otherwise a negative error code
 *
 * Register a notifier to get notified when backlight devices get registered
 * or unregistered.
 */
int backlight_register_notifier(struct notifier_block *nb)
{
	return blocking_notifier_chain_register(&backlight_notifier, nb);
}
EXPORT_SYMBOL(backlight_register_notifier);

/**
 * backlight_unregister_notifier - unregister a backlight notifier
 * @nb: notifier block to unregister
 *
 * @return 0 on success, otherwise a negative error code
 *
 * Register a notifier to get notified when backlight devices get registered
 * or unregistered.
 */
int backlight_unregister_notifier(struct notifier_block *nb)
{
	return blocking_notifier_chain_unregister(&backlight_notifier, nb);
}
EXPORT_SYMBOL(backlight_unregister_notifier);

/**
 * devm_backlight_device_register - resource managed backlight_device_register()
 * @dev: the device to register
 * @name: the name of the device
 * @parent: a pointer to the parent device
 * @devdata: an optional pointer to be stored for private driver use
 * @ops: the backlight operations structure
 * @props: the backlight properties
 *
 * @return a struct backlight on success, or an ERR_PTR on error
 *
 * Managed backlight_device_register(). The backlight_device returned
 * from this function are automatically freed on driver detach.
 * See backlight_device_register() for more information.
 */
struct backlight_device *devm_backlight_device_register(struct device *dev,
	const char *name, struct device *parent, void *devdata,
	const struct backlight_ops *ops,
	const struct backlight_properties *props)
{
	struct backlight_device **ptr, *backlight;

	ptr = devres_alloc(devm_backlight_device_release, sizeof(*ptr),
			GFP_KERNEL);
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	backlight = backlight_device_register(name, parent, devdata, ops,
						props);
	if (!IS_ERR(backlight)) {
		*ptr = backlight;
		devres_add(dev, ptr);
	} else {
		devres_free(ptr);
	}

	return backlight;
}
EXPORT_SYMBOL(devm_backlight_device_register);

/**
 * devm_backlight_device_unregister - resource managed backlight_device_unregister()
 * @dev: the device to unregister
 * @bd: the backlight device to unregister
 *
 * Deallocated a backlight allocated with devm_backlight_device_register().
 * Normally this function will not need to be called and the resource management
 * code will ensure that the resource is freed.
 */
void devm_backlight_device_unregister(struct device *dev,
				struct backlight_device *bd)
{
	int rc;

	rc = devres_release(dev, devm_backlight_device_release,
				devm_backlight_device_match, bd);
	WARN_ON(rc);
}
EXPORT_SYMBOL(devm_backlight_device_unregister);

#ifdef CONFIG_OF
static int of_parent_match(struct device *dev, const void *data)
{
	return dev->parent && dev->parent->of_node == data;
}

/**
 * of_find_backlight_by_node() - find backlight device by device-tree node
 * @node: device-tree node of the backlight device
 *
 * Returns a pointer to the backlight device corresponding to the given DT
 * node or NULL if no such backlight device exists or if the device hasn't
 * been probed yet.
 *
 * This function obtains a reference on the backlight device and it is the
 * caller's responsibility to drop the reference by calling put_device() on
 * the backlight device's .dev field.
 */
struct backlight_device *of_find_backlight_by_node(struct device_node *node)
{
	struct device *dev;

	dev = class_find_device(backlight_class, NULL, node, of_parent_match);

	return dev ? to_backlight_device(dev) : NULL;
}
EXPORT_SYMBOL(of_find_backlight_by_node);
#endif

/**
 * of_find_backlight - Get backlight device
 * @dev: Device
 *
 * This function looks for a property named 'backlight' on the DT node
 * connected to @dev and looks up the backlight device.
 *
 * Call backlight_put() to drop the reference on the backlight device.
 *
 * Returns:
 * A pointer to the backlight device if found.
 * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
 * device is found.
 * NULL if there's no backlight property.
 */
struct backlight_device *of_find_backlight(struct device *dev)
{
	struct backlight_device *bd = NULL;
	struct device_node *np;

	if (!dev)
		return NULL;

	if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
		np = of_parse_phandle(dev->of_node, "backlight", 0);
		if (np) {
			bd = of_find_backlight_by_node(np);
			of_node_put(np);
			if (!bd)
				return ERR_PTR(-EPROBE_DEFER);
			/*
			 * Note: gpio_backlight uses brightness as
			 * power state during probe
			 */
			if (!bd->props.brightness)
				bd->props.brightness = bd->props.max_brightness;
		}
	}

	return bd;
}
EXPORT_SYMBOL(of_find_backlight);

static void devm_backlight_release(void *data)
{
	backlight_put(data);
}

/**
 * devm_of_find_backlight - Resource-managed of_find_backlight()
 * @dev: Device
 *
 * Device managed version of of_find_backlight().
 * The reference on the backlight device is automatically
 * dropped on driver detach.
 */
struct backlight_device *devm_of_find_backlight(struct device *dev)
{
	struct backlight_device *bd;
	int ret;

	bd = of_find_backlight(dev);
	if (IS_ERR_OR_NULL(bd))
		return bd;
	ret = devm_add_action(dev, devm_backlight_release, bd);
	if (ret) {
		backlight_put(bd);
		return ERR_PTR(ret);
	}
	return bd;
}
EXPORT_SYMBOL(devm_of_find_backlight);

static void __exit backlight_class_exit(void)
{
	class_destroy(backlight_class);
}

static int __init backlight_class_init(void)
{
	backlight_class = class_create(THIS_MODULE, "backlight");
	if (IS_ERR(backlight_class)) {
		pr_warn("Unable to create backlight class; errno = %ld\n",
			PTR_ERR(backlight_class));
		return PTR_ERR(backlight_class);
	}

	backlight_class->dev_groups = bl_device_groups;
	backlight_class->pm = &backlight_class_dev_pm_ops;
	INIT_LIST_HEAD(&backlight_dev_list);
	mutex_init(&backlight_dev_list_mutex);
	BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);

	return 0;
}

/*
 * if this is compiled into the kernel, we need to ensure that the
 * class is registered before users of the class try to register lcd's
 */
postcore_initcall(backlight_class_init);
module_exit(backlight_class_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jamey Hicks <jamey.hicks@hp.com>, Andrew Zabolotny <zap@homelink.ru>");
MODULE_DESCRIPTION("Backlight Lowlevel Control Abstraction");