summaryrefslogtreecommitdiff
path: root/drivers/video/backlight/pwm_bl.c
blob: ffcebf6aa76a967a05716a1db8f316295a0c2f66 (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
709
710
711
712
713
714
715
716
717
718
719
720
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Simple PWM based backlight control, board code has to setup
 * 1) pin configuration so PWM waveforms can output
 * 2) platform_data being correctly configured
 */

#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/fb.h>
#include <linux/backlight.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/pwm_backlight.h>
#include <linux/regulator/consumer.h>
#include <linux/slab.h>

struct pwm_bl_data {
	struct pwm_device	*pwm;
	struct device		*dev;
	unsigned int		lth_brightness;
	unsigned int		*levels;
	bool			enabled;
	struct regulator	*power_supply;
	struct gpio_desc	*enable_gpio;
	unsigned int		scale;
	unsigned int		post_pwm_on_delay;
	unsigned int		pwm_off_delay;
	int			(*notify)(struct device *,
					  int brightness);
	void			(*notify_after)(struct device *,
					int brightness);
	int			(*check_fb)(struct device *, struct fb_info *);
	void			(*exit)(struct device *);
};

static void pwm_backlight_power_on(struct pwm_bl_data *pb)
{
	int err;

	if (pb->enabled)
		return;

	if (pb->power_supply) {
		err = regulator_enable(pb->power_supply);
		if (err < 0)
			dev_err(pb->dev, "failed to enable power supply\n");
	}

	if (pb->post_pwm_on_delay)
		msleep(pb->post_pwm_on_delay);

	gpiod_set_value_cansleep(pb->enable_gpio, 1);

	pb->enabled = true;
}

static void pwm_backlight_power_off(struct pwm_bl_data *pb)
{
	if (!pb->enabled)
		return;

	gpiod_set_value_cansleep(pb->enable_gpio, 0);

	if (pb->pwm_off_delay)
		msleep(pb->pwm_off_delay);

	if (pb->power_supply)
		regulator_disable(pb->power_supply);
	pb->enabled = false;
}

static int compute_duty_cycle(struct pwm_bl_data *pb, int brightness, struct pwm_state *state)
{
	unsigned int lth = pb->lth_brightness;
	u64 duty_cycle;

	if (pb->levels)
		duty_cycle = pb->levels[brightness];
	else
		duty_cycle = brightness;

	duty_cycle *= state->period - lth;
	do_div(duty_cycle, pb->scale);

	return duty_cycle + lth;
}

static int pwm_backlight_update_status(struct backlight_device *bl)
{
	struct pwm_bl_data *pb = bl_get_data(bl);
	int brightness = backlight_get_brightness(bl);
	struct pwm_state state;

	if (pb->notify)
		brightness = pb->notify(pb->dev, brightness);

	if (brightness > 0) {
		pwm_get_state(pb->pwm, &state);
		state.duty_cycle = compute_duty_cycle(pb, brightness, &state);
		state.enabled = true;
		pwm_apply_might_sleep(pb->pwm, &state);

		pwm_backlight_power_on(pb);
	} else {
		pwm_backlight_power_off(pb);

		pwm_get_state(pb->pwm, &state);
		state.duty_cycle = 0;
		/*
		 * We cannot assume a disabled PWM to drive its output to the
		 * inactive state. If we have an enable GPIO and/or a regulator
		 * we assume that this isn't relevant and we can disable the PWM
		 * to save power. If however there is neither an enable GPIO nor
		 * a regulator keep the PWM on be sure to get a constant
		 * inactive output.
		 */
		state.enabled = !pb->power_supply && !pb->enable_gpio;
		pwm_apply_might_sleep(pb->pwm, &state);
	}

	if (pb->notify_after)
		pb->notify_after(pb->dev, brightness);

	return 0;
}

static int pwm_backlight_check_fb(struct backlight_device *bl,
				  struct fb_info *info)
{
	struct pwm_bl_data *pb = bl_get_data(bl);

	return !pb->check_fb || pb->check_fb(pb->dev, info);
}

static const struct backlight_ops pwm_backlight_ops = {
	.update_status	= pwm_backlight_update_status,
	.check_fb	= pwm_backlight_check_fb,
};

#ifdef CONFIG_OF
#define PWM_LUMINANCE_SHIFT	16
#define PWM_LUMINANCE_SCALE	(1 << PWM_LUMINANCE_SHIFT) /* luminance scale */

/*
 * CIE lightness to PWM conversion.
 *
 * The CIE 1931 lightness formula is what actually describes how we perceive
 * light:
 *          Y = (L* / 903.3)           if L* ≤ 8
 *          Y = ((L* + 16) / 116)^3    if L* > 8
 *
 * Where Y is the luminance, the amount of light coming out of the screen, and
 * is a number between 0.0 and 1.0; and L* is the lightness, how bright a human
 * perceives the screen to be, and is a number between 0 and 100.
 *
 * The following function does the fixed point maths needed to implement the
 * above formula.
 */
static u64 cie1931(unsigned int lightness)
{
	u64 retval;

	/*
	 * @lightness is given as a number between 0 and 1, expressed
	 * as a fixed-point number in scale
	 * PWM_LUMINANCE_SCALE. Convert to a percentage, still
	 * expressed as a fixed-point number, so the above formulas
	 * can be applied.
	 */
	lightness *= 100;
	if (lightness <= (8 * PWM_LUMINANCE_SCALE)) {
		retval = DIV_ROUND_CLOSEST(lightness * 10, 9033);
	} else {
		retval = (lightness + (16 * PWM_LUMINANCE_SCALE)) / 116;
		retval *= retval * retval;
		retval += 1ULL << (2*PWM_LUMINANCE_SHIFT - 1);
		retval >>= 2*PWM_LUMINANCE_SHIFT;
	}

	return retval;
}

/*
 * Create a default correction table for PWM values to create linear brightness
 * for LED based backlights using the CIE1931 algorithm.
 */
static
int pwm_backlight_brightness_default(struct device *dev,
				     struct platform_pwm_backlight_data *data,
				     unsigned int period)
{
	unsigned int i;
	u64 retval;

	/*
	 * Once we have 4096 levels there's little point going much higher...
	 * neither interactive sliders nor animation benefits from having
	 * more values in the table.
	 */
	data->max_brightness =
		min((int)DIV_ROUND_UP(period, fls(period)), 4096);

	data->levels = devm_kcalloc(dev, data->max_brightness,
				    sizeof(*data->levels), GFP_KERNEL);
	if (!data->levels)
		return -ENOMEM;

	/* Fill the table using the cie1931 algorithm */
	for (i = 0; i < data->max_brightness; i++) {
		retval = cie1931((i * PWM_LUMINANCE_SCALE) /
				 data->max_brightness) * period;
		retval = DIV_ROUND_CLOSEST_ULL(retval, PWM_LUMINANCE_SCALE);
		if (retval > UINT_MAX)
			return -EINVAL;
		data->levels[i] = (unsigned int)retval;
	}

	data->dft_brightness = data->max_brightness / 2;
	data->max_brightness--;

	return 0;
}

static int pwm_backlight_parse_dt(struct device *dev,
				  struct platform_pwm_backlight_data *data)
{
	struct device_node *node = dev->of_node;
	unsigned int num_levels;
	unsigned int num_steps = 0;
	struct property *prop;
	unsigned int *table;
	int length;
	u32 value;
	int ret;

	if (!node)
		return -ENODEV;

	memset(data, 0, sizeof(*data));

	/*
	 * These values are optional and set as 0 by default, the out values
	 * are modified only if a valid u32 value can be decoded.
	 */
	of_property_read_u32(node, "post-pwm-on-delay-ms",
			     &data->post_pwm_on_delay);
	of_property_read_u32(node, "pwm-off-delay-ms", &data->pwm_off_delay);

	/*
	 * Determine the number of brightness levels, if this property is not
	 * set a default table of brightness levels will be used.
	 */
	prop = of_find_property(node, "brightness-levels", &length);
	if (!prop)
		return 0;

	num_levels = length / sizeof(u32);

	/* read brightness levels from DT property */
	if (num_levels > 0) {
		data->levels = devm_kcalloc(dev, num_levels,
					    sizeof(*data->levels), GFP_KERNEL);
		if (!data->levels)
			return -ENOMEM;

		ret = of_property_read_u32_array(node, "brightness-levels",
						 data->levels,
						 num_levels);
		if (ret < 0)
			return ret;

		ret = of_property_read_u32(node, "default-brightness-level",
					   &value);
		if (ret < 0)
			return ret;

		data->dft_brightness = value;

		/*
		 * This property is optional, if is set enables linear
		 * interpolation between each of the values of brightness levels
		 * and creates a new pre-computed table.
		 */
		of_property_read_u32(node, "num-interpolated-steps",
				     &num_steps);

		/*
		 * Make sure that there is at least two entries in the
		 * brightness-levels table, otherwise we can't interpolate
		 * between two points.
		 */
		if (num_steps) {
			unsigned int num_input_levels = num_levels;
			unsigned int i;
			u32 x1, x2, x, dx;
			u32 y1, y2;
			s64 dy;

			if (num_input_levels < 2) {
				dev_err(dev, "can't interpolate\n");
				return -EINVAL;
			}

			/*
			 * Recalculate the number of brightness levels, now
			 * taking in consideration the number of interpolated
			 * steps between two levels.
			 */
			num_levels = (num_input_levels - 1) * num_steps + 1;
			dev_dbg(dev, "new number of brightness levels: %d\n",
				num_levels);

			/*
			 * Create a new table of brightness levels with all the
			 * interpolated steps.
			 */
			table = devm_kcalloc(dev, num_levels, sizeof(*table),
					     GFP_KERNEL);
			if (!table)
				return -ENOMEM;
			/*
			 * Fill the interpolated table[x] = y
			 * by draw lines between each (x1, y1) to (x2, y2).
			 */
			dx = num_steps;
			for (i = 0; i < num_input_levels - 1; i++) {
				x1 = i * dx;
				x2 = x1 + dx;
				y1 = data->levels[i];
				y2 = data->levels[i + 1];
				dy = (s64)y2 - y1;

				for (x = x1; x < x2; x++) {
					table[x] = y1 +
						div_s64(dy * (x - x1), dx);
				}
			}
			/* Fill in the last point, since no line starts here. */
			table[x2] = y2;

			/*
			 * As we use interpolation lets remove current
			 * brightness levels table and replace for the
			 * new interpolated table.
			 */
			devm_kfree(dev, data->levels);
			data->levels = table;
		}

		data->max_brightness = num_levels - 1;
	}

	return 0;
}

static const struct of_device_id pwm_backlight_of_match[] = {
	{ .compatible = "pwm-backlight" },
	{ }
};

MODULE_DEVICE_TABLE(of, pwm_backlight_of_match);
#else
static int pwm_backlight_parse_dt(struct device *dev,
				  struct platform_pwm_backlight_data *data)
{
	return -ENODEV;
}

static
int pwm_backlight_brightness_default(struct device *dev,
				     struct platform_pwm_backlight_data *data,
				     unsigned int period)
{
	return -ENODEV;
}
#endif

static bool pwm_backlight_is_linear(struct platform_pwm_backlight_data *data)
{
	unsigned int nlevels = data->max_brightness + 1;
	unsigned int min_val = data->levels[0];
	unsigned int max_val = data->levels[nlevels - 1];
	/*
	 * Multiplying by 128 means that even in pathological cases such
	 * as (max_val - min_val) == nlevels the error at max_val is less
	 * than 1%.
	 */
	unsigned int slope = (128 * (max_val - min_val)) / nlevels;
	unsigned int margin = (max_val - min_val) / 20; /* 5% */
	int i;

	for (i = 1; i < nlevels; i++) {
		unsigned int linear_value = min_val + ((i * slope) / 128);
		unsigned int delta = abs(linear_value - data->levels[i]);

		if (delta > margin)
			return false;
	}

	return true;
}

static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
{
	struct device_node *node = pb->dev->of_node;
	bool active = true;

	/*
	 * If the enable GPIO is present, observable (either as input
	 * or output) and off then the backlight is not currently active.
	 * */
	if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0)
		active = false;

	if (pb->power_supply && !regulator_is_enabled(pb->power_supply))
		active = false;

	if (!pwm_is_enabled(pb->pwm))
		active = false;

	/*
	 * Synchronize the enable_gpio with the observed state of the
	 * hardware.
	 */
	gpiod_direction_output(pb->enable_gpio, active);

	/*
	 * Do not change pb->enabled here! pb->enabled essentially
	 * tells us if we own one of the regulator's use counts and
	 * right now we do not.
	 */

	/* Not booted with device tree or no phandle link to the node */
	if (!node || !node->phandle)
		return FB_BLANK_UNBLANK;

	/*
	 * If the driver is probed from the device tree and there is a
	 * phandle link pointing to the backlight node, it is safe to
	 * assume that another driver will enable the backlight at the
	 * appropriate time. Therefore, if it is disabled, keep it so.
	 */
	return active ? FB_BLANK_UNBLANK: FB_BLANK_POWERDOWN;
}

static int pwm_backlight_probe(struct platform_device *pdev)
{
	struct platform_pwm_backlight_data *data = dev_get_platdata(&pdev->dev);
	struct platform_pwm_backlight_data defdata;
	struct backlight_properties props;
	struct backlight_device *bl;
	struct pwm_bl_data *pb;
	struct pwm_state state;
	unsigned int i;
	int ret;

	if (!data) {
		ret = pwm_backlight_parse_dt(&pdev->dev, &defdata);
		if (ret < 0)
			return dev_err_probe(&pdev->dev, ret,
					     "failed to find platform data\n");

		data = &defdata;
	}

	if (data->init) {
		ret = data->init(&pdev->dev);
		if (ret < 0)
			return ret;
	}

	pb = devm_kzalloc(&pdev->dev, sizeof(*pb), GFP_KERNEL);
	if (!pb) {
		ret = -ENOMEM;
		goto err_alloc;
	}

	pb->notify = data->notify;
	pb->notify_after = data->notify_after;
	pb->check_fb = data->check_fb;
	pb->exit = data->exit;
	pb->dev = &pdev->dev;
	pb->enabled = false;
	pb->post_pwm_on_delay = data->post_pwm_on_delay;
	pb->pwm_off_delay = data->pwm_off_delay;

	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
						  GPIOD_ASIS);
	if (IS_ERR(pb->enable_gpio)) {
		ret = dev_err_probe(&pdev->dev, PTR_ERR(pb->enable_gpio),
				    "failed to acquire enable GPIO\n");
		goto err_alloc;
	}

	pb->power_supply = devm_regulator_get_optional(&pdev->dev, "power");
	if (IS_ERR(pb->power_supply)) {
		ret = PTR_ERR(pb->power_supply);
		if (ret == -ENODEV) {
			pb->power_supply = NULL;
		} else {
			dev_err_probe(&pdev->dev, ret,
				      "failed to acquire power regulator\n");
			goto err_alloc;
		}
	}

	pb->pwm = devm_pwm_get(&pdev->dev, NULL);
	if (IS_ERR(pb->pwm)) {
		ret = dev_err_probe(&pdev->dev, PTR_ERR(pb->pwm),
				    "unable to request PWM\n");
		goto err_alloc;
	}

	dev_dbg(&pdev->dev, "got pwm for backlight\n");

	/* Sync up PWM state. */
	pwm_init_state(pb->pwm, &state);

	/*
	 * The DT case will set the pwm_period_ns field to 0 and store the
	 * period, parsed from the DT, in the PWM device. For the non-DT case,
	 * set the period from platform data if it has not already been set
	 * via the PWM lookup table.
	 */
	if (!state.period && (data->pwm_period_ns > 0))
		state.period = data->pwm_period_ns;

	ret = pwm_apply_might_sleep(pb->pwm, &state);
	if (ret) {
		dev_err_probe(&pdev->dev, ret,
			      "failed to apply initial PWM state");
		goto err_alloc;
	}

	memset(&props, 0, sizeof(struct backlight_properties));

	if (data->levels) {
		pb->levels = data->levels;

		/*
		 * For the DT case, only when brightness levels is defined
		 * data->levels is filled. For the non-DT case, data->levels
		 * can come from platform data, however is not usual.
		 */
		for (i = 0; i <= data->max_brightness; i++)
			if (data->levels[i] > pb->scale)
				pb->scale = data->levels[i];

		if (pwm_backlight_is_linear(data))
			props.scale = BACKLIGHT_SCALE_LINEAR;
		else
			props.scale = BACKLIGHT_SCALE_NON_LINEAR;
	} else if (!data->max_brightness) {
		/*
		 * If no brightness levels are provided and max_brightness is
		 * not set, use the default brightness table. For the DT case,
		 * max_brightness is set to 0 when brightness levels is not
		 * specified. For the non-DT case, max_brightness is usually
		 * set to some value.
		 */

		/* Get the PWM period (in nanoseconds) */
		pwm_get_state(pb->pwm, &state);

		ret = pwm_backlight_brightness_default(&pdev->dev, data,
						       state.period);
		if (ret < 0) {
			dev_err_probe(&pdev->dev, ret,
				      "failed to setup default brightness table\n");
			goto err_alloc;
		}

		for (i = 0; i <= data->max_brightness; i++) {
			if (data->levels[i] > pb->scale)
				pb->scale = data->levels[i];

			pb->levels = data->levels;
		}

		props.scale = BACKLIGHT_SCALE_NON_LINEAR;
	} else {
		/*
		 * That only happens for the non-DT case, where platform data
		 * sets the max_brightness value.
		 */
		pb->scale = data->max_brightness;
	}

	pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
				pb->scale));

	props.type = BACKLIGHT_RAW;
	props.max_brightness = data->max_brightness;
	bl = backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb,
				       &pwm_backlight_ops, &props);
	if (IS_ERR(bl)) {
		ret = dev_err_probe(&pdev->dev, PTR_ERR(bl),
				    "failed to register backlight\n");
		goto err_alloc;
	}

	if (data->dft_brightness > data->max_brightness) {
		dev_warn(&pdev->dev,
			 "invalid default brightness level: %u, using %u\n",
			 data->dft_brightness, data->max_brightness);
		data->dft_brightness = data->max_brightness;
	}

	bl->props.brightness = data->dft_brightness;
	bl->props.power = pwm_backlight_initial_power_state(pb);
	backlight_update_status(bl);

	platform_set_drvdata(pdev, bl);
	return 0;

err_alloc:
	if (data->exit)
		data->exit(&pdev->dev);
	return ret;
}

static void pwm_backlight_remove(struct platform_device *pdev)
{
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct pwm_bl_data *pb = bl_get_data(bl);
	struct pwm_state state;

	backlight_device_unregister(bl);
	pwm_backlight_power_off(pb);
	pwm_get_state(pb->pwm, &state);
	state.duty_cycle = 0;
	state.enabled = false;
	pwm_apply_might_sleep(pb->pwm, &state);

	if (pb->exit)
		pb->exit(&pdev->dev);
}

static void pwm_backlight_shutdown(struct platform_device *pdev)
{
	struct backlight_device *bl = platform_get_drvdata(pdev);
	struct pwm_bl_data *pb = bl_get_data(bl);
	struct pwm_state state;

	pwm_backlight_power_off(pb);
	pwm_get_state(pb->pwm, &state);
	state.duty_cycle = 0;
	state.enabled = false;
	pwm_apply_might_sleep(pb->pwm, &state);
}

#ifdef CONFIG_PM_SLEEP
static int pwm_backlight_suspend(struct device *dev)
{
	struct backlight_device *bl = dev_get_drvdata(dev);
	struct pwm_bl_data *pb = bl_get_data(bl);
	struct pwm_state state;

	if (pb->notify)
		pb->notify(pb->dev, 0);

	pwm_backlight_power_off(pb);

	/*
	 * Note that disabling the PWM doesn't guarantee that the output stays
	 * at its inactive state. However without the PWM disabled, the PWM
	 * driver refuses to suspend. So disable here even though this might
	 * enable the backlight on poorly designed boards.
	 */
	pwm_get_state(pb->pwm, &state);
	state.duty_cycle = 0;
	state.enabled = false;
	pwm_apply_might_sleep(pb->pwm, &state);

	if (pb->notify_after)
		pb->notify_after(pb->dev, 0);

	return 0;
}

static int pwm_backlight_resume(struct device *dev)
{
	struct backlight_device *bl = dev_get_drvdata(dev);

	backlight_update_status(bl);

	return 0;
}
#endif

static const struct dev_pm_ops pwm_backlight_pm_ops = {
#ifdef CONFIG_PM_SLEEP
	.suspend = pwm_backlight_suspend,
	.resume = pwm_backlight_resume,
	.poweroff = pwm_backlight_suspend,
	.restore = pwm_backlight_resume,
#endif
};

static struct platform_driver pwm_backlight_driver = {
	.driver		= {
		.name		= "pwm-backlight",
		.pm		= &pwm_backlight_pm_ops,
		.of_match_table	= of_match_ptr(pwm_backlight_of_match),
	},
	.probe		= pwm_backlight_probe,
	.remove_new	= pwm_backlight_remove,
	.shutdown	= pwm_backlight_shutdown,
};

module_platform_driver(pwm_backlight_driver);

MODULE_DESCRIPTION("PWM based Backlight Driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:pwm-backlight");