summaryrefslogtreecommitdiff
path: root/drivers/iio/adc/ad_sigma_delta.c
blob: 7e21928707437baf9a2522f265d72194745205e6 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Support code for Analog Devices Sigma-Delta ADCs
 *
 * Copyright 2012 Analog Devices Inc.
 *  Author: Lars-Peter Clausen <lars@metafoo.de>
 */

#include <linux/align.h>
#include <linux/interrupt.h>
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
#include <linux/err.h>
#include <linux/module.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/iio/buffer.h>
#include <linux/iio/trigger.h>
#include <linux/iio/trigger_consumer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/adc/ad_sigma_delta.h>

#include <asm/unaligned.h>


#define AD_SD_COMM_CHAN_MASK	0x3

#define AD_SD_REG_COMM		0x00
#define AD_SD_REG_DATA		0x03

/**
 * ad_sd_set_comm() - Set communications register
 *
 * @sigma_delta: The sigma delta device
 * @comm: New value for the communications register
 */
void ad_sd_set_comm(struct ad_sigma_delta *sigma_delta, uint8_t comm)
{
	/* Some variants use the lower two bits of the communications register
	 * to select the channel */
	sigma_delta->comm = comm & AD_SD_COMM_CHAN_MASK;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_set_comm, IIO_AD_SIGMA_DELTA);

/**
 * ad_sd_write_reg() - Write a register
 *
 * @sigma_delta: The sigma delta device
 * @reg: Address of the register
 * @size: Size of the register (0-3)
 * @val: Value to write to the register
 *
 * Returns 0 on success, an error code otherwise.
 **/
int ad_sd_write_reg(struct ad_sigma_delta *sigma_delta, unsigned int reg,
	unsigned int size, unsigned int val)
{
	uint8_t *data = sigma_delta->tx_buf;
	struct spi_transfer t = {
		.tx_buf		= data,
		.len		= size + 1,
		.cs_change	= sigma_delta->keep_cs_asserted,
	};
	struct spi_message m;
	int ret;

	data[0] = (reg << sigma_delta->info->addr_shift) | sigma_delta->comm;

	switch (size) {
	case 3:
		put_unaligned_be24(val, &data[1]);
		break;
	case 2:
		put_unaligned_be16(val, &data[1]);
		break;
	case 1:
		data[1] = val;
		break;
	case 0:
		break;
	default:
		return -EINVAL;
	}

	spi_message_init(&m);
	spi_message_add_tail(&t, &m);

	if (sigma_delta->bus_locked)
		ret = spi_sync_locked(sigma_delta->spi, &m);
	else
		ret = spi_sync(sigma_delta->spi, &m);

	return ret;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_write_reg, IIO_AD_SIGMA_DELTA);

static int ad_sd_read_reg_raw(struct ad_sigma_delta *sigma_delta,
	unsigned int reg, unsigned int size, uint8_t *val)
{
	uint8_t *data = sigma_delta->tx_buf;
	int ret;
	struct spi_transfer t[] = {
		{
			.tx_buf = data,
			.len = 1,
		}, {
			.rx_buf = val,
			.len = size,
			.cs_change = sigma_delta->bus_locked,
		},
	};
	struct spi_message m;

	spi_message_init(&m);

	if (sigma_delta->info->has_registers) {
		data[0] = reg << sigma_delta->info->addr_shift;
		data[0] |= sigma_delta->info->read_mask;
		data[0] |= sigma_delta->comm;
		spi_message_add_tail(&t[0], &m);
	}
	spi_message_add_tail(&t[1], &m);

	if (sigma_delta->bus_locked)
		ret = spi_sync_locked(sigma_delta->spi, &m);
	else
		ret = spi_sync(sigma_delta->spi, &m);

	return ret;
}

/**
 * ad_sd_read_reg() - Read a register
 *
 * @sigma_delta: The sigma delta device
 * @reg: Address of the register
 * @size: Size of the register (1-4)
 * @val: Read value
 *
 * Returns 0 on success, an error code otherwise.
 **/
int ad_sd_read_reg(struct ad_sigma_delta *sigma_delta,
	unsigned int reg, unsigned int size, unsigned int *val)
{
	int ret;

	ret = ad_sd_read_reg_raw(sigma_delta, reg, size, sigma_delta->rx_buf);
	if (ret < 0)
		goto out;

	switch (size) {
	case 4:
		*val = get_unaligned_be32(sigma_delta->rx_buf);
		break;
	case 3:
		*val = get_unaligned_be24(sigma_delta->rx_buf);
		break;
	case 2:
		*val = get_unaligned_be16(sigma_delta->rx_buf);
		break;
	case 1:
		*val = sigma_delta->rx_buf[0];
		break;
	default:
		ret = -EINVAL;
		break;
	}

out:
	return ret;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_read_reg, IIO_AD_SIGMA_DELTA);

/**
 * ad_sd_reset() - Reset the serial interface
 *
 * @sigma_delta: The sigma delta device
 * @reset_length: Number of SCLKs with DIN = 1
 *
 * Returns 0 on success, an error code otherwise.
 **/
int ad_sd_reset(struct ad_sigma_delta *sigma_delta,
	unsigned int reset_length)
{
	uint8_t *buf;
	unsigned int size;
	int ret;

	size = DIV_ROUND_UP(reset_length, 8);
	buf = kcalloc(size, sizeof(*buf), GFP_KERNEL);
	if (!buf)
		return -ENOMEM;

	memset(buf, 0xff, size);
	ret = spi_write(sigma_delta->spi, buf, size);
	kfree(buf);

	return ret;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_reset, IIO_AD_SIGMA_DELTA);

int ad_sd_calibrate(struct ad_sigma_delta *sigma_delta,
	unsigned int mode, unsigned int channel)
{
	int ret;
	unsigned long timeout;

	ret = ad_sigma_delta_set_channel(sigma_delta, channel);
	if (ret)
		return ret;

	spi_bus_lock(sigma_delta->spi->master);
	sigma_delta->bus_locked = true;
	sigma_delta->keep_cs_asserted = true;
	reinit_completion(&sigma_delta->completion);

	ret = ad_sigma_delta_set_mode(sigma_delta, mode);
	if (ret < 0)
		goto out;

	sigma_delta->irq_dis = false;
	enable_irq(sigma_delta->spi->irq);
	timeout = wait_for_completion_timeout(&sigma_delta->completion, 2 * HZ);
	if (timeout == 0) {
		sigma_delta->irq_dis = true;
		disable_irq_nosync(sigma_delta->spi->irq);
		ret = -EIO;
	} else {
		ret = 0;
	}
out:
	sigma_delta->keep_cs_asserted = false;
	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);
	sigma_delta->bus_locked = false;
	spi_bus_unlock(sigma_delta->spi->master);

	return ret;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_calibrate, IIO_AD_SIGMA_DELTA);

/**
 * ad_sd_calibrate_all() - Performs channel calibration
 * @sigma_delta: The sigma delta device
 * @cb: Array of channels and calibration type to perform
 * @n: Number of items in cb
 *
 * Returns 0 on success, an error code otherwise.
 **/
int ad_sd_calibrate_all(struct ad_sigma_delta *sigma_delta,
	const struct ad_sd_calib_data *cb, unsigned int n)
{
	unsigned int i;
	int ret;

	for (i = 0; i < n; i++) {
		ret = ad_sd_calibrate(sigma_delta, cb[i].mode, cb[i].channel);
		if (ret)
			return ret;
	}

	return 0;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_calibrate_all, IIO_AD_SIGMA_DELTA);

/**
 * ad_sigma_delta_single_conversion() - Performs a single data conversion
 * @indio_dev: The IIO device
 * @chan: The conversion is done for this channel
 * @val: Pointer to the location where to store the read value
 *
 * Returns: 0 on success, an error value otherwise.
 */
int ad_sigma_delta_single_conversion(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, int *val)
{
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
	unsigned int sample, raw_sample;
	unsigned int data_reg;
	int ret = 0;

	ret = iio_device_claim_direct_mode(indio_dev);
	if (ret)
		return ret;

	ad_sigma_delta_set_channel(sigma_delta, chan->address);

	spi_bus_lock(sigma_delta->spi->master);
	sigma_delta->bus_locked = true;
	sigma_delta->keep_cs_asserted = true;
	reinit_completion(&sigma_delta->completion);

	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_SINGLE);

	sigma_delta->irq_dis = false;
	enable_irq(sigma_delta->spi->irq);
	ret = wait_for_completion_interruptible_timeout(
			&sigma_delta->completion, HZ);

	if (ret == 0)
		ret = -EIO;
	if (ret < 0)
		goto out;

	if (sigma_delta->info->data_reg != 0)
		data_reg = sigma_delta->info->data_reg;
	else
		data_reg = AD_SD_REG_DATA;

	ret = ad_sd_read_reg(sigma_delta, data_reg,
		DIV_ROUND_UP(chan->scan_type.realbits + chan->scan_type.shift, 8),
		&raw_sample);

out:
	if (!sigma_delta->irq_dis) {
		disable_irq_nosync(sigma_delta->spi->irq);
		sigma_delta->irq_dis = true;
	}

	sigma_delta->keep_cs_asserted = false;
	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);
	sigma_delta->bus_locked = false;
	spi_bus_unlock(sigma_delta->spi->master);
	iio_device_release_direct_mode(indio_dev);

	if (ret)
		return ret;

	sample = raw_sample >> chan->scan_type.shift;
	sample &= (1 << chan->scan_type.realbits) - 1;
	*val = sample;

	ret = ad_sigma_delta_postprocess_sample(sigma_delta, raw_sample);
	if (ret)
		return ret;

	return IIO_VAL_INT;
}
EXPORT_SYMBOL_NS_GPL(ad_sigma_delta_single_conversion, IIO_AD_SIGMA_DELTA);

static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
{
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
	unsigned int i, slot, samples_buf_size;
	unsigned int channel;
	uint8_t *samples_buf;
	int ret;

	if (sigma_delta->num_slots == 1) {
		channel = find_first_bit(indio_dev->active_scan_mask,
					 indio_dev->masklength);
		ret = ad_sigma_delta_set_channel(sigma_delta,
						 indio_dev->channels[channel].address);
		if (ret)
			return ret;
		slot = 1;
	} else {
		/*
		 * At this point update_scan_mode already enabled the required channels.
		 * For sigma-delta sequencer drivers with multiple slots, an update_scan_mode
		 * implementation is mandatory.
		 */
		slot = 0;
		for_each_set_bit(i, indio_dev->active_scan_mask, indio_dev->masklength) {
			sigma_delta->slots[slot] = indio_dev->channels[i].address;
			slot++;
		}
	}

	sigma_delta->active_slots = slot;
	sigma_delta->current_slot = 0;

	if (sigma_delta->active_slots > 1) {
		ret = ad_sigma_delta_append_status(sigma_delta, true);
		if (ret)
			return ret;
	}

	samples_buf_size = ALIGN(slot * indio_dev->channels[0].scan_type.storagebits, 8);
	samples_buf_size += sizeof(int64_t);
	samples_buf = devm_krealloc(&sigma_delta->spi->dev, sigma_delta->samples_buf,
				    samples_buf_size, GFP_KERNEL);
	if (!samples_buf)
		return -ENOMEM;

	sigma_delta->samples_buf = samples_buf;

	spi_bus_lock(sigma_delta->spi->master);
	sigma_delta->bus_locked = true;
	sigma_delta->keep_cs_asserted = true;

	ret = ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_CONTINUOUS);
	if (ret)
		goto err_unlock;

	sigma_delta->irq_dis = false;
	enable_irq(sigma_delta->spi->irq);

	return 0;

err_unlock:
	spi_bus_unlock(sigma_delta->spi->master);

	return ret;
}

static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev)
{
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);

	reinit_completion(&sigma_delta->completion);
	wait_for_completion_timeout(&sigma_delta->completion, HZ);

	if (!sigma_delta->irq_dis) {
		disable_irq_nosync(sigma_delta->spi->irq);
		sigma_delta->irq_dis = true;
	}

	sigma_delta->keep_cs_asserted = false;
	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);

	if (sigma_delta->status_appended)
		ad_sigma_delta_append_status(sigma_delta, false);

	ad_sigma_delta_disable_all(sigma_delta);
	sigma_delta->bus_locked = false;
	return spi_bus_unlock(sigma_delta->spi->master);
}

static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
{
	struct iio_poll_func *pf = p;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
	uint8_t *data = sigma_delta->rx_buf;
	unsigned int transfer_size;
	unsigned int sample_size;
	unsigned int sample_pos;
	unsigned int status_pos;
	unsigned int reg_size;
	unsigned int data_reg;

	reg_size = indio_dev->channels[0].scan_type.realbits +
			indio_dev->channels[0].scan_type.shift;
	reg_size = DIV_ROUND_UP(reg_size, 8);

	if (sigma_delta->info->data_reg != 0)
		data_reg = sigma_delta->info->data_reg;
	else
		data_reg = AD_SD_REG_DATA;

	/* Status word will be appended to the sample during transfer */
	if (sigma_delta->status_appended)
		transfer_size = reg_size + 1;
	else
		transfer_size = reg_size;

	switch (reg_size) {
	case 4:
	case 2:
	case 1:
		status_pos = reg_size;
		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[0]);
		break;
	case 3:
		/*
		 * Data array after transfer will look like (if status is appended):
		 * data[] = { [0][sample][sample][sample][status] }
		 * Keeping the first byte 0 shifts the status postion by 1 byte to the right.
		 */
		status_pos = reg_size + 1;

		/* We store 24 bit samples in a 32 bit word. Keep the upper
		 * byte set to zero. */
		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[1]);
		break;
	}

	/*
	 * For devices sampling only one channel at
	 * once, there is no need for sample number tracking.
	 */
	if (sigma_delta->active_slots == 1) {
		iio_push_to_buffers_with_timestamp(indio_dev, data, pf->timestamp);
		goto irq_handled;
	}

	if (sigma_delta->status_appended) {
		u8 converted_channel;

		converted_channel = data[status_pos] & sigma_delta->info->status_ch_mask;
		if (converted_channel != sigma_delta->slots[sigma_delta->current_slot]) {
			/*
			 * Desync occurred during continuous sampling of multiple channels.
			 * Drop this incomplete sample and start from first channel again.
			 */

			sigma_delta->current_slot = 0;
			goto irq_handled;
		}
	}

	sample_size = indio_dev->channels[0].scan_type.storagebits / 8;
	sample_pos = sample_size * sigma_delta->current_slot;
	memcpy(&sigma_delta->samples_buf[sample_pos], data, sample_size);
	sigma_delta->current_slot++;

	if (sigma_delta->current_slot == sigma_delta->active_slots) {
		sigma_delta->current_slot = 0;
		iio_push_to_buffers_with_timestamp(indio_dev, sigma_delta->samples_buf,
						   pf->timestamp);
	}

irq_handled:
	iio_trigger_notify_done(indio_dev->trig);
	sigma_delta->irq_dis = false;
	enable_irq(sigma_delta->spi->irq);

	return IRQ_HANDLED;
}

static bool ad_sd_validate_scan_mask(struct iio_dev *indio_dev, const unsigned long *mask)
{
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);

	return bitmap_weight(mask, indio_dev->masklength) <= sigma_delta->num_slots;
}

static const struct iio_buffer_setup_ops ad_sd_buffer_setup_ops = {
	.postenable = &ad_sd_buffer_postenable,
	.postdisable = &ad_sd_buffer_postdisable,
	.validate_scan_mask = &ad_sd_validate_scan_mask,
};

static irqreturn_t ad_sd_data_rdy_trig_poll(int irq, void *private)
{
	struct ad_sigma_delta *sigma_delta = private;

	complete(&sigma_delta->completion);
	disable_irq_nosync(irq);
	sigma_delta->irq_dis = true;
	iio_trigger_poll(sigma_delta->trig);

	return IRQ_HANDLED;
}

/**
 * ad_sd_validate_trigger() - validate_trigger callback for ad_sigma_delta devices
 * @indio_dev: The IIO device
 * @trig: The new trigger
 *
 * Returns: 0 if the 'trig' matches the trigger registered by the ad_sigma_delta
 * device, -EINVAL otherwise.
 */
int ad_sd_validate_trigger(struct iio_dev *indio_dev, struct iio_trigger *trig)
{
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);

	if (sigma_delta->trig != trig)
		return -EINVAL;

	return 0;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_validate_trigger, IIO_AD_SIGMA_DELTA);

static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_dev)
{
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
	int ret;

	if (dev != &sigma_delta->spi->dev) {
		dev_err(dev, "Trigger parent should be '%s', got '%s'\n",
			dev_name(dev), dev_name(&sigma_delta->spi->dev));
		return -EFAULT;
	}

	sigma_delta->trig = devm_iio_trigger_alloc(dev, "%s-dev%d", indio_dev->name,
						   iio_device_id(indio_dev));
	if (sigma_delta->trig == NULL)
		return -ENOMEM;

	init_completion(&sigma_delta->completion);

	sigma_delta->irq_dis = true;

	/* the IRQ core clears IRQ_DISABLE_UNLAZY flag when freeing an IRQ */
	irq_set_status_flags(sigma_delta->spi->irq, IRQ_DISABLE_UNLAZY);

	ret = devm_request_irq(dev, sigma_delta->spi->irq,
			       ad_sd_data_rdy_trig_poll,
			       sigma_delta->info->irq_flags | IRQF_NO_AUTOEN,
			       indio_dev->name,
			       sigma_delta);
	if (ret)
		return ret;

	iio_trigger_set_drvdata(sigma_delta->trig, sigma_delta);

	ret = devm_iio_trigger_register(dev, sigma_delta->trig);
	if (ret)
		return ret;

	/* select default trigger */
	indio_dev->trig = iio_trigger_get(sigma_delta->trig);

	return 0;
}

/**
 * devm_ad_sd_setup_buffer_and_trigger() - Device-managed buffer & trigger setup
 * @dev: Device object to which to bind the life-time of the resources attached
 * @indio_dev: The IIO device
 */
int devm_ad_sd_setup_buffer_and_trigger(struct device *dev, struct iio_dev *indio_dev)
{
	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
	int ret;

	sigma_delta->slots = devm_kcalloc(dev, sigma_delta->num_slots,
					  sizeof(*sigma_delta->slots), GFP_KERNEL);
	if (!sigma_delta->slots)
		return -ENOMEM;

	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
					      &iio_pollfunc_store_time,
					      &ad_sd_trigger_handler,
					      &ad_sd_buffer_setup_ops);
	if (ret)
		return ret;

	return devm_ad_sd_probe_trigger(dev, indio_dev);
}
EXPORT_SYMBOL_NS_GPL(devm_ad_sd_setup_buffer_and_trigger, IIO_AD_SIGMA_DELTA);

/**
 * ad_sd_init() - Initializes a ad_sigma_delta struct
 * @sigma_delta: The ad_sigma_delta device
 * @indio_dev: The IIO device which the Sigma Delta device is used for
 * @spi: The SPI device for the ad_sigma_delta device
 * @info: Device specific callbacks and options
 *
 * This function needs to be called before any other operations are performed on
 * the ad_sigma_delta struct.
 */
int ad_sd_init(struct ad_sigma_delta *sigma_delta, struct iio_dev *indio_dev,
	struct spi_device *spi, const struct ad_sigma_delta_info *info)
{
	sigma_delta->spi = spi;
	sigma_delta->info = info;

	/* If the field is unset in ad_sigma_delta_info, asume there can only be 1 slot. */
	if (!info->num_slots)
		sigma_delta->num_slots = 1;
	else
		sigma_delta->num_slots = info->num_slots;

	if (sigma_delta->num_slots > 1) {
		if (!indio_dev->info->update_scan_mode) {
			dev_err(&spi->dev, "iio_dev lacks update_scan_mode().\n");
			return -EINVAL;
		}

		if (!info->disable_all) {
			dev_err(&spi->dev, "ad_sigma_delta_info lacks disable_all().\n");
			return -EINVAL;
		}
	}

	iio_device_set_drvdata(indio_dev, sigma_delta);

	return 0;
}
EXPORT_SYMBOL_NS_GPL(ad_sd_init, IIO_AD_SIGMA_DELTA);

MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
MODULE_DESCRIPTION("Analog Devices Sigma-Delta ADCs");
MODULE_LICENSE("GPL v2");