drivers/iio/proximity/as3935.c - arm/linux - Git at Google

 /*
  * as3935.c - Support for AS3935 Franklin lightning sensor
  *
  * Copyright (C) 2014 Matt Ranostay <mranostay@gmail.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  * GNU General Public License for more details.
  *
  */

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/delay.h>
 #include <linux/workqueue.h>
 #include <linux/mutex.h>
 #include <linux/err.h>
 #include <linux/irq.h>
 #include <linux/gpio.h>
 #include <linux/spi/spi.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/trigger.h>
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/buffer.h>
 #include <linux/iio/triggered_buffer.h>
 #include <linux/of_gpio.h>


 #define AS3935_AFE_GAIN		0x00
 #define AS3935_AFE_MASK		0x3F
 #define AS3935_AFE_GAIN_MAX	0x1F
 #define AS3935_AFE_PWR_BIT	BIT(0)

 #define AS3935_INT		0x03
 #define AS3935_INT_MASK		0x0f
 #define AS3935_EVENT_INT	BIT(3)
 #define AS3935_NOISE_INT	BIT(0)

 #define AS3935_DATA		0x07
 #define AS3935_DATA_MASK	0x3F

 #define AS3935_TUNE_CAP		0x08
 #define AS3935_CALIBRATE	0x3D

 #define AS3935_READ_DATA	BIT(14)
 #define AS3935_ADDRESS(x)	((x) << 8)

 #define MAX_PF_CAP		120
 #define TUNE_CAP_DIV		8

 struct as3935_state {
 	struct spi_device *spi;
 	struct iio_trigger *trig;
 	struct mutex lock;
 	struct delayed_work work;

 	u32 tune_cap;
 	u8 buffer[16]; /* 8-bit data + 56-bit padding + 64-bit timestamp */
 	u8 buf[2] ____cacheline_aligned;
 };

 static const struct iio_chan_spec as3935_channels[] = {
 	{
 		.type           = IIO_PROXIMITY,
 		.info_mask_separate =
 			BIT(IIO_CHAN_INFO_RAW) |
 			BIT(IIO_CHAN_INFO_PROCESSED) |
 			BIT(IIO_CHAN_INFO_SCALE),
 		.scan_index     = 0,
 		.scan_type = {
 			.sign           = 'u',
 			.realbits       = 6,
 			.storagebits    = 8,
 		},
 	},
 	IIO_CHAN_SOFT_TIMESTAMP(1),
 };

 static int as3935_read(struct as3935_state *st, unsigned int reg, int *val)
 {
 	u8 cmd;
 	int ret;

 	cmd = (AS3935_READ_DATA | AS3935_ADDRESS(reg)) >> 8;
 	ret = spi_w8r8(st->spi, cmd);
 	if (ret < 0)
 		return ret;
 	*val = ret;

 	return 0;
 }

 static int as3935_write(struct as3935_state *st,
 				unsigned int reg,
 				unsigned int val)
 {
 	u8 *buf = st->buf;

 	buf[0] = AS3935_ADDRESS(reg) >> 8;
 	buf[1] = val;

 	return spi_write(st->spi, buf, 2);
 }

 static ssize_t as3935_sensor_sensitivity_show(struct device *dev,
 					struct device_attribute *attr,
 					char *buf)
 {
 	struct as3935_state *st = iio_priv(dev_to_iio_dev(dev));
 	int val, ret;

 	ret = as3935_read(st, AS3935_AFE_GAIN, &val);
 	if (ret)
 		return ret;
 	val = (val & AS3935_AFE_MASK) >> 1;

 	return sprintf(buf, "%d\n", val);
 }

 static ssize_t as3935_sensor_sensitivity_store(struct device *dev,
 					struct device_attribute *attr,
 					const char *buf, size_t len)
 {
 	struct as3935_state *st = iio_priv(dev_to_iio_dev(dev));
 	unsigned long val;
 	int ret;

 	ret = kstrtoul((const char *) buf, 10, &val);
 	if (ret)
 		return -EINVAL;

 	if (val > AS3935_AFE_GAIN_MAX)
 		return -EINVAL;

 	as3935_write(st, AS3935_AFE_GAIN, val << 1);

 	return len;
 }

 static IIO_DEVICE_ATTR(sensor_sensitivity, S_IRUGO | S_IWUSR,
 	as3935_sensor_sensitivity_show, as3935_sensor_sensitivity_store, 0);


 static struct attribute *as3935_attributes[] = {
 	&iio_dev_attr_sensor_sensitivity.dev_attr.attr,
 	NULL,
 };

 static const struct attribute_group as3935_attribute_group = {
 	.attrs = as3935_attributes,
 };

 static int as3935_read_raw(struct iio_dev *indio_dev,
 			   struct iio_chan_spec const *chan,
 			   int *val,
 			   int *val2,
 			   long m)
 {
 	struct as3935_state *st = iio_priv(indio_dev);
 	int ret;


 	switch (m) {
 	case IIO_CHAN_INFO_PROCESSED:
 	case IIO_CHAN_INFO_RAW:
 		*val2 = 0;
 		ret = as3935_read(st, AS3935_DATA, val);
 		if (ret)
 			return ret;

 		/* storm out of range */
 		if (*val == AS3935_DATA_MASK)
 			return -EINVAL;

 		if (m == IIO_CHAN_INFO_RAW)
 			return IIO_VAL_INT;

 		if (m == IIO_CHAN_INFO_PROCESSED)
 			*val *= 1000;
 		break;
 	case IIO_CHAN_INFO_SCALE:
 		*val = 1000;
 		break;
 	default:
 		return -EINVAL;
 	}

 	return IIO_VAL_INT;
 }

 static const struct iio_info as3935_info = {
 	.driver_module = THIS_MODULE,
 	.attrs = &as3935_attribute_group,
 	.read_raw = &as3935_read_raw,
 };

 static irqreturn_t as3935_trigger_handler(int irq, void *private)
 {
 	struct iio_poll_func *pf = private;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct as3935_state *st = iio_priv(indio_dev);
 	int val, ret;

 	ret = as3935_read(st, AS3935_DATA, &val);
 	if (ret)
 		goto err_read;

 	st->buffer[0] = val & AS3935_DATA_MASK;
 	iio_push_to_buffers_with_timestamp(indio_dev, &st->buffer,
 					   iio_get_time_ns(indio_dev));
 err_read:
 	iio_trigger_notify_done(indio_dev->trig);

 	return IRQ_HANDLED;
 }

 static const struct iio_trigger_ops iio_interrupt_trigger_ops = {
 	.owner = THIS_MODULE,
 };

 static void as3935_event_work(struct work_struct *work)
 {
 	struct as3935_state *st;
 	int val;
 	int ret;

 	st = container_of(work, struct as3935_state, work.work);

 	ret = as3935_read(st, AS3935_INT, &val);
 	if (ret) {
 		dev_warn(&st->spi->dev, "read error\n");
 		return;
 	}

 	val &= AS3935_INT_MASK;

 	switch (val) {
 	case AS3935_EVENT_INT:
 		iio_trigger_poll_chained(st->trig);
 		break;
 	case AS3935_NOISE_INT:
 		dev_warn(&st->spi->dev, "noise level is too high\n");
 		break;
 	}
 }

 static irqreturn_t as3935_interrupt_handler(int irq, void *private)
 {
 	struct iio_dev *indio_dev = private;
 	struct as3935_state *st = iio_priv(indio_dev);

 	/*
 	 * Delay work for >2 milliseconds after an interrupt to allow
 	 * estimated distance to recalculated.
 	 */

 	schedule_delayed_work(&st->work, msecs_to_jiffies(3));

 	return IRQ_HANDLED;
 }

 static void calibrate_as3935(struct as3935_state *st)
 {
 	/* mask disturber interrupt bit */
 	as3935_write(st, AS3935_INT, BIT(5));

 	as3935_write(st, AS3935_CALIBRATE, 0x96);
 	as3935_write(st, AS3935_TUNE_CAP,
 		BIT(5) | (st->tune_cap / TUNE_CAP_DIV));

 	mdelay(2);
 	as3935_write(st, AS3935_TUNE_CAP, (st->tune_cap / TUNE_CAP_DIV));
 }

 #ifdef CONFIG_PM_SLEEP
 static int as3935_suspend(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct as3935_state *st = iio_priv(indio_dev);
 	int val, ret;

 	mutex_lock(&st->lock);
 	ret = as3935_read(st, AS3935_AFE_GAIN, &val);
 	if (ret)
 		goto err_suspend;
 	val |= AS3935_AFE_PWR_BIT;

 	ret = as3935_write(st, AS3935_AFE_GAIN, val);

 err_suspend:
 	mutex_unlock(&st->lock);

 	return ret;
 }

 static int as3935_resume(struct device *dev)
 {
 	struct iio_dev *indio_dev = dev_get_drvdata(dev);
 	struct as3935_state *st = iio_priv(indio_dev);
 	int val, ret;

 	mutex_lock(&st->lock);
 	ret = as3935_read(st, AS3935_AFE_GAIN, &val);
 	if (ret)
 		goto err_resume;
 	val &= ~AS3935_AFE_PWR_BIT;
 	ret = as3935_write(st, AS3935_AFE_GAIN, val);

 	calibrate_as3935(st);

 err_resume:
 	mutex_unlock(&st->lock);

 	return ret;
 }

 static SIMPLE_DEV_PM_OPS(as3935_pm_ops, as3935_suspend, as3935_resume);
 #define AS3935_PM_OPS (&as3935_pm_ops)

 #else
 #define AS3935_PM_OPS NULL
 #endif

 static int as3935_probe(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev;
 	struct iio_trigger *trig;
 	struct as3935_state *st;
 	struct device_node *np = spi->dev.of_node;
 	int ret;

 	/* Be sure lightning event interrupt is specified */
 	if (!spi->irq) {
 		dev_err(&spi->dev, "unable to get event interrupt\n");
 		return -EINVAL;
 	}

 	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
 	if (!indio_dev)
 		return -ENOMEM;

 	st = iio_priv(indio_dev);
 	st->spi = spi;

 	spi_set_drvdata(spi, indio_dev);
 	mutex_init(&st->lock);
 	INIT_DELAYED_WORK(&st->work, as3935_event_work);

 	ret = of_property_read_u32(np,
 			"ams,tuning-capacitor-pf", &st->tune_cap);
 	if (ret) {
 		st->tune_cap = 0;
 		dev_warn(&spi->dev,
 			"no tuning-capacitor-pf set, defaulting to %d",
 			st->tune_cap);
 	}

 	if (st->tune_cap > MAX_PF_CAP) {
 		dev_err(&spi->dev,
 			"wrong tuning-capacitor-pf setting of %d\n",
 			st->tune_cap);
 		return -EINVAL;
 	}

 	indio_dev->dev.parent = &spi->dev;
 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->channels = as3935_channels;
 	indio_dev->num_channels = ARRAY_SIZE(as3935_channels);
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->info = &as3935_info;

 	trig = devm_iio_trigger_alloc(&spi->dev, "%s-dev%d",
 				      indio_dev->name, indio_dev->id);

 	if (!trig)
 		return -ENOMEM;

 	st->trig = trig;
 	trig->dev.parent = indio_dev->dev.parent;
 	iio_trigger_set_drvdata(trig, indio_dev);
 	trig->ops = &iio_interrupt_trigger_ops;

 	ret = iio_trigger_register(trig);
 	if (ret) {
 		dev_err(&spi->dev, "failed to register trigger\n");
 		return ret;
 	}

 	ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time,
 		&as3935_trigger_handler, NULL);

 	if (ret) {
 		dev_err(&spi->dev, "cannot setup iio trigger\n");
 		goto unregister_trigger;
 	}

 	calibrate_as3935(st);

 	ret = devm_request_irq(&spi->dev, spi->irq,
 				&as3935_interrupt_handler,
 				IRQF_TRIGGER_RISING,
 				dev_name(&spi->dev),
 				indio_dev);

 	if (ret) {
 		dev_err(&spi->dev, "unable to request irq\n");
 		goto unregister_buffer;
 	}

 	ret = iio_device_register(indio_dev);
 	if (ret < 0) {
 		dev_err(&spi->dev, "unable to register device\n");
 		goto unregister_buffer;
 	}
 	return 0;

 unregister_buffer:
 	iio_triggered_buffer_cleanup(indio_dev);

 unregister_trigger:
 	iio_trigger_unregister(st->trig);

 	return ret;
 }

 static int as3935_remove(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev = spi_get_drvdata(spi);
 	struct as3935_state *st = iio_priv(indio_dev);

 	iio_device_unregister(indio_dev);
 	iio_triggered_buffer_cleanup(indio_dev);
 	iio_trigger_unregister(st->trig);

 	return 0;
 }

 static const struct of_device_id as3935_of_match[] = {
 	{ .compatible = "ams,as3935", },
 	{ /* sentinel */ },
 };
 MODULE_DEVICE_TABLE(of, as3935_of_match);

 static const struct spi_device_id as3935_id[] = {
 	{"as3935", 0},
 	{},
 };
 MODULE_DEVICE_TABLE(spi, as3935_id);

 static struct spi_driver as3935_driver = {
 	.driver = {
 		.name	= "as3935",
 		.of_match_table = of_match_ptr(as3935_of_match),
 		.pm	= AS3935_PM_OPS,
 	},
 	.probe		= as3935_probe,
 	.remove		= as3935_remove,
 	.id_table	= as3935_id,
 };
 module_spi_driver(as3935_driver);

 MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
 MODULE_DESCRIPTION("AS3935 lightning sensor");
 MODULE_LICENSE("GPL");
	/*
	* as3935.c - Support for AS3935 Franklin lightning sensor
	*
	* Copyright (C) 2014 Matt Ranostay <mranostay@gmail.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	*/

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/delay.h>
	#include <linux/workqueue.h>
	#include <linux/mutex.h>
	#include <linux/err.h>
	#include <linux/irq.h>
	#include <linux/gpio.h>
	#include <linux/spi/spi.h>
	#include <linux/iio/iio.h>
	#include <linux/iio/sysfs.h>
	#include <linux/iio/trigger.h>
	#include <linux/iio/trigger_consumer.h>
	#include <linux/iio/buffer.h>
	#include <linux/iio/triggered_buffer.h>
	#include <linux/of_gpio.h>


	#define AS3935_AFE_GAIN 0x00
	#define AS3935_AFE_MASK 0x3F
	#define AS3935_AFE_GAIN_MAX 0x1F
	#define AS3935_AFE_PWR_BIT BIT(0)

	#define AS3935_INT 0x03
	#define AS3935_INT_MASK 0x0f
	#define AS3935_EVENT_INT BIT(3)
	#define AS3935_NOISE_INT BIT(0)

	#define AS3935_DATA 0x07
	#define AS3935_DATA_MASK 0x3F

	#define AS3935_TUNE_CAP 0x08
	#define AS3935_CALIBRATE 0x3D

	#define AS3935_READ_DATA BIT(14)
	#define AS3935_ADDRESS(x) ((x) << 8)

	#define MAX_PF_CAP 120
	#define TUNE_CAP_DIV 8

	struct as3935_state {
	struct spi_device *spi;
	struct iio_trigger *trig;
	struct mutex lock;
	struct delayed_work work;

	u32 tune_cap;
	u8 buffer[16]; /* 8-bit data + 56-bit padding + 64-bit timestamp */
	u8 buf[2] ____cacheline_aligned;
	};

	static const struct iio_chan_spec as3935_channels[] = {
	{
	.type = IIO_PROXIMITY,
	.info_mask_separate =
	BIT(IIO_CHAN_INFO_RAW) \|
	BIT(IIO_CHAN_INFO_PROCESSED) \|
	BIT(IIO_CHAN_INFO_SCALE),
	.scan_index = 0,
	.scan_type = {
	.sign = 'u',
	.realbits = 6,
	.storagebits = 8,
	},
	},
	IIO_CHAN_SOFT_TIMESTAMP(1),
	};

	static int as3935_read(struct as3935_state st, unsigned int reg, int val)
	{
	u8 cmd;
	int ret;

	cmd = (AS3935_READ_DATA \| AS3935_ADDRESS(reg)) >> 8;
	ret = spi_w8r8(st->spi, cmd);
	if (ret < 0)
	return ret;
	*val = ret;

	return 0;
	}

	static int as3935_write(struct as3935_state *st,
	unsigned int reg,
	unsigned int val)
	{
	u8 *buf = st->buf;

	buf[0] = AS3935_ADDRESS(reg) >> 8;
	buf[1] = val;

	return spi_write(st->spi, buf, 2);
	}

	static ssize_t as3935_sensor_sensitivity_show(struct device *dev,
	struct device_attribute *attr,
	char *buf)
	{
	struct as3935_state *st = iio_priv(dev_to_iio_dev(dev));
	int val, ret;

	ret = as3935_read(st, AS3935_AFE_GAIN, &val);
	if (ret)
	return ret;
	val = (val & AS3935_AFE_MASK) >> 1;

	return sprintf(buf, "%d\n", val);
	}

	static ssize_t as3935_sensor_sensitivity_store(struct device *dev,
	struct device_attribute *attr,
	const char *buf, size_t len)
	{
	struct as3935_state *st = iio_priv(dev_to_iio_dev(dev));
	unsigned long val;
	int ret;

	ret = kstrtoul((const char *) buf, 10, &val);
	if (ret)
	return -EINVAL;

	if (val > AS3935_AFE_GAIN_MAX)
	return -EINVAL;

	as3935_write(st, AS3935_AFE_GAIN, val << 1);

	return len;
	}

	static IIO_DEVICE_ATTR(sensor_sensitivity, S_IRUGO \| S_IWUSR,
	as3935_sensor_sensitivity_show, as3935_sensor_sensitivity_store, 0);


	static struct attribute *as3935_attributes[] = {
	&iio_dev_attr_sensor_sensitivity.dev_attr.attr,
	NULL,
	};

	static const struct attribute_group as3935_attribute_group = {
	.attrs = as3935_attributes,
	};

	static int as3935_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int *val,
	int *val2,
	long m)
	{
	struct as3935_state *st = iio_priv(indio_dev);
	int ret;


	switch (m) {
	case IIO_CHAN_INFO_PROCESSED:
	case IIO_CHAN_INFO_RAW:
	*val2 = 0;
	ret = as3935_read(st, AS3935_DATA, val);
	if (ret)
	return ret;

	/* storm out of range */
	if (*val == AS3935_DATA_MASK)
	return -EINVAL;

	if (m == IIO_CHAN_INFO_RAW)
	return IIO_VAL_INT;

	if (m == IIO_CHAN_INFO_PROCESSED)
	val = 1000;
	break;
	case IIO_CHAN_INFO_SCALE:
	*val = 1000;
	break;
	default:
	return -EINVAL;
	}

	return IIO_VAL_INT;
	}

	static const struct iio_info as3935_info = {
	.driver_module = THIS_MODULE,
	.attrs = &as3935_attribute_group,
	.read_raw = &as3935_read_raw,
	};

	static irqreturn_t as3935_trigger_handler(int irq, void *private)
	{
	struct iio_poll_func *pf = private;
	struct iio_dev *indio_dev = pf->indio_dev;
	struct as3935_state *st = iio_priv(indio_dev);
	int val, ret;

	ret = as3935_read(st, AS3935_DATA, &val);
	if (ret)
	goto err_read;

	st->buffer[0] = val & AS3935_DATA_MASK;
	iio_push_to_buffers_with_timestamp(indio_dev, &st->buffer,
	iio_get_time_ns(indio_dev));
	err_read:
	iio_trigger_notify_done(indio_dev->trig);

	return IRQ_HANDLED;
	}

	static const struct iio_trigger_ops iio_interrupt_trigger_ops = {
	.owner = THIS_MODULE,
	};

	static void as3935_event_work(struct work_struct *work)
	{
	struct as3935_state *st;
	int val;
	int ret;

	st = container_of(work, struct as3935_state, work.work);

	ret = as3935_read(st, AS3935_INT, &val);
	if (ret) {
	dev_warn(&st->spi->dev, "read error\n");
	return;
	}

	val &= AS3935_INT_MASK;

	switch (val) {
	case AS3935_EVENT_INT:
	iio_trigger_poll_chained(st->trig);
	break;
	case AS3935_NOISE_INT:
	dev_warn(&st->spi->dev, "noise level is too high\n");
	break;
	}
	}

	static irqreturn_t as3935_interrupt_handler(int irq, void *private)
	{
	struct iio_dev *indio_dev = private;
	struct as3935_state *st = iio_priv(indio_dev);

	/*
	* Delay work for >2 milliseconds after an interrupt to allow
	* estimated distance to recalculated.
	*/

	schedule_delayed_work(&st->work, msecs_to_jiffies(3));

	return IRQ_HANDLED;
	}

	static void calibrate_as3935(struct as3935_state *st)
	{
	/* mask disturber interrupt bit */
	as3935_write(st, AS3935_INT, BIT(5));

	as3935_write(st, AS3935_CALIBRATE, 0x96);
	as3935_write(st, AS3935_TUNE_CAP,
	BIT(5) \| (st->tune_cap / TUNE_CAP_DIV));

	mdelay(2);
	as3935_write(st, AS3935_TUNE_CAP, (st->tune_cap / TUNE_CAP_DIV));
	}

	#ifdef CONFIG_PM_SLEEP
	static int as3935_suspend(struct device *dev)
	{
	struct iio_dev *indio_dev = dev_get_drvdata(dev);
	struct as3935_state *st = iio_priv(indio_dev);
	int val, ret;

	mutex_lock(&st->lock);
	ret = as3935_read(st, AS3935_AFE_GAIN, &val);
	if (ret)
	goto err_suspend;
	val \|= AS3935_AFE_PWR_BIT;

	ret = as3935_write(st, AS3935_AFE_GAIN, val);

	err_suspend:
	mutex_unlock(&st->lock);

	return ret;
	}

	static int as3935_resume(struct device *dev)
	{
	struct iio_dev *indio_dev = dev_get_drvdata(dev);
	struct as3935_state *st = iio_priv(indio_dev);
	int val, ret;

	mutex_lock(&st->lock);
	ret = as3935_read(st, AS3935_AFE_GAIN, &val);
	if (ret)
	goto err_resume;
	val &= ~AS3935_AFE_PWR_BIT;
	ret = as3935_write(st, AS3935_AFE_GAIN, val);

	calibrate_as3935(st);

	err_resume:
	mutex_unlock(&st->lock);

	return ret;
	}

	static SIMPLE_DEV_PM_OPS(as3935_pm_ops, as3935_suspend, as3935_resume);
	#define AS3935_PM_OPS (&as3935_pm_ops)

	#else
	#define AS3935_PM_OPS NULL
	#endif

	static int as3935_probe(struct spi_device *spi)
	{
	struct iio_dev *indio_dev;
	struct iio_trigger *trig;
	struct as3935_state *st;
	struct device_node *np = spi->dev.of_node;
	int ret;

	/* Be sure lightning event interrupt is specified */
	if (!spi->irq) {
	dev_err(&spi->dev, "unable to get event interrupt\n");
	return -EINVAL;
	}

	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
	if (!indio_dev)
	return -ENOMEM;

	st = iio_priv(indio_dev);
	st->spi = spi;

	spi_set_drvdata(spi, indio_dev);
	mutex_init(&st->lock);
	INIT_DELAYED_WORK(&st->work, as3935_event_work);

	ret = of_property_read_u32(np,
	"ams,tuning-capacitor-pf", &st->tune_cap);
	if (ret) {
	st->tune_cap = 0;
	dev_warn(&spi->dev,
	"no tuning-capacitor-pf set, defaulting to %d",
	st->tune_cap);
	}

	if (st->tune_cap > MAX_PF_CAP) {
	dev_err(&spi->dev,
	"wrong tuning-capacitor-pf setting of %d\n",
	st->tune_cap);
	return -EINVAL;
	}

	indio_dev->dev.parent = &spi->dev;
	indio_dev->name = spi_get_device_id(spi)->name;
	indio_dev->channels = as3935_channels;
	indio_dev->num_channels = ARRAY_SIZE(as3935_channels);
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->info = &as3935_info;

	trig = devm_iio_trigger_alloc(&spi->dev, "%s-dev%d",
	indio_dev->name, indio_dev->id);

	if (!trig)
	return -ENOMEM;

	st->trig = trig;
	trig->dev.parent = indio_dev->dev.parent;
	iio_trigger_set_drvdata(trig, indio_dev);
	trig->ops = &iio_interrupt_trigger_ops;

	ret = iio_trigger_register(trig);
	if (ret) {
	dev_err(&spi->dev, "failed to register trigger\n");
	return ret;
	}

	ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time,
	&as3935_trigger_handler, NULL);

	if (ret) {
	dev_err(&spi->dev, "cannot setup iio trigger\n");
	goto unregister_trigger;
	}

	calibrate_as3935(st);

	ret = devm_request_irq(&spi->dev, spi->irq,
	&as3935_interrupt_handler,
	IRQF_TRIGGER_RISING,
	dev_name(&spi->dev),
	indio_dev);

	if (ret) {
	dev_err(&spi->dev, "unable to request irq\n");
	goto unregister_buffer;
	}

	ret = iio_device_register(indio_dev);
	if (ret < 0) {
	dev_err(&spi->dev, "unable to register device\n");
	goto unregister_buffer;
	}
	return 0;

	unregister_buffer:
	iio_triggered_buffer_cleanup(indio_dev);

	unregister_trigger:
	iio_trigger_unregister(st->trig);

	return ret;
	}

	static int as3935_remove(struct spi_device *spi)
	{
	struct iio_dev *indio_dev = spi_get_drvdata(spi);
	struct as3935_state *st = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);
	iio_triggered_buffer_cleanup(indio_dev);
	iio_trigger_unregister(st->trig);

	return 0;
	}

	static const struct of_device_id as3935_of_match[] = {
	{ .compatible = "ams,as3935", },
	{ /* sentinel */ },
	};
	MODULE_DEVICE_TABLE(of, as3935_of_match);

	static const struct spi_device_id as3935_id[] = {
	{"as3935", 0},
	{},
	};
	MODULE_DEVICE_TABLE(spi, as3935_id);

	static struct spi_driver as3935_driver = {
	.driver = {
	.name = "as3935",
	.of_match_table = of_match_ptr(as3935_of_match),
	.pm = AS3935_PM_OPS,
	},
	.probe = as3935_probe,
	.remove = as3935_remove,
	.id_table = as3935_id,
	};
	module_spi_driver(as3935_driver);

	MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
	MODULE_DESCRIPTION("AS3935 lightning sensor");
	MODULE_LICENSE("GPL");