drivers/iio/dac/ad5421.c - maze/linux - Git at Google

 /*
  * AD5421 Digital to analog converters  driver
  *
  * Copyright 2011 Analog Devices Inc.
  *
  * Licensed under the GPL-2.
  */

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

 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/events.h>
 #include <linux/iio/dac/ad5421.h>


 #define AD5421_REG_DAC_DATA		0x1
 #define AD5421_REG_CTRL			0x2
 #define AD5421_REG_OFFSET		0x3
 #define AD5421_REG_GAIN			0x4
 /* load dac and fault shared the same register number. Writing to it will cause
  * a dac load command, reading from it will return the fault status register */
 #define AD5421_REG_LOAD_DAC		0x5
 #define AD5421_REG_FAULT		0x5
 #define AD5421_REG_FORCE_ALARM_CURRENT	0x6
 #define AD5421_REG_RESET		0x7
 #define AD5421_REG_START_CONVERSION	0x8
 #define AD5421_REG_NOOP			0x9

 #define AD5421_CTRL_WATCHDOG_DISABLE	BIT(12)
 #define AD5421_CTRL_AUTO_FAULT_READBACK	BIT(11)
 #define AD5421_CTRL_MIN_CURRENT		BIT(9)
 #define AD5421_CTRL_ADC_SOURCE_TEMP	BIT(8)
 #define AD5421_CTRL_ADC_ENABLE		BIT(7)
 #define AD5421_CTRL_PWR_DOWN_INT_VREF	BIT(6)

 #define AD5421_FAULT_SPI			BIT(15)
 #define AD5421_FAULT_PEC			BIT(14)
 #define AD5421_FAULT_OVER_CURRENT		BIT(13)
 #define AD5421_FAULT_UNDER_CURRENT		BIT(12)
 #define AD5421_FAULT_TEMP_OVER_140		BIT(11)
 #define AD5421_FAULT_TEMP_OVER_100		BIT(10)
 #define AD5421_FAULT_UNDER_VOLTAGE_6V		BIT(9)
 #define AD5421_FAULT_UNDER_VOLTAGE_12V		BIT(8)

 /* These bits will cause the fault pin to go high */
 #define AD5421_FAULT_TRIGGER_IRQ \
 	(AD5421_FAULT_SPI | AD5421_FAULT_PEC | AD5421_FAULT_OVER_CURRENT | \
 	AD5421_FAULT_UNDER_CURRENT | AD5421_FAULT_TEMP_OVER_140)

 /**
  * struct ad5421_state - driver instance specific data
  * @spi:		spi_device
  * @ctrl:		control register cache
  * @current_range:	current range which the device is configured for
  * @data:		spi transfer buffers
  * @fault_mask:		software masking of events
  */
 struct ad5421_state {
 	struct spi_device		*spi;
 	unsigned int			ctrl;
 	enum ad5421_current_range	current_range;
 	unsigned int			fault_mask;

 	/*
 	 * DMA (thus cache coherency maintenance) requires the
 	 * transfer buffers to live in their own cache lines.
 	 */
 	union {
 		u32 d32;
 		u8 d8[4];
 	} data[2] ____cacheline_aligned;
 };

 static const struct iio_chan_spec ad5421_channels[] = {
 	{
 		.type = IIO_CURRENT,
 		.indexed = 1,
 		.output = 1,
 		.channel = 0,
 		.info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT |
 			IIO_CHAN_INFO_SCALE_SHARED_BIT |
 			IIO_CHAN_INFO_OFFSET_SHARED_BIT |
 			IIO_CHAN_INFO_CALIBSCALE_SEPARATE_BIT |
 			IIO_CHAN_INFO_CALIBBIAS_SEPARATE_BIT,
 		.scan_type = IIO_ST('u', 16, 16, 0),
 		.event_mask = IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING) |
 			IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_FALLING),
 	},
 	{
 		.type = IIO_TEMP,
 		.channel = -1,
 		.event_mask = IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
 	},
 };

 static int ad5421_write_unlocked(struct iio_dev *indio_dev,
 	unsigned int reg, unsigned int val)
 {
 	struct ad5421_state *st = iio_priv(indio_dev);

 	st->data[0].d32 = cpu_to_be32((reg << 16) | val);

 	return spi_write(st->spi, &st->data[0].d8[1], 3);
 }

 static int ad5421_write(struct iio_dev *indio_dev, unsigned int reg,
 	unsigned int val)
 {
 	int ret;

 	mutex_lock(&indio_dev->mlock);
 	ret = ad5421_write_unlocked(indio_dev, reg, val);
 	mutex_unlock(&indio_dev->mlock);

 	return ret;
 }

 static int ad5421_read(struct iio_dev *indio_dev, unsigned int reg)
 {
 	struct ad5421_state *st = iio_priv(indio_dev);
 	struct spi_message m;
 	int ret;
 	struct spi_transfer t[] = {
 		{
 			.tx_buf = &st->data[0].d8[1],
 			.len = 3,
 			.cs_change = 1,
 		}, {
 			.rx_buf = &st->data[1].d8[1],
 			.len = 3,
 		},
 	};

 	spi_message_init(&m);
 	spi_message_add_tail(&t[0], &m);
 	spi_message_add_tail(&t[1], &m);

 	mutex_lock(&indio_dev->mlock);

 	st->data[0].d32 = cpu_to_be32((1 << 23) | (reg << 16));

 	ret = spi_sync(st->spi, &m);
 	if (ret >= 0)
 		ret = be32_to_cpu(st->data[1].d32) & 0xffff;

 	mutex_unlock(&indio_dev->mlock);

 	return ret;
 }

 static int ad5421_update_ctrl(struct iio_dev *indio_dev, unsigned int set,
 	unsigned int clr)
 {
 	struct ad5421_state *st = iio_priv(indio_dev);
 	unsigned int ret;

 	mutex_lock(&indio_dev->mlock);

 	st->ctrl &= ~clr;
 	st->ctrl |= set;

 	ret = ad5421_write_unlocked(indio_dev, AD5421_REG_CTRL, st->ctrl);

 	mutex_unlock(&indio_dev->mlock);

 	return ret;
 }

 static irqreturn_t ad5421_fault_handler(int irq, void *data)
 {
 	struct iio_dev *indio_dev = data;
 	struct ad5421_state *st = iio_priv(indio_dev);
 	unsigned int fault;
 	unsigned int old_fault = 0;
 	unsigned int events;

 	fault = ad5421_read(indio_dev, AD5421_REG_FAULT);
 	if (!fault)
 		return IRQ_NONE;

 	/* If we had a fault, this might mean that the DAC has lost its state
 	 * and has been reset. Make sure that the control register actually
 	 * contains what we expect it to contain. Otherwise the watchdog might
 	 * be enabled and we get watchdog timeout faults, which will render the
 	 * DAC unusable. */
 	ad5421_update_ctrl(indio_dev, 0, 0);


 	/* The fault pin stays high as long as a fault condition is present and
 	 * it is not possible to mask fault conditions. For certain fault
 	 * conditions for example like over-temperature it takes some time
 	 * until the fault condition disappears. If we would exit the interrupt
 	 * handler immediately after handling the event it would be entered
 	 * again instantly. Thus we fall back to polling in case we detect that
 	 * a interrupt condition is still present.
 	 */
 	do {
 		/* 0xffff is a invalid value for the register and will only be
 		 * read if there has been a communication error */
 		if (fault == 0xffff)
 			fault = 0;

 		/* we are only interested in new events */
 		events = (old_fault ^ fault) & fault;
 		events &= st->fault_mask;

 		if (events & AD5421_FAULT_OVER_CURRENT) {
 			iio_push_event(indio_dev,
 				IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
 					0,
 					IIO_EV_TYPE_THRESH,
 					IIO_EV_DIR_RISING),
 			iio_get_time_ns());
 		}

 		if (events & AD5421_FAULT_UNDER_CURRENT) {
 			iio_push_event(indio_dev,
 				IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
 					0,
 					IIO_EV_TYPE_THRESH,
 					IIO_EV_DIR_FALLING),
 				iio_get_time_ns());
 		}

 		if (events & AD5421_FAULT_TEMP_OVER_140) {
 			iio_push_event(indio_dev,
 				IIO_UNMOD_EVENT_CODE(IIO_TEMP,
 					0,
 					IIO_EV_TYPE_MAG,
 					IIO_EV_DIR_RISING),
 				iio_get_time_ns());
 		}

 		old_fault = fault;
 		fault = ad5421_read(indio_dev, AD5421_REG_FAULT);

 		/* still active? go to sleep for some time */
 		if (fault & AD5421_FAULT_TRIGGER_IRQ)
 			msleep(1000);

 	} while (fault & AD5421_FAULT_TRIGGER_IRQ);


 	return IRQ_HANDLED;
 }

 static void ad5421_get_current_min_max(struct ad5421_state *st,
 	unsigned int *min, unsigned int *max)
 {
 	/* The current range is configured using external pins, which are
 	 * usually hard-wired and not run-time switchable. */
 	switch (st->current_range) {
 	case AD5421_CURRENT_RANGE_4mA_20mA:
 		*min = 4000;
 		*max = 20000;
 		break;
 	case AD5421_CURRENT_RANGE_3mA8_21mA:
 		*min = 3800;
 		*max = 21000;
 		break;
 	case AD5421_CURRENT_RANGE_3mA2_24mA:
 		*min = 3200;
 		*max = 24000;
 		break;
 	default:
 		*min = 0;
 		*max = 1;
 		break;
 	}
 }

 static inline unsigned int ad5421_get_offset(struct ad5421_state *st)
 {
 	unsigned int min, max;

 	ad5421_get_current_min_max(st, &min, &max);
 	return (min * (1 << 16)) / (max - min);
 }

 static inline unsigned int ad5421_get_scale(struct ad5421_state *st)
 {
 	unsigned int min, max;

 	ad5421_get_current_min_max(st, &min, &max);
 	return ((max - min) * 1000) / (1 << 16);
 }

 static int ad5421_read_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int *val, int *val2, long m)
 {
 	struct ad5421_state *st = iio_priv(indio_dev);
 	int ret;

 	if (chan->type != IIO_CURRENT)
 		return -EINVAL;

 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
 		ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
 		if (ret < 0)
 			return ret;
 		*val = ret;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		*val = 0;
 		*val2 = ad5421_get_scale(st);
 		return IIO_VAL_INT_PLUS_MICRO;
 	case IIO_CHAN_INFO_OFFSET:
 		*val = ad5421_get_offset(st);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_CALIBBIAS:
 		ret = ad5421_read(indio_dev, AD5421_REG_OFFSET);
 		if (ret < 0)
 			return ret;
 		*val = ret - 32768;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_CALIBSCALE:
 		ret = ad5421_read(indio_dev, AD5421_REG_GAIN);
 		if (ret < 0)
 			return ret;
 		*val = ret;
 		return IIO_VAL_INT;
 	}

 	return -EINVAL;
 }

 static int ad5421_write_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int val, int val2, long mask)
 {
 	const unsigned int max_val = 1 << 16;

 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		if (val >= max_val || val < 0)
 			return -EINVAL;

 		return ad5421_write(indio_dev, AD5421_REG_DAC_DATA, val);
 	case IIO_CHAN_INFO_CALIBBIAS:
 		val += 32768;
 		if (val >= max_val || val < 0)
 			return -EINVAL;

 		return ad5421_write(indio_dev, AD5421_REG_OFFSET, val);
 	case IIO_CHAN_INFO_CALIBSCALE:
 		if (val >= max_val || val < 0)
 			return -EINVAL;

 		return ad5421_write(indio_dev, AD5421_REG_GAIN, val);
 	default:
 		break;
 	}

 	return -EINVAL;
 }

 static int ad5421_write_event_config(struct iio_dev *indio_dev,
 	u64 event_code, int state)
 {
 	struct ad5421_state *st = iio_priv(indio_dev);
 	unsigned int mask;

 	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
 	case IIO_CURRENT:
 		if (IIO_EVENT_CODE_EXTRACT_DIR(event_code) ==
 			IIO_EV_DIR_RISING)
 			mask = AD5421_FAULT_OVER_CURRENT;
 		else
 			mask = AD5421_FAULT_UNDER_CURRENT;
 		break;
 	case IIO_TEMP:
 		mask = AD5421_FAULT_TEMP_OVER_140;
 		break;
 	default:
 		return -EINVAL;
 	}

 	mutex_lock(&indio_dev->mlock);
 	if (state)
 		st->fault_mask |= mask;
 	else
 		st->fault_mask &= ~mask;
 	mutex_unlock(&indio_dev->mlock);

 	return 0;
 }

 static int ad5421_read_event_config(struct iio_dev *indio_dev,
 	u64 event_code)
 {
 	struct ad5421_state *st = iio_priv(indio_dev);
 	unsigned int mask;

 	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
 	case IIO_CURRENT:
 		if (IIO_EVENT_CODE_EXTRACT_DIR(event_code) ==
 			IIO_EV_DIR_RISING)
 			mask = AD5421_FAULT_OVER_CURRENT;
 		else
 			mask = AD5421_FAULT_UNDER_CURRENT;
 		break;
 	case IIO_TEMP:
 		mask = AD5421_FAULT_TEMP_OVER_140;
 		break;
 	default:
 		return -EINVAL;
 	}

 	return (bool)(st->fault_mask & mask);
 }

 static int ad5421_read_event_value(struct iio_dev *indio_dev, u64 event_code,
 	int *val)
 {
 	int ret;

 	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
 	case IIO_CURRENT:
 		ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
 		if (ret < 0)
 			return ret;
 		*val = ret;
 		break;
 	case IIO_TEMP:
 		*val = 140000;
 		break;
 	default:
 		return -EINVAL;
 	}

 	return 0;
 }

 static const struct iio_info ad5421_info = {
 	.read_raw =		ad5421_read_raw,
 	.write_raw =		ad5421_write_raw,
 	.read_event_config =	ad5421_read_event_config,
 	.write_event_config =	ad5421_write_event_config,
 	.read_event_value =	ad5421_read_event_value,
 	.driver_module =	THIS_MODULE,
 };

 static int __devinit ad5421_probe(struct spi_device *spi)
 {
 	struct ad5421_platform_data *pdata = dev_get_platdata(&spi->dev);
 	struct iio_dev *indio_dev;
 	struct ad5421_state *st;
 	int ret;

 	indio_dev = iio_device_alloc(sizeof(*st));
 	if (indio_dev == NULL) {
 		dev_err(&spi->dev, "Failed to allocate iio device\n");
 		return  -ENOMEM;
 	}

 	st = iio_priv(indio_dev);
 	spi_set_drvdata(spi, indio_dev);

 	st->spi = spi;

 	indio_dev->dev.parent = &spi->dev;
 	indio_dev->name = "ad5421";
 	indio_dev->info = &ad5421_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = ad5421_channels;
 	indio_dev->num_channels = ARRAY_SIZE(ad5421_channels);

 	st->ctrl = AD5421_CTRL_WATCHDOG_DISABLE |
 			AD5421_CTRL_AUTO_FAULT_READBACK;

 	if (pdata) {
 		st->current_range = pdata->current_range;
 		if (pdata->external_vref)
 			st->ctrl |= AD5421_CTRL_PWR_DOWN_INT_VREF;
 	} else {
 		st->current_range = AD5421_CURRENT_RANGE_4mA_20mA;
 	}

 	/* write initial ctrl register value */
 	ad5421_update_ctrl(indio_dev, 0, 0);

 	if (spi->irq) {
 		ret = request_threaded_irq(spi->irq,
 					   NULL,
 					   ad5421_fault_handler,
 					   IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
 					   "ad5421 fault",
 					   indio_dev);
 		if (ret)
 			goto error_free;
 	}

 	ret = iio_device_register(indio_dev);
 	if (ret) {
 		dev_err(&spi->dev, "Failed to register iio device: %d\n", ret);
 		goto error_free_irq;
 	}

 	return 0;

 error_free_irq:
 	if (spi->irq)
 		free_irq(spi->irq, indio_dev);
 error_free:
 	iio_device_free(indio_dev);

 	return ret;
 }

 static int __devexit ad5421_remove(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev = spi_get_drvdata(spi);

 	iio_device_unregister(indio_dev);
 	if (spi->irq)
 		free_irq(spi->irq, indio_dev);
 	iio_device_free(indio_dev);

 	return 0;
 }

 static struct spi_driver ad5421_driver = {
 	.driver = {
 		   .name = "ad5421",
 		   .owner = THIS_MODULE,
 	},
 	.probe = ad5421_probe,
 	.remove = __devexit_p(ad5421_remove),
 };
 module_spi_driver(ad5421_driver);

 MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
 MODULE_DESCRIPTION("Analog Devices AD5421 DAC");
 MODULE_LICENSE("GPL v2");
 MODULE_ALIAS("spi:ad5421");
	/*
	* AD5421 Digital to analog converters driver
	*
	* Copyright 2011 Analog Devices Inc.
	*
	* Licensed under the GPL-2.
	*/

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

	#include <linux/iio/iio.h>
	#include <linux/iio/sysfs.h>
	#include <linux/iio/events.h>
	#include <linux/iio/dac/ad5421.h>


	#define AD5421_REG_DAC_DATA 0x1
	#define AD5421_REG_CTRL 0x2
	#define AD5421_REG_OFFSET 0x3
	#define AD5421_REG_GAIN 0x4
	/* load dac and fault shared the same register number. Writing to it will cause
	* a dac load command, reading from it will return the fault status register */
	#define AD5421_REG_LOAD_DAC 0x5
	#define AD5421_REG_FAULT 0x5
	#define AD5421_REG_FORCE_ALARM_CURRENT 0x6
	#define AD5421_REG_RESET 0x7
	#define AD5421_REG_START_CONVERSION 0x8
	#define AD5421_REG_NOOP 0x9

	#define AD5421_CTRL_WATCHDOG_DISABLE BIT(12)
	#define AD5421_CTRL_AUTO_FAULT_READBACK BIT(11)
	#define AD5421_CTRL_MIN_CURRENT BIT(9)
	#define AD5421_CTRL_ADC_SOURCE_TEMP BIT(8)
	#define AD5421_CTRL_ADC_ENABLE BIT(7)
	#define AD5421_CTRL_PWR_DOWN_INT_VREF BIT(6)

	#define AD5421_FAULT_SPI BIT(15)
	#define AD5421_FAULT_PEC BIT(14)
	#define AD5421_FAULT_OVER_CURRENT BIT(13)
	#define AD5421_FAULT_UNDER_CURRENT BIT(12)
	#define AD5421_FAULT_TEMP_OVER_140 BIT(11)
	#define AD5421_FAULT_TEMP_OVER_100 BIT(10)
	#define AD5421_FAULT_UNDER_VOLTAGE_6V BIT(9)
	#define AD5421_FAULT_UNDER_VOLTAGE_12V BIT(8)

	/* These bits will cause the fault pin to go high */
	#define AD5421_FAULT_TRIGGER_IRQ \
	(AD5421_FAULT_SPI \| AD5421_FAULT_PEC \| AD5421_FAULT_OVER_CURRENT \| \
	AD5421_FAULT_UNDER_CURRENT \| AD5421_FAULT_TEMP_OVER_140)

	/**
	* struct ad5421_state - driver instance specific data
	* @spi: spi_device
	* @ctrl: control register cache
	* @current_range: current range which the device is configured for
	* @data: spi transfer buffers
	* @fault_mask: software masking of events
	*/
	struct ad5421_state {
	struct spi_device *spi;
	unsigned int ctrl;
	enum ad5421_current_range current_range;
	unsigned int fault_mask;

	/*
	* DMA (thus cache coherency maintenance) requires the
	* transfer buffers to live in their own cache lines.
	*/
	union {
	u32 d32;
	u8 d8[4];
	} data[2] ____cacheline_aligned;
	};

	static const struct iio_chan_spec ad5421_channels[] = {
	{
	.type = IIO_CURRENT,
	.indexed = 1,
	.output = 1,
	.channel = 0,
	.info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT \|
	IIO_CHAN_INFO_SCALE_SHARED_BIT \|
	IIO_CHAN_INFO_OFFSET_SHARED_BIT \|
	IIO_CHAN_INFO_CALIBSCALE_SEPARATE_BIT \|
	IIO_CHAN_INFO_CALIBBIAS_SEPARATE_BIT,
	.scan_type = IIO_ST('u', 16, 16, 0),
	.event_mask = IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING) \|
	IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_FALLING),
	},
	{
	.type = IIO_TEMP,
	.channel = -1,
	.event_mask = IIO_EV_BIT(IIO_EV_TYPE_THRESH, IIO_EV_DIR_RISING),
	},
	};

	static int ad5421_write_unlocked(struct iio_dev *indio_dev,
	unsigned int reg, unsigned int val)
	{
	struct ad5421_state *st = iio_priv(indio_dev);

	st->data[0].d32 = cpu_to_be32((reg << 16) \| val);

	return spi_write(st->spi, &st->data[0].d8[1], 3);
	}

	static int ad5421_write(struct iio_dev *indio_dev, unsigned int reg,
	unsigned int val)
	{
	int ret;

	mutex_lock(&indio_dev->mlock);
	ret = ad5421_write_unlocked(indio_dev, reg, val);
	mutex_unlock(&indio_dev->mlock);

	return ret;
	}

	static int ad5421_read(struct iio_dev *indio_dev, unsigned int reg)
	{
	struct ad5421_state *st = iio_priv(indio_dev);
	struct spi_message m;
	int ret;
	struct spi_transfer t[] = {
	{
	.tx_buf = &st->data[0].d8[1],
	.len = 3,
	.cs_change = 1,
	}, {
	.rx_buf = &st->data[1].d8[1],
	.len = 3,
	},
	};

	spi_message_init(&m);
	spi_message_add_tail(&t[0], &m);
	spi_message_add_tail(&t[1], &m);

	mutex_lock(&indio_dev->mlock);

	st->data[0].d32 = cpu_to_be32((1 << 23) \| (reg << 16));

	ret = spi_sync(st->spi, &m);
	if (ret >= 0)
	ret = be32_to_cpu(st->data[1].d32) & 0xffff;

	mutex_unlock(&indio_dev->mlock);

	return ret;
	}

	static int ad5421_update_ctrl(struct iio_dev *indio_dev, unsigned int set,
	unsigned int clr)
	{
	struct ad5421_state *st = iio_priv(indio_dev);
	unsigned int ret;

	mutex_lock(&indio_dev->mlock);

	st->ctrl &= ~clr;
	st->ctrl \|= set;

	ret = ad5421_write_unlocked(indio_dev, AD5421_REG_CTRL, st->ctrl);

	mutex_unlock(&indio_dev->mlock);

	return ret;
	}

	static irqreturn_t ad5421_fault_handler(int irq, void *data)
	{
	struct iio_dev *indio_dev = data;
	struct ad5421_state *st = iio_priv(indio_dev);
	unsigned int fault;
	unsigned int old_fault = 0;
	unsigned int events;

	fault = ad5421_read(indio_dev, AD5421_REG_FAULT);
	if (!fault)
	return IRQ_NONE;

	/* If we had a fault, this might mean that the DAC has lost its state
	* and has been reset. Make sure that the control register actually
	* contains what we expect it to contain. Otherwise the watchdog might
	* be enabled and we get watchdog timeout faults, which will render the
	* DAC unusable. */
	ad5421_update_ctrl(indio_dev, 0, 0);


	/* The fault pin stays high as long as a fault condition is present and
	* it is not possible to mask fault conditions. For certain fault
	* conditions for example like over-temperature it takes some time
	* until the fault condition disappears. If we would exit the interrupt
	* handler immediately after handling the event it would be entered
	* again instantly. Thus we fall back to polling in case we detect that
	* a interrupt condition is still present.
	*/
	do {
	/* 0xffff is a invalid value for the register and will only be
	* read if there has been a communication error */
	if (fault == 0xffff)
	fault = 0;

	/* we are only interested in new events */
	events = (old_fault ^ fault) & fault;
	events &= st->fault_mask;

	if (events & AD5421_FAULT_OVER_CURRENT) {
	iio_push_event(indio_dev,
	IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
	0,
	IIO_EV_TYPE_THRESH,
	IIO_EV_DIR_RISING),
	iio_get_time_ns());
	}

	if (events & AD5421_FAULT_UNDER_CURRENT) {
	iio_push_event(indio_dev,
	IIO_UNMOD_EVENT_CODE(IIO_CURRENT,
	0,
	IIO_EV_TYPE_THRESH,
	IIO_EV_DIR_FALLING),
	iio_get_time_ns());
	}

	if (events & AD5421_FAULT_TEMP_OVER_140) {
	iio_push_event(indio_dev,
	IIO_UNMOD_EVENT_CODE(IIO_TEMP,
	0,
	IIO_EV_TYPE_MAG,
	IIO_EV_DIR_RISING),
	iio_get_time_ns());
	}

	old_fault = fault;
	fault = ad5421_read(indio_dev, AD5421_REG_FAULT);

	/* still active? go to sleep for some time */
	if (fault & AD5421_FAULT_TRIGGER_IRQ)
	msleep(1000);

	} while (fault & AD5421_FAULT_TRIGGER_IRQ);


	return IRQ_HANDLED;
	}

	static void ad5421_get_current_min_max(struct ad5421_state *st,
	unsigned int min, unsigned int max)
	{
	/* The current range is configured using external pins, which are
	* usually hard-wired and not run-time switchable. */
	switch (st->current_range) {
	case AD5421_CURRENT_RANGE_4mA_20mA:
	*min = 4000;
	*max = 20000;
	break;
	case AD5421_CURRENT_RANGE_3mA8_21mA:
	*min = 3800;
	*max = 21000;
	break;
	case AD5421_CURRENT_RANGE_3mA2_24mA:
	*min = 3200;
	*max = 24000;
	break;
	default:
	*min = 0;
	*max = 1;
	break;
	}
	}

	static inline unsigned int ad5421_get_offset(struct ad5421_state *st)
	{
	unsigned int min, max;

	ad5421_get_current_min_max(st, &min, &max);
	return (min * (1 << 16)) / (max - min);
	}

	static inline unsigned int ad5421_get_scale(struct ad5421_state *st)
	{
	unsigned int min, max;

	ad5421_get_current_min_max(st, &min, &max);
	return ((max - min) * 1000) / (1 << 16);
	}

	static int ad5421_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const chan, int val, int *val2, long m)
	{
	struct ad5421_state *st = iio_priv(indio_dev);
	int ret;

	if (chan->type != IIO_CURRENT)
	return -EINVAL;

	switch (m) {
	case IIO_CHAN_INFO_RAW:
	ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
	if (ret < 0)
	return ret;
	*val = ret;
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
	*val = 0;
	*val2 = ad5421_get_scale(st);
	return IIO_VAL_INT_PLUS_MICRO;
	case IIO_CHAN_INFO_OFFSET:
	*val = ad5421_get_offset(st);
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_CALIBBIAS:
	ret = ad5421_read(indio_dev, AD5421_REG_OFFSET);
	if (ret < 0)
	return ret;
	*val = ret - 32768;
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_CALIBSCALE:
	ret = ad5421_read(indio_dev, AD5421_REG_GAIN);
	if (ret < 0)
	return ret;
	*val = ret;
	return IIO_VAL_INT;
	}

	return -EINVAL;
	}

	static int ad5421_write_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan, int val, int val2, long mask)
	{
	const unsigned int max_val = 1 << 16;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
	if (val >= max_val \|\| val < 0)
	return -EINVAL;

	return ad5421_write(indio_dev, AD5421_REG_DAC_DATA, val);
	case IIO_CHAN_INFO_CALIBBIAS:
	val += 32768;
	if (val >= max_val \|\| val < 0)
	return -EINVAL;

	return ad5421_write(indio_dev, AD5421_REG_OFFSET, val);
	case IIO_CHAN_INFO_CALIBSCALE:
	if (val >= max_val \|\| val < 0)
	return -EINVAL;

	return ad5421_write(indio_dev, AD5421_REG_GAIN, val);
	default:
	break;
	}

	return -EINVAL;
	}

	static int ad5421_write_event_config(struct iio_dev *indio_dev,
	u64 event_code, int state)
	{
	struct ad5421_state *st = iio_priv(indio_dev);
	unsigned int mask;

	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
	case IIO_CURRENT:
	if (IIO_EVENT_CODE_EXTRACT_DIR(event_code) ==
	IIO_EV_DIR_RISING)
	mask = AD5421_FAULT_OVER_CURRENT;
	else
	mask = AD5421_FAULT_UNDER_CURRENT;
	break;
	case IIO_TEMP:
	mask = AD5421_FAULT_TEMP_OVER_140;
	break;
	default:
	return -EINVAL;
	}

	mutex_lock(&indio_dev->mlock);
	if (state)
	st->fault_mask \|= mask;
	else
	st->fault_mask &= ~mask;
	mutex_unlock(&indio_dev->mlock);

	return 0;
	}

	static int ad5421_read_event_config(struct iio_dev *indio_dev,
	u64 event_code)
	{
	struct ad5421_state *st = iio_priv(indio_dev);
	unsigned int mask;

	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
	case IIO_CURRENT:
	if (IIO_EVENT_CODE_EXTRACT_DIR(event_code) ==
	IIO_EV_DIR_RISING)
	mask = AD5421_FAULT_OVER_CURRENT;
	else
	mask = AD5421_FAULT_UNDER_CURRENT;
	break;
	case IIO_TEMP:
	mask = AD5421_FAULT_TEMP_OVER_140;
	break;
	default:
	return -EINVAL;
	}

	return (bool)(st->fault_mask & mask);
	}

	static int ad5421_read_event_value(struct iio_dev *indio_dev, u64 event_code,
	int *val)
	{
	int ret;

	switch (IIO_EVENT_CODE_EXTRACT_CHAN_TYPE(event_code)) {
	case IIO_CURRENT:
	ret = ad5421_read(indio_dev, AD5421_REG_DAC_DATA);
	if (ret < 0)
	return ret;
	*val = ret;
	break;
	case IIO_TEMP:
	*val = 140000;
	break;
	default:
	return -EINVAL;
	}

	return 0;
	}

	static const struct iio_info ad5421_info = {
	.read_raw = ad5421_read_raw,
	.write_raw = ad5421_write_raw,
	.read_event_config = ad5421_read_event_config,
	.write_event_config = ad5421_write_event_config,
	.read_event_value = ad5421_read_event_value,
	.driver_module = THIS_MODULE,
	};

	static int __devinit ad5421_probe(struct spi_device *spi)
	{
	struct ad5421_platform_data *pdata = dev_get_platdata(&spi->dev);
	struct iio_dev *indio_dev;
	struct ad5421_state *st;
	int ret;

	indio_dev = iio_device_alloc(sizeof(*st));
	if (indio_dev == NULL) {
	dev_err(&spi->dev, "Failed to allocate iio device\n");
	return -ENOMEM;
	}

	st = iio_priv(indio_dev);
	spi_set_drvdata(spi, indio_dev);

	st->spi = spi;

	indio_dev->dev.parent = &spi->dev;
	indio_dev->name = "ad5421";
	indio_dev->info = &ad5421_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = ad5421_channels;
	indio_dev->num_channels = ARRAY_SIZE(ad5421_channels);

	st->ctrl = AD5421_CTRL_WATCHDOG_DISABLE \|
	AD5421_CTRL_AUTO_FAULT_READBACK;

	if (pdata) {
	st->current_range = pdata->current_range;
	if (pdata->external_vref)
	st->ctrl \|= AD5421_CTRL_PWR_DOWN_INT_VREF;
	} else {
	st->current_range = AD5421_CURRENT_RANGE_4mA_20mA;
	}

	/* write initial ctrl register value */
	ad5421_update_ctrl(indio_dev, 0, 0);

	if (spi->irq) {
	ret = request_threaded_irq(spi->irq,
	NULL,
	ad5421_fault_handler,
	IRQF_TRIGGER_HIGH \| IRQF_ONESHOT,
	"ad5421 fault",
	indio_dev);
	if (ret)
	goto error_free;
	}

	ret = iio_device_register(indio_dev);
	if (ret) {
	dev_err(&spi->dev, "Failed to register iio device: %d\n", ret);
	goto error_free_irq;
	}

	return 0;

	error_free_irq:
	if (spi->irq)
	free_irq(spi->irq, indio_dev);
	error_free:
	iio_device_free(indio_dev);

	return ret;
	}

	static int __devexit ad5421_remove(struct spi_device *spi)
	{
	struct iio_dev *indio_dev = spi_get_drvdata(spi);

	iio_device_unregister(indio_dev);
	if (spi->irq)
	free_irq(spi->irq, indio_dev);
	iio_device_free(indio_dev);

	return 0;
	}

	static struct spi_driver ad5421_driver = {
	.driver = {
	.name = "ad5421",
	.owner = THIS_MODULE,
	},
	.probe = ad5421_probe,
	.remove = __devexit_p(ad5421_remove),
	};
	module_spi_driver(ad5421_driver);

	MODULE_AUTHOR("Lars-Peter Clausen <lars@metafoo.de>");
	MODULE_DESCRIPTION("Analog Devices AD5421 DAC");
	MODULE_LICENSE("GPL v2");
	MODULE_ALIAS("spi:ad5421");