drivers/iio/adc/ti-ads8688.c - kernel/msm-4.19 - Gitiles

 /*
  * Copyright (C) 2015 Prevas A/S
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */

 #include <linux/device.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
 #include <linux/spi/spi.h>
 #include <linux/regulator/consumer.h>
 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/of.h>

 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>

 #define ADS8688_CMD_REG(x)		(x << 8)
 #define ADS8688_CMD_REG_NOOP		0x00
 #define ADS8688_CMD_REG_RST		0x85
 #define ADS8688_CMD_REG_MAN_CH(chan)	(0xC0 | (4 * chan))
 #define ADS8688_CMD_DONT_CARE_BITS	16

 #define ADS8688_PROG_REG(x)		(x << 9)
 #define ADS8688_PROG_REG_RANGE_CH(chan)	(0x05 + chan)
 #define ADS8688_PROG_WR_BIT		BIT(8)
 #define ADS8688_PROG_DONT_CARE_BITS	8

 #define ADS8688_REG_PLUSMINUS25VREF	0
 #define ADS8688_REG_PLUSMINUS125VREF	1
 #define ADS8688_REG_PLUSMINUS0625VREF	2
 #define ADS8688_REG_PLUS25VREF		5
 #define ADS8688_REG_PLUS125VREF		6

 #define ADS8688_VREF_MV			4096
 #define ADS8688_REALBITS		16

 /*
  * enum ads8688_range - ADS8688 reference voltage range
  * @ADS8688_PLUSMINUS25VREF: Device is configured for input range ±2.5 * VREF
  * @ADS8688_PLUSMINUS125VREF: Device is configured for input range ±1.25 * VREF
  * @ADS8688_PLUSMINUS0625VREF: Device is configured for input range ±0.625 * VREF
  * @ADS8688_PLUS25VREF: Device is configured for input range 0 - 2.5 * VREF
  * @ADS8688_PLUS125VREF: Device is configured for input range 0 - 1.25 * VREF
  */
 enum ads8688_range {
 	ADS8688_PLUSMINUS25VREF,
 	ADS8688_PLUSMINUS125VREF,
 	ADS8688_PLUSMINUS0625VREF,
 	ADS8688_PLUS25VREF,
 	ADS8688_PLUS125VREF,
 };

 struct ads8688_chip_info {
 	const struct iio_chan_spec *channels;
 	unsigned int num_channels;
 };

 struct ads8688_state {
 	struct mutex			lock;
 	const struct ads8688_chip_info	*chip_info;
 	struct spi_device		*spi;
 	struct regulator		*reg;
 	unsigned int			vref_mv;
 	enum ads8688_range		range[8];
 	union {
 		__be32 d32;
 		u8 d8[4];
 	} data[2] ____cacheline_aligned;
 };

 enum ads8688_id {
 	ID_ADS8684,
 	ID_ADS8688,
 };

 struct ads8688_ranges {
 	enum ads8688_range range;
 	unsigned int scale;
 	int offset;
 	u8 reg;
 };

 static const struct ads8688_ranges ads8688_range_def[5] = {
 	{
 		.range = ADS8688_PLUSMINUS25VREF,
 		.scale = 76295,
 		.offset = -(1 << (ADS8688_REALBITS - 1)),
 		.reg = ADS8688_REG_PLUSMINUS25VREF,
 	}, {
 		.range = ADS8688_PLUSMINUS125VREF,
 		.scale = 38148,
 		.offset = -(1 << (ADS8688_REALBITS - 1)),
 		.reg = ADS8688_REG_PLUSMINUS125VREF,
 	}, {
 		.range = ADS8688_PLUSMINUS0625VREF,
 		.scale = 19074,
 		.offset = -(1 << (ADS8688_REALBITS - 1)),
 		.reg = ADS8688_REG_PLUSMINUS0625VREF,
 	}, {
 		.range = ADS8688_PLUS25VREF,
 		.scale = 38148,
 		.offset = 0,
 		.reg = ADS8688_REG_PLUS25VREF,
 	}, {
 		.range = ADS8688_PLUS125VREF,
 		.scale = 19074,
 		.offset = 0,
 		.reg = ADS8688_REG_PLUS125VREF,
 	}
 };

 static ssize_t ads8688_show_scales(struct device *dev,
 				   struct device_attribute *attr, char *buf)
 {
 	struct ads8688_state *st = iio_priv(dev_to_iio_dev(dev));

 	return sprintf(buf, "0.%09u 0.%09u 0.%09u\n",
 		       ads8688_range_def[0].scale * st->vref_mv,
 		       ads8688_range_def[1].scale * st->vref_mv,
 		       ads8688_range_def[2].scale * st->vref_mv);
 }

 static ssize_t ads8688_show_offsets(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
 	return sprintf(buf, "%d %d\n", ads8688_range_def[0].offset,
 		       ads8688_range_def[3].offset);
 }

 static IIO_DEVICE_ATTR(in_voltage_scale_available, S_IRUGO,
 		       ads8688_show_scales, NULL, 0);
 static IIO_DEVICE_ATTR(in_voltage_offset_available, S_IRUGO,
 		       ads8688_show_offsets, NULL, 0);

 static struct attribute *ads8688_attributes[] = {
 	&iio_dev_attr_in_voltage_scale_available.dev_attr.attr,
 	&iio_dev_attr_in_voltage_offset_available.dev_attr.attr,
 	NULL,
 };

 static const struct attribute_group ads8688_attribute_group = {
 	.attrs = ads8688_attributes,
 };

 #define ADS8688_CHAN(index)					\
 {								\
 	.type = IIO_VOLTAGE,					\
 	.indexed = 1,						\
 	.channel = index,					\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW)		\
 			      | BIT(IIO_CHAN_INFO_SCALE)	\
 			      | BIT(IIO_CHAN_INFO_OFFSET),	\
 }

 static const struct iio_chan_spec ads8684_channels[] = {
 	ADS8688_CHAN(0),
 	ADS8688_CHAN(1),
 	ADS8688_CHAN(2),
 	ADS8688_CHAN(3),
 };

 static const struct iio_chan_spec ads8688_channels[] = {
 	ADS8688_CHAN(0),
 	ADS8688_CHAN(1),
 	ADS8688_CHAN(2),
 	ADS8688_CHAN(3),
 	ADS8688_CHAN(4),
 	ADS8688_CHAN(5),
 	ADS8688_CHAN(6),
 	ADS8688_CHAN(7),
 };

 static int ads8688_prog_write(struct iio_dev *indio_dev, unsigned int addr,
 			      unsigned int val)
 {
 	struct ads8688_state *st = iio_priv(indio_dev);
 	u32 tmp;

 	tmp = ADS8688_PROG_REG(addr) | ADS8688_PROG_WR_BIT | val;
 	tmp <<= ADS8688_PROG_DONT_CARE_BITS;
 	st->data[0].d32 = cpu_to_be32(tmp);

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

 static int ads8688_reset(struct iio_dev *indio_dev)
 {
 	struct ads8688_state *st = iio_priv(indio_dev);
 	u32 tmp;

 	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_RST);
 	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
 	st->data[0].d32 = cpu_to_be32(tmp);

 	return spi_write(st->spi, &st->data[0].d8[0], 4);
 }

 static int ads8688_read(struct iio_dev *indio_dev, unsigned int chan)
 {
 	struct ads8688_state *st = iio_priv(indio_dev);
 	int ret;
 	u32 tmp;
 	struct spi_transfer t[] = {
 		{
 			.tx_buf = &st->data[0].d8[0],
 			.len = 4,
 			.cs_change = 1,
 		}, {
 			.tx_buf = &st->data[1].d8[0],
 			.rx_buf = &st->data[1].d8[0],
 			.len = 4,
 		},
 	};

 	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_MAN_CH(chan));
 	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
 	st->data[0].d32 = cpu_to_be32(tmp);

 	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_NOOP);
 	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
 	st->data[1].d32 = cpu_to_be32(tmp);

 	ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));
 	if (ret < 0)
 		return ret;

 	return be32_to_cpu(st->data[1].d32) & 0xffff;
 }

 static int ads8688_read_raw(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan,
 			    int *val, int *val2, long m)
 {
 	int ret, offset;
 	unsigned long scale_mv;

 	struct ads8688_state *st = iio_priv(indio_dev);

 	mutex_lock(&st->lock);
 	switch (m) {
 	case IIO_CHAN_INFO_RAW:
 		ret = ads8688_read(indio_dev, chan->channel);
 		mutex_unlock(&st->lock);
 		if (ret < 0)
 			return ret;
 		*val = ret;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		scale_mv = st->vref_mv;
 		scale_mv *= ads8688_range_def[st->range[chan->channel]].scale;
 		*val = 0;
 		*val2 = scale_mv;
 		mutex_unlock(&st->lock);
 		return IIO_VAL_INT_PLUS_NANO;
 	case IIO_CHAN_INFO_OFFSET:
 		offset = ads8688_range_def[st->range[chan->channel]].offset;
 		*val = offset;
 		mutex_unlock(&st->lock);
 		return IIO_VAL_INT;
 	}
 	mutex_unlock(&st->lock);

 	return -EINVAL;
 }

 static int ads8688_write_reg_range(struct iio_dev *indio_dev,
 				   struct iio_chan_spec const *chan,
 				   enum ads8688_range range)
 {
 	unsigned int tmp;
 	int ret;

 	tmp = ADS8688_PROG_REG_RANGE_CH(chan->channel);
 	ret = ads8688_prog_write(indio_dev, tmp, range);

 	return ret;
 }

 static int ads8688_write_raw(struct iio_dev *indio_dev,
 			     struct iio_chan_spec const *chan,
 			     int val, int val2, long mask)
 {
 	struct ads8688_state *st = iio_priv(indio_dev);
 	unsigned int scale = 0;
 	int ret = -EINVAL, i, offset = 0;

 	mutex_lock(&st->lock);
 	switch (mask) {
 	case IIO_CHAN_INFO_SCALE:
 		/* If the offset is 0 the ±2.5 * VREF mode is not available */
 		offset = ads8688_range_def[st->range[chan->channel]].offset;
 		if (offset == 0 && val2 == ads8688_range_def[0].scale * st->vref_mv) {
 			mutex_unlock(&st->lock);
 			return -EINVAL;
 		}

 		/* Lookup new mode */
 		for (i = 0; i < ARRAY_SIZE(ads8688_range_def); i++)
 			if (val2 == ads8688_range_def[i].scale * st->vref_mv &&
 			    offset == ads8688_range_def[i].offset) {
 				ret = ads8688_write_reg_range(indio_dev, chan,
 					ads8688_range_def[i].reg);
 				break;
 			}
 		break;
 	case IIO_CHAN_INFO_OFFSET:
 		/*
 		 * There are only two available offsets:
 		 * 0 and -(1 << (ADS8688_REALBITS - 1))
 		 */
 		if (!(ads8688_range_def[0].offset == val ||
 		    ads8688_range_def[3].offset == val)) {
 			mutex_unlock(&st->lock);
 			return -EINVAL;
 		}

 		/*
 		 * If the device are in ±2.5 * VREF mode, it's not allowed to
 		 * switch to a mode where the offset is 0
 		 */
 		if (val == 0 &&
 		    st->range[chan->channel] == ADS8688_PLUSMINUS25VREF) {
 			mutex_unlock(&st->lock);
 			return -EINVAL;
 		}

 		scale = ads8688_range_def[st->range[chan->channel]].scale;

 		/* Lookup new mode */
 		for (i = 0; i < ARRAY_SIZE(ads8688_range_def); i++)
 			if (val == ads8688_range_def[i].offset &&
 			    scale == ads8688_range_def[i].scale) {
 				ret = ads8688_write_reg_range(indio_dev, chan,
 					ads8688_range_def[i].reg);
 				break;
 			}
 		break;
 	}

 	if (!ret)
 		st->range[chan->channel] = ads8688_range_def[i].range;

 	mutex_unlock(&st->lock);

 	return ret;
 }

 static int ads8688_write_raw_get_fmt(struct iio_dev *indio_dev,
 				     struct iio_chan_spec const *chan,
 				     long mask)
 {
 	switch (mask) {
 	case IIO_CHAN_INFO_SCALE:
 		return IIO_VAL_INT_PLUS_NANO;
 	case IIO_CHAN_INFO_OFFSET:
 		return IIO_VAL_INT;
 	}

 	return -EINVAL;
 }

 static const struct iio_info ads8688_info = {
 	.read_raw = &ads8688_read_raw,
 	.write_raw = &ads8688_write_raw,
 	.write_raw_get_fmt = &ads8688_write_raw_get_fmt,
 	.attrs = &ads8688_attribute_group,
 	.driver_module = THIS_MODULE,
 };

 static const struct ads8688_chip_info ads8688_chip_info_tbl[] = {
 	[ID_ADS8684] = {
 		.channels = ads8684_channels,
 		.num_channels = ARRAY_SIZE(ads8684_channels),
 	},
 	[ID_ADS8688] = {
 		.channels = ads8688_channels,
 		.num_channels = ARRAY_SIZE(ads8688_channels),
 	},
 };

 static int ads8688_probe(struct spi_device *spi)
 {
 	struct ads8688_state *st;
 	struct iio_dev *indio_dev;
 	int ret;

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

 	st = iio_priv(indio_dev);

 	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
 	if (!IS_ERR(st->reg)) {
 		ret = regulator_enable(st->reg);
 		if (ret)
 			return ret;

 		ret = regulator_get_voltage(st->reg);
 		if (ret < 0)
 			goto error_out;

 		st->vref_mv = ret / 1000;
 	} else {
 		/* Use internal reference */
 		st->vref_mv = ADS8688_VREF_MV;
 	}

 	st->chip_info =	&ads8688_chip_info_tbl[spi_get_device_id(spi)->driver_data];

 	spi->mode = SPI_MODE_1;

 	spi_set_drvdata(spi, indio_dev);

 	st->spi = spi;

 	indio_dev->name = spi_get_device_id(spi)->name;
 	indio_dev->dev.parent = &spi->dev;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->channels = st->chip_info->channels;
 	indio_dev->num_channels = st->chip_info->num_channels;
 	indio_dev->info = &ads8688_info;

 	ads8688_reset(indio_dev);

 	mutex_init(&st->lock);

 	ret = iio_device_register(indio_dev);
 	if (ret)
 		goto error_out;

 	return 0;

 error_out:
 	if (!IS_ERR_OR_NULL(st->reg))
 		regulator_disable(st->reg);

 	return ret;
 }

 static int ads8688_remove(struct spi_device *spi)
 {
 	struct iio_dev *indio_dev = spi_get_drvdata(spi);
 	struct ads8688_state *st = iio_priv(indio_dev);

 	iio_device_unregister(indio_dev);

 	if (!IS_ERR_OR_NULL(st->reg))
 		regulator_disable(st->reg);

 	return 0;
 }

 static const struct spi_device_id ads8688_id[] = {
 	{"ads8684", ID_ADS8684},
 	{"ads8688", ID_ADS8688},
 	{}
 };
 MODULE_DEVICE_TABLE(spi, ads8688_id);

 static const struct of_device_id ads8688_of_match[] = {
 	{ .compatible = "ti,ads8684" },
 	{ .compatible = "ti,ads8688" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ads8688_of_match);

 static struct spi_driver ads8688_driver = {
 	.driver = {
 		.name	= "ads8688",
 		.owner	= THIS_MODULE,
 	},
 	.probe		= ads8688_probe,
 	.remove		= ads8688_remove,
 	.id_table	= ads8688_id,
 };
 module_spi_driver(ads8688_driver);

 MODULE_AUTHOR("Sean Nyekjaer <sean.nyekjaer@prevas.dk>");
 MODULE_DESCRIPTION("Texas Instruments ADS8688 driver");
 MODULE_LICENSE("GPL v2");
	/*
	* Copyright (C) 2015 Prevas A/S
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/

	#include <linux/device.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/sysfs.h>
	#include <linux/spi/spi.h>
	#include <linux/regulator/consumer.h>
	#include <linux/err.h>
	#include <linux/module.h>
	#include <linux/of.h>

	#include <linux/iio/iio.h>
	#include <linux/iio/sysfs.h>

	#define ADS8688_CMD_REG(x) (x << 8)
	#define ADS8688_CMD_REG_NOOP 0x00
	#define ADS8688_CMD_REG_RST 0x85
	#define ADS8688_CMD_REG_MAN_CH(chan) (0xC0 \| (4 * chan))
	#define ADS8688_CMD_DONT_CARE_BITS 16

	#define ADS8688_PROG_REG(x) (x << 9)
	#define ADS8688_PROG_REG_RANGE_CH(chan) (0x05 + chan)
	#define ADS8688_PROG_WR_BIT BIT(8)
	#define ADS8688_PROG_DONT_CARE_BITS 8

	#define ADS8688_REG_PLUSMINUS25VREF 0
	#define ADS8688_REG_PLUSMINUS125VREF 1
	#define ADS8688_REG_PLUSMINUS0625VREF 2
	#define ADS8688_REG_PLUS25VREF 5
	#define ADS8688_REG_PLUS125VREF 6

	#define ADS8688_VREF_MV 4096
	#define ADS8688_REALBITS 16

	/*
	* enum ads8688_range - ADS8688 reference voltage range
	* @ADS8688_PLUSMINUS25VREF: Device is configured for input range ±2.5 * VREF
	* @ADS8688_PLUSMINUS125VREF: Device is configured for input range ±1.25 * VREF
	* @ADS8688_PLUSMINUS0625VREF: Device is configured for input range ±0.625 * VREF
	* @ADS8688_PLUS25VREF: Device is configured for input range 0 - 2.5 * VREF
	* @ADS8688_PLUS125VREF: Device is configured for input range 0 - 1.25 * VREF
	*/
	enum ads8688_range {
	ADS8688_PLUSMINUS25VREF,
	ADS8688_PLUSMINUS125VREF,
	ADS8688_PLUSMINUS0625VREF,
	ADS8688_PLUS25VREF,
	ADS8688_PLUS125VREF,
	};

	struct ads8688_chip_info {
	const struct iio_chan_spec *channels;
	unsigned int num_channels;
	};

	struct ads8688_state {
	struct mutex lock;
	const struct ads8688_chip_info *chip_info;
	struct spi_device *spi;
	struct regulator *reg;
	unsigned int vref_mv;
	enum ads8688_range range[8];
	union {
	__be32 d32;
	u8 d8[4];
	} data[2] ____cacheline_aligned;
	};

	enum ads8688_id {
	ID_ADS8684,
	ID_ADS8688,
	};

	struct ads8688_ranges {
	enum ads8688_range range;
	unsigned int scale;
	int offset;
	u8 reg;
	};

	static const struct ads8688_ranges ads8688_range_def[5] = {
	{
	.range = ADS8688_PLUSMINUS25VREF,
	.scale = 76295,
	.offset = -(1 << (ADS8688_REALBITS - 1)),
	.reg = ADS8688_REG_PLUSMINUS25VREF,
	}, {
	.range = ADS8688_PLUSMINUS125VREF,
	.scale = 38148,
	.offset = -(1 << (ADS8688_REALBITS - 1)),
	.reg = ADS8688_REG_PLUSMINUS125VREF,
	}, {
	.range = ADS8688_PLUSMINUS0625VREF,
	.scale = 19074,
	.offset = -(1 << (ADS8688_REALBITS - 1)),
	.reg = ADS8688_REG_PLUSMINUS0625VREF,
	}, {
	.range = ADS8688_PLUS25VREF,
	.scale = 38148,
	.offset = 0,
	.reg = ADS8688_REG_PLUS25VREF,
	}, {
	.range = ADS8688_PLUS125VREF,
	.scale = 19074,
	.offset = 0,
	.reg = ADS8688_REG_PLUS125VREF,
	}
	};

	static ssize_t ads8688_show_scales(struct device *dev,
	struct device_attribute attr, char buf)
	{
	struct ads8688_state *st = iio_priv(dev_to_iio_dev(dev));

	return sprintf(buf, "0.%09u 0.%09u 0.%09u\n",
	ads8688_range_def[0].scale * st->vref_mv,
	ads8688_range_def[1].scale * st->vref_mv,
	ads8688_range_def[2].scale * st->vref_mv);
	}

	static ssize_t ads8688_show_offsets(struct device *dev,
	struct device_attribute attr, char buf)
	{
	return sprintf(buf, "%d %d\n", ads8688_range_def[0].offset,
	ads8688_range_def[3].offset);
	}

	static IIO_DEVICE_ATTR(in_voltage_scale_available, S_IRUGO,
	ads8688_show_scales, NULL, 0);
	static IIO_DEVICE_ATTR(in_voltage_offset_available, S_IRUGO,
	ads8688_show_offsets, NULL, 0);

	static struct attribute *ads8688_attributes[] = {
	&iio_dev_attr_in_voltage_scale_available.dev_attr.attr,
	&iio_dev_attr_in_voltage_offset_available.dev_attr.attr,
	NULL,
	};

	static const struct attribute_group ads8688_attribute_group = {
	.attrs = ads8688_attributes,
	};

	#define ADS8688_CHAN(index) \
	{ \
	.type = IIO_VOLTAGE, \
	.indexed = 1, \
	.channel = index, \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) \
	\| BIT(IIO_CHAN_INFO_SCALE) \
	\| BIT(IIO_CHAN_INFO_OFFSET), \
	}

	static const struct iio_chan_spec ads8684_channels[] = {
	ADS8688_CHAN(0),
	ADS8688_CHAN(1),
	ADS8688_CHAN(2),
	ADS8688_CHAN(3),
	};

	static const struct iio_chan_spec ads8688_channels[] = {
	ADS8688_CHAN(0),
	ADS8688_CHAN(1),
	ADS8688_CHAN(2),
	ADS8688_CHAN(3),
	ADS8688_CHAN(4),
	ADS8688_CHAN(5),
	ADS8688_CHAN(6),
	ADS8688_CHAN(7),
	};

	static int ads8688_prog_write(struct iio_dev *indio_dev, unsigned int addr,
	unsigned int val)
	{
	struct ads8688_state *st = iio_priv(indio_dev);
	u32 tmp;

	tmp = ADS8688_PROG_REG(addr) \| ADS8688_PROG_WR_BIT \| val;
	tmp <<= ADS8688_PROG_DONT_CARE_BITS;
	st->data[0].d32 = cpu_to_be32(tmp);

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

	static int ads8688_reset(struct iio_dev *indio_dev)
	{
	struct ads8688_state *st = iio_priv(indio_dev);
	u32 tmp;

	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_RST);
	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
	st->data[0].d32 = cpu_to_be32(tmp);

	return spi_write(st->spi, &st->data[0].d8[0], 4);
	}

	static int ads8688_read(struct iio_dev *indio_dev, unsigned int chan)
	{
	struct ads8688_state *st = iio_priv(indio_dev);
	int ret;
	u32 tmp;
	struct spi_transfer t[] = {
	{
	.tx_buf = &st->data[0].d8[0],
	.len = 4,
	.cs_change = 1,
	}, {
	.tx_buf = &st->data[1].d8[0],
	.rx_buf = &st->data[1].d8[0],
	.len = 4,
	},
	};

	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_MAN_CH(chan));
	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
	st->data[0].d32 = cpu_to_be32(tmp);

	tmp = ADS8688_CMD_REG(ADS8688_CMD_REG_NOOP);
	tmp <<= ADS8688_CMD_DONT_CARE_BITS;
	st->data[1].d32 = cpu_to_be32(tmp);

	ret = spi_sync_transfer(st->spi, t, ARRAY_SIZE(t));
	if (ret < 0)
	return ret;

	return be32_to_cpu(st->data[1].d32) & 0xffff;
	}

	static int ads8688_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int val, int val2, long m)
	{
	int ret, offset;
	unsigned long scale_mv;

	struct ads8688_state *st = iio_priv(indio_dev);

	mutex_lock(&st->lock);
	switch (m) {
	case IIO_CHAN_INFO_RAW:
	ret = ads8688_read(indio_dev, chan->channel);
	mutex_unlock(&st->lock);
	if (ret < 0)
	return ret;
	*val = ret;
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
	scale_mv = st->vref_mv;
	scale_mv *= ads8688_range_def[st->range[chan->channel]].scale;
	*val = 0;
	*val2 = scale_mv;
	mutex_unlock(&st->lock);
	return IIO_VAL_INT_PLUS_NANO;
	case IIO_CHAN_INFO_OFFSET:
	offset = ads8688_range_def[st->range[chan->channel]].offset;
	*val = offset;
	mutex_unlock(&st->lock);
	return IIO_VAL_INT;
	}
	mutex_unlock(&st->lock);

	return -EINVAL;
	}

	static int ads8688_write_reg_range(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	enum ads8688_range range)
	{
	unsigned int tmp;
	int ret;

	tmp = ADS8688_PROG_REG_RANGE_CH(chan->channel);
	ret = ads8688_prog_write(indio_dev, tmp, range);

	return ret;
	}

	static int ads8688_write_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	int val, int val2, long mask)
	{
	struct ads8688_state *st = iio_priv(indio_dev);
	unsigned int scale = 0;
	int ret = -EINVAL, i, offset = 0;

	mutex_lock(&st->lock);
	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
	/* If the offset is 0 the ±2.5 * VREF mode is not available */
	offset = ads8688_range_def[st->range[chan->channel]].offset;
	if (offset == 0 && val2 == ads8688_range_def[0].scale * st->vref_mv) {
	mutex_unlock(&st->lock);
	return -EINVAL;
	}

	/* Lookup new mode */
	for (i = 0; i < ARRAY_SIZE(ads8688_range_def); i++)
	if (val2 == ads8688_range_def[i].scale * st->vref_mv &&
	offset == ads8688_range_def[i].offset) {
	ret = ads8688_write_reg_range(indio_dev, chan,
	ads8688_range_def[i].reg);
	break;
	}
	break;
	case IIO_CHAN_INFO_OFFSET:
	/*
	* There are only two available offsets:
	* 0 and -(1 << (ADS8688_REALBITS - 1))
	*/
	if (!(ads8688_range_def[0].offset == val \|\|
	ads8688_range_def[3].offset == val)) {
	mutex_unlock(&st->lock);
	return -EINVAL;
	}

	/*
	* If the device are in ±2.5 * VREF mode, it's not allowed to
	* switch to a mode where the offset is 0
	*/
	if (val == 0 &&
	st->range[chan->channel] == ADS8688_PLUSMINUS25VREF) {
	mutex_unlock(&st->lock);
	return -EINVAL;
	}

	scale = ads8688_range_def[st->range[chan->channel]].scale;

	/* Lookup new mode */
	for (i = 0; i < ARRAY_SIZE(ads8688_range_def); i++)
	if (val == ads8688_range_def[i].offset &&
	scale == ads8688_range_def[i].scale) {
	ret = ads8688_write_reg_range(indio_dev, chan,
	ads8688_range_def[i].reg);
	break;
	}
	break;
	}

	if (!ret)
	st->range[chan->channel] = ads8688_range_def[i].range;

	mutex_unlock(&st->lock);

	return ret;
	}

	static int ads8688_write_raw_get_fmt(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan,
	long mask)
	{
	switch (mask) {
	case IIO_CHAN_INFO_SCALE:
	return IIO_VAL_INT_PLUS_NANO;
	case IIO_CHAN_INFO_OFFSET:
	return IIO_VAL_INT;
	}

	return -EINVAL;
	}

	static const struct iio_info ads8688_info = {
	.read_raw = &ads8688_read_raw,
	.write_raw = &ads8688_write_raw,
	.write_raw_get_fmt = &ads8688_write_raw_get_fmt,
	.attrs = &ads8688_attribute_group,
	.driver_module = THIS_MODULE,
	};

	static const struct ads8688_chip_info ads8688_chip_info_tbl[] = {
	[ID_ADS8684] = {
	.channels = ads8684_channels,
	.num_channels = ARRAY_SIZE(ads8684_channels),
	},
	[ID_ADS8688] = {
	.channels = ads8688_channels,
	.num_channels = ARRAY_SIZE(ads8688_channels),
	},
	};

	static int ads8688_probe(struct spi_device *spi)
	{
	struct ads8688_state *st;
	struct iio_dev *indio_dev;
	int ret;

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

	st = iio_priv(indio_dev);

	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
	if (!IS_ERR(st->reg)) {
	ret = regulator_enable(st->reg);
	if (ret)
	return ret;

	ret = regulator_get_voltage(st->reg);
	if (ret < 0)
	goto error_out;

	st->vref_mv = ret / 1000;
	} else {
	/* Use internal reference */
	st->vref_mv = ADS8688_VREF_MV;
	}

	st->chip_info = &ads8688_chip_info_tbl[spi_get_device_id(spi)->driver_data];

	spi->mode = SPI_MODE_1;

	spi_set_drvdata(spi, indio_dev);

	st->spi = spi;

	indio_dev->name = spi_get_device_id(spi)->name;
	indio_dev->dev.parent = &spi->dev;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->channels = st->chip_info->channels;
	indio_dev->num_channels = st->chip_info->num_channels;
	indio_dev->info = &ads8688_info;

	ads8688_reset(indio_dev);

	mutex_init(&st->lock);

	ret = iio_device_register(indio_dev);
	if (ret)
	goto error_out;

	return 0;

	error_out:
	if (!IS_ERR_OR_NULL(st->reg))
	regulator_disable(st->reg);

	return ret;
	}

	static int ads8688_remove(struct spi_device *spi)
	{
	struct iio_dev *indio_dev = spi_get_drvdata(spi);
	struct ads8688_state *st = iio_priv(indio_dev);

	iio_device_unregister(indio_dev);

	if (!IS_ERR_OR_NULL(st->reg))
	regulator_disable(st->reg);

	return 0;
	}

	static const struct spi_device_id ads8688_id[] = {
	{"ads8684", ID_ADS8684},
	{"ads8688", ID_ADS8688},
	{}
	};
	MODULE_DEVICE_TABLE(spi, ads8688_id);

	static const struct of_device_id ads8688_of_match[] = {
	{ .compatible = "ti,ads8684" },
	{ .compatible = "ti,ads8688" },
	{ }
	};
	MODULE_DEVICE_TABLE(of, ads8688_of_match);

	static struct spi_driver ads8688_driver = {
	.driver = {
	.name = "ads8688",
	.owner = THIS_MODULE,
	},
	.probe = ads8688_probe,
	.remove = ads8688_remove,
	.id_table = ads8688_id,
	};
	module_spi_driver(ads8688_driver);

	MODULE_AUTHOR("Sean Nyekjaer <sean.nyekjaer@prevas.dk>");
	MODULE_DESCRIPTION("Texas Instruments ADS8688 driver");
	MODULE_LICENSE("GPL v2");