drivers/iio/adc/stx104.c - LeafOS-Devices/android_kernel_samsung_gta4xl - Gitiles

 /*
  * IIO driver for the Apex Embedded Systems STX104
  * Copyright (C) 2016 William Breathitt Gray
  *
  * 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.
  *
  * 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/bitops.h>
 #include <linux/device.h>
 #include <linux/errno.h>
 #include <linux/gpio/driver.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/types.h>
 #include <linux/io.h>
 #include <linux/ioport.h>
 #include <linux/isa.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>

 #define STX104_OUT_CHAN(chan) {				\
 	.type = IIO_VOLTAGE,				\
 	.channel = chan,				\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
 	.indexed = 1,					\
 	.output = 1					\
 }
 #define STX104_IN_CHAN(chan, diff) {					\
 	.type = IIO_VOLTAGE,						\
 	.channel = chan,						\
 	.channel2 = chan,						\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_HARDWAREGAIN) |	\
 		BIT(IIO_CHAN_INFO_OFFSET) | BIT(IIO_CHAN_INFO_SCALE),	\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
 	.indexed = 1,							\
 	.differential = diff						\
 }

 #define STX104_NUM_OUT_CHAN 2

 #define STX104_EXTENT 16

 static unsigned int base[max_num_isa_dev(STX104_EXTENT)];
 static unsigned int num_stx104;
 module_param_hw_array(base, uint, ioport, &num_stx104, 0);
 MODULE_PARM_DESC(base, "Apex Embedded Systems STX104 base addresses");

 /**
  * struct stx104_iio - IIO device private data structure
  * @lock: synchronization lock to prevent I/O race conditions
  * @chan_out_states:	channels' output states
  * @base:		base port address of the IIO device
  */
 struct stx104_iio {
 	struct mutex lock;
 	unsigned int chan_out_states[STX104_NUM_OUT_CHAN];
 	unsigned int base;
 };

 /**
  * struct stx104_gpio - GPIO device private data structure
  * @chip:	instance of the gpio_chip
  * @lock:	synchronization lock to prevent I/O race conditions
  * @base:	base port address of the GPIO device
  * @out_state:	output bits state
  */
 struct stx104_gpio {
 	struct gpio_chip chip;
 	spinlock_t lock;
 	unsigned int base;
 	unsigned int out_state;
 };

 static int stx104_read_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
 {
 	struct stx104_iio *const priv = iio_priv(indio_dev);
 	unsigned int adc_config;
 	int adbu;
 	int gain;

 	switch (mask) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
 		/* get gain configuration */
 		adc_config = inb(priv->base + 11);
 		gain = adc_config & 0x3;

 		*val = 1 << gain;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_RAW:
 		if (chan->output) {
 			*val = priv->chan_out_states[chan->channel];
 			return IIO_VAL_INT;
 		}

 		/* select ADC channel */
 		outb(chan->channel | (chan->channel << 4), priv->base + 2);

 		/* trigger ADC sample capture and wait for completion */
 		outb(0, priv->base);
 		while (inb(priv->base + 8) & BIT(7));

 		*val = inw(priv->base);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_OFFSET:
 		/* get ADC bipolar/unipolar configuration */
 		adc_config = inb(priv->base + 11);
 		adbu = !(adc_config & BIT(2));

 		*val = -32768 * adbu;
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		/* get ADC bipolar/unipolar and gain configuration */
 		adc_config = inb(priv->base + 11);
 		adbu = !(adc_config & BIT(2));
 		gain = adc_config & 0x3;

 		*val = 5;
 		*val2 = 15 - adbu + gain;
 		return IIO_VAL_FRACTIONAL_LOG2;
 	}

 	return -EINVAL;
 }

 static int stx104_write_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int val, int val2, long mask)
 {
 	struct stx104_iio *const priv = iio_priv(indio_dev);

 	switch (mask) {
 	case IIO_CHAN_INFO_HARDWAREGAIN:
 		/* Only four gain states (x1, x2, x4, x8) */
 		switch (val) {
 		case 1:
 			outb(0, priv->base + 11);
 			break;
 		case 2:
 			outb(1, priv->base + 11);
 			break;
 		case 4:
 			outb(2, priv->base + 11);
 			break;
 		case 8:
 			outb(3, priv->base + 11);
 			break;
 		default:
 			return -EINVAL;
 		}

 		return 0;
 	case IIO_CHAN_INFO_RAW:
 		if (chan->output) {
 			/* DAC can only accept up to a 16-bit value */
 			if ((unsigned int)val > 65535)
 				return -EINVAL;

 			mutex_lock(&priv->lock);

 			priv->chan_out_states[chan->channel] = val;
 			outw(val, priv->base + 4 + 2 * chan->channel);

 			mutex_unlock(&priv->lock);
 			return 0;
 		}
 		return -EINVAL;
 	}

 	return -EINVAL;
 }

 static const struct iio_info stx104_info = {
 	.driver_module = THIS_MODULE,
 	.read_raw = stx104_read_raw,
 	.write_raw = stx104_write_raw
 };

 /* single-ended input channels configuration */
 static const struct iio_chan_spec stx104_channels_sing[] = {
 	STX104_OUT_CHAN(0), STX104_OUT_CHAN(1),
 	STX104_IN_CHAN(0, 0), STX104_IN_CHAN(1, 0), STX104_IN_CHAN(2, 0),
 	STX104_IN_CHAN(3, 0), STX104_IN_CHAN(4, 0), STX104_IN_CHAN(5, 0),
 	STX104_IN_CHAN(6, 0), STX104_IN_CHAN(7, 0), STX104_IN_CHAN(8, 0),
 	STX104_IN_CHAN(9, 0), STX104_IN_CHAN(10, 0), STX104_IN_CHAN(11, 0),
 	STX104_IN_CHAN(12, 0), STX104_IN_CHAN(13, 0), STX104_IN_CHAN(14, 0),
 	STX104_IN_CHAN(15, 0)
 };
 /* differential input channels configuration */
 static const struct iio_chan_spec stx104_channels_diff[] = {
 	STX104_OUT_CHAN(0), STX104_OUT_CHAN(1),
 	STX104_IN_CHAN(0, 1), STX104_IN_CHAN(1, 1), STX104_IN_CHAN(2, 1),
 	STX104_IN_CHAN(3, 1), STX104_IN_CHAN(4, 1), STX104_IN_CHAN(5, 1),
 	STX104_IN_CHAN(6, 1), STX104_IN_CHAN(7, 1)
 };

 static int stx104_gpio_get_direction(struct gpio_chip *chip,
 	unsigned int offset)
 {
 	/* GPIO 0-3 are input only, while the rest are output only */
 	if (offset < 4)
 		return 1;

 	return 0;
 }

 static int stx104_gpio_direction_input(struct gpio_chip *chip,
 	unsigned int offset)
 {
 	if (offset >= 4)
 		return -EINVAL;

 	return 0;
 }

 static int stx104_gpio_direction_output(struct gpio_chip *chip,
 	unsigned int offset, int value)
 {
 	if (offset < 4)
 		return -EINVAL;

 	chip->set(chip, offset, value);
 	return 0;
 }

 static int stx104_gpio_get(struct gpio_chip *chip, unsigned int offset)
 {
 	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);

 	if (offset >= 4)
 		return -EINVAL;

 	return !!(inb(stx104gpio->base) & BIT(offset));
 }

 static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
 	int value)
 {
 	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
 	const unsigned int mask = BIT(offset) >> 4;
 	unsigned long flags;

 	if (offset < 4)
 		return;

 	spin_lock_irqsave(&stx104gpio->lock, flags);

 	if (value)
 		stx104gpio->out_state |= mask;
 	else
 		stx104gpio->out_state &= ~mask;

 	outb(stx104gpio->out_state, stx104gpio->base);

 	spin_unlock_irqrestore(&stx104gpio->lock, flags);
 }

 #define STX104_NGPIO 8
 static const char *stx104_names[STX104_NGPIO] = {
 	"DIN0", "DIN1", "DIN2", "DIN3", "DOUT0", "DOUT1", "DOUT2", "DOUT3"
 };

 static void stx104_gpio_set_multiple(struct gpio_chip *chip,
 	unsigned long *mask, unsigned long *bits)
 {
 	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
 	unsigned long flags;

 	/* verify masked GPIO are output */
 	if (!(*mask & 0xF0))
 		return;

 	*mask >>= 4;
 	*bits >>= 4;

 	spin_lock_irqsave(&stx104gpio->lock, flags);

 	stx104gpio->out_state &= ~*mask;
 	stx104gpio->out_state |= *mask & *bits;
 	outb(stx104gpio->out_state, stx104gpio->base);

 	spin_unlock_irqrestore(&stx104gpio->lock, flags);
 }

 static int stx104_probe(struct device *dev, unsigned int id)
 {
 	struct iio_dev *indio_dev;
 	struct stx104_iio *priv;
 	struct stx104_gpio *stx104gpio;
 	int err;

 	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
 	if (!indio_dev)
 		return -ENOMEM;

 	stx104gpio = devm_kzalloc(dev, sizeof(*stx104gpio), GFP_KERNEL);
 	if (!stx104gpio)
 		return -ENOMEM;

 	if (!devm_request_region(dev, base[id], STX104_EXTENT,
 		dev_name(dev))) {
 		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
 			base[id], base[id] + STX104_EXTENT);
 		return -EBUSY;
 	}

 	indio_dev->info = &stx104_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;

 	/* determine if differential inputs */
 	if (inb(base[id] + 8) & BIT(5)) {
 		indio_dev->num_channels = ARRAY_SIZE(stx104_channels_diff);
 		indio_dev->channels = stx104_channels_diff;
 	} else {
 		indio_dev->num_channels = ARRAY_SIZE(stx104_channels_sing);
 		indio_dev->channels = stx104_channels_sing;
 	}

 	indio_dev->name = dev_name(dev);
 	indio_dev->dev.parent = dev;

 	priv = iio_priv(indio_dev);
 	priv->base = base[id];

 	mutex_init(&priv->lock);

 	/* configure device for software trigger operation */
 	outb(0, base[id] + 9);

 	/* initialize gain setting to x1 */
 	outb(0, base[id] + 11);

 	/* initialize DAC output to 0V */
 	outw(0, base[id] + 4);
 	outw(0, base[id] + 6);

 	stx104gpio->chip.label = dev_name(dev);
 	stx104gpio->chip.parent = dev;
 	stx104gpio->chip.owner = THIS_MODULE;
 	stx104gpio->chip.base = -1;
 	stx104gpio->chip.ngpio = STX104_NGPIO;
 	stx104gpio->chip.names = stx104_names;
 	stx104gpio->chip.get_direction = stx104_gpio_get_direction;
 	stx104gpio->chip.direction_input = stx104_gpio_direction_input;
 	stx104gpio->chip.direction_output = stx104_gpio_direction_output;
 	stx104gpio->chip.get = stx104_gpio_get;
 	stx104gpio->chip.set = stx104_gpio_set;
 	stx104gpio->chip.set_multiple = stx104_gpio_set_multiple;
 	stx104gpio->base = base[id] + 3;
 	stx104gpio->out_state = 0x0;

 	spin_lock_init(&stx104gpio->lock);

 	err = devm_gpiochip_add_data(dev, &stx104gpio->chip, stx104gpio);
 	if (err) {
 		dev_err(dev, "GPIO registering failed (%d)\n", err);
 		return err;
 	}

 	return devm_iio_device_register(dev, indio_dev);
 }

 static struct isa_driver stx104_driver = {
 	.probe = stx104_probe,
 	.driver = {
 		.name = "stx104"
 	},
 };

 module_isa_driver(stx104_driver, num_stx104);

 MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
 MODULE_DESCRIPTION("Apex Embedded Systems STX104 IIO driver");
 MODULE_LICENSE("GPL v2");
	/*
	* IIO driver for the Apex Embedded Systems STX104
	* Copyright (C) 2016 William Breathitt Gray
	*
	* 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.
	*
	* 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/bitops.h>
	#include <linux/device.h>
	#include <linux/errno.h>
	#include <linux/gpio/driver.h>
	#include <linux/iio/iio.h>
	#include <linux/iio/types.h>
	#include <linux/io.h>
	#include <linux/ioport.h>
	#include <linux/isa.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/moduleparam.h>
	#include <linux/mutex.h>
	#include <linux/spinlock.h>

	#define STX104_OUT_CHAN(chan) { \
	.type = IIO_VOLTAGE, \
	.channel = chan, \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
	.indexed = 1, \
	.output = 1 \
	}
	#define STX104_IN_CHAN(chan, diff) { \
	.type = IIO_VOLTAGE, \
	.channel = chan, \
	.channel2 = chan, \
	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_HARDWAREGAIN) \| \
	BIT(IIO_CHAN_INFO_OFFSET) \| BIT(IIO_CHAN_INFO_SCALE), \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
	.indexed = 1, \
	.differential = diff \
	}

	#define STX104_NUM_OUT_CHAN 2

	#define STX104_EXTENT 16

	static unsigned int base[max_num_isa_dev(STX104_EXTENT)];
	static unsigned int num_stx104;
	module_param_hw_array(base, uint, ioport, &num_stx104, 0);
	MODULE_PARM_DESC(base, "Apex Embedded Systems STX104 base addresses");

	/**
	* struct stx104_iio - IIO device private data structure
	* @lock: synchronization lock to prevent I/O race conditions
	* @chan_out_states: channels' output states
	* @base: base port address of the IIO device
	*/
	struct stx104_iio {
	struct mutex lock;
	unsigned int chan_out_states[STX104_NUM_OUT_CHAN];
	unsigned int base;
	};

	/**
	* struct stx104_gpio - GPIO device private data structure
	* @chip: instance of the gpio_chip
	* @lock: synchronization lock to prevent I/O race conditions
	* @base: base port address of the GPIO device
	* @out_state: output bits state
	*/
	struct stx104_gpio {
	struct gpio_chip chip;
	spinlock_t lock;
	unsigned int base;
	unsigned int out_state;
	};

	static int stx104_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const chan, int val, int *val2, long mask)
	{
	struct stx104_iio *const priv = iio_priv(indio_dev);
	unsigned int adc_config;
	int adbu;
	int gain;

	switch (mask) {
	case IIO_CHAN_INFO_HARDWAREGAIN:
	/* get gain configuration */
	adc_config = inb(priv->base + 11);
	gain = adc_config & 0x3;

	*val = 1 << gain;
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_RAW:
	if (chan->output) {
	*val = priv->chan_out_states[chan->channel];
	return IIO_VAL_INT;
	}

	/* select ADC channel */
	outb(chan->channel \| (chan->channel << 4), priv->base + 2);

	/* trigger ADC sample capture and wait for completion */
	outb(0, priv->base);
	while (inb(priv->base + 8) & BIT(7));

	*val = inw(priv->base);
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_OFFSET:
	/* get ADC bipolar/unipolar configuration */
	adc_config = inb(priv->base + 11);
	adbu = !(adc_config & BIT(2));

	val = -32768 adbu;
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
	/* get ADC bipolar/unipolar and gain configuration */
	adc_config = inb(priv->base + 11);
	adbu = !(adc_config & BIT(2));
	gain = adc_config & 0x3;

	*val = 5;
	*val2 = 15 - adbu + gain;
	return IIO_VAL_FRACTIONAL_LOG2;
	}

	return -EINVAL;
	}

	static int stx104_write_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan, int val, int val2, long mask)
	{
	struct stx104_iio *const priv = iio_priv(indio_dev);

	switch (mask) {
	case IIO_CHAN_INFO_HARDWAREGAIN:
	/* Only four gain states (x1, x2, x4, x8) */
	switch (val) {
	case 1:
	outb(0, priv->base + 11);
	break;
	case 2:
	outb(1, priv->base + 11);
	break;
	case 4:
	outb(2, priv->base + 11);
	break;
	case 8:
	outb(3, priv->base + 11);
	break;
	default:
	return -EINVAL;
	}

	return 0;
	case IIO_CHAN_INFO_RAW:
	if (chan->output) {
	/* DAC can only accept up to a 16-bit value */
	if ((unsigned int)val > 65535)
	return -EINVAL;

	mutex_lock(&priv->lock);

	priv->chan_out_states[chan->channel] = val;
	outw(val, priv->base + 4 + 2 * chan->channel);

	mutex_unlock(&priv->lock);
	return 0;
	}
	return -EINVAL;
	}

	return -EINVAL;
	}

	static const struct iio_info stx104_info = {
	.driver_module = THIS_MODULE,
	.read_raw = stx104_read_raw,
	.write_raw = stx104_write_raw
	};

	/* single-ended input channels configuration */
	static const struct iio_chan_spec stx104_channels_sing[] = {
	STX104_OUT_CHAN(0), STX104_OUT_CHAN(1),
	STX104_IN_CHAN(0, 0), STX104_IN_CHAN(1, 0), STX104_IN_CHAN(2, 0),
	STX104_IN_CHAN(3, 0), STX104_IN_CHAN(4, 0), STX104_IN_CHAN(5, 0),
	STX104_IN_CHAN(6, 0), STX104_IN_CHAN(7, 0), STX104_IN_CHAN(8, 0),
	STX104_IN_CHAN(9, 0), STX104_IN_CHAN(10, 0), STX104_IN_CHAN(11, 0),
	STX104_IN_CHAN(12, 0), STX104_IN_CHAN(13, 0), STX104_IN_CHAN(14, 0),
	STX104_IN_CHAN(15, 0)
	};
	/* differential input channels configuration */
	static const struct iio_chan_spec stx104_channels_diff[] = {
	STX104_OUT_CHAN(0), STX104_OUT_CHAN(1),
	STX104_IN_CHAN(0, 1), STX104_IN_CHAN(1, 1), STX104_IN_CHAN(2, 1),
	STX104_IN_CHAN(3, 1), STX104_IN_CHAN(4, 1), STX104_IN_CHAN(5, 1),
	STX104_IN_CHAN(6, 1), STX104_IN_CHAN(7, 1)
	};

	static int stx104_gpio_get_direction(struct gpio_chip *chip,
	unsigned int offset)
	{
	/* GPIO 0-3 are input only, while the rest are output only */
	if (offset < 4)
	return 1;

	return 0;
	}

	static int stx104_gpio_direction_input(struct gpio_chip *chip,
	unsigned int offset)
	{
	if (offset >= 4)
	return -EINVAL;

	return 0;
	}

	static int stx104_gpio_direction_output(struct gpio_chip *chip,
	unsigned int offset, int value)
	{
	if (offset < 4)
	return -EINVAL;

	chip->set(chip, offset, value);
	return 0;
	}

	static int stx104_gpio_get(struct gpio_chip *chip, unsigned int offset)
	{
	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);

	if (offset >= 4)
	return -EINVAL;

	return !!(inb(stx104gpio->base) & BIT(offset));
	}

	static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
	int value)
	{
	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
	const unsigned int mask = BIT(offset) >> 4;
	unsigned long flags;

	if (offset < 4)
	return;

	spin_lock_irqsave(&stx104gpio->lock, flags);

	if (value)
	stx104gpio->out_state \|= mask;
	else
	stx104gpio->out_state &= ~mask;

	outb(stx104gpio->out_state, stx104gpio->base);

	spin_unlock_irqrestore(&stx104gpio->lock, flags);
	}

	#define STX104_NGPIO 8
	static const char *stx104_names[STX104_NGPIO] = {
	"DIN0", "DIN1", "DIN2", "DIN3", "DOUT0", "DOUT1", "DOUT2", "DOUT3"
	};

	static void stx104_gpio_set_multiple(struct gpio_chip *chip,
	unsigned long mask, unsigned long bits)
	{
	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
	unsigned long flags;

	/* verify masked GPIO are output */
	if (!(*mask & 0xF0))
	return;

	*mask >>= 4;
	*bits >>= 4;

	spin_lock_irqsave(&stx104gpio->lock, flags);

	stx104gpio->out_state &= ~*mask;
	stx104gpio->out_state \|= mask & bits;
	outb(stx104gpio->out_state, stx104gpio->base);

	spin_unlock_irqrestore(&stx104gpio->lock, flags);
	}

	static int stx104_probe(struct device *dev, unsigned int id)
	{
	struct iio_dev *indio_dev;
	struct stx104_iio *priv;
	struct stx104_gpio *stx104gpio;
	int err;

	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
	if (!indio_dev)
	return -ENOMEM;

	stx104gpio = devm_kzalloc(dev, sizeof(*stx104gpio), GFP_KERNEL);
	if (!stx104gpio)
	return -ENOMEM;

	if (!devm_request_region(dev, base[id], STX104_EXTENT,
	dev_name(dev))) {
	dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
	base[id], base[id] + STX104_EXTENT);
	return -EBUSY;
	}

	indio_dev->info = &stx104_info;
	indio_dev->modes = INDIO_DIRECT_MODE;

	/* determine if differential inputs */
	if (inb(base[id] + 8) & BIT(5)) {
	indio_dev->num_channels = ARRAY_SIZE(stx104_channels_diff);
	indio_dev->channels = stx104_channels_diff;
	} else {
	indio_dev->num_channels = ARRAY_SIZE(stx104_channels_sing);
	indio_dev->channels = stx104_channels_sing;
	}

	indio_dev->name = dev_name(dev);
	indio_dev->dev.parent = dev;

	priv = iio_priv(indio_dev);
	priv->base = base[id];

	mutex_init(&priv->lock);

	/* configure device for software trigger operation */
	outb(0, base[id] + 9);

	/* initialize gain setting to x1 */
	outb(0, base[id] + 11);

	/* initialize DAC output to 0V */
	outw(0, base[id] + 4);
	outw(0, base[id] + 6);

	stx104gpio->chip.label = dev_name(dev);
	stx104gpio->chip.parent = dev;
	stx104gpio->chip.owner = THIS_MODULE;
	stx104gpio->chip.base = -1;
	stx104gpio->chip.ngpio = STX104_NGPIO;
	stx104gpio->chip.names = stx104_names;
	stx104gpio->chip.get_direction = stx104_gpio_get_direction;
	stx104gpio->chip.direction_input = stx104_gpio_direction_input;
	stx104gpio->chip.direction_output = stx104_gpio_direction_output;
	stx104gpio->chip.get = stx104_gpio_get;
	stx104gpio->chip.set = stx104_gpio_set;
	stx104gpio->chip.set_multiple = stx104_gpio_set_multiple;
	stx104gpio->base = base[id] + 3;
	stx104gpio->out_state = 0x0;

	spin_lock_init(&stx104gpio->lock);

	err = devm_gpiochip_add_data(dev, &stx104gpio->chip, stx104gpio);
	if (err) {
	dev_err(dev, "GPIO registering failed (%d)\n", err);
	return err;
	}

	return devm_iio_device_register(dev, indio_dev);
	}

	static struct isa_driver stx104_driver = {
	.probe = stx104_probe,
	.driver = {
	.name = "stx104"
	},
	};

	module_isa_driver(stx104_driver, num_stx104);

	MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
	MODULE_DESCRIPTION("Apex Embedded Systems STX104 IIO driver");
	MODULE_LICENSE("GPL v2");