drivers/iio/counter/104-quad-8.c - linux - Git at Google

 /*
  * IIO driver for the ACCES 104-QUAD-8
  * 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.
  *
  * This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
  */
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/errno.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/types.h>

 #define QUAD8_EXTENT 32

 static unsigned int base[max_num_isa_dev(QUAD8_EXTENT)];
 static unsigned int num_quad8;
 module_param_array(base, uint, &num_quad8, 0);
 MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");

 #define QUAD8_NUM_COUNTERS 8

 /**
  * struct quad8_iio - IIO device private data structure
  * @preset:		array of preset values
  * @count_mode:		array of count mode configurations
  * @quadrature_mode:	array of quadrature mode configurations
  * @quadrature_scale:	array of quadrature mode scale configurations
  * @ab_enable:		array of A and B inputs enable configurations
  * @preset_enable:	array of set_to_preset_on_index attribute configurations
  * @synchronous_mode:	array of index function synchronous mode configurations
  * @index_polarity:	array of index function polarity configurations
  * @base:		base port address of the IIO device
  */
 struct quad8_iio {
 	unsigned int preset[QUAD8_NUM_COUNTERS];
 	unsigned int count_mode[QUAD8_NUM_COUNTERS];
 	unsigned int quadrature_mode[QUAD8_NUM_COUNTERS];
 	unsigned int quadrature_scale[QUAD8_NUM_COUNTERS];
 	unsigned int ab_enable[QUAD8_NUM_COUNTERS];
 	unsigned int preset_enable[QUAD8_NUM_COUNTERS];
 	unsigned int synchronous_mode[QUAD8_NUM_COUNTERS];
 	unsigned int index_polarity[QUAD8_NUM_COUNTERS];
 	unsigned int base;
 };

 static int quad8_read_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const int base_offset = priv->base + 2 * chan->channel;
 	unsigned int flags;
 	unsigned int borrow;
 	unsigned int carry;
 	int i;

 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		if (chan->type == IIO_INDEX) {
 			*val = !!(inb(priv->base + 0x16) & BIT(chan->channel));
 			return IIO_VAL_INT;
 		}

 		flags = inb(base_offset);
 		borrow = flags & BIT(0);
 		carry = !!(flags & BIT(1));

 		/* Borrow XOR Carry effectively doubles count range */
 		*val = (borrow ^ carry) << 24;

 		/* Reset Byte Pointer; transfer Counter to Output Latch */
 		outb(0x11, base_offset + 1);

 		for (i = 0; i < 3; i++)
 			*val |= (unsigned int)inb(base_offset) << (8 * i);

 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_ENABLE:
 		*val = priv->ab_enable[chan->channel];
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		*val = 1;
 		*val2 = priv->quadrature_scale[chan->channel];
 		return IIO_VAL_FRACTIONAL_LOG2;
 	}

 	return -EINVAL;
 }

 static int quad8_write_raw(struct iio_dev *indio_dev,
 	struct iio_chan_spec const *chan, int val, int val2, long mask)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const int base_offset = priv->base + 2 * chan->channel;
 	int i;
 	unsigned int ior_cfg;

 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		if (chan->type == IIO_INDEX)
 			return -EINVAL;

 		/* Only 24-bit values are supported */
 		if ((unsigned int)val > 0xFFFFFF)
 			return -EINVAL;

 		/* Reset Byte Pointer */
 		outb(0x01, base_offset + 1);

 		/* Counter can only be set via Preset Register */
 		for (i = 0; i < 3; i++)
 			outb(val >> (8 * i), base_offset);

 		/* Transfer Preset Register to Counter */
 		outb(0x08, base_offset + 1);

 		/* Reset Byte Pointer */
 		outb(0x01, base_offset + 1);

 		/* Set Preset Register back to original value */
 		val = priv->preset[chan->channel];
 		for (i = 0; i < 3; i++)
 			outb(val >> (8 * i), base_offset);

 		/* Reset Borrow, Carry, Compare, and Sign flags */
 		outb(0x02, base_offset + 1);
 		/* Reset Error flag */
 		outb(0x06, base_offset + 1);

 		return 0;
 	case IIO_CHAN_INFO_ENABLE:
 		/* only boolean values accepted */
 		if (val < 0 || val > 1)
 			return -EINVAL;

 		priv->ab_enable[chan->channel] = val;

 		ior_cfg = val | priv->preset_enable[chan->channel] << 1;

 		/* Load I/O control configuration */
 		outb(0x40 | ior_cfg, base_offset + 1);

 		return 0;
 	case IIO_CHAN_INFO_SCALE:
 		/* Quadrature scaling only available in quadrature mode */
 		if (!priv->quadrature_mode[chan->channel] && (val2 || val != 1))
 			return -EINVAL;

 		/* Only three gain states (1, 0.5, 0.25) */
 		if (val == 1 && !val2)
 			priv->quadrature_scale[chan->channel] = 0;
 		else if (!val)
 			switch (val2) {
 			case 500000:
 				priv->quadrature_scale[chan->channel] = 1;
 				break;
 			case 250000:
 				priv->quadrature_scale[chan->channel] = 2;
 				break;
 			default:
 				return -EINVAL;
 			}
 		else
 			return -EINVAL;

 		return 0;
 	}

 	return -EINVAL;
 }

 static const struct iio_info quad8_info = {
 	.driver_module = THIS_MODULE,
 	.read_raw = quad8_read_raw,
 	.write_raw = quad8_write_raw
 };

 static ssize_t quad8_read_preset(struct iio_dev *indio_dev, uintptr_t private,
 	const struct iio_chan_spec *chan, char *buf)
 {
 	const struct quad8_iio *const priv = iio_priv(indio_dev);

 	return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset[chan->channel]);
 }

 static ssize_t quad8_write_preset(struct iio_dev *indio_dev, uintptr_t private,
 	const struct iio_chan_spec *chan, const char *buf, size_t len)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const int base_offset = priv->base + 2 * chan->channel;
 	unsigned int preset;
 	int ret;
 	int i;

 	ret = kstrtouint(buf, 0, &preset);
 	if (ret)
 		return ret;

 	/* Only 24-bit values are supported */
 	if (preset > 0xFFFFFF)
 		return -EINVAL;

 	priv->preset[chan->channel] = preset;

 	/* Reset Byte Pointer */
 	outb(0x01, base_offset + 1);

 	/* Set Preset Register */
 	for (i = 0; i < 3; i++)
 		outb(preset >> (8 * i), base_offset);

 	return len;
 }

 static ssize_t quad8_read_set_to_preset_on_index(struct iio_dev *indio_dev,
 	uintptr_t private, const struct iio_chan_spec *chan, char *buf)
 {
 	const struct quad8_iio *const priv = iio_priv(indio_dev);

 	return snprintf(buf, PAGE_SIZE, "%u\n",
 		!priv->preset_enable[chan->channel]);
 }

 static ssize_t quad8_write_set_to_preset_on_index(struct iio_dev *indio_dev,
 	uintptr_t private, const struct iio_chan_spec *chan, const char *buf,
 	size_t len)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const int base_offset = priv->base + 2 * chan->channel + 1;
 	bool preset_enable;
 	int ret;
 	unsigned int ior_cfg;

 	ret = kstrtobool(buf, &preset_enable);
 	if (ret)
 		return ret;

 	/* Preset enable is active low in Input/Output Control register */
 	preset_enable = !preset_enable;

 	priv->preset_enable[chan->channel] = preset_enable;

 	ior_cfg = priv->ab_enable[chan->channel] |
 		(unsigned int)preset_enable << 1;

 	/* Load I/O control configuration to Input / Output Control Register */
 	outb(0x40 | ior_cfg, base_offset);

 	return len;
 }

 static const char *const quad8_noise_error_states[] = {
 	"No excessive noise is present at the count inputs",
 	"Excessive noise is present at the count inputs"
 };

 static int quad8_get_noise_error(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const int base_offset = priv->base + 2 * chan->channel + 1;

 	return !!(inb(base_offset) & BIT(4));
 }

 static const struct iio_enum quad8_noise_error_enum = {
 	.items = quad8_noise_error_states,
 	.num_items = ARRAY_SIZE(quad8_noise_error_states),
 	.get = quad8_get_noise_error
 };

 static const char *const quad8_count_direction_states[] = {
 	"down",
 	"up"
 };

 static int quad8_get_count_direction(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const int base_offset = priv->base + 2 * chan->channel + 1;

 	return !!(inb(base_offset) & BIT(5));
 }

 static const struct iio_enum quad8_count_direction_enum = {
 	.items = quad8_count_direction_states,
 	.num_items = ARRAY_SIZE(quad8_count_direction_states),
 	.get = quad8_get_count_direction
 };

 static const char *const quad8_count_modes[] = {
 	"normal",
 	"range limit",
 	"non-recycle",
 	"modulo-n"
 };

 static int quad8_set_count_mode(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan, unsigned int count_mode)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	unsigned int mode_cfg = count_mode << 1;
 	const int base_offset = priv->base + 2 * chan->channel + 1;

 	priv->count_mode[chan->channel] = count_mode;

 	/* Add quadrature mode configuration */
 	if (priv->quadrature_mode[chan->channel])
 		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;

 	/* Load mode configuration to Counter Mode Register */
 	outb(0x20 | mode_cfg, base_offset);

 	return 0;
 }

 static int quad8_get_count_mode(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan)
 {
 	const struct quad8_iio *const priv = iio_priv(indio_dev);

 	return priv->count_mode[chan->channel];
 }

 static const struct iio_enum quad8_count_mode_enum = {
 	.items = quad8_count_modes,
 	.num_items = ARRAY_SIZE(quad8_count_modes),
 	.set = quad8_set_count_mode,
 	.get = quad8_get_count_mode
 };

 static const char *const quad8_synchronous_modes[] = {
 	"non-synchronous",
 	"synchronous"
 };

 static int quad8_set_synchronous_mode(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan, unsigned int synchronous_mode)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const unsigned int idr_cfg = synchronous_mode |
 		priv->index_polarity[chan->channel] << 1;
 	const int base_offset = priv->base + 2 * chan->channel + 1;

 	/* Index function must be non-synchronous in non-quadrature mode */
 	if (synchronous_mode && !priv->quadrature_mode[chan->channel])
 		return -EINVAL;

 	priv->synchronous_mode[chan->channel] = synchronous_mode;

 	/* Load Index Control configuration to Index Control Register */
 	outb(0x60 | idr_cfg, base_offset);

 	return 0;
 }

 static int quad8_get_synchronous_mode(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan)
 {
 	const struct quad8_iio *const priv = iio_priv(indio_dev);

 	return priv->synchronous_mode[chan->channel];
 }

 static const struct iio_enum quad8_synchronous_mode_enum = {
 	.items = quad8_synchronous_modes,
 	.num_items = ARRAY_SIZE(quad8_synchronous_modes),
 	.set = quad8_set_synchronous_mode,
 	.get = quad8_get_synchronous_mode
 };

 static const char *const quad8_quadrature_modes[] = {
 	"non-quadrature",
 	"quadrature"
 };

 static int quad8_set_quadrature_mode(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan, unsigned int quadrature_mode)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	unsigned int mode_cfg = priv->count_mode[chan->channel] << 1;
 	const int base_offset = priv->base + 2 * chan->channel + 1;

 	if (quadrature_mode)
 		mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;
 	else {
 		/* Quadrature scaling only available in quadrature mode */
 		priv->quadrature_scale[chan->channel] = 0;

 		/* Synchronous function not supported in non-quadrature mode */
 		if (priv->synchronous_mode[chan->channel])
 			quad8_set_synchronous_mode(indio_dev, chan, 0);
 	}

 	priv->quadrature_mode[chan->channel] = quadrature_mode;

 	/* Load mode configuration to Counter Mode Register */
 	outb(0x20 | mode_cfg, base_offset);

 	return 0;
 }

 static int quad8_get_quadrature_mode(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan)
 {
 	const struct quad8_iio *const priv = iio_priv(indio_dev);

 	return priv->quadrature_mode[chan->channel];
 }

 static const struct iio_enum quad8_quadrature_mode_enum = {
 	.items = quad8_quadrature_modes,
 	.num_items = ARRAY_SIZE(quad8_quadrature_modes),
 	.set = quad8_set_quadrature_mode,
 	.get = quad8_get_quadrature_mode
 };

 static const char *const quad8_index_polarity_modes[] = {
 	"negative",
 	"positive"
 };

 static int quad8_set_index_polarity(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan, unsigned int index_polarity)
 {
 	struct quad8_iio *const priv = iio_priv(indio_dev);
 	const unsigned int idr_cfg = priv->synchronous_mode[chan->channel] |
 		index_polarity << 1;
 	const int base_offset = priv->base + 2 * chan->channel + 1;

 	priv->index_polarity[chan->channel] = index_polarity;

 	/* Load Index Control configuration to Index Control Register */
 	outb(0x60 | idr_cfg, base_offset);

 	return 0;
 }

 static int quad8_get_index_polarity(struct iio_dev *indio_dev,
 	const struct iio_chan_spec *chan)
 {
 	const struct quad8_iio *const priv = iio_priv(indio_dev);

 	return priv->index_polarity[chan->channel];
 }

 static const struct iio_enum quad8_index_polarity_enum = {
 	.items = quad8_index_polarity_modes,
 	.num_items = ARRAY_SIZE(quad8_index_polarity_modes),
 	.set = quad8_set_index_polarity,
 	.get = quad8_get_index_polarity
 };

 static const struct iio_chan_spec_ext_info quad8_count_ext_info[] = {
 	{
 		.name = "preset",
 		.shared = IIO_SEPARATE,
 		.read = quad8_read_preset,
 		.write = quad8_write_preset
 	},
 	{
 		.name = "set_to_preset_on_index",
 		.shared = IIO_SEPARATE,
 		.read = quad8_read_set_to_preset_on_index,
 		.write = quad8_write_set_to_preset_on_index
 	},
 	IIO_ENUM("noise_error", IIO_SEPARATE, &quad8_noise_error_enum),
 	IIO_ENUM_AVAILABLE("noise_error", &quad8_noise_error_enum),
 	IIO_ENUM("count_direction", IIO_SEPARATE, &quad8_count_direction_enum),
 	IIO_ENUM_AVAILABLE("count_direction", &quad8_count_direction_enum),
 	IIO_ENUM("count_mode", IIO_SEPARATE, &quad8_count_mode_enum),
 	IIO_ENUM_AVAILABLE("count_mode", &quad8_count_mode_enum),
 	IIO_ENUM("quadrature_mode", IIO_SEPARATE, &quad8_quadrature_mode_enum),
 	IIO_ENUM_AVAILABLE("quadrature_mode", &quad8_quadrature_mode_enum),
 	{}
 };

 static const struct iio_chan_spec_ext_info quad8_index_ext_info[] = {
 	IIO_ENUM("synchronous_mode", IIO_SEPARATE,
 		&quad8_synchronous_mode_enum),
 	IIO_ENUM_AVAILABLE("synchronous_mode", &quad8_synchronous_mode_enum),
 	IIO_ENUM("index_polarity", IIO_SEPARATE, &quad8_index_polarity_enum),
 	IIO_ENUM_AVAILABLE("index_polarity", &quad8_index_polarity_enum),
 	{}
 };

 #define QUAD8_COUNT_CHAN(_chan) {					\
 	.type = IIO_COUNT,						\
 	.channel = (_chan),						\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |			\
 		BIT(IIO_CHAN_INFO_ENABLE) | BIT(IIO_CHAN_INFO_SCALE),	\
 	.ext_info = quad8_count_ext_info,				\
 	.indexed = 1							\
 }

 #define QUAD8_INDEX_CHAN(_chan) {			\
 	.type = IIO_INDEX,				\
 	.channel = (_chan),				\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),	\
 	.ext_info = quad8_index_ext_info,		\
 	.indexed = 1					\
 }

 static const struct iio_chan_spec quad8_channels[] = {
 	QUAD8_COUNT_CHAN(0), QUAD8_INDEX_CHAN(0),
 	QUAD8_COUNT_CHAN(1), QUAD8_INDEX_CHAN(1),
 	QUAD8_COUNT_CHAN(2), QUAD8_INDEX_CHAN(2),
 	QUAD8_COUNT_CHAN(3), QUAD8_INDEX_CHAN(3),
 	QUAD8_COUNT_CHAN(4), QUAD8_INDEX_CHAN(4),
 	QUAD8_COUNT_CHAN(5), QUAD8_INDEX_CHAN(5),
 	QUAD8_COUNT_CHAN(6), QUAD8_INDEX_CHAN(6),
 	QUAD8_COUNT_CHAN(7), QUAD8_INDEX_CHAN(7)
 };

 static int quad8_probe(struct device *dev, unsigned int id)
 {
 	struct iio_dev *indio_dev;
 	struct quad8_iio *priv;
 	int i, j;
 	unsigned int base_offset;

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

 	if (!devm_request_region(dev, base[id], QUAD8_EXTENT,
 		dev_name(dev))) {
 		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
 			base[id], base[id] + QUAD8_EXTENT);
 		return -EBUSY;
 	}

 	indio_dev->info = &quad8_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 	indio_dev->num_channels = ARRAY_SIZE(quad8_channels);
 	indio_dev->channels = quad8_channels;
 	indio_dev->name = dev_name(dev);

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

 	/* Reset all counters and disable interrupt function */
 	outb(0x01, base[id] + 0x11);
 	/* Set initial configuration for all counters */
 	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
 		base_offset = base[id] + 2 * i;
 		/* Reset Byte Pointer */
 		outb(0x01, base_offset + 1);
 		/* Reset Preset Register */
 		for (j = 0; j < 3; j++)
 			outb(0x00, base_offset);
 		/* Reset Borrow, Carry, Compare, and Sign flags */
 		outb(0x04, base_offset + 1);
 		/* Reset Error flag */
 		outb(0x06, base_offset + 1);
 		/* Binary encoding; Normal count; non-quadrature mode */
 		outb(0x20, base_offset + 1);
 		/* Disable A and B inputs; preset on index; FLG1 as Carry */
 		outb(0x40, base_offset + 1);
 		/* Disable index function; negative index polarity */
 		outb(0x60, base_offset + 1);
 	}
 	/* Enable all counters */
 	outb(0x00, base[id] + 0x11);

 	return devm_iio_device_register(dev, indio_dev);
 }

 static struct isa_driver quad8_driver = {
 	.probe = quad8_probe,
 	.driver = {
 		.name = "104-quad-8"
 	}
 };

 module_isa_driver(quad8_driver, num_quad8);

 MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
 MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
 MODULE_LICENSE("GPL v2");
	/*
	* IIO driver for the ACCES 104-QUAD-8
	* 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.
	*
	* This driver supports the ACCES 104-QUAD-8 and ACCES 104-QUAD-4.
	*/
	#include <linux/bitops.h>
	#include <linux/device.h>
	#include <linux/errno.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/types.h>

	#define QUAD8_EXTENT 32

	static unsigned int base[max_num_isa_dev(QUAD8_EXTENT)];
	static unsigned int num_quad8;
	module_param_array(base, uint, &num_quad8, 0);
	MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");

	#define QUAD8_NUM_COUNTERS 8

	/**
	* struct quad8_iio - IIO device private data structure
	* @preset: array of preset values
	* @count_mode: array of count mode configurations
	* @quadrature_mode: array of quadrature mode configurations
	* @quadrature_scale: array of quadrature mode scale configurations
	* @ab_enable: array of A and B inputs enable configurations
	* @preset_enable: array of set_to_preset_on_index attribute configurations
	* @synchronous_mode: array of index function synchronous mode configurations
	* @index_polarity: array of index function polarity configurations
	* @base: base port address of the IIO device
	*/
	struct quad8_iio {
	unsigned int preset[QUAD8_NUM_COUNTERS];
	unsigned int count_mode[QUAD8_NUM_COUNTERS];
	unsigned int quadrature_mode[QUAD8_NUM_COUNTERS];
	unsigned int quadrature_scale[QUAD8_NUM_COUNTERS];
	unsigned int ab_enable[QUAD8_NUM_COUNTERS];
	unsigned int preset_enable[QUAD8_NUM_COUNTERS];
	unsigned int synchronous_mode[QUAD8_NUM_COUNTERS];
	unsigned int index_polarity[QUAD8_NUM_COUNTERS];
	unsigned int base;
	};

	static int quad8_read_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const chan, int val, int *val2, long mask)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel;
	unsigned int flags;
	unsigned int borrow;
	unsigned int carry;
	int i;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
	if (chan->type == IIO_INDEX) {
	*val = !!(inb(priv->base + 0x16) & BIT(chan->channel));
	return IIO_VAL_INT;
	}

	flags = inb(base_offset);
	borrow = flags & BIT(0);
	carry = !!(flags & BIT(1));

	/* Borrow XOR Carry effectively doubles count range */
	*val = (borrow ^ carry) << 24;

	/* Reset Byte Pointer; transfer Counter to Output Latch */
	outb(0x11, base_offset + 1);

	for (i = 0; i < 3; i++)
	val \|= (unsigned int)inb(base_offset) << (8 i);

	return IIO_VAL_INT;
	case IIO_CHAN_INFO_ENABLE:
	*val = priv->ab_enable[chan->channel];
	return IIO_VAL_INT;
	case IIO_CHAN_INFO_SCALE:
	*val = 1;
	*val2 = priv->quadrature_scale[chan->channel];
	return IIO_VAL_FRACTIONAL_LOG2;
	}

	return -EINVAL;
	}

	static int quad8_write_raw(struct iio_dev *indio_dev,
	struct iio_chan_spec const *chan, int val, int val2, long mask)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel;
	int i;
	unsigned int ior_cfg;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:
	if (chan->type == IIO_INDEX)
	return -EINVAL;

	/* Only 24-bit values are supported */
	if ((unsigned int)val > 0xFFFFFF)
	return -EINVAL;

	/* Reset Byte Pointer */
	outb(0x01, base_offset + 1);

	/* Counter can only be set via Preset Register */
	for (i = 0; i < 3; i++)
	outb(val >> (8 * i), base_offset);

	/* Transfer Preset Register to Counter */
	outb(0x08, base_offset + 1);

	/* Reset Byte Pointer */
	outb(0x01, base_offset + 1);

	/* Set Preset Register back to original value */
	val = priv->preset[chan->channel];
	for (i = 0; i < 3; i++)
	outb(val >> (8 * i), base_offset);

	/* Reset Borrow, Carry, Compare, and Sign flags */
	outb(0x02, base_offset + 1);
	/* Reset Error flag */
	outb(0x06, base_offset + 1);

	return 0;
	case IIO_CHAN_INFO_ENABLE:
	/* only boolean values accepted */
	if (val < 0 \|\| val > 1)
	return -EINVAL;

	priv->ab_enable[chan->channel] = val;

	ior_cfg = val \| priv->preset_enable[chan->channel] << 1;

	/* Load I/O control configuration */
	outb(0x40 \| ior_cfg, base_offset + 1);

	return 0;
	case IIO_CHAN_INFO_SCALE:
	/* Quadrature scaling only available in quadrature mode */
	if (!priv->quadrature_mode[chan->channel] && (val2 \|\| val != 1))
	return -EINVAL;

	/* Only three gain states (1, 0.5, 0.25) */
	if (val == 1 && !val2)
	priv->quadrature_scale[chan->channel] = 0;
	else if (!val)
	switch (val2) {
	case 500000:
	priv->quadrature_scale[chan->channel] = 1;
	break;
	case 250000:
	priv->quadrature_scale[chan->channel] = 2;
	break;
	default:
	return -EINVAL;
	}
	else
	return -EINVAL;

	return 0;
	}

	return -EINVAL;
	}

	static const struct iio_info quad8_info = {
	.driver_module = THIS_MODULE,
	.read_raw = quad8_read_raw,
	.write_raw = quad8_write_raw
	};

	static ssize_t quad8_read_preset(struct iio_dev *indio_dev, uintptr_t private,
	const struct iio_chan_spec chan, char buf)
	{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return snprintf(buf, PAGE_SIZE, "%u\n", priv->preset[chan->channel]);
	}

	static ssize_t quad8_write_preset(struct iio_dev *indio_dev, uintptr_t private,
	const struct iio_chan_spec chan, const char buf, size_t len)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel;
	unsigned int preset;
	int ret;
	int i;

	ret = kstrtouint(buf, 0, &preset);
	if (ret)
	return ret;

	/* Only 24-bit values are supported */
	if (preset > 0xFFFFFF)
	return -EINVAL;

	priv->preset[chan->channel] = preset;

	/* Reset Byte Pointer */
	outb(0x01, base_offset + 1);

	/* Set Preset Register */
	for (i = 0; i < 3; i++)
	outb(preset >> (8 * i), base_offset);

	return len;
	}

	static ssize_t quad8_read_set_to_preset_on_index(struct iio_dev *indio_dev,
	uintptr_t private, const struct iio_chan_spec chan, char buf)
	{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return snprintf(buf, PAGE_SIZE, "%u\n",
	!priv->preset_enable[chan->channel]);
	}

	static ssize_t quad8_write_set_to_preset_on_index(struct iio_dev *indio_dev,
	uintptr_t private, const struct iio_chan_spec chan, const char buf,
	size_t len)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel + 1;
	bool preset_enable;
	int ret;
	unsigned int ior_cfg;

	ret = kstrtobool(buf, &preset_enable);
	if (ret)
	return ret;

	/* Preset enable is active low in Input/Output Control register */
	preset_enable = !preset_enable;

	priv->preset_enable[chan->channel] = preset_enable;

	ior_cfg = priv->ab_enable[chan->channel] \|
	(unsigned int)preset_enable << 1;

	/* Load I/O control configuration to Input / Output Control Register */
	outb(0x40 \| ior_cfg, base_offset);

	return len;
	}

	static const char *const quad8_noise_error_states[] = {
	"No excessive noise is present at the count inputs",
	"Excessive noise is present at the count inputs"
	};

	static int quad8_get_noise_error(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel + 1;

	return !!(inb(base_offset) & BIT(4));
	}

	static const struct iio_enum quad8_noise_error_enum = {
	.items = quad8_noise_error_states,
	.num_items = ARRAY_SIZE(quad8_noise_error_states),
	.get = quad8_get_noise_error
	};

	static const char *const quad8_count_direction_states[] = {
	"down",
	"up"
	};

	static int quad8_get_count_direction(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const int base_offset = priv->base + 2 * chan->channel + 1;

	return !!(inb(base_offset) & BIT(5));
	}

	static const struct iio_enum quad8_count_direction_enum = {
	.items = quad8_count_direction_states,
	.num_items = ARRAY_SIZE(quad8_count_direction_states),
	.get = quad8_get_count_direction
	};

	static const char *const quad8_count_modes[] = {
	"normal",
	"range limit",
	"non-recycle",
	"modulo-n"
	};

	static int quad8_set_count_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int count_mode)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	unsigned int mode_cfg = count_mode << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	priv->count_mode[chan->channel] = count_mode;

	/* Add quadrature mode configuration */
	if (priv->quadrature_mode[chan->channel])
	mode_cfg \|= (priv->quadrature_scale[chan->channel] + 1) << 3;

	/* Load mode configuration to Counter Mode Register */
	outb(0x20 \| mode_cfg, base_offset);

	return 0;
	}

	static int quad8_get_count_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
	{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->count_mode[chan->channel];
	}

	static const struct iio_enum quad8_count_mode_enum = {
	.items = quad8_count_modes,
	.num_items = ARRAY_SIZE(quad8_count_modes),
	.set = quad8_set_count_mode,
	.get = quad8_get_count_mode
	};

	static const char *const quad8_synchronous_modes[] = {
	"non-synchronous",
	"synchronous"
	};

	static int quad8_set_synchronous_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int synchronous_mode)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const unsigned int idr_cfg = synchronous_mode \|
	priv->index_polarity[chan->channel] << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	/* Index function must be non-synchronous in non-quadrature mode */
	if (synchronous_mode && !priv->quadrature_mode[chan->channel])
	return -EINVAL;

	priv->synchronous_mode[chan->channel] = synchronous_mode;

	/* Load Index Control configuration to Index Control Register */
	outb(0x60 \| idr_cfg, base_offset);

	return 0;
	}

	static int quad8_get_synchronous_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
	{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->synchronous_mode[chan->channel];
	}

	static const struct iio_enum quad8_synchronous_mode_enum = {
	.items = quad8_synchronous_modes,
	.num_items = ARRAY_SIZE(quad8_synchronous_modes),
	.set = quad8_set_synchronous_mode,
	.get = quad8_get_synchronous_mode
	};

	static const char *const quad8_quadrature_modes[] = {
	"non-quadrature",
	"quadrature"
	};

	static int quad8_set_quadrature_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int quadrature_mode)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	unsigned int mode_cfg = priv->count_mode[chan->channel] << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	if (quadrature_mode)
	mode_cfg \|= (priv->quadrature_scale[chan->channel] + 1) << 3;
	else {
	/* Quadrature scaling only available in quadrature mode */
	priv->quadrature_scale[chan->channel] = 0;

	/* Synchronous function not supported in non-quadrature mode */
	if (priv->synchronous_mode[chan->channel])
	quad8_set_synchronous_mode(indio_dev, chan, 0);
	}

	priv->quadrature_mode[chan->channel] = quadrature_mode;

	/* Load mode configuration to Counter Mode Register */
	outb(0x20 \| mode_cfg, base_offset);

	return 0;
	}

	static int quad8_get_quadrature_mode(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
	{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->quadrature_mode[chan->channel];
	}

	static const struct iio_enum quad8_quadrature_mode_enum = {
	.items = quad8_quadrature_modes,
	.num_items = ARRAY_SIZE(quad8_quadrature_modes),
	.set = quad8_set_quadrature_mode,
	.get = quad8_get_quadrature_mode
	};

	static const char *const quad8_index_polarity_modes[] = {
	"negative",
	"positive"
	};

	static int quad8_set_index_polarity(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan, unsigned int index_polarity)
	{
	struct quad8_iio *const priv = iio_priv(indio_dev);
	const unsigned int idr_cfg = priv->synchronous_mode[chan->channel] \|
	index_polarity << 1;
	const int base_offset = priv->base + 2 * chan->channel + 1;

	priv->index_polarity[chan->channel] = index_polarity;

	/* Load Index Control configuration to Index Control Register */
	outb(0x60 \| idr_cfg, base_offset);

	return 0;
	}

	static int quad8_get_index_polarity(struct iio_dev *indio_dev,
	const struct iio_chan_spec *chan)
	{
	const struct quad8_iio *const priv = iio_priv(indio_dev);

	return priv->index_polarity[chan->channel];
	}

	static const struct iio_enum quad8_index_polarity_enum = {
	.items = quad8_index_polarity_modes,
	.num_items = ARRAY_SIZE(quad8_index_polarity_modes),
	.set = quad8_set_index_polarity,
	.get = quad8_get_index_polarity
	};

	static const struct iio_chan_spec_ext_info quad8_count_ext_info[] = {
	{
	.name = "preset",
	.shared = IIO_SEPARATE,
	.read = quad8_read_preset,
	.write = quad8_write_preset
	},
	{
	.name = "set_to_preset_on_index",
	.shared = IIO_SEPARATE,
	.read = quad8_read_set_to_preset_on_index,
	.write = quad8_write_set_to_preset_on_index
	},
	IIO_ENUM("noise_error", IIO_SEPARATE, &quad8_noise_error_enum),
	IIO_ENUM_AVAILABLE("noise_error", &quad8_noise_error_enum),
	IIO_ENUM("count_direction", IIO_SEPARATE, &quad8_count_direction_enum),
	IIO_ENUM_AVAILABLE("count_direction", &quad8_count_direction_enum),
	IIO_ENUM("count_mode", IIO_SEPARATE, &quad8_count_mode_enum),
	IIO_ENUM_AVAILABLE("count_mode", &quad8_count_mode_enum),
	IIO_ENUM("quadrature_mode", IIO_SEPARATE, &quad8_quadrature_mode_enum),
	IIO_ENUM_AVAILABLE("quadrature_mode", &quad8_quadrature_mode_enum),
	{}
	};

	static const struct iio_chan_spec_ext_info quad8_index_ext_info[] = {
	IIO_ENUM("synchronous_mode", IIO_SEPARATE,
	&quad8_synchronous_mode_enum),
	IIO_ENUM_AVAILABLE("synchronous_mode", &quad8_synchronous_mode_enum),
	IIO_ENUM("index_polarity", IIO_SEPARATE, &quad8_index_polarity_enum),
	IIO_ENUM_AVAILABLE("index_polarity", &quad8_index_polarity_enum),
	{}
	};

	#define QUAD8_COUNT_CHAN(_chan) { \
	.type = IIO_COUNT, \
	.channel = (_chan), \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) \| \
	BIT(IIO_CHAN_INFO_ENABLE) \| BIT(IIO_CHAN_INFO_SCALE), \
	.ext_info = quad8_count_ext_info, \
	.indexed = 1 \
	}

	#define QUAD8_INDEX_CHAN(_chan) { \
	.type = IIO_INDEX, \
	.channel = (_chan), \
	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
	.ext_info = quad8_index_ext_info, \
	.indexed = 1 \
	}

	static const struct iio_chan_spec quad8_channels[] = {
	QUAD8_COUNT_CHAN(0), QUAD8_INDEX_CHAN(0),
	QUAD8_COUNT_CHAN(1), QUAD8_INDEX_CHAN(1),
	QUAD8_COUNT_CHAN(2), QUAD8_INDEX_CHAN(2),
	QUAD8_COUNT_CHAN(3), QUAD8_INDEX_CHAN(3),
	QUAD8_COUNT_CHAN(4), QUAD8_INDEX_CHAN(4),
	QUAD8_COUNT_CHAN(5), QUAD8_INDEX_CHAN(5),
	QUAD8_COUNT_CHAN(6), QUAD8_INDEX_CHAN(6),
	QUAD8_COUNT_CHAN(7), QUAD8_INDEX_CHAN(7)
	};

	static int quad8_probe(struct device *dev, unsigned int id)
	{
	struct iio_dev *indio_dev;
	struct quad8_iio *priv;
	int i, j;
	unsigned int base_offset;

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

	if (!devm_request_region(dev, base[id], QUAD8_EXTENT,
	dev_name(dev))) {
	dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
	base[id], base[id] + QUAD8_EXTENT);
	return -EBUSY;
	}

	indio_dev->info = &quad8_info;
	indio_dev->modes = INDIO_DIRECT_MODE;
	indio_dev->num_channels = ARRAY_SIZE(quad8_channels);
	indio_dev->channels = quad8_channels;
	indio_dev->name = dev_name(dev);

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

	/* Reset all counters and disable interrupt function */
	outb(0x01, base[id] + 0x11);
	/* Set initial configuration for all counters */
	for (i = 0; i < QUAD8_NUM_COUNTERS; i++) {
	base_offset = base[id] + 2 * i;
	/* Reset Byte Pointer */
	outb(0x01, base_offset + 1);
	/* Reset Preset Register */
	for (j = 0; j < 3; j++)
	outb(0x00, base_offset);
	/* Reset Borrow, Carry, Compare, and Sign flags */
	outb(0x04, base_offset + 1);
	/* Reset Error flag */
	outb(0x06, base_offset + 1);
	/* Binary encoding; Normal count; non-quadrature mode */
	outb(0x20, base_offset + 1);
	/* Disable A and B inputs; preset on index; FLG1 as Carry */
	outb(0x40, base_offset + 1);
	/* Disable index function; negative index polarity */
	outb(0x60, base_offset + 1);
	}
	/* Enable all counters */
	outb(0x00, base[id] + 0x11);

	return devm_iio_device_register(dev, indio_dev);
	}

	static struct isa_driver quad8_driver = {
	.probe = quad8_probe,
	.driver = {
	.name = "104-quad-8"
	}
	};

	module_isa_driver(quad8_driver, num_quad8);

	MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
	MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
	MODULE_LICENSE("GPL v2");