Re: [PATCH v3 2/2] iio: 104-quad-8: Add IIO support for the ACCES 104-QUAD-8

[Jonathan Cameron]

On 15/09/16 15:51, William Breathitt Gray wrote:
> The ACCES 104-QUAD-8 is a general purpose quadrature encoder
> counter/interface board. The 104-QUAD-8 is capable of monitoring the
> outputs of eight encoders via four on-board LSI/CSI LS7266R1 24-bit
> dual-axis quadrature counter chips. Core functions handled by the
> LS7266R1, such as direction and total count, are available.
> 
> Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
> also clears the counter's respective clearable flags (BORROW, CARRY,
> COMPARE, SIGN, and ERROR). Interrupts are not supported by this driver.
> 
> This driver adds IIO support for the ACCES 104-QUAD-8 and ACCES
> 104-QUAD-4. The base port addresses for the devices may be configured
> via the base array module parameter.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
Hi William

Good to see you have broken things up nicely.  What's needed now is
some Docs ;)  I had a go at figuring out what all the new ABI is about
but there were still some corners that looked rather unusual / unclear
that I don't really follow.  I've used a fair number of encoder driven
systems in my day job where we use a lot of conveyors and slides etc.
We need sufficient docs to allow others to plough in with reviews as well.
There is a lot of new ABI in here so I'd like to get more opinions on
whether we have it right!

So all in all : Needs docs.

Jonathan
> ---
>  MAINTAINERS                      |   6 +
>  drivers/iio/Kconfig              |   1 +
>  drivers/iio/Makefile             |   1 +
>  drivers/iio/counter/104-quad-8.c | 654 +++++++++++++++++++++++++++++++++++++++
>  drivers/iio/counter/Kconfig      |  22 ++
>  drivers/iio/counter/Makefile     |   7 +
>  6 files changed, 691 insertions(+)
>  create mode 100644 drivers/iio/counter/104-quad-8.c
>  create mode 100644 drivers/iio/counter/Kconfig
>  create mode 100644 drivers/iio/counter/Makefile
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 6f0ff72..759a2ea 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -255,6 +255,12 @@ L:	linux-gpio@xxxxxxxxxxxxxxx
>  S:	Maintained
>  F:	drivers/gpio/gpio-104-idio-16.c
>  
> +ACCES 104-QUAD-8 IIO DRIVER
> +M:	William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
> +L:	linux-iio@xxxxxxxxxxxxxxx
> +S:	Maintained
> +F:	drivers/iio/counter/104-quad-8.c
> +
>  ACENIC DRIVER
>  M:	Jes Sorensen <jes@xxxxxxxxxxxxxxxxxx>
>  L:	linux-acenic@xxxxxxxxxx
> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> index 6743b18..574d1fb 100644
> --- a/drivers/iio/Kconfig
> +++ b/drivers/iio/Kconfig
> @@ -73,6 +73,7 @@ source "drivers/iio/adc/Kconfig"
>  source "drivers/iio/amplifiers/Kconfig"
>  source "drivers/iio/chemical/Kconfig"
>  source "drivers/iio/common/Kconfig"
> +source "drivers/iio/counter/Kconfig"
>  source "drivers/iio/dac/Kconfig"
>  source "drivers/iio/dummy/Kconfig"
>  source "drivers/iio/frequency/Kconfig"
> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
> index 87e4c43..77b2000 100644
> --- a/drivers/iio/Makefile
> +++ b/drivers/iio/Makefile
> @@ -18,6 +18,7 @@ obj-y += amplifiers/
>  obj-y += buffer/
>  obj-y += chemical/
>  obj-y += common/
> +obj-y += counter/
>  obj-y += dac/
>  obj-y += dummy/
>  obj-y += gyro/
> diff --git a/drivers/iio/counter/104-quad-8.c b/drivers/iio/counter/104-quad-8.c
> new file mode 100644
> index 0000000..518e01c
> --- /dev/null
> +++ b/drivers/iio/counter/104-quad-8.c
> @@ -0,0 +1,654 @@
> +/*
> + * 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/kernel.h>
> +#include <linux/isa.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.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
> + * @encoding:		array of encoding configurations
> + * @counter_mode:	array of counter_mode configurations
> + * @quadrature_mode:	array of quadrature_mode configurations
> + * @ab_enable:		array of A and B inputs enable configurations
> + * @preset_enable:	array of preset enable configurations
> + * @index_function:	array of index function enable configurations
> + * @index_polarity:	array of index polarity configurations
> + * @base:		base port address of the IIO device
> + */
> +struct quad8_iio {
> +	unsigned int preset[QUAD8_NUM_COUNTERS];
> +	unsigned int encoding[QUAD8_NUM_COUNTERS];
> +	unsigned int counter_mode[QUAD8_NUM_COUNTERS];
> +	unsigned int quadrature_mode[QUAD8_NUM_COUNTERS];
> +	unsigned int ab_enable[QUAD8_NUM_COUNTERS];
> +	unsigned int preset_enable[QUAD8_NUM_COUNTERS];
> +	unsigned int index_function[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;
> +	int i;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (chan->type == IIO_INDEX) {
> +			*val = !!(inb(base_offset + 1) & BIT(6));
> +			return IIO_VAL_INT;
> +		}
> +
> +		/* Reset Byte Pointer; transfer Counter to Output Latch */
> +		outb(0x11, base_offset + 1);
> +
> +		*val = 0;
> +		for (i = 0; i < 3; i++)
> +			*val |= (unsigned int)inb(base_offset) << (8 * i);
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_PRESET:
> +		*val = priv->preset[chan->channel];
> +		return IIO_VAL_INT;
> +	}
> +
> +	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;
> +
> +	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);
> +
> +		/* Set Preset Register */
> +		for (i = 0; i < 3; i++)
> +			outb(val >> (8 * i), base_offset);
> +
> +		/* Transfer Preset Register to Counter */
> +		outb(0x08, base_offset + 1);
Nice dirty hack ;)
> +
> +		/* 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_PRESET:
> +		/* Only 24-bit values are supported */
> +		if ((unsigned int)val > 0xFFFFFF)
> +			return -EINVAL;
> +
> +		priv->preset[chan->channel] = val;
> +
> +		/* Reset Byte Pointer */
> +		outb(0x01, base_offset + 1);
> +
> +		/* Set Preset Register */
> +		for (i = 0; i < 3; i++)
> +			outb(val >> (8 * i), base_offset);
> +
> +		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 const char *const quad8_toggle_states[] = {
> +	"0",
> +	"1"
> +};
These are numeric - not sure an enum is really the appropriate way to
handle it.  Certainly not if you then need an available attribute to
give the two values.
> +
> +static int quad8_get_borrow(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(0);
> +}
> +
> +static const struct iio_enum quad8_borrow_enum = {
> +	.items = quad8_toggle_states,
> +	.num_items = ARRAY_SIZE(quad8_toggle_states),
> +	.get = quad8_get_borrow
> +};
> +
> +static int quad8_get_carry(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(1));
> +}
> +
> +static const struct iio_enum quad8_carry_enum = {
> +	.items = quad8_toggle_states,
> +	.num_items = ARRAY_SIZE(quad8_toggle_states),
> +	.get = quad8_get_carry
> +};
> +
> +static int quad8_get_compare(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(2));
> +}
> +
> +static const struct iio_enum quad8_compare_enum = {
> +	.items = quad8_toggle_states,
> +	.num_items = ARRAY_SIZE(quad8_toggle_states),
> +	.get = quad8_get_compare
> +};
> +
> +static const char *const quad8_sign_states[] = {
> +	"+",
> +	"-"
> +};
> +
> +static int quad8_get_sign(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(3));
> +}
> +
> +static const struct iio_enum quad8_sign_enum = {
> +	.items = quad8_sign_states,
> +	.num_items = ARRAY_SIZE(quad8_sign_states),
> +	.get = quad8_get_sign
> +};
> +
> +static const char *const quad8_error_states[] = {
> +	"No errors detected",
> +	"Excessive noise detected at the count inputs"
> +};
> +
> +static int quad8_get_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_error_enum = {
> +	.items = quad8_error_states,
> +	.num_items = ARRAY_SIZE(quad8_error_states),
> +	.get = quad8_get_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_encoding_modes[] = {
> +	"binary",
> +	"binary-coded decimal"
> +};
> +
> +static int quad8_set_encoding(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan, unsigned int encoding)
> +{
> +	struct quad8_iio *const priv = iio_priv(indio_dev);
> +	const unsigned int mode_cfg = encoding |
> +		priv->counter_mode[chan->channel] << 1 |
> +		priv->quadrature_mode[chan->channel] << 3;
> +	const int base_offset = priv->base + 2 * chan->channel + 1;
> +
> +	priv->encoding[chan->channel] = encoding;
> +
> +	/* Load mode configuration to Counter Mode Register */
> +	outb(0x20 | mode_cfg, base_offset);
> +
> +	return 0;
> +}
> +
> +static int quad8_get_encoding(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan)
> +{
> +	const struct quad8_iio *const priv = iio_priv(indio_dev);
> +
> +	return priv->encoding[chan->channel];
> +}
> +
> +static const struct iio_enum quad8_encoding_enum = {
> +	.items = quad8_encoding_modes,
> +	.num_items = ARRAY_SIZE(quad8_encoding_modes),
> +	.set = quad8_set_encoding,
> +	.get = quad8_get_encoding
> +};
> +
> +static const char *const quad8_counter_modes[] = {
> +	"normal",
> +	"range limit",
> +	"non-recycle",
> +	"modulo-n"
> +};
> +
> +static int quad8_set_counter_mode(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan, unsigned int counter_mode)
> +{
> +	struct quad8_iio *const priv = iio_priv(indio_dev);
> +	const unsigned int mode_cfg = priv->encoding[chan->channel] |
> +		counter_mode << 1 | priv->quadrature_mode[chan->channel] << 3;
> +	const int base_offset = priv->base + 2 * chan->channel + 1;
> +
> +	priv->counter_mode[chan->channel] = counter_mode;
> +
> +	/* Load mode configuration to Counter Mode Register */
> +	outb(0x20 | mode_cfg, base_offset);
> +
> +	return 0;
> +}
> +
> +static int quad8_get_counter_mode(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan)
> +{
> +	const struct quad8_iio *const priv = iio_priv(indio_dev);
> +
> +	return priv->counter_mode[chan->channel];
> +}
> +
> +static const struct iio_enum quad8_counter_mode_enum = {
> +	.items = quad8_counter_modes,
> +	.num_items = ARRAY_SIZE(quad8_counter_modes),
> +	.set = quad8_set_counter_mode,
> +	.get = quad8_get_counter_mode
> +};
> +
> +static const char *const quad8_enable_modes[] = {
> +	"disabled",
> +	"enabled"
> +};
> +
> +static int quad8_set_index_function(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan, unsigned int index_function)
> +{
> +	struct quad8_iio *const priv = iio_priv(indio_dev);
> +	const unsigned int idr_cfg = index_function |
> +		priv->index_polarity[chan->channel] << 1;
> +	const int base_offset = priv->base + 2 * chan->channel + 1;
> +
> +	/* Index function must be disabled in non-quadrature mode */
> +	if (index_function && !priv->quadrature_mode[chan->channel])
> +		return -EINVAL;
> +
> +	priv->index_function[chan->channel] = index_function;
> +
> +	/* Load Index Control configuration to Index Control Register */
> +	outb(0x60 | idr_cfg, base_offset);
> +
> +	return 0;
> +}
> +
> +static int quad8_get_index_function(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan)
> +{
> +	const struct quad8_iio *const priv = iio_priv(indio_dev);
> +
> +	return priv->index_function[chan->channel];
> +}
> +
> +static const struct iio_enum quad8_index_function_enum = {
> +	.items = quad8_enable_modes,
> +	.num_items = ARRAY_SIZE(quad8_enable_modes),
> +	.set = quad8_set_index_function,
> +	.get = quad8_get_index_function
> +};
> +
> +static const char *const quad8_quadrature_modes[] = {
> +	"non-quadrature",
> +	"quadrature x1",
> +	"quadrature x2",
> +	"quadrature x4"
> +};
> +
> +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);
> +	const unsigned int mode_cfg = priv->encoding[chan->channel] |
> +		priv->counter_mode[chan->channel] << 1 | quadrature_mode << 3;
> +	const int base_offset = priv->base + 2 * chan->channel + 1;
> +
> +	priv->quadrature_mode[chan->channel] = quadrature_mode;
> +
> +	/* Index function must be disabled in non-quadrature mode */
> +	if (!quadrature_mode && priv->index_function[chan->channel])
> +		quad8_set_index_function(indio_dev, chan, 0);
> +
> +	/* 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 int quad8_set_ab_enable(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan, unsigned int ab_enable)
> +{
> +	struct quad8_iio *const priv = iio_priv(indio_dev);
> +	const unsigned int ioc_cfg = ab_enable |
> +		priv->preset_enable[chan->channel] << 1;
> +	const int base_offset = priv->base + 2 * chan->channel + 1;
> +
> +	priv->ab_enable[chan->channel] = ab_enable;
> +
> +	/* Load I/O control configuration to Input / Output Control Register */
> +	outb(0x40 | ioc_cfg, base_offset);
> +
> +	return 0;
> +}
> +
> +static int quad8_get_ab_enable(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan)
> +{
> +	const struct quad8_iio *const priv = iio_priv(indio_dev);
> +
> +	return priv->ab_enable[chan->channel];
> +}
> +
> +static const struct iio_enum quad8_ab_enable_enum = {
> +	.items = quad8_enable_modes,
> +	.num_items = ARRAY_SIZE(quad8_enable_modes),
> +	.set = quad8_set_ab_enable,
> +	.get = quad8_get_ab_enable
> +};
> +
> +static const char *const quad8_preset_enable_modes[] = {
> +	"index active",
> +	"disabled"
> +};
> +
> +static int quad8_set_preset_enable(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan, unsigned int preset_enable)
> +{
> +	struct quad8_iio *const priv = iio_priv(indio_dev);
> +	const unsigned int ioc_cfg = priv->ab_enable[chan->channel] |
> +		preset_enable << 1;
> +	const int base_offset = priv->base + 2 * chan->channel + 1;
> +
> +	priv->preset_enable[chan->channel] = preset_enable;
> +
> +	/* Load I/O control configuration to Input / Output Control Register */
> +	outb(0x40 | ioc_cfg, base_offset);
> +
> +	return 0;
> +}
> +
> +static int quad8_get_preset_enable(struct iio_dev *indio_dev,
> +	const struct iio_chan_spec *chan)
> +{
> +	const struct quad8_iio *const priv = iio_priv(indio_dev);
> +
> +	return priv->preset_enable[chan->channel];
> +}
> +
> +static const struct iio_enum quad8_preset_enable_enum = {
> +	.items = quad8_preset_enable_modes,
> +	.num_items = ARRAY_SIZE(quad8_preset_enable_modes),
> +	.set = quad8_set_preset_enable,
> +	.get = quad8_get_preset_enable
> +};
> +
> +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->index_function[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[] = {
> +	IIO_ENUM("borrow", IIO_SEPARATE, &quad8_borrow_enum),
Docs?  Need something under Documentation/ABI/testing/sysfs-bus-iio-*
describing each of these.  Right now I can guess what they are, but don't
know for sure!

I'll see what I can figure out from above to give some quick responses..
> +	IIO_ENUM_AVAILABLE("borrow", &quad8_borrow_enum),
> +	IIO_ENUM("carry", IIO_SEPARATE, &quad8_carry_enum),
> +	IIO_ENUM_AVAILABLE("carry", &quad8_carry_enum),
If this is just a carry bit that toggles on cycles, surely it just gives
us double the count range and should be included directly in there?

> +	IIO_ENUM("compare", IIO_SEPARATE, &quad8_compare_enum),
> +	IIO_ENUM_AVAILABLE("compare", &quad8_compare_enum),

> +	IIO_ENUM("sign", IIO_SEPARATE, &quad8_sign_enum),
> +	IIO_ENUM_AVAILABLE("sign", &quad8_sign_enum),
This particular one sort of feels like it would be simpler to handle as a
boolean 0/1 called say 'positive' - not entirely sure how this differs
from the count direction below.

> +	IIO_ENUM("error", IIO_SEPARATE, &quad8_error_enum),
> +	IIO_ENUM_AVAILABLE("error", &quad8_error_enum),
Perhaps give this a name that describes the possible states.
error is way to flexible / easily abused a bit of ABI. No one would ever
know what might come out of it. Also, more than plausible that more than
one error could occur at the same time.

Perhaps, error_noise_high or something like that?

> +	IIO_ENUM("count_direction", IIO_SEPARATE, &quad8_count_direction_enum),
> +	IIO_ENUM_AVAILABLE("count_direction", &quad8_count_direction_enum),
> +	IIO_ENUM("encoding", IIO_SEPARATE, &quad8_encoding_enum),
> +	IIO_ENUM_AVAILABLE("encoding", &quad8_encoding_enum),
>From a userspace point of view, do we care?  Usual trick when hardware
offers multiple output formats (that we can quickly converty between)
is to pick one and not bother supporting any others.  BCD is bonkers for
this sort of thing so let's not go with that one ;)  Makes kind of sense
if you want to display it on a seven seg display but not really otherwise.

> +	IIO_ENUM("counter_mode", IIO_SEPARATE, &quad8_counter_mode_enum),
> +	IIO_ENUM_AVAILABLE("counter_mode", &quad8_counter_mode_enum),
> +	IIO_ENUM("quadrature_mode", IIO_SEPARATE, &quad8_quadrature_mode_enum),
> +	IIO_ENUM_AVAILABLE("quadrature_mode", &quad8_quadrature_mode_enum)
I know a reasonable amount about encoders and by the name I had no idea what
this would be ;) I guess it's whether you count each crossing or just whole
cycles but definitely needs docs. Might be worth splitting as well into
an element on whether it is quadrature or not and a standard 'scale' info_mask
element.
,
> +	IIO_ENUM("ab_enable", IIO_SEPARATE, &quad8_ab_enable_enum),
> +	IIO_ENUM_AVAILABLE("ab_enable", &quad8_ab_enable_enum),
> +	IIO_ENUM("preset_enable", IIO_SEPARATE, &quad8_preset_enable_enum),
> +	IIO_ENUM_AVAILABLE("preset_enable", &quad8_preset_enable_enum),
> +	{}
> +};
> +
> +static const struct iio_chan_spec_ext_info quad8_index_ext_info[] = {
> +	IIO_ENUM("index_function", IIO_SEPARATE, &quad8_index_function_enum),
> +	IIO_ENUM_AVAILABLE("index_function", &quad8_index_function_enum),
> +	IIO_ENUM("index_polarity", IIO_SEPARATE, &quad8_index_polarity_enum),
Hmm.  This is an odd one.  Guessing we have a reset on the index option?
Otherwise it just inverts the value output to userspace.  In which case
I'd pick one option and drop this control.
> +	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_PRESET),		\
> +	.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 */
> +		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@xxxxxxxxx>");
> +MODULE_DESCRIPTION("ACCES 104-QUAD-8 IIO driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
> new file mode 100644
> index 0000000..887021e
> --- /dev/null
> +++ b/drivers/iio/counter/Kconfig
> @@ -0,0 +1,22 @@
> +#
> +# Counter devices
> +#
> +# When adding new entries keep the list in alphabetical order
> +
> +menu "Counters"
> +
> +config 104_QUAD_8
> +	tristate "ACCES 104-QUAD-8 driver"
> +	depends on X86 && ISA_BUS_API
> +	help
> +	  Say yes here to build support for the ACCES 104-QUAD-8 quadrature
> +	  encoder counter/interface device family (104-QUAD-8, 104-QUAD-4).
> +
> +	  Performing a write to a counter's IIO_CHAN_INFO_RAW sets the counter and
> +	  also clears the counter's respective clearable flags (BORROW, CARRY,
> +	  COMPARE, SIGN, and ERROR). Interrupts are not supported by this driver.
> +
> +	  The base port addresses for the devices may be configured via the base
> +	  array module parameter.
> +
> +endmenu
> diff --git a/drivers/iio/counter/Makefile b/drivers/iio/counter/Makefile
> new file mode 100644
> index 0000000..007e884
> --- /dev/null
> +++ b/drivers/iio/counter/Makefile
> @@ -0,0 +1,7 @@
> +#
> +# Makefile for IIO counter devices
> +#
> +
> +# When adding new entries keep the list in alphabetical order
> +
> +obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
>