Re: [PATCH v4 2/2] iio: 104-quad-8: Add IIO support for the ACCES 104-QUAD-8

[Jonathan Cameron <jic23@kernel.org>]

On 21/09/16 21:16, 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 error flag. Although the counters
> have a 25-bit range, only the lower 24 bits may be set, either directly
> or via IIO_CHAN_INFO_PRESET. 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@gmail.com>
Looking at the fact that preset is rather device specific, I'd be tempted to
not put it info_mask yet, but keep it as an ext_info element until we
get a feel for how it is used in more devices.

Good docs on the whole.

This new ABI was always going to take a few rounds to
come to an agreement!

Thanks,

Jonathan
> ---
>  .../ABI/testing/sysfs-bus-iio-counter-104-quad-8   | 124 +++++
>  MAINTAINERS                                        |   6 +
>  drivers/iio/Kconfig                                |   1 +
>  drivers/iio/Makefile                               |   1 +
>  drivers/iio/counter/104-quad-8.c                   | 582 +++++++++++++++++++++
>  drivers/iio/counter/Kconfig                        |  24 +
>  drivers/iio/counter/Makefile                       |   7 +
>  7 files changed, 745 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
>  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/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8 b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> new file mode 100644
> index 0000000..d1b3f15
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-counter-104-quad-8
> @@ -0,0 +1,124 @@
> +What:		/sys/bus/iio/devices/iio:deviceX/in_count_ab_enable_available
> +What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_direction_available
> +What:		/sys/bus/iio/devices/iio:deviceX/in_count_count_mode_available
> +What:		/sys/bus/iio/devices/iio:deviceX/in_count_noise_error_available
> +What:		/sys/bus/iio/devices/iio:deviceX/in_count_preset_enable_available
> +What:		/sys/bus/iio/devices/iio:deviceX/in_count_quadrature_mode_available
> +What:		/sys/bus/iio/devices/iio:deviceX/in_index_index_polarity_available
> +What:		/sys/bus/iio/devices/iio:deviceX/in_index_synchronous_mode_available
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Discrete set of available values for the respective counter
> +		configuration are listed in this file.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_countY_ab_enable
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Enable or disable the encoder A and B inputs for channel Y.
State what values it can take.  Actually I'd make this a conventional boolean
and use the fuzzy stuff in str_to_bool.
(so basically 0 or 1)

I'm still confused on what this is actually doing.   What are the A and B inputs?
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_direction
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates whether the counter for
> +		channel Y is counting up or down.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_countY_count_mode
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Count mode for channel Y. Four count modes are available:
> +		normal, range limit, non-recycle, and modulo-n. The preset value
> +		for channel Y is used by the count mode where required.
> +
> +		Normal:
> +			Counting is continuous in either direction.
> +
> +		Range Limit:
> +			An upper or lower limit is set, mimicking limit switches
> +			in the mechanical counterpart. The upper limit is set to
> +			the preset value, while the lower limit is set to 0. The
> +			counter freezes at count = preset when counting up, and
> +			at count = 0 when counting down. At either of these
> +			limits, the counting is resumed only when the count
> +			direction is reversed.
Presumably this of for cases with phsical limits and a system that will slip.
(i.e. stepper that is ramming into an end stop).  Horrible ;)
> +
> +		Non-recycle:
> +			Counter is disabled whenever a 24-bit count overflow or
> +			underflow takes place. The counter is re-enabled when a
> +			new count value is loaded to the counter via a preset
> +			operation or write to raw.
> +
> +		Modulo-N:
> +			A count boundary is set between 0 and the preset value.
> +			The counter is reset to 0 at count = preset when
> +			counting up, while the counter is set to the preset
> +			value at count = 0 when counting down; the counter does
> +			not freeze at the bundary points, but counts continously
> +			throughout.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_countY_noise_error
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute that indicates whether excessive noise is
> +		present at the channel Y count inputs in quadrature clock mode;
> +		irrelevant in non-quadrature clock mode.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_countY_preset_enable
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Whether to set channel Y counter with channel Y preset value
> +		when channel Y index input is active, or continously count.
Perhaps we can have a more informative name, afterall preset is used for all
sorts of things depending on mode.

in_countY_set_to_preset_on_index (wordy but makes it clear I think?)
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_countY_quadrature_mode
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Configure channel Y counter for non-quadrature or quadrature
> +		clock mode. Selecting non-quadrature clock mode will disable
> +		synchronous load mode. In quadrature clock mode, the channel Y
> +		scale attribute selects the encoder phase division
> +		(1 = full-cycle, 2 = half-cycle, 4 = quarter-cycle) processed by
> +		the channel Y counter.
> +
> +		Non-quadrature:
> +			The filter and decoder circuit are bypassed. Encoder A
> +			input serves as the count input and B as the UP/DOWN
> +			direction control input, with B = 1 selecting UP Count
> +			mode and B = 0 selecting Down Count mode.
> +
> +		Quadrature:
> +			Encoder A and B inputs are digitally filtered and
> +			decoded for UP/DN clock.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_index_polarity
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Active level of channel Y index input; irrelevant in
> +		non-synchronous load mode.
> +
> +What:		/sys/bus/iio/devices/iio:deviceX/in_indexY_synchronous_mode
> +KernelVersion:	4.9
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Configure channel Y counter for non-synchronous or synchronous
> +		load mode. Synchronous load mode cannot be selected in
> +		non-quadrature clock mode.
> +
> +		Non-synchronous:
> +			A logic low level is the active level at this index
> +			input. The index function (as configured via
> +			preset_enable) is performed directly on the active
> +			level of the index input.
> +
> +		Synchronous:
> +			Intended for interfacing with encoder Index output in
> +			quadrature clock mode. The active level is configured
> +			via index_polarity. The index function (as configured
> +			via preset_enable) is performed synchronously with the
> +			quadrature clock on the active level of the index input.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 1b65477..2780a3f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -255,6 +255,12 @@ L:	linux-gpio@vger.kernel.org
>  S:	Maintained
>  F:	drivers/gpio/gpio-104-idio-16.c
>  
> +ACCES 104-QUAD-8 IIO DRIVER
> +M:	William Breathitt Gray <vilhelm.gray@gmail.com>
> +L:	linux-iio@vger.kernel.org
> +S:	Maintained
> +F:	drivers/iio/counter/104-quad-8.c
> +
>  ACENIC DRIVER
>  M:	Jes Sorensen <jes@trained-monkey.org>
>  L:	linux-acenic@sunsite.dk
> 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..9a287f9
> --- /dev/null
> +++ b/drivers/iio/counter/104-quad-8.c
> @@ -0,0 +1,582 @@
> +/*
> + * 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
> + * @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 preset enable 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_PRESET:
> +		*val = priv->preset[chan->channel];
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		*val = 1 << priv->quadrature_scale[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);
> +
> +		/* 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_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;
> +	case IIO_CHAN_INFO_SCALE:
> +		/* Quadrature scaling only available in quadrature mode */
> +		if (!priv->quadrature_mode[chan->channel] && val != 1)
> +			return -EINVAL;
> +
> +		/* Only three gain states (x1, x2, x4) */
> +		switch (val) {
> +		case 1:
> +			priv->quadrature_scale[chan->channel] = 0;
> +			break;
> +		case 2:
> +			priv->quadrature_scale[chan->channel] = 1;
> +			break;
> +		case 4:
> +			priv->quadrature_scale[chan->channel] = 2;
> +			break;
> +		default:
> +			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 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(0x40 | 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;
> +
> +		/* Index function must be non-synchronous 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_ab_enable_modes[] = {
> +	"disabled",
> +	"enabled"
> +};
> +
> +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 ior_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 | ior_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_ab_enable_modes,
> +	.num_items = ARRAY_SIZE(quad8_ab_enable_modes),
> +	.set = quad8_set_ab_enable,
> +	.get = quad8_get_ab_enable
> +};
> +
> +static const char *const quad8_preset_enable_modes[] = {
> +	"Preset counter on index active",
> +	"Continuously count"
Change the naming as suggested above and this can become
a boolean (0,1).  We pretty much always want to avoid
strings if the meaning can be conveyed as well by an
appropriate boolean or numeric value.

> +};
> +
> +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 ior_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 | ior_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->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(0x40 | 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("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),
> +	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("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_PRESET) | 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");
> diff --git a/drivers/iio/counter/Kconfig b/drivers/iio/counter/Kconfig
> new file mode 100644
> index 0000000..0ed8f46
> --- /dev/null
> +++ b/drivers/iio/counter/Kconfig
> @@ -0,0 +1,24 @@
> +#
> +# 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 error flag. Although the counters
> +	  have a 25-bit range, only the lower 24 bits may be set, either directly
> +	  or via IIO_CHAN_INFO_PRESET. 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
>