diff mbox series

[v10,01/18] counter: Introduce the Generic Counter interface

Message ID ad3a8c427a911848373eae1c08e89353ffb6cb6d.1554184734.git.vilhelm.gray@gmail.com
State Not Applicable
Headers show
Series Introduce the Counter subsystem | expand

Commit Message

William Breathitt Gray April 2, 2019, 6:30 a.m. UTC
This patch introduces the Generic Counter interface for supporting
counter devices.

In the context of the Generic Counter interface, a counter is defined as
a device that reports one or more "counts" based on the state changes of
one or more "signals" as evaluated by a defined "count function."

Driver callbacks should be provided to communicate with the device: to
read and write various Signals and Counts, and to set and get the
"action mode" and "count function" for various Synapses and Counts
respectively.

To support a counter device, a driver must first allocate the available
Counter Signals via counter_signal structures. These Signals should
be stored as an array and set to the signals array member of an
allocated counter_device structure before the Counter is registered to
the system.

Counter Counts may be allocated via counter_count structures, and
respective Counter Signal associations (Synapses) made via
counter_synapse structures. Associated counter_synapse structures are
stored as an array and set to the the synapses array member of the
respective counter_count structure. These counter_count structures are
set to the counts array member of an allocated counter_device structure
before the Counter is registered to the system.

A counter device is registered to the system by passing the respective
initialized counter_device structure to the counter_register function;
similarly, the counter_unregister function unregisters the respective
Counter. The devm_counter_register and devm_counter_unregister functions
serve as device memory-managed versions of the counter_register and
counter_unregister functions respectively.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 MAINTAINERS                  |    8 +
 drivers/Kconfig              |    2 +
 drivers/Makefile             |    1 +
 drivers/counter/Kconfig      |   10 +
 drivers/counter/Makefile     |    5 +
 drivers/counter/counter.c    | 1567 ++++++++++++++++++++++++++++++++++
 include/linux/counter.h      |  510 +++++++++++
 include/linux/counter_enum.h |   45 +
 8 files changed, 2148 insertions(+)
 create mode 100644 drivers/counter/Kconfig
 create mode 100644 drivers/counter/Makefile
 create mode 100644 drivers/counter/counter.c
 create mode 100644 include/linux/counter.h
 create mode 100644 include/linux/counter_enum.h

Comments

Pavel Machek April 8, 2019, 9:55 p.m. UTC | #1
Hi!

> +const char *const counter_count_direction_str[2] = {
> +	[COUNTER_COUNT_DIRECTION_FORWARD] = "forward",
> +	[COUNTER_COUNT_DIRECTION_BACKWARD] = "backward"
> +};
> +EXPORT_SYMBOL_GPL(counter_count_direction_str);
> +
> +const char *const counter_count_mode_str[4] = {
> +	[COUNTER_COUNT_MODE_NORMAL] = "normal",
> +	[COUNTER_COUNT_MODE_RANGE_LIMIT] = "range limit",
> +	[COUNTER_COUNT_MODE_NON_RECYCLE] = "non-recycle",
> +	[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n"
> +};
> +EXPORT_SYMBOL_GPL(counter_count_mode_str);

Dunno. Exporting const tables saying "forward" and "backward". Can we
... somehow make it work without need to export this?
William Breathitt Gray April 9, 2019, 4:57 a.m. UTC | #2
On Mon, Apr 08, 2019 at 11:55:15PM +0200, Pavel Machek wrote:
> Hi!
> 
> > +const char *const counter_count_direction_str[2] = {
> > +	[COUNTER_COUNT_DIRECTION_FORWARD] = "forward",
> > +	[COUNTER_COUNT_DIRECTION_BACKWARD] = "backward"
> > +};
> > +EXPORT_SYMBOL_GPL(counter_count_direction_str);
> > +
> > +const char *const counter_count_mode_str[4] = {
> > +	[COUNTER_COUNT_MODE_NORMAL] = "normal",
> > +	[COUNTER_COUNT_MODE_RANGE_LIMIT] = "range limit",
> > +	[COUNTER_COUNT_MODE_NON_RECYCLE] = "non-recycle",
> > +	[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n"
> > +};
> > +EXPORT_SYMBOL_GPL(counter_count_mode_str);
> 
> Dunno. Exporting const tables saying "forward" and "backward". Can we
> ... somehow make it work without need to export this?
> 
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Right now there are only have 4 counter devices supported in this
patchset, but it is expected that support for a greater variety of
devices will be added. For these future cases, new count directions will
be added to match their functionality.

For example, suppose support for a rotary encoder device is added. These
type of devices do not move forward/backward but rather rotate. In these
cases, the following count directions may be added:

    [COUNTER_COUNT_DIRECTION_CLOCKWISE] = "clockwise",
    [COUNTER_COUNT_DIRECTION_COUNTERCLOCKWISE] = "counterclockwise"

Or as another example, suppose support for a two-axis precision
positioning table is added. These devices support positioning in a
cartesian coordinate system. In these cases, spatial direction may serve
as useful count directions:

    [COUNTER_COUNT_DIRECTION_NORTH] = "north",
    [COUNTER_COUNT_DIRECTION_NORTHEAST] = "northeast",
    [COUNTER_COUNT_DIRECTION_EAST] = "east",
    [COUNTER_COUNT_DIRECTION_SOUTHEAST] = "southeast",
    [COUNTER_COUNT_DIRECTION_SOUTH] = "south",
    [COUNTER_COUNT_DIRECTION_SOUTHWEST] = "southwest",
    [COUNTER_COUNT_DIRECTION_WEST] = "west",
    [COUNTER_COUNT_DIRECTION_NORTHWEST] = "northwest"

A const table is conveinent in these scenarios because support for new
count directions may be easily added by simple entry into the table.

William Breathitt Gray
diff mbox series

Patch

diff --git a/MAINTAINERS b/MAINTAINERS
index ff2c2f2e6da3..ef497d470501 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3966,6 +3966,14 @@  W:	http://www.fi.muni.cz/~kas/cosa/
 S:	Maintained
 F:	drivers/net/wan/cosa*
 
+COUNTER SUBSYSTEM
+M:	William Breathitt Gray <vilhelm.gray@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/counter/
+F:	include/linux/counter.h
+F:	include/linux/counter_enum.h
+
 CPMAC ETHERNET DRIVER
 M:	Florian Fainelli <f.fainelli@gmail.com>
 L:	netdev@vger.kernel.org
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 4f9f99057ff8..e1fd5d783e39 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -228,4 +228,6 @@  source "drivers/siox/Kconfig"
 
 source "drivers/slimbus/Kconfig"
 
+source "drivers/counter/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index e1ce029d28fd..7ea509ad6d43 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -186,3 +186,4 @@  obj-$(CONFIG_MULTIPLEXER)	+= mux/
 obj-$(CONFIG_UNISYS_VISORBUS)	+= visorbus/
 obj-$(CONFIG_SIOX)		+= siox/
 obj-$(CONFIG_GNSS)		+= gnss/
+obj-$(CONFIG_COUNTER)		+= counter/
diff --git a/drivers/counter/Kconfig b/drivers/counter/Kconfig
new file mode 100644
index 000000000000..a74998400282
--- /dev/null
+++ b/drivers/counter/Kconfig
@@ -0,0 +1,10 @@ 
+#
+# Counter devices
+#
+
+menuconfig COUNTER
+	tristate "Counter support"
+	help
+	  This enables counter device support through the Generic Counter
+	  interface. You only need to enable this, if you also want to enable
+	  one or more of the counter device drivers below.
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
new file mode 100644
index 000000000000..b1464604bdbe
--- /dev/null
+++ b/drivers/counter/Makefile
@@ -0,0 +1,5 @@ 
+#
+# Makefile for Counter devices
+#
+
+obj-$(CONFIG_COUNTER) += counter.o
diff --git a/drivers/counter/counter.c b/drivers/counter/counter.c
new file mode 100644
index 000000000000..106bc7180cd8
--- /dev/null
+++ b/drivers/counter/counter.c
@@ -0,0 +1,1567 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic Counter interface
+ * Copyright (C) 2018 William Breathitt Gray
+ */
+#include <linux/counter.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/gfp.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+const char *const counter_count_direction_str[2] = {
+	[COUNTER_COUNT_DIRECTION_FORWARD] = "forward",
+	[COUNTER_COUNT_DIRECTION_BACKWARD] = "backward"
+};
+EXPORT_SYMBOL_GPL(counter_count_direction_str);
+
+const char *const counter_count_mode_str[4] = {
+	[COUNTER_COUNT_MODE_NORMAL] = "normal",
+	[COUNTER_COUNT_MODE_RANGE_LIMIT] = "range limit",
+	[COUNTER_COUNT_MODE_NON_RECYCLE] = "non-recycle",
+	[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n"
+};
+EXPORT_SYMBOL_GPL(counter_count_mode_str);
+
+ssize_t counter_signal_enum_read(struct counter_device *counter,
+				 struct counter_signal *signal, void *priv,
+				 char *buf)
+{
+	const struct counter_signal_enum_ext *const e = priv;
+	int err;
+	size_t index;
+
+	if (!e->get)
+		return -EINVAL;
+
+	err = e->get(counter, signal, &index);
+	if (err)
+		return err;
+
+	if (index >= e->num_items)
+		return -EINVAL;
+
+	return sprintf(buf, "%s\n", e->items[index]);
+}
+EXPORT_SYMBOL_GPL(counter_signal_enum_read);
+
+ssize_t counter_signal_enum_write(struct counter_device *counter,
+				  struct counter_signal *signal, void *priv,
+				  const char *buf, size_t len)
+{
+	const struct counter_signal_enum_ext *const e = priv;
+	ssize_t index;
+	int err;
+
+	if (!e->set)
+		return -EINVAL;
+
+	index = __sysfs_match_string(e->items, e->num_items, buf);
+	if (index < 0)
+		return index;
+
+	err = e->set(counter, signal, index);
+	if (err)
+		return err;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(counter_signal_enum_write);
+
+ssize_t counter_signal_enum_available_read(struct counter_device *counter,
+					   struct counter_signal *signal,
+					   void *priv, char *buf)
+{
+	const struct counter_signal_enum_ext *const e = priv;
+	size_t i;
+	size_t len = 0;
+
+	if (!e->num_items)
+		return 0;
+
+	for (i = 0; i < e->num_items; i++)
+		len += sprintf(buf + len, "%s\n", e->items[i]);
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(counter_signal_enum_available_read);
+
+ssize_t counter_count_enum_read(struct counter_device *counter,
+				struct counter_count *count, void *priv,
+				char *buf)
+{
+	const struct counter_count_enum_ext *const e = priv;
+	int err;
+	size_t index;
+
+	if (!e->get)
+		return -EINVAL;
+
+	err = e->get(counter, count, &index);
+	if (err)
+		return err;
+
+	if (index >= e->num_items)
+		return -EINVAL;
+
+	return sprintf(buf, "%s\n", e->items[index]);
+}
+EXPORT_SYMBOL_GPL(counter_count_enum_read);
+
+ssize_t counter_count_enum_write(struct counter_device *counter,
+				 struct counter_count *count, void *priv,
+				 const char *buf, size_t len)
+{
+	const struct counter_count_enum_ext *const e = priv;
+	ssize_t index;
+	int err;
+
+	if (!e->set)
+		return -EINVAL;
+
+	index = __sysfs_match_string(e->items, e->num_items, buf);
+	if (index < 0)
+		return index;
+
+	err = e->set(counter, count, index);
+	if (err)
+		return err;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(counter_count_enum_write);
+
+ssize_t counter_count_enum_available_read(struct counter_device *counter,
+					  struct counter_count *count,
+					  void *priv, char *buf)
+{
+	const struct counter_count_enum_ext *const e = priv;
+	size_t i;
+	size_t len = 0;
+
+	if (!e->num_items)
+		return 0;
+
+	for (i = 0; i < e->num_items; i++)
+		len += sprintf(buf + len, "%s\n", e->items[i]);
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(counter_count_enum_available_read);
+
+ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
+				 char *buf)
+{
+	const struct counter_device_enum_ext *const e = priv;
+	int err;
+	size_t index;
+
+	if (!e->get)
+		return -EINVAL;
+
+	err = e->get(counter, &index);
+	if (err)
+		return err;
+
+	if (index >= e->num_items)
+		return -EINVAL;
+
+	return sprintf(buf, "%s\n", e->items[index]);
+}
+EXPORT_SYMBOL_GPL(counter_device_enum_read);
+
+ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
+				  const char *buf, size_t len)
+{
+	const struct counter_device_enum_ext *const e = priv;
+	ssize_t index;
+	int err;
+
+	if (!e->set)
+		return -EINVAL;
+
+	index = __sysfs_match_string(e->items, e->num_items, buf);
+	if (index < 0)
+		return index;
+
+	err = e->set(counter, index);
+	if (err)
+		return err;
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(counter_device_enum_write);
+
+ssize_t counter_device_enum_available_read(struct counter_device *counter,
+					   void *priv, char *buf)
+{
+	const struct counter_device_enum_ext *const e = priv;
+	size_t i;
+	size_t len = 0;
+
+	if (!e->num_items)
+		return 0;
+
+	for (i = 0; i < e->num_items; i++)
+		len += sprintf(buf + len, "%s\n", e->items[i]);
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(counter_device_enum_available_read);
+
+static const char *const counter_signal_level_str[] = {
+	[COUNTER_SIGNAL_LEVEL_LOW] = "low",
+	[COUNTER_SIGNAL_LEVEL_HIGH] = "high"
+};
+
+/**
+ * counter_signal_read_value_set - set counter_signal_read_value data
+ * @val:	counter_signal_read_value structure to set
+ * @type:	property Signal data represents
+ * @data:	Signal data
+ *
+ * This function sets an opaque counter_signal_read_value structure with the
+ * provided Signal data.
+ */
+void counter_signal_read_value_set(struct counter_signal_read_value *const val,
+				   const enum counter_signal_value_type type,
+				   void *const data)
+{
+	if (type == COUNTER_SIGNAL_LEVEL)
+		val->len = sprintf(val->buf, "%s\n",
+				   counter_signal_level_str[*(enum counter_signal_level *)data]);
+	else
+		val->len = 0;
+}
+EXPORT_SYMBOL_GPL(counter_signal_read_value_set);
+
+/**
+ * counter_count_read_value_set - set counter_count_read_value data
+ * @val:	counter_count_read_value structure to set
+ * @type:	property Count data represents
+ * @data:	Count data
+ *
+ * This function sets an opaque counter_count_read_value structure with the
+ * provided Count data.
+ */
+void counter_count_read_value_set(struct counter_count_read_value *const val,
+				  const enum counter_count_value_type type,
+				  void *const data)
+{
+	switch (type) {
+	case COUNTER_COUNT_POSITION:
+		val->len = sprintf(val->buf, "%lu\n", *(unsigned long *)data);
+		break;
+	default:
+		val->len = 0;
+	}
+}
+EXPORT_SYMBOL_GPL(counter_count_read_value_set);
+
+/**
+ * counter_count_write_value_get - get counter_count_write_value data
+ * @data:	Count data
+ * @type:	property Count data represents
+ * @val:	counter_count_write_value structure containing data
+ *
+ * This function extracts Count data from the provided opaque
+ * counter_count_write_value structure and stores it at the address provided by
+ * @data.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int counter_count_write_value_get(void *const data,
+				  const enum counter_count_value_type type,
+				  const struct counter_count_write_value *const val)
+{
+	int err;
+
+	switch (type) {
+	case COUNTER_COUNT_POSITION:
+		err = kstrtoul(val->buf, 0, data);
+		if (err)
+			return err;
+		break;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(counter_count_write_value_get);
+
+struct counter_attr_parm {
+	struct counter_device_attr_group *group;
+	const char *prefix;
+	const char *name;
+	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
+			char *buf);
+	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
+			 const char *buf, size_t len);
+	void *component;
+};
+
+struct counter_device_attr {
+	struct device_attribute dev_attr;
+	struct list_head l;
+	void *component;
+};
+
+static int counter_attribute_create(const struct counter_attr_parm *const parm)
+{
+	struct counter_device_attr *counter_attr;
+	struct device_attribute *dev_attr;
+	int err;
+	struct list_head *const attr_list = &parm->group->attr_list;
+
+	/* Allocate a Counter device attribute */
+	counter_attr = kzalloc(sizeof(*counter_attr), GFP_KERNEL);
+	if (!counter_attr)
+		return -ENOMEM;
+	dev_attr = &counter_attr->dev_attr;
+
+	sysfs_attr_init(&dev_attr->attr);
+
+	/* Configure device attribute */
+	dev_attr->attr.name = kasprintf(GFP_KERNEL, "%s%s", parm->prefix,
+					parm->name);
+	if (!dev_attr->attr.name) {
+		err = -ENOMEM;
+		goto err_free_counter_attr;
+	}
+	if (parm->show) {
+		dev_attr->attr.mode |= 0444;
+		dev_attr->show = parm->show;
+	}
+	if (parm->store) {
+		dev_attr->attr.mode |= 0200;
+		dev_attr->store = parm->store;
+	}
+
+	/* Store associated Counter component with attribute */
+	counter_attr->component = parm->component;
+
+	/* Keep track of the attribute for later cleanup */
+	list_add(&counter_attr->l, attr_list);
+	parm->group->num_attr++;
+
+	return 0;
+
+err_free_counter_attr:
+	kfree(counter_attr);
+	return err;
+}
+
+#define to_counter_attr(_dev_attr) \
+	container_of(_dev_attr, struct counter_device_attr, dev_attr)
+
+struct counter_signal_unit {
+	struct counter_signal *signal;
+};
+
+static ssize_t counter_signal_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_signal_unit *const component = devattr->component;
+	struct counter_signal *const signal = component->signal;
+	int err;
+	struct counter_signal_read_value val = { .buf = buf };
+
+	err = counter->ops->signal_read(counter, signal, &val);
+	if (err)
+		return err;
+
+	return val.len;
+}
+
+struct counter_name_unit {
+	const char *name;
+};
+
+static ssize_t counter_device_attr_name_show(struct device *dev,
+					     struct device_attribute *attr,
+					     char *buf)
+{
+	const struct counter_name_unit *const comp = to_counter_attr(attr)->component;
+
+	return sprintf(buf, "%s\n", comp->name);
+}
+
+static int counter_name_attribute_create(
+	struct counter_device_attr_group *const group,
+	const char *const name)
+{
+	struct counter_name_unit *name_comp;
+	struct counter_attr_parm parm;
+	int err;
+
+	/* Skip if no name */
+	if (!name)
+		return 0;
+
+	/* Allocate name attribute component */
+	name_comp = kmalloc(sizeof(*name_comp), GFP_KERNEL);
+	if (!name_comp)
+		return -ENOMEM;
+	name_comp->name = name;
+
+	/* Allocate Signal name attribute */
+	parm.group = group;
+	parm.prefix = "";
+	parm.name = "name";
+	parm.show = counter_device_attr_name_show;
+	parm.store = NULL;
+	parm.component = name_comp;
+	err = counter_attribute_create(&parm);
+	if (err)
+		goto err_free_name_comp;
+
+	return 0;
+
+err_free_name_comp:
+	kfree(name_comp);
+	return err;
+}
+
+struct counter_signal_ext_unit {
+	struct counter_signal *signal;
+	const struct counter_signal_ext *ext;
+};
+
+static ssize_t counter_signal_ext_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_signal_ext_unit *const comp = devattr->component;
+	const struct counter_signal_ext *const ext = comp->ext;
+
+	return ext->read(dev_get_drvdata(dev), comp->signal, ext->priv, buf);
+}
+
+static ssize_t counter_signal_ext_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_signal_ext_unit *const comp = devattr->component;
+	const struct counter_signal_ext *const ext = comp->ext;
+
+	return ext->write(dev_get_drvdata(dev), comp->signal, ext->priv, buf,
+		len);
+}
+
+static void counter_device_attr_list_free(struct list_head *attr_list)
+{
+	struct counter_device_attr *p, *n;
+
+	list_for_each_entry_safe(p, n, attr_list, l) {
+		/* free attribute name and associated component memory */
+		kfree(p->dev_attr.attr.name);
+		kfree(p->component);
+		list_del(&p->l);
+		kfree(p);
+	}
+}
+
+static int counter_signal_ext_register(
+	struct counter_device_attr_group *const group,
+	struct counter_signal *const signal)
+{
+	const size_t num_ext = signal->num_ext;
+	size_t i;
+	const struct counter_signal_ext *ext;
+	struct counter_signal_ext_unit *signal_ext_comp;
+	struct counter_attr_parm parm;
+	int err;
+
+	/* Create an attribute for each extension */
+	for (i = 0 ; i < num_ext; i++) {
+		ext = signal->ext + i;
+
+		/* Allocate signal_ext attribute component */
+		signal_ext_comp = kmalloc(sizeof(*signal_ext_comp), GFP_KERNEL);
+		if (!signal_ext_comp) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+		signal_ext_comp->signal = signal;
+		signal_ext_comp->ext = ext;
+
+		/* Allocate a Counter device attribute */
+		parm.group = group;
+		parm.prefix = "";
+		parm.name = ext->name;
+		parm.show = (ext->read) ? counter_signal_ext_show : NULL;
+		parm.store = (ext->write) ? counter_signal_ext_store : NULL;
+		parm.component = signal_ext_comp;
+		err = counter_attribute_create(&parm);
+		if (err) {
+			kfree(signal_ext_comp);
+			goto err_free_attr_list;
+		}
+	}
+
+	return 0;
+
+err_free_attr_list:
+	counter_device_attr_list_free(&group->attr_list);
+	return err;
+}
+
+static int counter_signal_attributes_create(
+	struct counter_device_attr_group *const group,
+	const struct counter_device *const counter,
+	struct counter_signal *const signal)
+{
+	struct counter_signal_unit *signal_comp;
+	struct counter_attr_parm parm;
+	int err;
+
+	/* Allocate Signal attribute component */
+	signal_comp = kmalloc(sizeof(*signal_comp), GFP_KERNEL);
+	if (!signal_comp)
+		return -ENOMEM;
+	signal_comp->signal = signal;
+
+	/* Create main Signal attribute */
+	parm.group = group;
+	parm.prefix = "";
+	parm.name = "signal";
+	parm.show = (counter->ops->signal_read) ? counter_signal_show : NULL;
+	parm.store = NULL;
+	parm.component = signal_comp;
+	err = counter_attribute_create(&parm);
+	if (err) {
+		kfree(signal_comp);
+		return err;
+	}
+
+	/* Create Signal name attribute */
+	err = counter_name_attribute_create(group, signal->name);
+	if (err)
+		goto err_free_attr_list;
+
+	/* Register Signal extension attributes */
+	err = counter_signal_ext_register(group, signal);
+	if (err)
+		goto err_free_attr_list;
+
+	return 0;
+
+err_free_attr_list:
+	counter_device_attr_list_free(&group->attr_list);
+	return err;
+}
+
+static int counter_signals_register(
+	struct counter_device_attr_group *const groups_list,
+	const struct counter_device *const counter)
+{
+	const size_t num_signals = counter->num_signals;
+	size_t i;
+	struct counter_signal *signal;
+	const char *name;
+	int err;
+
+	/* Register each Signal */
+	for (i = 0; i < num_signals; i++) {
+		signal = counter->signals + i;
+
+		/* Generate Signal attribute directory name */
+		name = kasprintf(GFP_KERNEL, "signal%d", signal->id);
+		if (!name) {
+			err = -ENOMEM;
+			goto err_free_attr_groups;
+		}
+		groups_list[i].attr_group.name = name;
+
+		/* Create all attributes associated with Signal */
+		err = counter_signal_attributes_create(groups_list + i, counter,
+						       signal);
+		if (err)
+			goto err_free_attr_groups;
+	}
+
+	return 0;
+
+err_free_attr_groups:
+	do {
+		kfree(groups_list[i].attr_group.name);
+		counter_device_attr_list_free(&groups_list[i].attr_list);
+	} while (i--);
+	return err;
+}
+
+static const char *const counter_synapse_action_str[] = {
+	[COUNTER_SYNAPSE_ACTION_NONE] = "none",
+	[COUNTER_SYNAPSE_ACTION_RISING_EDGE] = "rising edge",
+	[COUNTER_SYNAPSE_ACTION_FALLING_EDGE] = "falling edge",
+	[COUNTER_SYNAPSE_ACTION_BOTH_EDGES] = "both edges"
+};
+
+struct counter_action_unit {
+	struct counter_synapse *synapse;
+	struct counter_count *count;
+};
+
+static ssize_t counter_action_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_action_unit *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	struct counter_synapse *const synapse = component->synapse;
+	size_t action_index;
+	enum counter_synapse_action action;
+
+	err = counter->ops->action_get(counter, count, synapse, &action_index);
+	if (err)
+		return err;
+
+	synapse->action = action_index;
+
+	action = synapse->actions_list[action_index];
+	return sprintf(buf, "%s\n", counter_synapse_action_str[action]);
+}
+
+static ssize_t counter_action_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_action_unit *const component = devattr->component;
+	struct counter_synapse *const synapse = component->synapse;
+	size_t action_index;
+	const size_t num_actions = synapse->num_actions;
+	enum counter_synapse_action action;
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	struct counter_count *const count = component->count;
+
+	/* Find requested action mode */
+	for (action_index = 0; action_index < num_actions; action_index++) {
+		action = synapse->actions_list[action_index];
+		if (sysfs_streq(buf, counter_synapse_action_str[action]))
+			break;
+	}
+	/* If requested action mode not found */
+	if (action_index >= num_actions)
+		return -EINVAL;
+
+	err = counter->ops->action_set(counter, count, synapse, action_index);
+	if (err)
+		return err;
+
+	synapse->action = action_index;
+
+	return len;
+}
+
+struct counter_action_avail_unit {
+	const enum counter_synapse_action *actions_list;
+	size_t num_actions;
+};
+
+static ssize_t counter_synapse_action_available_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_action_avail_unit *const component = devattr->component;
+	size_t i;
+	enum counter_synapse_action action;
+	ssize_t len = 0;
+
+	for (i = 0; i < component->num_actions; i++) {
+		action = component->actions_list[i];
+		len += sprintf(buf + len, "%s\n",
+			       counter_synapse_action_str[action]);
+	}
+
+	return len;
+}
+
+static int counter_synapses_register(
+	struct counter_device_attr_group *const group,
+	const struct counter_device *const counter,
+	struct counter_count *const count, const char *const count_attr_name)
+{
+	size_t i;
+	struct counter_synapse *synapse;
+	const char *prefix;
+	struct counter_action_unit *action_comp;
+	struct counter_attr_parm parm;
+	int err;
+	struct counter_action_avail_unit *avail_comp;
+
+	/* Register each Synapse */
+	for (i = 0; i < count->num_synapses; i++) {
+		synapse = count->synapses + i;
+
+		/* Generate attribute prefix */
+		prefix = kasprintf(GFP_KERNEL, "signal%d_",
+				   synapse->signal->id);
+		if (!prefix) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+
+		/* Allocate action attribute component */
+		action_comp = kmalloc(sizeof(*action_comp), GFP_KERNEL);
+		if (!action_comp) {
+			err = -ENOMEM;
+			goto err_free_prefix;
+		}
+		action_comp->synapse = synapse;
+		action_comp->count = count;
+
+		/* Create action attribute */
+		parm.group = group;
+		parm.prefix = prefix;
+		parm.name = "action";
+		parm.show = (counter->ops->action_get) ? counter_action_show : NULL;
+		parm.store = (counter->ops->action_set) ? counter_action_store : NULL;
+		parm.component = action_comp;
+		err = counter_attribute_create(&parm);
+		if (err) {
+			kfree(action_comp);
+			goto err_free_prefix;
+		}
+
+		/* Allocate action available attribute component */
+		avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
+		if (!avail_comp) {
+			err = -ENOMEM;
+			goto err_free_prefix;
+		}
+		avail_comp->actions_list = synapse->actions_list;
+		avail_comp->num_actions = synapse->num_actions;
+
+		/* Create action_available attribute */
+		parm.group = group;
+		parm.prefix = prefix;
+		parm.name = "action_available";
+		parm.show = counter_synapse_action_available_show;
+		parm.store = NULL;
+		parm.component = avail_comp;
+		err = counter_attribute_create(&parm);
+		if (err) {
+			kfree(avail_comp);
+			goto err_free_prefix;
+		}
+
+		kfree(prefix);
+	}
+
+	return 0;
+
+err_free_prefix:
+	kfree(prefix);
+err_free_attr_list:
+	counter_device_attr_list_free(&group->attr_list);
+	return err;
+}
+
+struct counter_count_unit {
+	struct counter_count *count;
+};
+
+static ssize_t counter_count_show(struct device *dev,
+				  struct device_attribute *attr,
+				  char *buf)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_count_unit *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	int err;
+	struct counter_count_read_value val = { .buf = buf };
+
+	err = counter->ops->count_read(counter, count, &val);
+	if (err)
+		return err;
+
+	return val.len;
+}
+
+static ssize_t counter_count_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t len)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_count_unit *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	int err;
+	struct counter_count_write_value val = { .buf = buf };
+
+	err = counter->ops->count_write(counter, count, &val);
+	if (err)
+		return err;
+
+	return len;
+}
+
+static const char *const counter_count_function_str[] = {
+	[COUNTER_COUNT_FUNCTION_INCREASE] = "increase",
+	[COUNTER_COUNT_FUNCTION_DECREASE] = "decrease",
+	[COUNTER_COUNT_FUNCTION_PULSE_DIRECTION] = "pulse-direction",
+	[COUNTER_COUNT_FUNCTION_QUADRATURE_X1_A] = "quadrature x1 a",
+	[COUNTER_COUNT_FUNCTION_QUADRATURE_X1_B] = "quadrature x1 b",
+	[COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A] = "quadrature x2 a",
+	[COUNTER_COUNT_FUNCTION_QUADRATURE_X2_B] = "quadrature x2 b",
+	[COUNTER_COUNT_FUNCTION_QUADRATURE_X4] = "quadrature x4"
+};
+
+static ssize_t counter_function_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_count_unit *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	size_t func_index;
+	enum counter_count_function function;
+
+	err = counter->ops->function_get(counter, count, &func_index);
+	if (err)
+		return err;
+
+	count->function = func_index;
+
+	function = count->functions_list[func_index];
+	return sprintf(buf, "%s\n", counter_count_function_str[function]);
+}
+
+static ssize_t counter_function_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_count_unit *const component = devattr->component;
+	struct counter_count *const count = component->count;
+	const size_t num_functions = count->num_functions;
+	size_t func_index;
+	enum counter_count_function function;
+	int err;
+	struct counter_device *const counter = dev_get_drvdata(dev);
+
+	/* Find requested Count function mode */
+	for (func_index = 0; func_index < num_functions; func_index++) {
+		function = count->functions_list[func_index];
+		if (sysfs_streq(buf, counter_count_function_str[function]))
+			break;
+	}
+	/* Return error if requested Count function mode not found */
+	if (func_index >= num_functions)
+		return -EINVAL;
+
+	err = counter->ops->function_set(counter, count, func_index);
+	if (err)
+		return err;
+
+	count->function = func_index;
+
+	return len;
+}
+
+struct counter_count_ext_unit {
+	struct counter_count *count;
+	const struct counter_count_ext *ext;
+};
+
+static ssize_t counter_count_ext_show(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_count_ext_unit *const comp = devattr->component;
+	const struct counter_count_ext *const ext = comp->ext;
+
+	return ext->read(dev_get_drvdata(dev), comp->count, ext->priv, buf);
+}
+
+static ssize_t counter_count_ext_store(struct device *dev,
+				       struct device_attribute *attr,
+				       const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_count_ext_unit *const comp = devattr->component;
+	const struct counter_count_ext *const ext = comp->ext;
+
+	return ext->write(dev_get_drvdata(dev), comp->count, ext->priv, buf,
+		len);
+}
+
+static int counter_count_ext_register(
+	struct counter_device_attr_group *const group,
+	struct counter_count *const count)
+{
+	size_t i;
+	const struct counter_count_ext *ext;
+	struct counter_count_ext_unit *count_ext_comp;
+	struct counter_attr_parm parm;
+	int err;
+
+	/* Create an attribute for each extension */
+	for (i = 0 ; i < count->num_ext; i++) {
+		ext = count->ext + i;
+
+		/* Allocate count_ext attribute component */
+		count_ext_comp = kmalloc(sizeof(*count_ext_comp), GFP_KERNEL);
+		if (!count_ext_comp) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+		count_ext_comp->count = count;
+		count_ext_comp->ext = ext;
+
+		/* Allocate count_ext attribute */
+		parm.group = group;
+		parm.prefix = "";
+		parm.name = ext->name;
+		parm.show = (ext->read) ? counter_count_ext_show : NULL;
+		parm.store = (ext->write) ? counter_count_ext_store : NULL;
+		parm.component = count_ext_comp;
+		err = counter_attribute_create(&parm);
+		if (err) {
+			kfree(count_ext_comp);
+			goto err_free_attr_list;
+		}
+	}
+
+	return 0;
+
+err_free_attr_list:
+	counter_device_attr_list_free(&group->attr_list);
+	return err;
+}
+
+struct counter_func_avail_unit {
+	const enum counter_count_function *functions_list;
+	size_t num_functions;
+};
+
+static ssize_t counter_count_function_available_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_func_avail_unit *const component = devattr->component;
+	const enum counter_count_function *const func_list = component->functions_list;
+	const size_t num_functions = component->num_functions;
+	size_t i;
+	enum counter_count_function function;
+	ssize_t len = 0;
+
+	for (i = 0; i < num_functions; i++) {
+		function = func_list[i];
+		len += sprintf(buf + len, "%s\n",
+			       counter_count_function_str[function]);
+	}
+
+	return len;
+}
+
+static int counter_count_attributes_create(
+	struct counter_device_attr_group *const group,
+	const struct counter_device *const counter,
+	struct counter_count *const count)
+{
+	struct counter_count_unit *count_comp;
+	struct counter_attr_parm parm;
+	int err;
+	struct counter_count_unit *func_comp;
+	struct counter_func_avail_unit *avail_comp;
+
+	/* Allocate count attribute component */
+	count_comp = kmalloc(sizeof(*count_comp), GFP_KERNEL);
+	if (!count_comp)
+		return -ENOMEM;
+	count_comp->count = count;
+
+	/* Create main Count attribute */
+	parm.group = group;
+	parm.prefix = "";
+	parm.name = "count";
+	parm.show = (counter->ops->count_read) ? counter_count_show : NULL;
+	parm.store = (counter->ops->count_write) ? counter_count_store : NULL;
+	parm.component = count_comp;
+	err = counter_attribute_create(&parm);
+	if (err) {
+		kfree(count_comp);
+		return err;
+	}
+
+	/* Allocate function attribute component */
+	func_comp = kmalloc(sizeof(*func_comp), GFP_KERNEL);
+	if (!func_comp) {
+		err = -ENOMEM;
+		goto err_free_attr_list;
+	}
+	func_comp->count = count;
+
+	/* Create Count function attribute */
+	parm.group = group;
+	parm.prefix = "";
+	parm.name = "function";
+	parm.show = (counter->ops->function_get) ? counter_function_show : NULL;
+	parm.store = (counter->ops->function_set) ? counter_function_store : NULL;
+	parm.component = func_comp;
+	err = counter_attribute_create(&parm);
+	if (err) {
+		kfree(func_comp);
+		goto err_free_attr_list;
+	}
+
+	/* Allocate function available attribute component */
+	avail_comp = kmalloc(sizeof(*avail_comp), GFP_KERNEL);
+	if (!avail_comp) {
+		err = -ENOMEM;
+		goto err_free_attr_list;
+	}
+	avail_comp->functions_list = count->functions_list;
+	avail_comp->num_functions = count->num_functions;
+
+	/* Create Count function_available attribute */
+	parm.group = group;
+	parm.prefix = "";
+	parm.name = "function_available";
+	parm.show = counter_count_function_available_show;
+	parm.store = NULL;
+	parm.component = avail_comp;
+	err = counter_attribute_create(&parm);
+	if (err) {
+		kfree(avail_comp);
+		goto err_free_attr_list;
+	}
+
+	/* Create Count name attribute */
+	err = counter_name_attribute_create(group, count->name);
+	if (err)
+		goto err_free_attr_list;
+
+	/* Register Count extension attributes */
+	err = counter_count_ext_register(group, count);
+	if (err)
+		goto err_free_attr_list;
+
+	return 0;
+
+err_free_attr_list:
+	counter_device_attr_list_free(&group->attr_list);
+	return err;
+}
+
+static int counter_counts_register(
+	struct counter_device_attr_group *const groups_list,
+	const struct counter_device *const counter)
+{
+	size_t i;
+	struct counter_count *count;
+	const char *name;
+	int err;
+
+	/* Register each Count */
+	for (i = 0; i < counter->num_counts; i++) {
+		count = counter->counts + i;
+
+		/* Generate Count attribute directory name */
+		name = kasprintf(GFP_KERNEL, "count%d", count->id);
+		if (!name) {
+			err = -ENOMEM;
+			goto err_free_attr_groups;
+		}
+		groups_list[i].attr_group.name = name;
+
+		/* Register the Synapses associated with each Count */
+		err = counter_synapses_register(groups_list + i, counter, count,
+						name);
+		if (err)
+			goto err_free_attr_groups;
+
+		/* Create all attributes associated with Count */
+		err = counter_count_attributes_create(groups_list + i, counter,
+						      count);
+		if (err)
+			goto err_free_attr_groups;
+	}
+
+	return 0;
+
+err_free_attr_groups:
+	do {
+		kfree(groups_list[i].attr_group.name);
+		counter_device_attr_list_free(&groups_list[i].attr_list);
+	} while (i--);
+	return err;
+}
+
+struct counter_size_unit {
+	size_t size;
+};
+
+static ssize_t counter_device_attr_size_show(struct device *dev,
+					     struct device_attribute *attr,
+					     char *buf)
+{
+	const struct counter_size_unit *const comp = to_counter_attr(attr)->component;
+
+	return sprintf(buf, "%zu\n", comp->size);
+}
+
+static int counter_size_attribute_create(
+	struct counter_device_attr_group *const group,
+	const size_t size, const char *const name)
+{
+	struct counter_size_unit *size_comp;
+	struct counter_attr_parm parm;
+	int err;
+
+	/* Allocate size attribute component */
+	size_comp = kmalloc(sizeof(*size_comp), GFP_KERNEL);
+	if (!size_comp)
+		return -ENOMEM;
+	size_comp->size = size;
+
+	parm.group = group;
+	parm.prefix = "";
+	parm.name = name;
+	parm.show = counter_device_attr_size_show;
+	parm.store = NULL;
+	parm.component = size_comp;
+	err = counter_attribute_create(&parm);
+	if (err)
+		goto err_free_size_comp;
+
+	return 0;
+
+err_free_size_comp:
+	kfree(size_comp);
+	return err;
+}
+
+struct counter_ext_unit {
+	const struct counter_device_ext *ext;
+};
+
+static ssize_t counter_device_ext_show(struct device *dev,
+				       struct device_attribute *attr, char *buf)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_ext_unit *const component = devattr->component;
+	const struct counter_device_ext *const ext = component->ext;
+
+	return ext->read(dev_get_drvdata(dev), ext->priv, buf);
+}
+
+static ssize_t counter_device_ext_store(struct device *dev,
+					struct device_attribute *attr,
+					const char *buf, size_t len)
+{
+	const struct counter_device_attr *const devattr = to_counter_attr(attr);
+	const struct counter_ext_unit *const component = devattr->component;
+	const struct counter_device_ext *const ext = component->ext;
+
+	return ext->write(dev_get_drvdata(dev), ext->priv, buf, len);
+}
+
+static int counter_device_ext_register(
+	struct counter_device_attr_group *const group,
+	struct counter_device *const counter)
+{
+	size_t i;
+	struct counter_ext_unit *ext_comp;
+	struct counter_attr_parm parm;
+	int err;
+
+	/* Create an attribute for each extension */
+	for (i = 0 ; i < counter->num_ext; i++) {
+		/* Allocate extension attribute component */
+		ext_comp = kmalloc(sizeof(*ext_comp), GFP_KERNEL);
+		if (!ext_comp) {
+			err = -ENOMEM;
+			goto err_free_attr_list;
+		}
+
+		ext_comp->ext = counter->ext + i;
+
+		/* Allocate extension attribute */
+		parm.group = group;
+		parm.prefix = "";
+		parm.name = counter->ext[i].name;
+		parm.show = (counter->ext[i].read) ? counter_device_ext_show : NULL;
+		parm.store = (counter->ext[i].write) ? counter_device_ext_store : NULL;
+		parm.component = ext_comp;
+		err = counter_attribute_create(&parm);
+		if (err) {
+			kfree(ext_comp);
+			goto err_free_attr_list;
+		}
+	}
+
+	return 0;
+
+err_free_attr_list:
+	counter_device_attr_list_free(&group->attr_list);
+	return err;
+}
+
+static int counter_global_attr_register(
+	struct counter_device_attr_group *const group,
+	struct counter_device *const counter)
+{
+	int err;
+
+	/* Create name attribute */
+	err = counter_name_attribute_create(group, counter->name);
+	if (err)
+		return err;
+
+	/* Create num_counts attribute */
+	err = counter_size_attribute_create(group, counter->num_counts,
+					    "num_counts");
+	if (err)
+		goto err_free_attr_list;
+
+	/* Create num_signals attribute */
+	err = counter_size_attribute_create(group, counter->num_signals,
+					    "num_signals");
+	if (err)
+		goto err_free_attr_list;
+
+	/* Register Counter device extension attributes */
+	err = counter_device_ext_register(group, counter);
+	if (err)
+		goto err_free_attr_list;
+
+	return 0;
+
+err_free_attr_list:
+	counter_device_attr_list_free(&group->attr_list);
+	return err;
+}
+
+static void counter_device_groups_list_free(
+	struct counter_device_attr_group *const groups_list,
+	const size_t num_groups)
+{
+	struct counter_device_attr_group *group;
+	size_t i;
+
+	/* loop through all attribute groups (signals, counts, global, etc.) */
+	for (i = 0; i < num_groups; i++) {
+		group = groups_list + i;
+
+		/* free all attribute group and associated attributes memory */
+		kfree(group->attr_group.name);
+		kfree(group->attr_group.attrs);
+		counter_device_attr_list_free(&group->attr_list);
+	}
+
+	kfree(groups_list);
+}
+
+static int counter_device_groups_list_prepare(
+	struct counter_device *const counter)
+{
+	const size_t total_num_groups =
+		counter->num_signals + counter->num_counts + 1;
+	struct counter_device_attr_group *groups_list;
+	size_t i;
+	int err;
+	size_t num_groups = 0;
+
+	/* Allocate space for attribute groups (signals, counts, and ext) */
+	groups_list = kcalloc(total_num_groups, sizeof(*groups_list),
+			      GFP_KERNEL);
+	if (!groups_list)
+		return -ENOMEM;
+
+	/* Initialize attribute lists */
+	for (i = 0; i < total_num_groups; i++)
+		INIT_LIST_HEAD(&groups_list[i].attr_list);
+
+	/* Register Signals */
+	err = counter_signals_register(groups_list, counter);
+	if (err)
+		goto err_free_groups_list;
+	num_groups += counter->num_signals;
+
+	/* Register Counts and respective Synapses */
+	err = counter_counts_register(groups_list + num_groups, counter);
+	if (err)
+		goto err_free_groups_list;
+	num_groups += counter->num_counts;
+
+	/* Register Counter global attributes */
+	err = counter_global_attr_register(groups_list + num_groups, counter);
+	if (err)
+		goto err_free_groups_list;
+	num_groups++;
+
+	/* Store groups_list in device_state */
+	counter->device_state->groups_list = groups_list;
+	counter->device_state->num_groups = num_groups;
+
+	return 0;
+
+err_free_groups_list:
+	counter_device_groups_list_free(groups_list, num_groups);
+	return err;
+}
+
+static int counter_device_groups_prepare(
+	struct counter_device_state *const device_state)
+{
+	size_t i, j;
+	struct counter_device_attr_group *group;
+	int err;
+	struct counter_device_attr *p;
+
+	/* Allocate attribute groups for association with device */
+	device_state->groups = kcalloc(device_state->num_groups + 1,
+				       sizeof(*device_state->groups),
+				       GFP_KERNEL);
+	if (!device_state->groups)
+		return -ENOMEM;
+
+	/* Prepare each group of attributes for association */
+	for (i = 0; i < device_state->num_groups; i++) {
+		group = device_state->groups_list + i;
+
+		/* Allocate space for attribute pointers in attribute group */
+		group->attr_group.attrs = kcalloc(group->num_attr + 1,
+			sizeof(*group->attr_group.attrs), GFP_KERNEL);
+		if (!group->attr_group.attrs) {
+			err = -ENOMEM;
+			goto err_free_groups;
+		}
+
+		/* Add attribute pointers to attribute group */
+		j = 0;
+		list_for_each_entry(p, &group->attr_list, l)
+			group->attr_group.attrs[j++] = &p->dev_attr.attr;
+
+		/* Group attributes in attribute group */
+		device_state->groups[i] = &group->attr_group;
+	}
+	/* Associate attributes with device */
+	device_state->dev.groups = device_state->groups;
+
+	return 0;
+
+err_free_groups:
+	do {
+		group = device_state->groups_list + i;
+		kfree(group->attr_group.attrs);
+		group->attr_group.attrs = NULL;
+	} while (i--);
+	kfree(device_state->groups);
+	return err;
+}
+
+/* Provides a unique ID for each counter device */
+static DEFINE_IDA(counter_ida);
+
+static void counter_device_release(struct device *dev)
+{
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	struct counter_device_state *const device_state = counter->device_state;
+
+	kfree(device_state->groups);
+	counter_device_groups_list_free(device_state->groups_list,
+					device_state->num_groups);
+	ida_simple_remove(&counter_ida, device_state->id);
+	kfree(device_state);
+}
+
+static struct device_type counter_device_type = {
+	.name = "counter_device",
+	.release = counter_device_release
+};
+
+static struct bus_type counter_bus_type = {
+	.name = "counter"
+};
+
+/**
+ * counter_register - register Counter to the system
+ * @counter:	pointer to Counter to register
+ *
+ * This function registers a Counter to the system. A sysfs "counter" directory
+ * will be created and populated with sysfs attributes correlating with the
+ * Counter Signals, Synapses, and Counts respectively.
+ */
+int counter_register(struct counter_device *const counter)
+{
+	struct counter_device_state *device_state;
+	int err;
+
+	/* Allocate internal state container for Counter device */
+	device_state = kzalloc(sizeof(*device_state), GFP_KERNEL);
+	if (!device_state)
+		return -ENOMEM;
+	counter->device_state = device_state;
+
+	/* Acquire unique ID */
+	device_state->id = ida_simple_get(&counter_ida, 0, 0, GFP_KERNEL);
+	if (device_state->id < 0) {
+		err = device_state->id;
+		goto err_free_device_state;
+	}
+
+	/* Configure device structure for Counter */
+	device_state->dev.type = &counter_device_type;
+	device_state->dev.bus = &counter_bus_type;
+	if (counter->parent) {
+		device_state->dev.parent = counter->parent;
+		device_state->dev.of_node = counter->parent->of_node;
+	}
+	dev_set_name(&device_state->dev, "counter%d", device_state->id);
+	device_initialize(&device_state->dev);
+	dev_set_drvdata(&device_state->dev, counter);
+
+	/* Prepare device attributes */
+	err = counter_device_groups_list_prepare(counter);
+	if (err)
+		goto err_free_id;
+
+	/* Organize device attributes to groups and match to device */
+	err = counter_device_groups_prepare(device_state);
+	if (err)
+		goto err_free_groups_list;
+
+	/* Add device to system */
+	err = device_add(&device_state->dev);
+	if (err)
+		goto err_free_groups;
+
+	return 0;
+
+err_free_groups:
+	kfree(device_state->groups);
+err_free_groups_list:
+	counter_device_groups_list_free(device_state->groups_list,
+					device_state->num_groups);
+err_free_id:
+	ida_simple_remove(&counter_ida, device_state->id);
+err_free_device_state:
+	kfree(device_state);
+	return err;
+}
+EXPORT_SYMBOL_GPL(counter_register);
+
+/**
+ * counter_unregister - unregister Counter from the system
+ * @counter:	pointer to Counter to unregister
+ *
+ * The Counter is unregistered from the system; all allocated memory is freed.
+ */
+void counter_unregister(struct counter_device *const counter)
+{
+	if (counter)
+		device_del(&counter->device_state->dev);
+}
+EXPORT_SYMBOL_GPL(counter_unregister);
+
+static void devm_counter_unreg(struct device *dev, void *res)
+{
+	counter_unregister(*(struct counter_device **)res);
+}
+
+/**
+ * devm_counter_register - Resource-managed counter_register
+ * @dev:	device to allocate counter_device for
+ * @counter:	pointer to Counter to register
+ *
+ * Managed counter_register. The Counter registered with this function is
+ * automatically unregistered on driver detach. This function calls
+ * counter_register internally. Refer to that function for more information.
+ *
+ * If an Counter registered with this function needs to be unregistered
+ * separately, devm_counter_unregister must be used.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int devm_counter_register(struct device *dev,
+			  struct counter_device *const counter)
+{
+	struct counter_device **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_counter_unreg, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = counter_register(counter);
+	if (!ret) {
+		*ptr = counter;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(devm_counter_register);
+
+static int devm_counter_match(struct device *dev, void *res, void *data)
+{
+	struct counter_device **r = res;
+
+	if (!r || !*r) {
+		WARN_ON(!r || !*r);
+		return 0;
+	}
+
+	return *r == data;
+}
+
+/**
+ * devm_counter_unregister - Resource-managed counter_unregister
+ * @dev:	device this counter_device belongs to
+ * @counter:	pointer to Counter associated with the device
+ *
+ * Unregister Counter registered with devm_counter_register.
+ */
+void devm_counter_unregister(struct device *dev,
+			     struct counter_device *const counter)
+{
+	int rc;
+
+	rc = devres_release(dev, devm_counter_unreg, devm_counter_match,
+			    counter);
+	WARN_ON(rc);
+}
+EXPORT_SYMBOL_GPL(devm_counter_unregister);
+
+static int __init counter_init(void)
+{
+	return bus_register(&counter_bus_type);
+}
+
+static void __exit counter_exit(void)
+{
+	bus_unregister(&counter_bus_type);
+}
+
+subsys_initcall(counter_init);
+module_exit(counter_exit);
+
+MODULE_AUTHOR("William Breathitt Gray <vilhelm.gray@gmail.com>");
+MODULE_DESCRIPTION("Generic Counter interface");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/counter.h b/include/linux/counter.h
new file mode 100644
index 000000000000..a061cdcdef7c
--- /dev/null
+++ b/include/linux/counter.h
@@ -0,0 +1,510 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Counter interface
+ * Copyright (C) 2018 William Breathitt Gray
+ */
+#ifndef _COUNTER_H_
+#define _COUNTER_H_
+
+#include <linux/counter_enum.h>
+#include <linux/device.h>
+#include <linux/types.h>
+
+enum counter_count_direction {
+	COUNTER_COUNT_DIRECTION_FORWARD = 0,
+	COUNTER_COUNT_DIRECTION_BACKWARD
+};
+extern const char *const counter_count_direction_str[2];
+
+enum counter_count_mode {
+	COUNTER_COUNT_MODE_NORMAL = 0,
+	COUNTER_COUNT_MODE_RANGE_LIMIT,
+	COUNTER_COUNT_MODE_NON_RECYCLE,
+	COUNTER_COUNT_MODE_MODULO_N
+};
+extern const char *const counter_count_mode_str[4];
+
+struct counter_device;
+struct counter_signal;
+
+/**
+ * struct counter_signal_ext - Counter Signal extensions
+ * @name:	attribute name
+ * @read:	read callback for this attribute; may be NULL
+ * @write:	write callback for this attribute; may be NULL
+ * @priv:	data private to the driver
+ */
+struct counter_signal_ext {
+	const char *name;
+	ssize_t (*read)(struct counter_device *counter,
+			struct counter_signal *signal, void *priv, char *buf);
+	ssize_t (*write)(struct counter_device *counter,
+			 struct counter_signal *signal, void *priv,
+			 const char *buf, size_t len);
+	void *priv;
+};
+
+/**
+ * struct counter_signal - Counter Signal node
+ * @id:		unique ID used to identify signal
+ * @name:	device-specific Signal name; ideally, this should match the name
+ *		as it appears in the datasheet documentation
+ * @ext:	optional array of Counter Signal extensions
+ * @num_ext:	number of Counter Signal extensions specified in @ext
+ * @priv:	optional private data supplied by driver
+ */
+struct counter_signal {
+	int id;
+	const char *name;
+
+	const struct counter_signal_ext *ext;
+	size_t num_ext;
+
+	void *priv;
+};
+
+/**
+ * struct counter_signal_enum_ext - Signal enum extension attribute
+ * @items:	Array of strings
+ * @num_items:	Number of items specified in @items
+ * @set:	Set callback function; may be NULL
+ * @get:	Get callback function; may be NULL
+ *
+ * The counter_signal_enum_ext structure can be used to implement enum style
+ * Signal extension attributes. Enum style attributes are those which have a set
+ * of strings that map to unsigned integer values. The Generic Counter Signal
+ * enum extension helper code takes care of mapping between value and string, as
+ * well as generating a "_available" file which contains a list of all available
+ * items. The get callback is used to query the currently active item; the index
+ * of the item within the respective items array is returned via the 'item'
+ * parameter. The set callback is called when the attribute is updated; the
+ * 'item' parameter contains the index of the newly activated item within the
+ * respective items array.
+ */
+struct counter_signal_enum_ext {
+	const char * const *items;
+	size_t num_items;
+	int (*get)(struct counter_device *counter,
+		   struct counter_signal *signal, size_t *item);
+	int (*set)(struct counter_device *counter,
+		   struct counter_signal *signal, size_t item);
+};
+
+/**
+ * COUNTER_SIGNAL_ENUM() - Initialize Signal enum extension
+ * @_name:	Attribute name
+ * @_e:		Pointer to a counter_signal_enum_ext structure
+ *
+ * This should usually be used together with COUNTER_SIGNAL_ENUM_AVAILABLE()
+ */
+#define COUNTER_SIGNAL_ENUM(_name, _e) \
+{ \
+	.name = (_name), \
+	.read = counter_signal_enum_read, \
+	.write = counter_signal_enum_write, \
+	.priv = (_e) \
+}
+
+/**
+ * COUNTER_SIGNAL_ENUM_AVAILABLE() - Initialize Signal enum available extension
+ * @_name:	Attribute name ("_available" will be appended to the name)
+ * @_e:		Pointer to a counter_signal_enum_ext structure
+ *
+ * Creates a read only attribute that lists all the available enum items in a
+ * newline separated list. This should usually be used together with
+ * COUNTER_SIGNAL_ENUM()
+ */
+#define COUNTER_SIGNAL_ENUM_AVAILABLE(_name, _e) \
+{ \
+	.name = (_name "_available"), \
+	.read = counter_signal_enum_available_read, \
+	.priv = (_e) \
+}
+
+enum counter_synapse_action {
+	COUNTER_SYNAPSE_ACTION_NONE = 0,
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+	COUNTER_SYNAPSE_ACTION_FALLING_EDGE,
+	COUNTER_SYNAPSE_ACTION_BOTH_EDGES
+};
+
+/**
+ * struct counter_synapse - Counter Synapse node
+ * @action:		index of current action mode
+ * @actions_list:	array of available action modes
+ * @num_actions:	number of action modes specified in @actions_list
+ * @signal:		pointer to associated signal
+ */
+struct counter_synapse {
+	size_t action;
+	const enum counter_synapse_action *actions_list;
+	size_t num_actions;
+
+	struct counter_signal *signal;
+};
+
+struct counter_count;
+
+/**
+ * struct counter_count_ext - Counter Count extension
+ * @name:	attribute name
+ * @read:	read callback for this attribute; may be NULL
+ * @write:	write callback for this attribute; may be NULL
+ * @priv:	data private to the driver
+ */
+struct counter_count_ext {
+	const char *name;
+	ssize_t (*read)(struct counter_device *counter,
+			struct counter_count *count, void *priv, char *buf);
+	ssize_t (*write)(struct counter_device *counter,
+			 struct counter_count *count, void *priv,
+			 const char *buf, size_t len);
+	void *priv;
+};
+
+enum counter_count_function {
+	COUNTER_COUNT_FUNCTION_INCREASE = 0,
+	COUNTER_COUNT_FUNCTION_DECREASE,
+	COUNTER_COUNT_FUNCTION_PULSE_DIRECTION,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X1_A,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X1_B,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X2_B,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X4
+};
+
+/**
+ * struct counter_count - Counter Count node
+ * @id:			unique ID used to identify Count
+ * @name:		device-specific Count name; ideally, this should match
+ *			the name as it appears in the datasheet documentation
+ * @function:		index of current function mode
+ * @functions_list:	array available function modes
+ * @num_functions:	number of function modes specified in @functions_list
+ * @synapses:		array of synapses for initialization
+ * @num_synapses:	number of synapses specified in @synapses
+ * @ext:		optional array of Counter Count extensions
+ * @num_ext:		number of Counter Count extensions specified in @ext
+ * @priv:		optional private data supplied by driver
+ */
+struct counter_count {
+	int id;
+	const char *name;
+
+	size_t function;
+	const enum counter_count_function *functions_list;
+	size_t num_functions;
+
+	struct counter_synapse *synapses;
+	size_t num_synapses;
+
+	const struct counter_count_ext *ext;
+	size_t num_ext;
+
+	void *priv;
+};
+
+/**
+ * struct counter_count_enum_ext - Count enum extension attribute
+ * @items:	Array of strings
+ * @num_items:	Number of items specified in @items
+ * @set:	Set callback function; may be NULL
+ * @get:	Get callback function; may be NULL
+ *
+ * The counter_count_enum_ext structure can be used to implement enum style
+ * Count extension attributes. Enum style attributes are those which have a set
+ * of strings that map to unsigned integer values. The Generic Counter Count
+ * enum extension helper code takes care of mapping between value and string, as
+ * well as generating a "_available" file which contains a list of all available
+ * items. The get callback is used to query the currently active item; the index
+ * of the item within the respective items array is returned via the 'item'
+ * parameter. The set callback is called when the attribute is updated; the
+ * 'item' parameter contains the index of the newly activated item within the
+ * respective items array.
+ */
+struct counter_count_enum_ext {
+	const char * const *items;
+	size_t num_items;
+	int (*get)(struct counter_device *counter, struct counter_count *count,
+		   size_t *item);
+	int (*set)(struct counter_device *counter, struct counter_count *count,
+		   size_t item);
+};
+
+/**
+ * COUNTER_COUNT_ENUM() - Initialize Count enum extension
+ * @_name:	Attribute name
+ * @_e:		Pointer to a counter_count_enum_ext structure
+ *
+ * This should usually be used together with COUNTER_COUNT_ENUM_AVAILABLE()
+ */
+#define COUNTER_COUNT_ENUM(_name, _e) \
+{ \
+	.name = (_name), \
+	.read = counter_count_enum_read, \
+	.write = counter_count_enum_write, \
+	.priv = (_e) \
+}
+
+/**
+ * COUNTER_COUNT_ENUM_AVAILABLE() - Initialize Count enum available extension
+ * @_name:	Attribute name ("_available" will be appended to the name)
+ * @_e:		Pointer to a counter_count_enum_ext structure
+ *
+ * Creates a read only attribute that lists all the available enum items in a
+ * newline separated list. This should usually be used together with
+ * COUNTER_COUNT_ENUM()
+ */
+#define COUNTER_COUNT_ENUM_AVAILABLE(_name, _e) \
+{ \
+	.name = (_name "_available"), \
+	.read = counter_count_enum_available_read, \
+	.priv = (_e) \
+}
+
+/**
+ * struct counter_device_attr_group - internal container for attribute group
+ * @attr_group:	Counter sysfs attributes group
+ * @attr_list:	list to keep track of created Counter sysfs attributes
+ * @num_attr:	number of Counter sysfs attributes
+ */
+struct counter_device_attr_group {
+	struct attribute_group attr_group;
+	struct list_head attr_list;
+	size_t num_attr;
+};
+
+/**
+ * struct counter_device_state - internal state container for a Counter device
+ * @id:			unique ID used to identify the Counter
+ * @dev:		internal device structure
+ * @groups_list:	attribute groups list (for Signals, Counts, and ext)
+ * @num_groups:		number of attribute groups containers
+ * @groups:		Counter sysfs attribute groups (to populate @dev.groups)
+ */
+struct counter_device_state {
+	int id;
+	struct device dev;
+	struct counter_device_attr_group *groups_list;
+	size_t num_groups;
+	const struct attribute_group **groups;
+};
+
+/**
+ * struct counter_signal_read_value - Opaque Signal read value
+ * @buf:	string representation of Signal read value
+ * @len:	length of string in @buf
+ */
+struct counter_signal_read_value {
+	char *buf;
+	size_t len;
+};
+
+/**
+ * struct counter_count_read_value - Opaque Count read value
+ * @buf:	string representation of Count read value
+ * @len:	length of string in @buf
+ */
+struct counter_count_read_value {
+	char *buf;
+	size_t len;
+};
+
+/**
+ * struct counter_count_write_value - Opaque Count write value
+ * @buf:	string representation of Count write value
+ */
+struct counter_count_write_value {
+	const char *buf;
+};
+
+/**
+ * struct counter_ops - Callbacks from driver
+ * @signal_read:	optional read callback for Signal attribute. The read
+ *			value of the respective Signal should be passed back via
+ *			the val parameter. val points to an opaque type which
+ *			should be set only by calling the
+ *			counter_signal_read_value_set function from within the
+ *			signal_read callback.
+ * @count_read:		optional read callback for Count attribute. The read
+ *			value of the respective Count should be passed back via
+ *			the val parameter. val points to an opaque type which
+ *			should be set only by calling the
+ *			counter_count_read_value_set function from within the
+ *			count_read callback.
+ * @count_write:	optional write callback for Count attribute. The write
+ *			value for the respective Count is passed in via the val
+ *			parameter. val points to an opaque type which should be
+ *			accessed only by calling the
+ *			counter_count_write_value_get function.
+ * @function_get:	function to get the current count function mode. Returns
+ *			0 on success and negative error code on error. The index
+ *			of the respective Count's returned function mode should
+ *			be passed back via the function parameter.
+ * @function_set:	function to set the count function mode. function is the
+ *			index of the requested function mode from the respective
+ *			Count's functions_list array.
+ * @action_get:		function to get the current action mode. Returns 0 on
+ *			success and negative error code on error. The index of
+ *			the respective Signal's returned action mode should be
+ *			passed back via the action parameter.
+ * @action_set:		function to set the action mode. action is the index of
+ *			the requested action mode from the respective Synapse's
+ *			actions_list array.
+ */
+struct counter_ops {
+	int (*signal_read)(struct counter_device *counter,
+			   struct counter_signal *signal,
+			   struct counter_signal_read_value *val);
+	int (*count_read)(struct counter_device *counter,
+			  struct counter_count *count,
+			  struct counter_count_read_value *val);
+	int (*count_write)(struct counter_device *counter,
+			   struct counter_count *count,
+			   struct counter_count_write_value *val);
+	int (*function_get)(struct counter_device *counter,
+			    struct counter_count *count, size_t *function);
+	int (*function_set)(struct counter_device *counter,
+			    struct counter_count *count, size_t function);
+	int (*action_get)(struct counter_device *counter,
+			  struct counter_count *count,
+			  struct counter_synapse *synapse, size_t *action);
+	int (*action_set)(struct counter_device *counter,
+			  struct counter_count *count,
+			  struct counter_synapse *synapse, size_t action);
+};
+
+/**
+ * struct counter_device_ext - Counter device extension
+ * @name:	attribute name
+ * @read:	read callback for this attribute; may be NULL
+ * @write:	write callback for this attribute; may be NULL
+ * @priv:	data private to the driver
+ */
+struct counter_device_ext {
+	const char *name;
+	ssize_t (*read)(struct counter_device *counter, void *priv, char *buf);
+	ssize_t (*write)(struct counter_device *counter, void *priv,
+			 const char *buf, size_t len);
+	void *priv;
+};
+
+/**
+ * struct counter_device_enum_ext - Counter enum extension attribute
+ * @items:	Array of strings
+ * @num_items:	Number of items specified in @items
+ * @set:	Set callback function; may be NULL
+ * @get:	Get callback function; may be NULL
+ *
+ * The counter_device_enum_ext structure can be used to implement enum style
+ * Counter extension attributes. Enum style attributes are those which have a
+ * set of strings that map to unsigned integer values. The Generic Counter enum
+ * extension helper code takes care of mapping between value and string, as well
+ * as generating a "_available" file which contains a list of all available
+ * items. The get callback is used to query the currently active item; the index
+ * of the item within the respective items array is returned via the 'item'
+ * parameter. The set callback is called when the attribute is updated; the
+ * 'item' parameter contains the index of the newly activated item within the
+ * respective items array.
+ */
+struct counter_device_enum_ext {
+	const char * const *items;
+	size_t num_items;
+	int (*get)(struct counter_device *counter, size_t *item);
+	int (*set)(struct counter_device *counter, size_t item);
+};
+
+/**
+ * COUNTER_DEVICE_ENUM() - Initialize Counter enum extension
+ * @_name:	Attribute name
+ * @_e:		Pointer to a counter_device_enum_ext structure
+ *
+ * This should usually be used together with COUNTER_DEVICE_ENUM_AVAILABLE()
+ */
+#define COUNTER_DEVICE_ENUM(_name, _e) \
+{ \
+	.name = (_name), \
+	.read = counter_device_enum_read, \
+	.write = counter_device_enum_write, \
+	.priv = (_e) \
+}
+
+/**
+ * COUNTER_DEVICE_ENUM_AVAILABLE() - Initialize Counter enum available extension
+ * @_name:	Attribute name ("_available" will be appended to the name)
+ * @_e:		Pointer to a counter_device_enum_ext structure
+ *
+ * Creates a read only attribute that lists all the available enum items in a
+ * newline separated list. This should usually be used together with
+ * COUNTER_DEVICE_ENUM()
+ */
+#define COUNTER_DEVICE_ENUM_AVAILABLE(_name, _e) \
+{ \
+	.name = (_name "_available"), \
+	.read = counter_device_enum_available_read, \
+	.priv = (_e) \
+}
+
+/**
+ * struct counter_device - Counter data structure
+ * @name:		name of the device as it appears in the datasheet
+ * @parent:		optional parent device providing the counters
+ * @device_state:	internal device state container
+ * @ops:		callbacks from driver
+ * @signals:		array of Signals
+ * @num_signals:	number of Signals specified in @signals
+ * @counts:		array of Counts
+ * @num_counts:		number of Counts specified in @counts
+ * @ext:		optional array of Counter device extensions
+ * @num_ext:		number of Counter device extensions specified in @ext
+ * @priv:		optional private data supplied by driver
+ */
+struct counter_device {
+	const char *name;
+	struct device *parent;
+	struct counter_device_state *device_state;
+
+	const struct counter_ops *ops;
+
+	struct counter_signal *signals;
+	size_t num_signals;
+	struct counter_count *counts;
+	size_t num_counts;
+
+	const struct counter_device_ext *ext;
+	size_t num_ext;
+
+	void *priv;
+};
+
+enum counter_signal_level {
+	COUNTER_SIGNAL_LEVEL_LOW = 0,
+	COUNTER_SIGNAL_LEVEL_HIGH
+};
+
+enum counter_signal_value_type {
+	COUNTER_SIGNAL_LEVEL = 0
+};
+
+enum counter_count_value_type {
+	COUNTER_COUNT_POSITION = 0,
+};
+
+void counter_signal_read_value_set(struct counter_signal_read_value *const val,
+				   const enum counter_signal_value_type type,
+				   void *const data);
+void counter_count_read_value_set(struct counter_count_read_value *const val,
+				  const enum counter_count_value_type type,
+				  void *const data);
+int counter_count_write_value_get(void *const data,
+				  const enum counter_count_value_type type,
+				  const struct counter_count_write_value *const val);
+
+int counter_register(struct counter_device *const counter);
+void counter_unregister(struct counter_device *const counter);
+int devm_counter_register(struct device *dev,
+			  struct counter_device *const counter);
+void devm_counter_unregister(struct device *dev,
+			     struct counter_device *const counter);
+
+#endif /* _COUNTER_H_ */
diff --git a/include/linux/counter_enum.h b/include/linux/counter_enum.h
new file mode 100644
index 000000000000..9f917298a88f
--- /dev/null
+++ b/include/linux/counter_enum.h
@@ -0,0 +1,45 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Counter interface enum functions
+ * Copyright (C) 2018 William Breathitt Gray
+ */
+#ifndef _COUNTER_ENUM_H_
+#define _COUNTER_ENUM_H_
+
+#include <linux/types.h>
+
+struct counter_device;
+struct counter_signal;
+struct counter_count;
+
+ssize_t counter_signal_enum_read(struct counter_device *counter,
+				 struct counter_signal *signal, void *priv,
+				 char *buf);
+ssize_t counter_signal_enum_write(struct counter_device *counter,
+				  struct counter_signal *signal, void *priv,
+				  const char *buf, size_t len);
+
+ssize_t counter_signal_enum_available_read(struct counter_device *counter,
+					   struct counter_signal *signal,
+					   void *priv, char *buf);
+
+ssize_t counter_count_enum_read(struct counter_device *counter,
+				struct counter_count *count, void *priv,
+				char *buf);
+ssize_t counter_count_enum_write(struct counter_device *counter,
+				 struct counter_count *count, void *priv,
+				 const char *buf, size_t len);
+
+ssize_t counter_count_enum_available_read(struct counter_device *counter,
+					  struct counter_count *count,
+					  void *priv, char *buf);
+
+ssize_t counter_device_enum_read(struct counter_device *counter, void *priv,
+				 char *buf);
+ssize_t counter_device_enum_write(struct counter_device *counter, void *priv,
+				  const char *buf, size_t len);
+
+ssize_t counter_device_enum_available_read(struct counter_device *counter,
+					   void *priv, char *buf);
+
+#endif /* _COUNTER_ENUM_H_ */