Introduce the Counter character device interface

This is a reimplementation of the Generic Counter driver interface. There are no modifications to the Counter subsystem userspace interface, so existing userspace applications should continue to run seamlessly.

Overview
========

The purpose of this patch is to internalize the sysfs interface code among the various counter drivers into a shared module. Counter drivers pass and take data natively (i.e. u8, u64, char *, etc.) and the shared counter module handles the translation between the sysfs interface. This gurantees a standard userspace interface for all counter drivers, and helps generalize the Generic Counter driver ABI in order to support the Generic Counter chrdev interface (introduced in a subsequent patch) without significant changes to the existing counter drivers.

A high-level view of how a count value is passed down from a counter driver can be exemplified by the following:

                 ----------------------
                / Counter device       \
                +----------------------+
                | Count register: 0x28 |
                +----------------------+
                        |
                 -----------------
                / raw count data /
                -----------------
                        |
                        V
                +----------------------------+
                | Counter device driver      |----------+
                +----------------------------+          |
                | Processes data from device |   -------------------
                |----------------------------|  / driver callbacks /
                | Type: unsigned long        |  -------------------
                | Value: 42                  |          |
                +----------------------------+          |
                        |                               |
                 ----------------                       |
                / unsigned long /                       |
                ----------------                        |
                        |                               |
                        |                               V
                        |               +----------------------+
                        |               | Counter core         |
                        |               +----------------------+
                        |               | Routes device driver |
                        |               | callbacks to the     |
                        |               | userspace interfaces |
                        |               +----------------------+
                        |                       |
                        |                -------------------
                        |               / driver callbacks /
                        |               -------------------
                        |                       |
                +-------+                       |
                |                               |
                |               +---------------+
                |               |
                V               |
        +--------------------+  |
        | Counter sysfs      |<-+
        +--------------------+
        | Translates to the  |
        | standard Counter   |
        | sysfs output       |
        |--------------------|
        | Type: const char * |
        | Value: "42"        |
        +--------------------+
                |
         ---------------
        / const char * /
        ---------------
                |
                V
        +--------------------------------------------------+
        | `/sys/bus/counter/devices/counterX/countY/count` |
        +--------------------------------------------------+
        \ Count: "42"                                      /
         --------------------------------------------------

There are three primary components involved:

Counter device driver
---------------------
Communicates with the hardware device to read/write data; e.g. counter drivers for 104-quad-8, stm32-timer, etc.

Counter core
------------
Registers the counter device driver to the system so that the respective callbacks are called during userspace interaction

Counter sysfs
-------------
Translates counter data to the standard Counter sysfs interface format and vice versa

Driver ABI
==========

This reimplementation entails several changes to the driver ABI. In particular, the device driver callbacks are now expected to handle standard C datatypes rather than translating the sysfs I/O directly.

To that end, the struct counter_data structure is introduced to establish counter extensions for Signals, Synapses, and Counts.

The "type" member specifies the type of high-level data (e.g. BOOL, COUNT_DIRECTION, etc.) handled by this extension. The "*_read" and "*_write" members can then be set by the counter device driver with callbacks to handle that data using native C data types (i.e. u8, u64, char *, etc.).

Convenience macros such as COUNTER_DATA_COUNT_U64 are provided for use by driver authors. In particular, driver authors are expected to use the provided macros for standard Counter subsystem attributes in order to maintain a consistent interface for userspace. For example, a counter device driver may define several standard attributes like so:

struct counter_data count_ext[] = {
COUNTER_DATA_DIRECTION(count_direction_read), COUNTER_DATA_ENABLE(count_enable_read, count_enable_write), COUNTER_DATA_CEILING(count_ceiling_read, count_ceiling_write),
};

This makes it intuitive to see, add, and modify the attributes that are supported by this driver ("direction", "enable", and "ceiling") and to maintain this code without getting lost in a web of struct braces.

Callbacks must match the function type expected for the respective component or extension. These function types are defined in the struct counter_data structure as the "*_read" and "*_write" union members.

The corresponding callback prototypes for the extensions above would be:

int count_direction_read(struct counter_device *counter,

			 struct counter_count *count, u8 *direction);
int count_enable_read(struct counter_device *counter,
		      struct counter_count *count, u8 *enable);
int count_enable_write(struct counter_device *counter,
		       struct counter_count *count, u8 enable);
int count_ceiling_read(struct counter_device *counter,
		       struct counter_count *count, u64 *ceiling);
int count_ceiling_write(struct counter_device *counter,
			struct counter_count *count, u64 ceiling);

In this way, driver authors no longer need to mess with sysfs strings and are instead able to focus on what they actually care about doing -- getting data to/from the devices -- while the Generic Counter interface handles the translation of that data for them between the various userspace interfaces (e.g. sysfs and chardev).

Architecture
============

Counter device registration is the same as before: drivers populate a struct counter_device with components and callbacks, then pass the structure to the devm_counter_register function. However, what's different now is how the Counter subsystem code handles this registration internally.

Whereas before callbacks would interact directly with sysfs data, this interaction is now abstracted and instead callbacks interact with native C data types. The counter_data structure forms the basis for Counter extentions.

The counter-sysfs.c file contains the code to parse through the counter_device structure and register the requested components and extensions. Attributes are created and populated based on type, with respective translation functions to handle the mapping between sysfs and the counter driver callbacks.

The translation performed for each attribute is straightforward: the attribute type and data is parsed from the counter_attribute structure, the respective counter driver read/write callback is called, and sysfs I/O is handled before or after the driver read/write function is called.

Cc Syed Nayyar Waris <[email protected]>

Cc Patrick Havelange <[email protected]>

Cc Fabrice Gasnier <[email protected]>

Cc Maxime Coquelin <[email protected]>

Cc Alexandre Torgue <[email protected]>

Cc David Lechner <[email protected]>

Signed-off-by William Breathitt Gray <[email protected]>

---
 MAINTAINERS                         |    2 +-
 drivers/counter/104-quad-8.c        |  547 +++++-----
 drivers/counter/Makefile            |    1 +
 drivers/counter/counter-core.c      |  157 +++
 drivers/counter/counter-sysfs.c     |  881 ++++++++++++++++
 drivers/counter/counter-sysfs.h     |   14 +
 drivers/counter/counter.c           | 1496 ---------------------------
 drivers/counter/ftm-quaddec.c       |   89 +-
 drivers/counter/stm32-lptimer-cnt.c |  161 +--
 drivers/counter/stm32-timer-cnt.c   |  139 +--
 drivers/counter/ti-eqep.c           |  211 ++--
 include/linux/counter.h             |  610 +++++------
 include/linux/counter_enum.h        |   45 -
 include/uapi/linux/counter-types.h  |   45 +
 14 files changed, 1908 insertions(+), 2490 deletions(-)
 create mode 100644 drivers/counter/counter-core.c
 create mode 100644 drivers/counter/counter-sysfs.c
 create mode 100644 drivers/counter/counter-sysfs.h
 delete mode 100644 drivers/counter/counter.c
 delete mode 100644 include/linux/counter_enum.h
 create mode 100644 include/uapi/linux/counter-types.h

MAINTAINERS +1 -1

index 60ed2963efaa..ef72b5755793 100644
@@ -4365,7 +4365,7 @@ F:	Documentation/ABI/testing/sysfs-bus-counter*
 F:	Documentation/driver-api/generic-counter.rst
 F:	drivers/counter/
 F:	include/linux/counter.h
-F:	include/linux/counter_enum.h
+F:	include/uapi/linux/counter-types.h
 
 CPMAC ETHERNET DRIVER
 M:	Florian Fainelli <[email protected]>

drivers/counter/104-quad-8.c +259 -288

index aa13708c2bc3..ff1c8f8d1417 100644
@@ -17,6 +17,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
+#include <linux/string.h>
 #include <linux/types.h>
 
 #define QUAD8_EXTENT 32

@@ -621,7 +622,7 @@ static const struct iio_chan_spec quad8_channels[] = {
 };
 
 static int quad8_signal_read(struct counter_device *counter,
-	struct counter_signal *signal, enum counter_signal_value *val)
+			     struct counter_signal *signal, u8 *val)
 {
 	const struct quad8_iio *const priv = counter->priv;
 	unsigned int state;

@@ -639,7 +640,7 @@ static int quad8_signal_read(struct counter_device *counter,
 }
 
 static int quad8_count_read(struct counter_device *counter,
-	struct counter_count *count, unsigned long *val)
+			    struct counter_count *count, u64 *val)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const int base_offset = priv->base + 2 * count->id;

@@ -670,7 +671,7 @@ static int quad8_count_read(struct counter_device *counter,
 }
 
 static int quad8_count_write(struct counter_device *counter,
-	struct counter_count *count, unsigned long val)
+			     struct counter_count *count, u64 val)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const int base_offset = priv->base + 2 * count->id;

@@ -710,22 +711,16 @@ static int quad8_count_write(struct counter_device *counter,
 	return 0;
 }
 
-enum quad8_count_function {
-	QUAD8_COUNT_FUNCTION_PULSE_DIRECTION = 0,
-	QUAD8_COUNT_FUNCTION_QUADRATURE_X1,
-	QUAD8_COUNT_FUNCTION_QUADRATURE_X2,
-	QUAD8_COUNT_FUNCTION_QUADRATURE_X4
-};
 
-static enum counter_count_function quad8_count_functions_list[] = {
-	[QUAD8_COUNT_FUNCTION_PULSE_DIRECTION] = COUNTER_COUNT_FUNCTION_PULSE_DIRECTION,
-	[QUAD8_COUNT_FUNCTION_QUADRATURE_X1] = COUNTER_COUNT_FUNCTION_QUADRATURE_X1_A,
-	[QUAD8_COUNT_FUNCTION_QUADRATURE_X2] = COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A,
-	[QUAD8_COUNT_FUNCTION_QUADRATURE_X4] = COUNTER_COUNT_FUNCTION_QUADRATURE_X4
+static const u8 quad8_count_functions_list[] = {
+	COUNTER_COUNT_FUNCTION_PULSE_DIRECTION,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X1_A,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A,
+	COUNTER_COUNT_FUNCTION_QUADRATURE_X4,
 };
 
-static int quad8_function_get(struct counter_device *counter,
-	struct counter_count *count, size_t *function)
+static int quad8_function_read(struct counter_device *counter,
+			       struct counter_count *count, u8 *function)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const int id = count->id;

@@ -735,25 +730,25 @@ static int quad8_function_get(struct counter_device *counter,
 	if (priv->quadrature_mode[id])
 		switch (priv->quadrature_scale[id]) {
 		case 0:
-			*function = QUAD8_COUNT_FUNCTION_QUADRATURE_X1;
+			*function = COUNTER_COUNT_FUNCTION_QUADRATURE_X1_A;
 			break;
 		case 1:
-			*function = QUAD8_COUNT_FUNCTION_QUADRATURE_X2;
+			*function = COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A;
 			break;
 		case 2:
-			*function = QUAD8_COUNT_FUNCTION_QUADRATURE_X4;
+			*function = COUNTER_COUNT_FUNCTION_QUADRATURE_X4;
 			break;
 		}
 	else
-		*function = QUAD8_COUNT_FUNCTION_PULSE_DIRECTION;
+		*function = COUNTER_COUNT_FUNCTION_PULSE_DIRECTION;
 
 	mutex_unlock(&priv->lock);
 
 	return 0;
 }
 
-static int quad8_function_set(struct counter_device *counter,
-	struct counter_count *count, size_t function)
+static int quad8_function_write(struct counter_device *counter,
+				struct counter_count *count, u8 function)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const int id = count->id;

@@ -769,7 +764,7 @@ static int quad8_function_set(struct counter_device *counter,
 	mode_cfg = priv->count_mode[id] << 1;
 	idr_cfg = priv->index_polarity[id] << 1;
 
-	if (function == QUAD8_COUNT_FUNCTION_PULSE_DIRECTION) {
+	if (function == COUNTER_COUNT_FUNCTION_PULSE_DIRECTION) {
 		*quadrature_mode = 0;
 
 		/* Quadrature scaling only available in quadrature mode */

@@ -785,15 +780,15 @@ static int quad8_function_set(struct counter_device *counter,
 		*quadrature_mode = 1;
 
 		switch (function) {
-		case QUAD8_COUNT_FUNCTION_QUADRATURE_X1:
+		case COUNTER_COUNT_FUNCTION_QUADRATURE_X1_A:
 			*scale = 0;
 			mode_cfg |= QUAD8_CMR_QUADRATURE_X1;
 			break;
-		case QUAD8_COUNT_FUNCTION_QUADRATURE_X2:
+		case COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A:
 			*scale = 1;
 			mode_cfg |= QUAD8_CMR_QUADRATURE_X2;
 			break;
-		case QUAD8_COUNT_FUNCTION_QUADRATURE_X4:
+		case COUNTER_COUNT_FUNCTION_QUADRATURE_X4:
 			*scale = 2;
 			mode_cfg |= QUAD8_CMR_QUADRATURE_X4;
 			break;

@@ -808,8 +803,8 @@ static int quad8_function_set(struct counter_device *counter,
 	return 0;
 }
 
-static void quad8_direction_get(struct counter_device *counter,
-	struct counter_count *count, enum counter_count_direction *direction)
+static int quad8_direction_read(struct counter_device *counter,
+				struct counter_count *count, u8 *direction)
 {
 	const struct quad8_iio *const priv = counter->priv;
 	unsigned int ud_flag;

@@ -820,153 +815,155 @@ static void quad8_direction_get(struct counter_device *counter,
 
 	*direction = (ud_flag) ? COUNTER_COUNT_DIRECTION_FORWARD :
 		COUNTER_COUNT_DIRECTION_BACKWARD;
-}
 
-enum quad8_synapse_action {
-	QUAD8_SYNAPSE_ACTION_NONE = 0,
-	QUAD8_SYNAPSE_ACTION_RISING_EDGE,
-	QUAD8_SYNAPSE_ACTION_FALLING_EDGE,
-	QUAD8_SYNAPSE_ACTION_BOTH_EDGES
-};
+	return 0;
+}
 
-static enum counter_synapse_action quad8_index_actions_list[] = {
-	[QUAD8_SYNAPSE_ACTION_NONE] = COUNTER_SYNAPSE_ACTION_NONE,
-	[QUAD8_SYNAPSE_ACTION_RISING_EDGE] = COUNTER_SYNAPSE_ACTION_RISING_EDGE
+static const u8 quad8_index_actions_list[] = {
+	COUNTER_SYNAPSE_ACTION_NONE,
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
 };
 
-static enum counter_synapse_action quad8_synapse_actions_list[] = {
-	[QUAD8_SYNAPSE_ACTION_NONE] = COUNTER_SYNAPSE_ACTION_NONE,
-	[QUAD8_SYNAPSE_ACTION_RISING_EDGE] = COUNTER_SYNAPSE_ACTION_RISING_EDGE,
-	[QUAD8_SYNAPSE_ACTION_FALLING_EDGE] = COUNTER_SYNAPSE_ACTION_FALLING_EDGE,
-	[QUAD8_SYNAPSE_ACTION_BOTH_EDGES] = COUNTER_SYNAPSE_ACTION_BOTH_EDGES
+static const u8 quad8_synapse_actions_list[] = {
+	COUNTER_SYNAPSE_ACTION_NONE,
+	COUNTER_SYNAPSE_ACTION_RISING_EDGE,
+	COUNTER_SYNAPSE_ACTION_FALLING_EDGE,
+	COUNTER_SYNAPSE_ACTION_BOTH_EDGES,
 };
 
-static int quad8_action_get(struct counter_device *counter,
-	struct counter_count *count, struct counter_synapse *synapse,
-	size_t *action)
+static int quad8_action_read(struct counter_device *counter,
+			     struct counter_count *count,
+			     struct counter_synapse *synapse, u8 *action)
 {
 	struct quad8_iio *const priv = counter->priv;
 	int err;
-	size_t function = 0;
+	u8 function;
 	const size_t signal_a_id = count->synapses[0].signal->id;
-	enum counter_count_direction direction;
+	u8 direction;
 
 	/* Handle Index signals */
 	if (synapse->signal->id >= 16) {
 		if (priv->preset_enable[count->id])
-			*action = QUAD8_SYNAPSE_ACTION_RISING_EDGE;
+			*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
 		else
-			*action = QUAD8_SYNAPSE_ACTION_NONE;
+			*action = COUNTER_SYNAPSE_ACTION_NONE;
 
 		return 0;
 	}
 
-	err = quad8_function_get(counter, count, &function);
+	err = quad8_function_read(counter, count, &function);
 	if (err)
 		return err;
 
 	/* Default action mode */
-	*action = QUAD8_SYNAPSE_ACTION_NONE;
+	*action = COUNTER_SYNAPSE_ACTION_NONE;
 
 	/* Determine action mode based on current count function mode */
 	switch (function) {
-	case QUAD8_COUNT_FUNCTION_PULSE_DIRECTION:
+	case COUNTER_COUNT_FUNCTION_PULSE_DIRECTION:
 		if (synapse->signal->id == signal_a_id)
-			*action = QUAD8_SYNAPSE_ACTION_RISING_EDGE;
+			*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
 		break;
-	case QUAD8_COUNT_FUNCTION_QUADRATURE_X1:
+	case COUNTER_COUNT_FUNCTION_QUADRATURE_X1_A:
 		if (synapse->signal->id == signal_a_id) {
-			quad8_direction_get(counter, count, &direction);
+			err = quad8_direction_read(counter, count, &direction);
+			if (err)
+				return err;
 
 			if (direction == COUNTER_COUNT_DIRECTION_FORWARD)
-				*action = QUAD8_SYNAPSE_ACTION_RISING_EDGE;
+				*action = COUNTER_SYNAPSE_ACTION_RISING_EDGE;
 			else
-				*action = QUAD8_SYNAPSE_ACTION_FALLING_EDGE;
+				*action = COUNTER_SYNAPSE_ACTION_FALLING_EDGE;
 		}
 		break;
-	case QUAD8_COUNT_FUNCTION_QUADRATURE_X2:
+	case COUNTER_COUNT_FUNCTION_QUADRATURE_X2_A:
 		if (synapse->signal->id == signal_a_id)
-			*action = QUAD8_SYNAPSE_ACTION_BOTH_EDGES;
+			*action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES;
 		break;
-	case QUAD8_COUNT_FUNCTION_QUADRATURE_X4:
-		*action = QUAD8_SYNAPSE_ACTION_BOTH_EDGES;
+	case COUNTER_COUNT_FUNCTION_QUADRATURE_X4:
+		*action = COUNTER_SYNAPSE_ACTION_BOTH_EDGES;
 		break;
 	}
 
 	return 0;
 }
 
-static const struct counter_ops quad8_ops = {
-	.signal_read = quad8_signal_read,
-	.count_read = quad8_count_read,
-	.count_write = quad8_count_write,
-	.function_get = quad8_function_get,
-	.function_set = quad8_function_set,
-	.action_get = quad8_action_get
-};
-
-static int quad8_index_polarity_get(struct counter_device *counter,
-	struct counter_signal *signal, size_t *index_polarity)
+static ssize_t quad8_index_polarity_read(struct counter_device *counter,
+					 struct counter_signal *signal,
+					 char *buf, size_t size)
 {
 	const struct quad8_iio *const priv = counter->priv;
-	const size_t channel_id = signal->id - 16;
-
-	*index_polarity = priv->index_polarity[channel_id];
+	const size_t index = priv->index_polarity[signal->id - 16];
 
-	return 0;
+	return snprintf(buf, size, "%s\n", quad8_index_polarity_modes[index]);
 }
 
-static int quad8_index_polarity_set(struct counter_device *counter,
-	struct counter_signal *signal, size_t index_polarity)
+static ssize_t quad8_index_polarity_write(struct counter_device *counter,
+					  struct counter_signal *signal,
+					  const char *buf, size_t size)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const size_t channel_id = signal->id - 16;
 	const int base_offset = priv->base + 2 * channel_id + 1;
-	unsigned int idr_cfg = index_polarity << 1;
+	int index_polarity;
+	unsigned int idr_cfg;
 
-	mutex_lock(&priv->lock);
+	index_polarity = sysfs_match_string(quad8_index_polarity_modes, buf);
+	if (index_polarity < 0)
+		return index_polarity;
 
-	idr_cfg |= priv->synchronous_mode[channel_id];
+	mutex_lock(&priv->lock);
 
 	priv->index_polarity[channel_id] = index_polarity;
 
 	/* Load Index Control configuration to Index Control Register */
+	idr_cfg = priv->synchronous_mode[channel_id] | index_polarity << 1;
 	outb(QUAD8_CTR_IDR | idr_cfg, base_offset);
 
 	mutex_unlock(&priv->lock);
 
-	return 0;
+	return size;
 }
 
-static struct counter_signal_enum_ext quad8_index_pol_enum = {
-	.items = quad8_index_polarity_modes,
-	.num_items = ARRAY_SIZE(quad8_index_polarity_modes),
-	.get = quad8_index_polarity_get,
-	.set = quad8_index_polarity_set
-};
+static ssize_t quad8_index_polarity_available_read(
+	struct counter_device *counter, struct counter_signal *signal,
+	char *buf, size_t size)
+{
+	size_t i;
+	size_t len = 0;
 
-static int quad8_synchronous_mode_get(struct counter_device *counter,
-	struct counter_signal *signal, size_t *synchronous_mode)
+	for (i = 0; i < ARRAY_SIZE(quad8_index_polarity_modes) && size > 1; i++)
+		len += scnprintf(buf + len, size - len, "%s\n",
+				 quad8_index_polarity_modes[i]);
+
+	return len;
+}
+
+static ssize_t quad8_synchronous_mode_read(struct counter_device *counter,
+					   struct counter_signal *signal,
+					   char *buf, size_t size)
 {
 	const struct quad8_iio *const priv = counter->priv;
-	const size_t channel_id = signal->id - 16;
-
-	*synchronous_mode = priv->synchronous_mode[channel_id];
+	const size_t index = priv->synchronous_mode[signal->id - 16];
 
-	return 0;
+	return snprintf(buf, size, "%s\n", quad8_synchronous_modes[index]);
 }
 
-static int quad8_synchronous_mode_set(struct counter_device *counter,
-	struct counter_signal *signal, size_t synchronous_mode)
+static ssize_t quad8_synchronous_mode_write(struct counter_device *counter,
+					    struct counter_signal *signal,
+					    const char *buf, size_t size)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const size_t channel_id = signal->id - 16;
 	const int base_offset = priv->base + 2 * channel_id + 1;
-	unsigned int idr_cfg = synchronous_mode;
+	int synchronous_mode;
+	unsigned int idr_cfg;
 
-	mutex_lock(&priv->lock);
+	synchronous_mode = sysfs_match_string(quad8_synchronous_modes, buf);
+	if (synchronous_mode < 0)
+		return synchronous_mode;
 
-	idr_cfg |= priv->index_polarity[channel_id] << 1;
+	mutex_lock(&priv->lock);
 
 	/* Index function must be non-synchronous in non-quadrature mode */
 	if (synchronous_mode && !priv->quadrature_mode[channel_id]) {

@@ -977,29 +974,39 @@ static int quad8_synchronous_mode_set(struct counter_device *counter,
 	priv->synchronous_mode[channel_id] = synchronous_mode;
 
 	/* Load Index Control configuration to Index Control Register */
+	idr_cfg = synchronous_mode | priv->index_polarity[channel_id] << 1;
 	outb(QUAD8_CTR_IDR | idr_cfg, base_offset);
 
 	mutex_unlock(&priv->lock);
 
-	return 0;
+	return size;
 }
 
-static struct counter_signal_enum_ext quad8_syn_mode_enum = {
-	.items = quad8_synchronous_modes,
-	.num_items = ARRAY_SIZE(quad8_synchronous_modes),
-	.get = quad8_synchronous_mode_get,
-	.set = quad8_synchronous_mode_set
-};
+static ssize_t quad8_synchronous_mode_available_read(
+	struct counter_device *counter, struct counter_signal *signal,
+	char *buf, size_t size)
+{
+	size_t i;
+	size_t len = 0;
 
-static ssize_t quad8_count_floor_read(struct counter_device *counter,
-	struct counter_count *count, void *private, char *buf)
+	for (i = 0; i < ARRAY_SIZE(quad8_synchronous_modes) && size > 1; i++)
+		len += scnprintf(buf + len, size - len, "%s\n",
+				 quad8_synchronous_modes[i]);
+
+	return len;
+}
+
+static int quad8_count_floor_read(struct counter_device *counter,
+				  struct counter_count *count, u64 *floor)
 {
 	/* Only a floor of 0 is supported */
-	return sprintf(buf, "0\n");
+	*floor = 0;
+
+	return 0;
 }
 
-static int quad8_count_mode_get(struct counter_device *counter,
-	struct counter_count *count, size_t *cnt_mode)
+static int quad8_count_mode_read(struct counter_device *counter,
+				 struct counter_count *count, u8 *cnt_mode)
 {
 	const struct quad8_iio *const priv = counter->priv;
 

@@ -1022,35 +1029,36 @@ static int quad8_count_mode_get(struct counter_device *counter,
 	return 0;
 }
 
-static int quad8_count_mode_set(struct counter_device *counter,
-	struct counter_count *count, size_t cnt_mode)
+static int quad8_count_mode_write(struct counter_device *counter,
+				  struct counter_count *count, u8 cnt_mode)
 {
 	struct quad8_iio *const priv = counter->priv;
+	unsigned int count_mode;
 	unsigned int mode_cfg;
 	const int base_offset = priv->base + 2 * count->id + 1;
 
 	/* Map Generic Counter count mode to 104-QUAD-8 count mode */
 	switch (cnt_mode) {
 	case COUNTER_COUNT_MODE_NORMAL:
-		cnt_mode = 0;
+		count_mode = 0;
 		break;
 	case COUNTER_COUNT_MODE_RANGE_LIMIT:
-		cnt_mode = 1;
+		count_mode = 1;
 		break;
 	case COUNTER_COUNT_MODE_NON_RECYCLE:
-		cnt_mode = 2;
+		count_mode = 2;
 		break;
 	case COUNTER_COUNT_MODE_MODULO_N:
-		cnt_mode = 3;
+		count_mode = 3;
 		break;
 	}
 
 	mutex_lock(&priv->lock);
 
-	priv->count_mode[count->id] = cnt_mode;
+	priv->count_mode[count->id] = count_mode;
 
 	/* Set count mode configuration value */
-	mode_cfg = cnt_mode << 1;
+	mode_cfg = count_mode << 1;
 
 	/* Add quadrature mode configuration */
 	if (priv->quadrature_mode[count->id])

@@ -1064,85 +1072,86 @@ static int quad8_count_mode_set(struct counter_device *counter,
 	return 0;
 }
 
-static struct counter_count_enum_ext quad8_cnt_mode_enum = {
-	.items = counter_count_mode_str,
-	.num_items = ARRAY_SIZE(counter_count_mode_str),
-	.get = quad8_count_mode_get,
-	.set = quad8_count_mode_set
+static const u8 quad8_cnt_modes[] = {
+	COUNTER_COUNT_MODE_NORMAL,
+	COUNTER_COUNT_MODE_RANGE_LIMIT,
+	COUNTER_COUNT_MODE_NON_RECYCLE,
+	COUNTER_COUNT_MODE_MODULO_N,
 };
 
-static ssize_t quad8_count_direction_read(struct counter_device *counter,
-	struct counter_count *count, void *priv, char *buf)
-{
-	enum counter_count_direction dir;
-
-	quad8_direction_get(counter, count, &dir);
-
-	return sprintf(buf, "%s\n", counter_count_direction_str[dir]);
-}
+static DEFINE_COUNTER_AVAILABLE(quad8_count_mode_available, quad8_cnt_modes);
 
-static ssize_t quad8_count_enable_read(struct counter_device *counter,
-	struct counter_count *count, void *private, char *buf)
+static int quad8_count_enable_read(struct counter_device *counter,
+				   struct counter_count *count, u8 *enable)
 {
 	const struct quad8_iio *const priv = counter->priv;
 
-	return sprintf(buf, "%u\n", priv->ab_enable[count->id]);
+	*enable = priv->ab_enable[count->id];
+
+	return 0;
 }
 
-static ssize_t quad8_count_enable_write(struct counter_device *counter,
-	struct counter_count *count, void *private, const char *buf, size_t len)
+static int quad8_count_enable_write(struct counter_device *counter,
+				    struct counter_count *count, u8 enable)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const int base_offset = priv->base + 2 * count->id;
-	int err;
-	bool ab_enable;
 	unsigned int ior_cfg;
 
-	err = kstrtobool(buf, &ab_enable);
-	if (err)
-		return err;
-
 	mutex_lock(&priv->lock);
 
-	priv->ab_enable[count->id] = ab_enable;
+	priv->ab_enable[count->id] = enable;
 
-	ior_cfg = ab_enable | priv->preset_enable[count->id] << 1;
+	ior_cfg = enable | priv->preset_enable[count->id] << 1;
 
 	/* Load I/O control configuration */
 	outb(QUAD8_CTR_IOR | ior_cfg, base_offset + 1);
 
 	mutex_unlock(&priv->lock);
 
-	return len;
+	return 0;
 }
 
-static int quad8_error_noise_get(struct counter_device *counter,
-	struct counter_count *count, size_t *noise_error)
+static ssize_t quad8_error_noise_read(struct counter_device *counter,
+				      struct counter_count *count, char *buf,
+				      size_t size)
 {
 	const struct quad8_iio *const priv = counter->priv;
 	const int base_offset = priv->base + 2 * count->id + 1;
+	size_t noise_error;
 
-	*noise_error = !!(inb(base_offset) & QUAD8_FLAG_E);
+	noise_error = !!(inb(base_offset) & QUAD8_FLAG_E);
 
-	return 0;
+	return snprintf(buf, size, "%s\n",
+			quad8_noise_error_states[noise_error]);
 }
 
-static struct counter_count_enum_ext quad8_error_noise_enum = {
-	.items = quad8_noise_error_states,
-	.num_items = ARRAY_SIZE(quad8_noise_error_states),
-	.get = quad8_error_noise_get
-};
+static ssize_t quad8_error_noise_available_read(struct counter_device *counter,
+						struct counter_count *count,
+						char *buf, size_t size)
+{
+	size_t i;
+	size_t len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(quad8_noise_error_states) && size > 1; i++)
+		len += scnprintf(buf + len, size - len, "%s\n",
+				 quad8_noise_error_states[i]);
+
+	return len;
+}
 
-static ssize_t quad8_count_preset_read(struct counter_device *counter,
-	struct counter_count *count, void *private, char *buf)
+static int quad8_count_preset_read(struct counter_device *counter,
+				   struct counter_count *count, u64 *preset)
 {
 	const struct quad8_iio *const priv = counter->priv;
 
-	return sprintf(buf, "%u\n", priv->preset[count->id]);
+	*preset = priv->preset[count->id];
+
+	return 0;
 }
 
-static void quad8_preset_register_set(struct quad8_iio *quad8iio, int id,
-		unsigned int preset)
+static void quad8_preset_register_set(struct quad8_iio *const quad8iio,
+				      const int id, const u64 preset)
 {
 	const unsigned int base_offset = quad8iio->base + 2 * id;
 	int i;

@@ -1157,16 +1166,10 @@ static void quad8_preset_register_set(struct quad8_iio *quad8iio, int id,
 		outb(preset >> (8 * i), base_offset);
 }
 
-static ssize_t quad8_count_preset_write(struct counter_device *counter,
-	struct counter_count *count, void *private, const char *buf, size_t len)
+static int quad8_count_preset_write(struct counter_device *counter,
+				    struct counter_count *count, u64 preset)
 {
 	struct quad8_iio *const priv = counter->priv;
-	unsigned int preset;
-	int ret;
-
-	ret = kstrtouint(buf, 0, &preset);
-	if (ret)
-		return ret;
 
 	/* Only 24-bit values are supported */
 	if (preset > 0xFFFFFF)

@@ -1178,11 +1181,11 @@ static ssize_t quad8_count_preset_write(struct counter_device *counter,
 
 	mutex_unlock(&priv->lock);
 
-	return len;
+	return 0;
 }
 
-static ssize_t quad8_count_ceiling_read(struct counter_device *counter,
-	struct counter_count *count, void *private, char *buf)
+static int quad8_count_ceiling_read(struct counter_device *counter,
+				    struct counter_count *count, u64 *ceiling)
 {
 	struct quad8_iio *const priv = counter->priv;
 

@@ -1193,25 +1196,21 @@ static ssize_t quad8_count_ceiling_read(struct counter_device *counter,
 	case 1:
 	case 3:
 		mutex_unlock(&priv->lock);
-		return sprintf(buf, "%u\n", priv->preset[count->id]);
+		return quad8_count_preset_read(counter, count, ceiling);
 	}
 
 	mutex_unlock(&priv->lock);
 
 	/* By default 0x1FFFFFF (25 bits unsigned) is maximum count */
-	return sprintf(buf, "33554431\n");
+	*ceiling = 0x1FFFFFF;
+
+	return 0;
 }
 
-static ssize_t quad8_count_ceiling_write(struct counter_device *counter,
-	struct counter_count *count, void *private, const char *buf, size_t len)
+static int quad8_count_ceiling_write(struct counter_device *counter,
+				     struct counter_count *count, u64 ceiling)
 {
 	struct quad8_iio *const priv = counter->priv;
-	unsigned int ceiling;
-	int ret;
-
-	ret = kstrtouint(buf, 0, &ceiling);
-	if (ret)
-		return ret;
 
 	/* Only 24-bit values are supported */
 	if (ceiling > 0xFFFFFF)

@@ -1223,36 +1222,33 @@ static ssize_t quad8_count_ceiling_write(struct counter_device *counter,
 	switch (priv->count_mode[count->id]) {
 	case 1:
 	case 3:
-		quad8_preset_register_set(priv, count->id, ceiling);
-		break;
+		return quad8_count_preset_write(counter, count, ceiling);
 	}
 
 	mutex_unlock(&priv->lock);
 
-	return len;
+	return -EINVAL;
 }
 
-static ssize_t quad8_count_preset_enable_read(struct counter_device *counter,
-	struct counter_count *count, void *private, char *buf)
+static int quad8_count_preset_enable_read(struct counter_device *counter,
+					  struct counter_count *count,
+					  u8 *preset_enable)
 {
 	const struct quad8_iio *const priv = counter->priv;
 
-	return sprintf(buf, "%u\n", !priv->preset_enable[count->id]);
+	*preset_enable = !priv->preset_enable[count->id];
+
+	return 0;
 }
 
-static ssize_t quad8_count_preset_enable_write(struct counter_device *counter,
-	struct counter_count *count, void *private, const char *buf, size_t len)
+static int quad8_count_preset_enable_write(struct counter_device *counter,
+					   struct counter_count *count,
+					   u8 preset_enable)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const int base_offset = priv->base + 2 * count->id + 1;
-	bool preset_enable;
-	int ret;
 	unsigned int ior_cfg;
 
-	ret = kstrtobool(buf, &preset_enable);
-	if (ret)
-		return ret;
-
 	/* Preset enable is active low in Input/Output Control register */
 	preset_enable = !preset_enable;
 

@@ -1260,25 +1256,24 @@ static ssize_t quad8_count_preset_enable_write(struct counter_device *counter,
 
 	priv->preset_enable[count->id] = preset_enable;
 
-	ior_cfg = priv->ab_enable[count->id] | (unsigned int)preset_enable << 1;
+	ior_cfg = priv->ab_enable[count->id] | preset_enable << 1;
 
 	/* Load I/O control configuration to Input / Output Control Register */
 	outb(QUAD8_CTR_IOR | ior_cfg, base_offset);
 
 	mutex_unlock(&priv->lock);
 
-	return len;
+	return 0;
 }
 
-static ssize_t quad8_signal_cable_fault_read(struct counter_device *counter,
-					     struct counter_signal *signal,
-					     void *private, char *buf)
+static int quad8_signal_cable_fault_read(struct counter_device *counter,
+					 struct counter_signal *signal,
+					 u8 *cable_fault)
 {
 	const struct quad8_iio *const priv = counter->priv;
 	const size_t channel_id = signal->id / 2;
 	const bool disabled = !(priv->cable_fault_enable & BIT(channel_id));
 	unsigned int status;
-	unsigned int fault;
 
 	if (disabled)
 		return -EINVAL;

@@ -1287,36 +1282,31 @@ static ssize_t quad8_signal_cable_fault_read(struct counter_device *counter,
 	status = inb(priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS);
 
 	/* Mask respective channel and invert logic */
-	fault = !(status & BIT(channel_id));
+	*cable_fault = !(status & BIT(channel_id));
 
-	return sprintf(buf, "%u\n", fault);
+	return 0;
 }
 
-static ssize_t quad8_signal_cable_fault_enable_read(
-	struct counter_device *counter, struct counter_signal *signal,
-	void *private, char *buf)
+static int quad8_signal_cable_fault_enable_read(struct counter_device *counter,
+						struct counter_signal *signal,
+						u8 *enable)
 {
 	const struct quad8_iio *const priv = counter->priv;
 	const size_t channel_id = signal->id / 2;
-	const unsigned int enb = !!(priv->cable_fault_enable & BIT(channel_id));
 
-	return sprintf(buf, "%u\n", enb);
+	*enable = !!(priv->cable_fault_enable & BIT(channel_id));
+
+	return 0;
 }
 
-static ssize_t quad8_signal_cable_fault_enable_write(
-	struct counter_device *counter, struct counter_signal *signal,
-	void *private, const char *buf, size_t len)
+static int quad8_signal_cable_fault_enable_write(struct counter_device *counter,
+						 struct counter_signal *signal,
+						 u8 enable)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const size_t channel_id = signal->id / 2;
-	bool enable;
-	int ret;
 	unsigned int cable_fault_enable;
 
-	ret = kstrtobool(buf, &enable);
-	if (ret)
-		return ret;
-
 	if (enable)
 		priv->cable_fault_enable |= BIT(channel_id);
 	else

@@ -1327,31 +1317,27 @@ static ssize_t quad8_signal_cable_fault_enable_write(
 
 	outb(cable_fault_enable, priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS);
 
-	return len;
+	return 0;
 }
 
-static ssize_t quad8_signal_fck_prescaler_read(struct counter_device *counter,
-	struct counter_signal *signal, void *private, char *buf)
+static int quad8_signal_fck_prescaler_read(struct counter_device *counter,
+					   struct counter_signal *signal,
+					   u8 *prescaler)
 {
 	const struct quad8_iio *const priv = counter->priv;
-	const size_t channel_id = signal->id / 2;
 
-	return sprintf(buf, "%u\n", priv->fck_prescaler[channel_id]);
+	*prescaler = priv->fck_prescaler[signal->id / 2];
+
+	return 0;
 }
 
-static ssize_t quad8_signal_fck_prescaler_write(struct counter_device *counter,
-	struct counter_signal *signal, void *private, const char *buf,
-	size_t len)
+static int quad8_signal_fck_prescaler_write(struct counter_device *counter,
+					    struct counter_signal *signal,
+					    u8 prescaler)
 {
 	struct quad8_iio *const priv = counter->priv;
 	const size_t channel_id = signal->id / 2;
 	const int base_offset = priv->base + 2 * channel_id;
-	u8 prescaler;
-	int ret;
-
-	ret = kstrtou8(buf, 0, &prescaler);
-	if (ret)
-		return ret;
 
 	priv->fck_prescaler[channel_id] = prescaler;
 

@@ -1363,31 +1349,30 @@ static ssize_t quad8_signal_fck_prescaler_write(struct counter_device *counter,
 	outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_PRESET_PSC,
 	     base_offset + 1);
 
-	return len;
+	return 0;
 }
 
-static const struct counter_signal_ext quad8_signal_ext[] = {
-	{
-		.name = "cable_fault",
-		.read = quad8_signal_cable_fault_read
-	},
-	{
-		.name = "cable_fault_enable",
-		.read = quad8_signal_cable_fault_enable_read,
-		.write = quad8_signal_cable_fault_enable_write
-	},
-	{
-		.name = "filter_clock_prescaler",
-		.read = quad8_signal_fck_prescaler_read,
-		.write = quad8_signal_fck_prescaler_write
-	}
+static struct counter_data quad8_signal_ext[] = {
+	COUNTER_DATA_SIGNAL_BOOL("cable_fault", quad8_signal_cable_fault_read,
+				 NULL),
+	COUNTER_DATA_SIGNAL_BOOL("cable_fault_enable",
+				 quad8_signal_cable_fault_enable_read,
+				 quad8_signal_cable_fault_enable_write),
+	COUNTER_DATA_SIGNAL_U8("filter_clock_prescaler",
+			       quad8_signal_fck_prescaler_read,
+			       quad8_signal_fck_prescaler_write)
 };
 
-static const struct counter_signal_ext quad8_index_ext[] = {
-	COUNTER_SIGNAL_ENUM("index_polarity", &quad8_index_pol_enum),
-	COUNTER_SIGNAL_ENUM_AVAILABLE("index_polarity",	&quad8_index_pol_enum),
-	COUNTER_SIGNAL_ENUM("synchronous_mode", &quad8_syn_mode_enum),
-	COUNTER_SIGNAL_ENUM_AVAILABLE("synchronous_mode", &quad8_syn_mode_enum)
+static struct counter_data quad8_index_ext[] = {
+	COUNTER_DATA_SIGNAL_STRING("index_polarity", quad8_index_polarity_read,
+				   quad8_index_polarity_write),
+	COUNTER_DATA_SIGNAL_STRING("index_polarity_available",
+				   quad8_index_polarity_available_read, NULL),
+	COUNTER_DATA_SIGNAL_STRING("synchronous_mode",
+				   quad8_synchronous_mode_read,
+				   quad8_synchronous_mode_write),
+	COUNTER_DATA_SIGNAL_STRING("synchronous_mode_available",
+				   quad8_synchronous_mode_available_read, NULL),
 };
 
 #define QUAD8_QUAD_SIGNAL(_id, _name) {		\

@@ -1456,39 +1441,20 @@ static struct counter_synapse quad8_count_synapses[][3] = {
 	QUAD8_COUNT_SYNAPSES(6), QUAD8_COUNT_SYNAPSES(7)
 };
 
-static const struct counter_count_ext quad8_count_ext[] = {
-	{
-		.name = "ceiling",
-		.read = quad8_count_ceiling_read,
-		.write = quad8_count_ceiling_write
-	},
-	{
-		.name = "floor",
-		.read = quad8_count_floor_read
-	},
-	COUNTER_COUNT_ENUM("count_mode", &quad8_cnt_mode_enum),
-	COUNTER_COUNT_ENUM_AVAILABLE("count_mode", &quad8_cnt_mode_enum),
-	{
-		.name = "direction",
-		.read = quad8_count_direction_read
-	},
-	{
-		.name = "enable",
-		.read = quad8_count_enable_read,
-		.write = quad8_count_enable_write
-	},
-	COUNTER_COUNT_ENUM("error_noise", &quad8_error_noise_enum),
-	COUNTER_COUNT_ENUM_AVAILABLE("error_noise", &quad8_error_noise_enum),
-	{
-		.name = "preset",
-		.read = quad8_count_preset_read,
-		.write = quad8_count_preset_write
-	},
-	{
-		.name = "preset_enable",
-		.read = quad8_count_preset_enable_read,
-		.write = quad8_count_preset_enable_write
-	}
+static struct counter_data quad8_count_ext[] = {
+	COUNTER_DATA_CEILING(quad8_count_ceiling_read,
+			     quad8_count_ceiling_write),
+	COUNTER_DATA_FLOOR(quad8_count_floor_read, NULL),
+	COUNTER_DATA_COUNT_MODE(quad8_count_mode_read, quad8_count_mode_write,
+				quad8_count_mode_available),
+	COUNTER_DATA_DIRECTION(quad8_direction_read),
+	COUNTER_DATA_ENABLE(quad8_count_enable_read, quad8_count_enable_write),
+	COUNTER_DATA_COUNT_STRING("error_noise", quad8_error_noise_read, NULL),
+	COUNTER_DATA_COUNT_STRING("error_noise_available",
+				  quad8_error_noise_available_read, NULL),
+	COUNTER_DATA_PRESET(quad8_count_preset_read, quad8_count_preset_write),
+	COUNTER_DATA_PRESET_ENABLE(quad8_count_preset_enable_read,
+				   quad8_count_preset_enable_write),
 };
 
 #define QUAD8_COUNT(_id, _cntname) {					\

@@ -1544,7 +1510,12 @@ static int quad8_probe(struct device *dev, unsigned int id)
 	quad8iio = iio_priv(indio_dev);
 	quad8iio->counter.name = dev_name(dev);
 	quad8iio->counter.parent = dev;
-	quad8iio->counter.ops = &quad8_ops;
+	quad8iio->counter.signal_read = quad8_signal_read;
+	quad8iio->counter.count_read = quad8_count_read;
+	quad8iio->counter.count_write = quad8_count_write;
+	quad8iio->counter.function_read = quad8_function_read;
+	quad8iio->counter.function_write = quad8_function_write;
+	quad8iio->counter.action_read = quad8_action_read;
 	quad8iio->counter.counts = quad8_counts;
 	quad8iio->counter.num_counts = ARRAY_SIZE(quad8_counts);
 	quad8iio->counter.signals = quad8_signals;

drivers/counter/Makefile +1 -0

index 55142d1f4c43..f48e337cbd85 100644
@@ -4,6 +4,7 @@
 #
 
 obj-$(CONFIG_COUNTER) += counter.o
+counter-y := counter-core.o counter-sysfs.o
 
 obj-$(CONFIG_104_QUAD_8)	+= 104-quad-8.o
 obj-$(CONFIG_STM32_TIMER_CNT)	+= stm32-timer-cnt.o

drivers/counter/counter-core.c new file +157 -0

new file mode 100644
index 000000000000..499664809c75
@@ -0,0 +1,157 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic Counter interface
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+#include <linux/counter.h>
+#include <linux/device.h>
+#include <linux/export.h>
+#include <linux/gfp.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/module.h>
+
+#include "counter-sysfs.h"
+
+/* 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);
+
+	counter_sysfs_free(counter);
+	ida_simple_remove(&counter_ida, counter->id);
+}
+
+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 device *const dev = &counter->dev;
+	int err;
+
+	/* Acquire unique ID */
+	counter->id = ida_simple_get(&counter_ida, 0, 0, GFP_KERNEL);
+	if (counter->id < 0)
+		return counter->id;
+
+	/* Configure device structure for Counter */
+	dev->type = &counter_device_type;
+	dev->bus = &counter_bus_type;
+	if (counter->parent) {
+		dev->parent = counter->parent;
+		dev->of_node = counter->parent->of_node;
+	}
+	dev_set_name(dev, "counter%d", counter->id);
+	device_initialize(dev);
+	dev_set_drvdata(dev, counter);
+
+	/* Add Counter sysfs attributes */
+	err = counter_sysfs_add(counter);
+	if (err)
+		goto err_free_id;
+
+	/* Add device to system */
+	err = device_add(dev);
+	if (err)
+		goto err_free_sysfs;
+
+	return 0;
+
+err_free_sysfs:
+	counter_sysfs_free(counter);
+err_free_id:
+	ida_simple_remove(&counter_ida, counter->id);
+	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->dev);
+		counter_sysfs_free(counter);
+	}
+}
+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 __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 <[email protected]>");
+MODULE_DESCRIPTION("Generic Counter interface");
+MODULE_LICENSE("GPL v2");

drivers/counter/counter-sysfs.c new file +881 -0

new file mode 100644
index 000000000000..d30a3239eb41
@@ -0,0 +1,881 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic Counter sysfs interface
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+#include <linux/counter.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gfp.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+enum counter_owner_type {
+	COUNTER_OWNER_TYPE_DEVICE,
+	COUNTER_OWNER_TYPE_SIGNAL,
+	COUNTER_OWNER_TYPE_COUNT,
+};
+
+struct counter_attribute {
+	struct device_attribute dev_attr;
+	struct list_head l;
+
+	struct counter_data data;
+	enum counter_owner_type type;
+	void *owner;
+};
+
+#define to_counter_attribute(_dev_attr) \
+	container_of(_dev_attr, struct counter_attribute, dev_attr)
+
+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 const char *const counter_signal_value_str[] = {
+	[COUNTER_SIGNAL_LOW] = "low",
+	[COUNTER_SIGNAL_HIGH] = "high"
+};
+
+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"
+};
+
+static const char *const counter_count_direction_str[] = {
+	[COUNTER_COUNT_DIRECTION_FORWARD] = "forward",
+	[COUNTER_COUNT_DIRECTION_BACKWARD] = "backward"
+};
+
+static const char *const counter_count_mode_str[] = {
+	[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"
+};
+
+static ssize_t counter_data_u8_show(struct device *dev,
+				    struct device_attribute *attr, char *buf)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	int err;
+	u8 data;
+
+	switch (a->type) {
+	case COUNTER_OWNER_TYPE_DEVICE:
+		err = a->data.device_u8_read(counter, &data);
+		break;
+	case COUNTER_OWNER_TYPE_SIGNAL:
+		err = a->data.signal_u8_read(counter, a->owner, &data);
+		break;
+	case COUNTER_OWNER_TYPE_COUNT:
+		if (a->data.type == COUNTER_DATA_TYPE_SYNAPSE_ACTION)
+			err = a->data.action_read(counter, a->owner,
+						  a->data.priv, &data);
+		else
+			err = a->data.count_u8_read(counter, a->owner, &data);
+		break;
+	default: return -EINVAL;
+	}
+	if (err)
+		return err;
+
+	switch (a->data.type) {
+	case COUNTER_DATA_TYPE_BOOL:
+		return sprintf(buf, "%u\n", (unsigned int)!!data);
+	case COUNTER_DATA_TYPE_COUNT_FUNCTION:
+		return sprintf(buf, "%s\n", counter_count_function_str[data]);
+	case COUNTER_DATA_TYPE_SIGNAL:
+		return sprintf(buf, "%s\n", counter_signal_value_str[data]);
+	case COUNTER_DATA_TYPE_SYNAPSE_ACTION:
+		return sprintf(buf, "%s\n", counter_synapse_action_str[data]);
+	case COUNTER_DATA_TYPE_COUNT_DIRECTION:
+		return sprintf(buf, "%s\n", counter_count_direction_str[data]);
+	case COUNTER_DATA_TYPE_COUNT_MODE:
+		return sprintf(buf, "%s\n", counter_count_mode_str[data]);
+	}
+
+	return sprintf(buf, "%u\n", (unsigned int)data);
+}
+
+static int find_in_string_array(u8 *const item, const u8 *const items,
+				const size_t num_items, const char *const buf,
+				const char *const string_array[])
+{
+	size_t index;
+
+	for (index = 0; index < num_items; index++) {
+		*item = items[index];
+		if (sysfs_streq(buf, string_array[*item]))
+			return 0;
+	}
+
+	return -EINVAL;
+}
+
+static ssize_t counter_data_u8_store(struct device *dev,
+				     struct device_attribute *attr,
+				     const char *buf, size_t len)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	struct counter_count *const count = a->owner;
+	struct counter_synapse *const synapse = a->data.priv;
+	const struct counter_available *const available = a->data.priv;
+	int err;
+	bool bool_data;
+	u8 data;
+
+	switch (a->data.type) {
+	case COUNTER_DATA_TYPE_BOOL:
+		err = kstrtobool(buf, &bool_data);
+		data = bool_data;
+		break;
+	case COUNTER_DATA_TYPE_COUNT_FUNCTION:
+		err = find_in_string_array(&data, count->functions_list,
+					   count->num_functions, buf,
+					   counter_count_function_str);
+		break;
+	case COUNTER_DATA_TYPE_SYNAPSE_ACTION:
+		err = find_in_string_array(&data, synapse->actions_list,
+					   synapse->num_actions, buf,
+					   counter_synapse_action_str);
+		break;
+	case COUNTER_DATA_TYPE_COUNT_MODE:
+		err = find_in_string_array(&data, available->items,
+					   available->num_items, buf,
+					   counter_count_mode_str);
+		break;
+	default:
+		err = kstrtou8(buf, 0, &data);
+		break;
+	}
+	if (err)
+		return err;
+
+	switch (a->type) {
+	case COUNTER_OWNER_TYPE_DEVICE:
+		err = a->data.device_u8_write(counter, data);
+		break;
+	case COUNTER_OWNER_TYPE_SIGNAL:
+		err = a->data.signal_u8_write(counter, a->owner, data);
+		break;
+	case COUNTER_OWNER_TYPE_COUNT:
+		if (a->data.type == COUNTER_DATA_TYPE_SYNAPSE_ACTION)
+			err = a->data.action_write(counter, count, synapse,
+						   data);
+		else
+			err = a->data.count_u8_write(counter, count, data);
+		break;
+	}
+	if (err)
+		return err;
+
+	return len;
+}
+
+static ssize_t counter_data_u64_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	int err;
+	u64 data;
+
+	switch (a->type) {
+	case COUNTER_OWNER_TYPE_DEVICE:
+		err = a->data.device_u64_read(counter, &data);
+		break;
+	case COUNTER_OWNER_TYPE_SIGNAL:
+		err = a->data.signal_u64_read(counter, a->owner, &data);
+		break;
+	case COUNTER_OWNER_TYPE_COUNT:
+		err = a->data.count_u64_read(counter, a->owner, &data);
+		break;
+	default: return -EINVAL;
+	}
+	if (err)
+		return err;
+
+	return sprintf(buf, "%llu\n", (unsigned long long)data);
+}
+
+static ssize_t counter_data_u64_store(struct device *dev,
+				      struct device_attribute *attr,
+				      const char *buf, size_t len)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	struct counter_device *const counter = dev_get_drvdata(dev);
+	int err;
+	u64 data;
+
+	err = kstrtou64(buf, 0, &data);
+	if (err)
+		return err;
+
+	switch (a->type) {
+	case COUNTER_OWNER_TYPE_DEVICE:
+		err = a->data.device_u64_write(counter, data);
+		break;
+	case COUNTER_OWNER_TYPE_SIGNAL:
+		err = a->data.signal_u64_write(counter, a->owner, data);
+		break;
+	case COUNTER_OWNER_TYPE_COUNT:
+		err = a->data.count_u64_write(counter, a->owner, data);
+		break;
+	}
+	if (err)
+		return err;
+
+	return len;
+}
+
+static ssize_t counter_data_string_show(struct device *dev,
+					struct device_attribute *attr,
+					char *buf)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	struct counter_device *const counter = dev_get_drvdata(dev);
+
+	switch (a->type) {
+	case COUNTER_OWNER_TYPE_DEVICE:
+		return a->data.device_string_read(counter, buf, PAGE_SIZE);
+	case COUNTER_OWNER_TYPE_SIGNAL:
+		return a->data.signal_string_read(counter, a->owner, buf,
+						  PAGE_SIZE);
+	case COUNTER_OWNER_TYPE_COUNT:
+		return a->data.count_string_read(counter, a->owner, buf,
+						 PAGE_SIZE);
+	}
+
+	return -EINVAL;
+}
+
+static ssize_t counter_data_string_store(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t len)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	struct counter_device *const counter = dev_get_drvdata(dev);
+
+	switch (a->type) {
+	case COUNTER_OWNER_TYPE_DEVICE:
+		return a->data.device_string_write(counter, buf, len);
+	case COUNTER_OWNER_TYPE_SIGNAL:
+		return a->data.signal_string_write(counter, a->owner, buf, len);
+	case COUNTER_OWNER_TYPE_COUNT:
+		return a->data.count_string_write(counter, a->owner, buf, len);
+	}
+
+	return -EINVAL;
+}
+
+static ssize_t items_available_show(const u8 *const items,
+				    const size_t num_items,
+				    const char *const string_array[], char *buf)
+{
+	size_t len = 0;
+	size_t index;
+
+	for (index = 0; index < num_items; index++)
+		len += sprintf(buf + len, "%s\n", string_array[items[index]]);
+
+	return len;
+}
+
+static ssize_t counter_data_available_show(struct device *dev,
+					   struct device_attribute *attr,
+					   char *buf)
+{
+	const struct counter_attribute *const a = to_counter_attribute(attr);
+	const struct counter_count *const count = a->owner;
+	const struct counter_synapse *const synapse = a->data.priv;
+	const struct counter_available *const available = a->data.priv;
+
+	switch (a->data.type) {
+	case COUNTER_DATA_TYPE_COUNT_FUNCTION:
+		return items_available_show(count->functions_list,
+					    count->num_functions,
+					    counter_count_function_str, buf);
+	case COUNTER_DATA_TYPE_SYNAPSE_ACTION:
+		return items_available_show(synapse->actions_list,
+					    synapse->num_actions,
+					    counter_synapse_action_str, buf);
+	case COUNTER_DATA_TYPE_COUNT_MODE:
+		return items_available_show(available->items,
+					    available->num_items,
+					    counter_count_mode_str, buf);
+	}
+
+	return -EINVAL;
+}
+
+struct counter_dynamic_name {
+	struct list_head l;
+	const char *name;
+};
+
+static int counter_available_attribute_create(
+	struct counter_attribute_group *const group,
+	struct list_head *const names, const struct counter_data *const data,
+	void *const owner)
+{
+	struct counter_attribute *counter_attr;
+	struct device_attribute *dev_attr;
+	struct counter_dynamic_name *dyn_name;
+
+	/* Allocate Counter attribute */
+	counter_attr = kzalloc(sizeof(*counter_attr), GFP_KERNEL);
+	if (!counter_attr)
+		return -ENOMEM;
+	list_add(&counter_attr->l, &group->attr_list);
+	group->num_attr++;
+
+	/* Configure Counter attribute */
+	counter_attr->data = *data;
+	counter_attr->owner = owner;
+
+	/* Initialize sysfs attribute */
+	dev_attr = &counter_attr->dev_attr;
+	sysfs_attr_init(&dev_attr->attr);
+
+	/* Generate dynamic name list item */
+	dyn_name = kmalloc(sizeof(*dyn_name), GFP_KERNEL);
+	if (!dyn_name)
+		return -ENOMEM;
+	list_add(&dyn_name->l, names);
+
+	/* Generate available attribute name */
+	dyn_name->name = kasprintf(GFP_KERNEL, "%s_available", data->name);
+	if (!dyn_name->name)
+		return -ENOMEM;
+
+	/* Configure device attribute */
+	dev_attr->attr.name = dyn_name->name;
+	dev_attr->attr.mode = 0444;
+	dev_attr->show = counter_data_available_show;
+
+	return 0;
+}
+
+static int counter_attribute_create(struct counter_attribute_group *const group,
+				    struct list_head *const names,
+				    const struct counter_data *const data,
+				    const enum counter_owner_type type,
+				    void *const owner)
+{
+	struct counter_attribute *counter_attr;
+	struct device_attribute *dev_attr;
+
+	/* Allocate Counter attribute */
+	counter_attr = kzalloc(sizeof(*counter_attr), GFP_KERNEL);
+	if (!counter_attr)
+		return -ENOMEM;
+	list_add(&counter_attr->l, &group->attr_list);
+	group->num_attr++;
+
+	/* Configure Counter attribute */
+	counter_attr->data = *data;
+	counter_attr->type = type;
+	counter_attr->owner = owner;
+
+	/* Configure device attribute */
+	dev_attr = &counter_attr->dev_attr;
+	sysfs_attr_init(&dev_attr->attr);
+	dev_attr->attr.name = data->name;
+	switch (data->type) {
+	case COUNTER_DATA_TYPE_U8:
+	case COUNTER_DATA_TYPE_BOOL:
+	case COUNTER_DATA_TYPE_SIGNAL:
+	case COUNTER_DATA_TYPE_COUNT_FUNCTION:
+	case COUNTER_DATA_TYPE_SYNAPSE_ACTION:
+	case COUNTER_DATA_TYPE_COUNT_DIRECTION:
+	case COUNTER_DATA_TYPE_COUNT_MODE:
+		if (data->device_u8_read) {
+			dev_attr->attr.mode |= 0444;
+			dev_attr->show = counter_data_u8_show;
+		}
+		if (data->device_u8_write) {
+			dev_attr->attr.mode |= 0200;
+			dev_attr->store = counter_data_u8_store;
+		}
+		break;
+	case COUNTER_DATA_TYPE_U64:
+		if (data->device_u64_read) {
+			dev_attr->attr.mode |= 0444;
+			dev_attr->show = counter_data_u64_show;
+		}
+		if (data->device_u64_write) {
+			dev_attr->attr.mode |= 0200;
+			dev_attr->store = counter_data_u64_store;
+		}
+		break;
+	case COUNTER_DATA_TYPE_STRING:
+		if (data->device_string_read) {
+			dev_attr->attr.mode |= 0444;
+			dev_attr->show = counter_data_string_show;
+		}
+		if (data->device_string_write) {
+			dev_attr->attr.mode |= 0200;
+			dev_attr->store = counter_data_string_store;
+		}
+		break;
+	}
+
+	switch (data->type) {
+	case COUNTER_DATA_TYPE_COUNT_FUNCTION:
+	case COUNTER_DATA_TYPE_SYNAPSE_ACTION:
+	case COUNTER_DATA_TYPE_COUNT_MODE:
+		return counter_available_attribute_create(group, names, data,
+							  owner);
+	}
+
+	return 0;
+}
+
+static struct counter_data counter_signal_data = {
+	.type = COUNTER_DATA_TYPE_SIGNAL,
+	.name = "signal",
+};
+
+static struct counter_data counter_name_data =
+	COUNTER_DATA_DEVICE_STRING("name", NULL, NULL);
+
+static ssize_t counter_signal_name_read(struct counter_device *counter,
+					struct counter_signal *signal,
+					char *buf, size_t size)
+{
+	return snprintf(buf, size, "%s\n", signal->name);
+}
+
+static int counter_signal_attributes_create(
+	struct counter_attribute_group *const group,
+	struct counter_device *const counter,
+	struct counter_signal *const signal)
+{
+	struct list_head *const names = &counter->dynamic_names_list;
+	const enum counter_owner_type type = COUNTER_OWNER_TYPE_SIGNAL;
+	int err;
+	struct counter_data data;
+	size_t i;
+	const struct counter_data *ext;
+
+	/* Create main Signal attribute */
+	data = counter_signal_data;
+	data.signal_u8_read = counter->signal_read;
+	err = counter_attribute_create(group, names, &data, type, signal);
+	if (err)
+		return err;
+
+	/* Create Signal name attribute */
+	data = counter_name_data;
+	data.signal_string_read = counter_signal_name_read;
+	err = counter_attribute_create(group, names, &data, type, signal);
+	if (err)
+		return err;
+
+	/* Create an attribute for each extension */
+	for (i = 0; i < signal->num_ext; i++) {
+		ext = signal->ext + i;
+		err = counter_attribute_create(group, names, ext, type, signal);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int counter_signals_register(
+	struct counter_attribute_group *const groups_list,
+	struct counter_device *const counter)
+{
+	size_t i;
+	struct counter_signal *signal;
+	const char *name;
+	int err;
+
+	/* Register each Signal */
+	for (i = 0; i < counter->num_signals; i++) {
+		signal = counter->signals + i;
+
+		/* Generate Signal attribute directory name */
+		name = kasprintf(GFP_KERNEL, "signal%d", signal->id);
+		if (!name)
+			return -ENOMEM;
+		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)
+			return err;
+	}
+
+	return 0;
+}
+
+static int counter_synapses_register(
+	struct counter_attribute_group *const group,
+	struct counter_device *const counter, struct counter_count *const count)
+{
+	struct list_head *const names = &counter->dynamic_names_list;
+	const enum counter_owner_type type = COUNTER_OWNER_TYPE_COUNT;
+	size_t i;
+	struct counter_synapse *synapse;
+	int id;
+	struct counter_dynamic_name *dyn_name;
+	struct counter_data data;
+	int err;
+
+	/* Register each Synapse */
+	for (i = 0; i < count->num_synapses; i++) {
+		synapse = count->synapses + i;
+		id = synapse->signal->id;
+
+		/* Generate dynamic name list item */
+		dyn_name = kmalloc(sizeof(*dyn_name), GFP_KERNEL);
+		if (!dyn_name)
+			return -ENOMEM;
+		list_add(&dyn_name->l, names);
+
+		/* Generate Synapse action name */
+		dyn_name->name = kasprintf(GFP_KERNEL, "signal%d_action", id);
+		if (!dyn_name->name)
+			return -ENOMEM;
+
+		/* Create action attribute */
+		data.type = COUNTER_DATA_TYPE_SYNAPSE_ACTION;
+		data.name = dyn_name->name;
+		data.action_read = counter->action_read;
+		data.action_write = counter->action_write;
+		data.priv = synapse;
+		err = counter_attribute_create(group, names, &data, type,
+					       count);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static struct counter_data counter_count_data =
+	COUNTER_DATA_COUNT_U64("count", NULL, NULL);
+
+static ssize_t counter_count_name_read(struct counter_device *counter,
+				       struct counter_count *count, char *buf,
+				       size_t size)
+{
+	return snprintf(buf, size, "%s\n", count->name);
+}
+
+static struct counter_data counter_count_function_data = {
+	.type = COUNTER_DATA_TYPE_COUNT_FUNCTION,
+	.name = "function",
+};
+
+static int counter_count_attributes_create(
+	struct counter_attribute_group *const group,
+	struct counter_device *const counter,
+	struct counter_count *const count)
+{
+	struct list_head *const names = &counter->dynamic_names_list;
+	const enum counter_owner_type type = COUNTER_OWNER_TYPE_COUNT;
+	int err;
+	struct counter_data data;
+	size_t i;
+	const struct counter_data *ext;
+
+	/* Create main Count attribute */
+	data = counter_count_data;
+	data.count_u64_read = counter->count_read;
+	data.count_u64_write = counter->count_write;
+	err = counter_attribute_create(group, names, &data, type, count);
+	if (err)
+		return err;
+
+	/* Create Count name attribute */
+	data = counter_name_data;
+	data.count_string_read = counter_count_name_read;
+	err = counter_attribute_create(group, names, &data, type, count);
+	if (err)
+		return err;
+
+	/* Create Count function attribute */
+	data = counter_count_function_data;
+	data.count_u8_read = counter->function_read;
+	data.count_u8_write = counter->function_write;
+	err = counter_attribute_create(group, names, &data, type, count);
+	if (err)
+		return err;
+
+	/* Create an attribute for each extension */
+	for (i = 0; i < count->num_ext; i++) {
+		ext = count->ext + i;
+		err = counter_attribute_create(group, names, ext, type, count);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static int counter_counts_register(
+	struct counter_attribute_group *const groups_list,
+	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)
+			return -ENOMEM;
+		groups_list[i].attr_group.name = name;
+
+		/* Register the Synapses associated with each Count */
+		err = counter_synapses_register(groups_list + i, counter,
+						count);
+		if (err)
+			return err;
+
+		/* Create all attributes associated with Count */
+		err = counter_count_attributes_create(groups_list + i, counter,
+						      count);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+static ssize_t counter_name_read(struct counter_device *counter, char *buf,
+				 size_t size)
+{
+	return snprintf(buf, size, "%s\n", counter->name);
+}
+
+static int counter_num_signals_read(struct counter_device *counter, u8 *val)
+{
+	*val = counter->num_signals;
+	return 0;
+}
+
+static int counter_num_counts_read(struct counter_device *counter, u8 *val)
+{
+	*val = counter->num_counts;
+	return 0;
+}
+
+static struct counter_data counter_num_signals_data =
+	COUNTER_DATA_DEVICE_U8("num_signals", counter_num_signals_read, NULL);
+
+static struct counter_data counter_num_counts_data =
+	COUNTER_DATA_DEVICE_U8("num_counts", counter_num_counts_read, NULL);
+
+static void counter_groups_list_free(struct counter_device *const counter)
+{
+	struct counter_attribute_group *group;
+	struct counter_attribute *p, *n;
+
+	/* Loop through all attribute groups (signals, counts, device, etc.) */
+	while (counter->num_groups--) {
+		group = counter->groups_list + counter->num_groups;
+
+		/* Free all attribute group and associated attributes memory */
+		kfree(group->attr_group.name);
+		kfree(group->attr_group.attrs);
+
+		/* Free attribute list */
+		list_for_each_entry_safe(p, n, &group->attr_list, l)
+			kfree(p);
+	}
+
+	kfree(counter->groups_list);
+}
+
+static int counter_device_register(struct counter_attribute_group *group,
+				   struct counter_device *const counter)
+{
+	struct list_head *const names = &counter->dynamic_names_list;
+	const enum counter_owner_type type = COUNTER_OWNER_TYPE_DEVICE;
+	struct counter_data data;
+	int err;
+	size_t i;
+	const struct counter_data *ext;
+
+	/* Register Signals */
+	err = counter_signals_register(group, counter);
+	if (err)
+		goto err_free_groups_list;
+	group += counter->num_signals;
+
+	/* Register Counts and respective Synapses */
+	err = counter_counts_register(group, counter);
+	if (err)
+		goto err_free_groups_list;
+	group += counter->num_counts;
+
+	/* Create name attribute */
+	data = counter_name_data;
+	data.device_string_read = counter_name_read;
+	err = counter_attribute_create(group, names, &data, type, NULL);
+	if (err)
+		goto err_free_groups_list;
+
+	/* Create num_signals attribute */
+	data = counter_num_signals_data;
+	err = counter_attribute_create(group, names, &data, type, NULL);
+	if (err)
+		goto err_free_groups_list;
+
+	/* Create num_counts attribute */
+	data = counter_num_counts_data;
+	err = counter_attribute_create(group, names, &data, type, NULL);
+	if (err)
+		goto err_free_groups_list;
+
+	/* Create an attribute for each extension */
+	for (i = 0; i < counter->num_ext; i++) {
+		ext = counter->ext + i;
+		err = counter_attribute_create(group, names, ext, type, NULL);
+		if (err)
+			goto err_free_groups_list;
+	}
+
+	return 0;
+
+err_free_groups_list:
+	counter_groups_list_free(counter);
+	return err;
+}
+
+static int counter_groups_list_prepare(struct counter_device *const counter)
+{
+	const size_t num_grps = counter->num_signals + counter->num_counts + 1;
+	struct counter_attribute_group *groups_list;
+	size_t i;
+
+	/* Allocate space for attribute groups (signals, counts, and ext) */
+	groups_list = kcalloc(num_grps, sizeof(*groups_list), GFP_KERNEL);
+	if (!groups_list)
+		return -ENOMEM;
+
+	/* Store groups_list in counter structure */
+	counter->groups_list = groups_list;
+	counter->num_groups = num_grps;
+
+	/* Initialize attribute lists */
+	for (i = 0; i < num_grps; i++)
+		INIT_LIST_HEAD(&groups_list[i].attr_list);
+
+	/* Register Counter device attributes */
+	return counter_device_register(groups_list, counter);
+}
+
+static int counter_groups_prepare(struct counter_device *const counter)
+{
+	size_t i, j;
+	struct counter_attribute_group *group;
+	struct attribute **attrs;
+	int err;
+	struct counter_attribute *p;
+
+	/* Allocate attribute groups for association with device */
+	counter->groups = kcalloc(counter->num_groups + 1,
+				  sizeof(*counter->groups), GFP_KERNEL);
+	if (!counter->groups)
+		return -ENOMEM;
+
+	/* Prepare each group of attributes for association */
+	for (i = 0; i < counter->num_groups; i++) {
+		group = counter->groups_list + i;
+
+		/* Allocate space for attribute pointers */
+		attrs = kcalloc(group->num_attr + 1, sizeof(*attrs),
+				GFP_KERNEL);
+		if (!attrs) {
+			err = -ENOMEM;
+			goto err_free_groups;
+		}
+		group->attr_group.attrs = attrs;
+
+		/* Add attribute pointers to attribute group */
+		j = 0;
+		list_for_each_entry(p, &group->attr_list, l)
+			attrs[j++] = &p->dev_attr.attr;
+
+		/* Group attributes in attribute group */
+		counter->groups[i] = &group->attr_group;
+	}
+	/* Associate attributes with device */
+	counter->dev.groups = counter->groups;
+
+	return 0;
+
+err_free_groups:
+	kfree(counter->groups);
+	return err;
+}
+
+static void counter_dynamic_names_free(struct list_head *const names)
+{
+	struct counter_dynamic_name *p, *n;
+
+	list_for_each_entry_safe(p, n, names, l) {
+		kfree(p->name);
+		kfree(p);
+	}
+}
+
+int counter_sysfs_add(struct counter_device *const counter)
+{
+	int err;
+
+	/* Initialize Synapse names list */
+	INIT_LIST_HEAD(&counter->dynamic_names_list);
+
+	/* Prepare device attributes */
+	err = counter_groups_list_prepare(counter);
+	if (err)
+		goto err_free_names;
+
+	/* Organize device attributes to groups and match to device */
+	err = counter_groups_prepare(counter);
+	if (err)
+		goto err_free_groups_list;
+
+	return 0;
+
+err_free_groups_list:
+	counter_groups_list_free(counter);
+err_free_names:
+	counter_dynamic_names_free(&counter->dynamic_names_list);
+	return err;
+}
+
+void counter_sysfs_free(struct counter_device *const counter)
+{
+	kfree(counter->groups);
+	counter_groups_list_free(counter);
+	counter_dynamic_names_free(&counter->dynamic_names_list);
+}

drivers/counter/counter-sysfs.h new file +14 -0

new file mode 100644
index 000000000000..00e7cd6ea083
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Counter sysfs interface
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+#ifndef _COUNTER_SYSFS_H_
+#define _COUNTER_SYSFS_H_
+
+#include <linux/counter.h>
+
+int counter_sysfs_add(struct counter_device *const counter);
+void counter_sysfs_free(struct counter_device *const counter);
+
+#endif /* _COUNTER_SYSFS_H_ */

drivers/counter/counter.c deleted +0 -1496

deleted file mode 100644
index 6a683d086008..000000000000
@@ -1,1496 +0,0 @@
-// 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);
-
-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 const char *const counter_signal_value_str[] = {
-	[COUNTER_SIGNAL_LOW] = "low",
-	[COUNTER_SIGNAL_HIGH] = "high"
-};
-
-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;
-	enum counter_signal_value val;
-
-	err = counter->ops->signal_read(counter, signal, &val);
-	if (err)
-		return err;
-
-	return sprintf(buf, "%s\n", counter_signal_value_str[val]);
-}
-
-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;
-	unsigned long val;
-
-	err = counter->ops->count_read(counter, count, &val);
-	if (err)
-		return err;
-
-	return sprintf(buf, "%lu\n", val);
-}
-
-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;
-	unsigned long val;
-
-	err = kstrtoul(buf, 0, &val);
-	if (err)
-		return err;
-
-	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);
[… more lines in the raw message]

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drivers/counter/ftm-quaddec.c +51 -38

index c2b3fdfd8b77..ea6cb18c7170 100644

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drivers/counter/stm32-lptimer-cnt.c +84 -77

index 8e276eb655f5..4a1ec895717c 100644

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drivers/counter/stm32-timer-cnt.c +53 -86

index ef2a974a2f10..502e525836a9 100644

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drivers/counter/ti-eqep.c +107 -104

index 1ff07faef27f..7152f0b3c2de 100644

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include/linux/counter.h +255 -355

index 9dbd5df4cd34..e8abbaf47a4b 100644

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include/linux/counter_enum.h deleted +0 -45

deleted file mode 100644
index 9f917298a88f..000000000000

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include/uapi/linux/counter-types.h new file +45 -0

new file mode 100644
index 000000000000..d19616df0e1c

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The Counter subsystem architecture and driver implementations have changed in order to handle Counter sysfs interactions in a more consistent way. This patch updates the Generic Counter interface documentation to reflect the changes.

Signed-off-by William Breathitt Gray <[email protected]>

---
 Documentation/driver-api/generic-counter.rst | 215 +++++++++++++------
 1 file changed, 149 insertions(+), 66 deletions(-)

Documentation/driver-api/generic-counter.rst +149 -66

index e622f8f6e56a..8f85c30dea0b 100644
@@ -250,8 +250,8 @@ for defining a counter device.
 .. kernel-doc:: drivers/counter/counter.c
    :export:
 
-Implementation
-==============
+Driver Implementation
+=====================
 
 To support a counter device, a driver must first allocate the available
 Counter Signals via counter_signal structures. These Signals should

@@ -267,25 +267,58 @@ 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.
 
-Driver callbacks should be provided to the counter_device structure via
-a constant counter_ops structure in order to communicate with the
-device: to read and write various Signals and Counts, and to set and get
-the "action mode" and "function mode" for various Synapses and Counts
-respectively.
+Driver callbacks must be provided to the counter_device structure in
+order to communicate with the device: to read and write various Signals
+and Counts, and to set and get the "action mode" and "function mode" for
+various Synapses and Counts respectively.
 
 A defined counter_device structure may be registered to the system by
 passing it to the counter_register function, and unregistered by passing
 it to the counter_unregister function. Similarly, the
-devm_counter_register and devm_counter_unregister functions may be used
-if device memory-managed registration is desired.
-
-Extension sysfs attributes can be created for auxiliary functionality
-and data by passing in defined counter_device_ext, counter_count_ext,
-and counter_signal_ext structures. In these cases, the
-counter_device_ext structure is used for global/miscellaneous exposure
-and configuration of the respective Counter device, while the
-counter_count_ext and counter_signal_ext structures allow for auxiliary
-exposure and configuration of a specific Count or Signal respectively.
+devm_counter_register function may be used if device memory-managed
+registration is desired.
+
+The struct counter_data structure is used to define counter extensions
+for Signals, Synapses, and Counts.
+
+The "type" member specifies the type of data (e.g. unsigned long,
+boolean, etc.) handled by this extension. The "read" and "write" members
+can then be set by the counter device driver with callbacks to handle
+that data.
+
+Convenience macros such as `COUNTER_DATA_COUNT_U64` are provided for use
+by driver authors. In particular, driver authors are expected to use
+the provided macros for standard Counter subsystem attributes in order
+to maintain a consistent interface for userspace. For example, a counter
+device driver may define several standard attributes like so::
+
+	struct counter_data count_ext[] = {
+		COUNTER_DATA_DIRECTION(count_direction_read),
+		COUNTER_DATA_ENABLE(count_enable_read, count_enable_write),
+		COUNTER_DATA_CEILING(count_ceiling_read, count_ceiling_write),
+	};
+
+This makes it intuitive to see, add, and modify the attributes that are
+supported by this driver ("direction", "enable", and "ceiling") and to
+maintain this code without getting lost in a web of struct braces.
+
+Callbacks must match the function type expected for the respective
+component or extension. These function types are defined in the struct
+counter_data structure as the "`*_read`" and "`*_write`" union members.
+
+The corresponding callback prototypes for the extensions mentioned in
+the previous example above would be::
+
+	int count_direction_read(struct counter_device *counter,
+				 struct counter_count *count, u8 *direction);
+	int count_enable_read(struct counter_device *counter,
+			      struct counter_count *count, u8 *enable);
+	int count_enable_write(struct counter_device *counter,
+			       struct counter_count *count, u8 enable);
+	int count_ceiling_read(struct counter_device *counter,
+			       struct counter_count *count, u64 *ceiling);
+	int count_ceiling_write(struct counter_device *counter,
+				struct counter_count *count, u64 ceiling);
 
 Determining the type of extension to create is a matter of scope.
 

@@ -313,52 +346,102 @@ Determining the type of extension to create is a matter of scope.
   chip overheated via a device extension called "error_overtemp":
   /sys/bus/counter/devices/counterX/error_overtemp
 
-Architecture
-============
-
-When the Generic Counter interface counter module is loaded, the
-counter_init function is called which registers a bus_type named
-"counter" to the system. Subsequently, when the module is unloaded, the
-counter_exit function is called which unregisters the bus_type named
-"counter" from the system.
-
-Counter devices are registered to the system via the counter_register
-function, and later removed via the counter_unregister function. The
-counter_register function establishes a unique ID for the Counter
-device and creates a respective sysfs directory, where X is the
-mentioned unique ID:
-
-    /sys/bus/counter/devices/counterX
-
-Sysfs attributes are created within the counterX directory to expose
-functionality, configurations, and data relating to the Counts, Signals,
-and Synapses of the Counter device, as well as options and information
-for the Counter device itself.
-
-Each Signal has a directory created to house its relevant sysfs
-attributes, where Y is the unique ID of the respective Signal:
-
-    /sys/bus/counter/devices/counterX/signalY
-
-Similarly, each Count has a directory created to house its relevant
-sysfs attributes, where Y is the unique ID of the respective Count:
-
-    /sys/bus/counter/devices/counterX/countY
-
-For a more detailed breakdown of the available Generic Counter interface
-sysfs attributes, please refer to the
-Documentation/ABI/testing/sysfs-bus-counter file.
-
-The Signals and Counts associated with the Counter device are registered
-to the system as well by the counter_register function. The
-signal_read/signal_write driver callbacks are associated with their
-respective Signal attributes, while the count_read/count_write and
-function_get/function_set driver callbacks are associated with their
-respective Count attributes; similarly, the same is true for the
-action_get/action_set driver callbacks and their respective Synapse
-attributes. If a driver callback is left undefined, then the respective
-read/write permission is left disabled for the relevant attributes.
-
-Similarly, extension sysfs attributes are created for the defined
-counter_device_ext, counter_count_ext, and counter_signal_ext
-structures that are passed in.
+Subsystem Architecture
+======================
+
+Counter drivers pass and take data natively (i.e. `u8`, `u64`, `char *`,
+etc.) and the shared counter module handles the translation between the
+sysfs interface. This gurantees a standard userspace interface for all
+counter drivers, and helps generalize the Generic Counter driver ABI in
+order to support the Generic Counter chrdev interface without
+significant changes to the existing counter drivers.
+
+A high-level view of how a count value is passed down from a counter
+driver can be exemplified by the following::
+
+       Count data request:
+       ~~~~~~~~~~~~~~~~~~~
+                 ----------------------
+                / Counter device       \
+                +----------------------+
+                | Count register: 0x28 |
+                +----------------------+
+                        |
+                 -----------------
+                / raw count data /
+                -----------------
+                        |
+                        V
+                +----------------------------+
+                | Counter device driver      |----------+
+                +----------------------------+          |
+                | Processes data from device |   -------------------
+                |----------------------------|  / driver callbacks /
+                | Type: unsigned long        |  -------------------
+                | Value: 42                  |          |
+                +----------------------------+          |
+                        |                               |
+                 ----------------                       |
+                / unsigned long /                       |
+                ----------------                        |
+                        |                               |
+                        |                               V
+                        |               +----------------------+
+                        |               | Counter core         |
+                        |               +----------------------+
+                        |               | Routes device driver |
+                        |               | callbacks to the     |
+                        |               | userspace interfaces |
+                        |               +----------------------+
+                        |                       |
+                        |                -------------------
+                        |               / driver callbacks /
+                        |               -------------------
+                        |                       |
+                +-------+                       |
+                |                               |
+                |               +---------------+
+                |               |
+                V               |
+        +--------------------+  |
+        | Counter sysfs      |<-+
+        +--------------------+
+        | Translates to the  |
+        | standard Counter   |
+        | sysfs output       |
+        |--------------------|
+        | Type: const char * |
+        | Value: "42"        |
+        +--------------------+
+                |
+         ---------------
+        / const char * /
+        ---------------
+                |
+                V
+        +--------------------------------------------------+
+        | `/sys/bus/counter/devices/counterX/countY/count` |
+        +--------------------------------------------------+
+        \ Count: "42"                                      /
+         --------------------------------------------------
+
+There are three primary components involved:
+
+Counter device driver
+---------------------
+Communicates with the hardware device to read/write data; e.g. counter
+drivers for quadrature encoders, timers, etc.
+
+Counter core
+------------
+Registers the counter device driver to the system so that the respective
+callbacks are called during userspace interaction.
+
+Counter sysfs
+-------------
+Translates counter data to the standard Counter sysfs interface format
+and vice versa.
+
+Please refer to the `Documentation/ABI/testing/sysfs-bus-counter` file
+for a detailed breakdown of the available Generic Counter interface
+sysfs attributes.