linux-kernel - [PATCH v3 1/4] counter: Introduce the Signal polarity component

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Message-Id: <dbf9d9cfb9ba3b46b177e0a2c24520e8e2def1bb.1663511054.git.william.gray@linaro.org>
Date:   Sun, 18 Sep 2022 10:36:31 -0400
From:   William Breathitt Gray <william.gray@...aro.org>
To:     linux-iio@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mranostay@...com,
        jpanis@...libre.com, gwendal@...omium.org, bleung@...omium.org,
        groeck@...omium.org, jic23@...nel.org, david@...hnology.com,
        robertcnelson@...il.com,
        William Breathitt Gray <william.gray@...aro.org>
Subject: [PATCH v3 1/4] counter: Introduce the Signal polarity component

The Signal polarity component represents the active level of a
respective Signal. There are two possible states: positive (rising edge)
and negative (falling edge); enum counter_signal_polarity represents
these states. A convenience macro COUNTER_COMP_POLARITY() is provided
for driver authors to declare a Signal polarity component.

Cc: Julien Panis <jpanis@...libre.com>
Signed-off-by: William Breathitt Gray <william.gray@...aro.org>
---
 Documentation/ABI/testing/sysfs-bus-counter | 13 +++++++++++++
 drivers/counter/counter-sysfs.c             | 11 +++++++++++
 include/linux/counter.h                     | 10 ++++++++++
 include/uapi/linux/counter.h                |  6 ++++++
 4 files changed, 40 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
index 06c2b3e27e0b..a234022f9add 100644
--- a/Documentation/ABI/testing/sysfs-bus-counter
+++ b/Documentation/ABI/testing/sysfs-bus-counter
@@ -303,6 +303,19 @@ Description:
 		Discrete set of available values for the respective Signal Y
 		configuration are listed in this file.
 
+What:		/sys/bus/counter/devices/counterX/signalY/polarity
+KernelVersion:	6.1
+Contact:	linux-iio@...r.kernel.org
+Description:
+		Active level of Signal Y. The following polarity values are
+		available:
+
+		positive:
+			Signal high state considered active level (rising edge).
+
+		negative:
+			Signal low state considered active level (falling edge).
+
 What:		/sys/bus/counter/devices/counterX/signalY/name
 KernelVersion:	5.2
 Contact:	linux-iio@...r.kernel.org
diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c
index 04eac41dad33..92d3d4f549cb 100644
--- a/drivers/counter/counter-sysfs.c
+++ b/drivers/counter/counter-sysfs.c
@@ -91,6 +91,11 @@ static const char *const counter_count_mode_str[] = {
 	[COUNTER_COUNT_MODE_MODULO_N] = "modulo-n"
 };
 
+static const char *const counter_signal_polarity_str[] = {
+	[COUNTER_SIGNAL_POLARITY_POSITIVE] = "positive",
+	[COUNTER_SIGNAL_POLARITY_NEGATIVE] = "negative"
+};
+
 static ssize_t counter_comp_u8_show(struct device *dev,
 				    struct device_attribute *attr, char *buf)
 {
@@ -201,6 +206,8 @@ static ssize_t counter_comp_u32_show(struct device *dev,
 		return sysfs_emit(buf, "%s\n", counter_count_direction_str[data]);
 	case COUNTER_COMP_COUNT_MODE:
 		return sysfs_emit(buf, "%s\n", counter_count_mode_str[data]);
+	case COUNTER_COMP_SIGNAL_POLARITY:
+		return sysfs_emit(buf, "%s\n", counter_signal_polarity_str[data]);
 	default:
 		return sysfs_emit(buf, "%u\n", (unsigned int)data);
 	}
@@ -252,6 +259,10 @@ static ssize_t counter_comp_u32_store(struct device *dev,
 		err = counter_find_enum(&data, avail->enums, avail->num_items,
 					buf, counter_count_mode_str);
 		break;
+	case COUNTER_COMP_SIGNAL_POLARITY:
+		err = counter_find_enum(&data, avail->enums, avail->num_items,
+					buf, counter_signal_polarity_str);
+		break;
 	default:
 		err = kstrtou32(buf, 0, &data);
 		break;
diff --git a/include/linux/counter.h b/include/linux/counter.h
index 1fe17f5adb09..d508b260aaca 100644
--- a/include/linux/counter.h
+++ b/include/linux/counter.h
@@ -31,6 +31,7 @@ enum counter_comp_type {
 	COUNTER_COMP_ENUM,
 	COUNTER_COMP_COUNT_DIRECTION,
 	COUNTER_COMP_COUNT_MODE,
+	COUNTER_COMP_SIGNAL_POLARITY,
 };
 
 /**
@@ -483,4 +484,13 @@ struct counter_available {
 #define COUNTER_COMP_PRESET_ENABLE(_read, _write) \
 	COUNTER_COMP_COUNT_BOOL("preset_enable", _read, _write)
 
+#define COUNTER_COMP_POLARITY(_read, _write, _available) \
+{ \
+	.type = COUNTER_COMP_SIGNAL_POLARITY, \
+	.name = "polarity", \
+	.signal_u32_read = (_read), \
+	.signal_u32_write = (_write), \
+	.priv = &(_available), \
+}
+
 #endif /* _COUNTER_H_ */
diff --git a/include/uapi/linux/counter.h b/include/uapi/linux/counter.h
index 96c5ffd368ad..e9610e1944dc 100644
--- a/include/uapi/linux/counter.h
+++ b/include/uapi/linux/counter.h
@@ -153,4 +153,10 @@ enum counter_synapse_action {
 	COUNTER_SYNAPSE_ACTION_BOTH_EDGES,
 };
 
+/* Signal polarity values */
+enum counter_signal_polarity {
+	COUNTER_SIGNAL_POLARITY_POSITIVE,
+	COUNTER_SIGNAL_POLARITY_NEGATIVE,
+};
+
 #endif /* _UAPI_COUNTER_H_ */
-- 
2.37.3