Message-Id: <20231020-topic-chipcap2-v4-5-7940cfa7613a@gmail.com>
Date: Mon, 18 Dec 2023 20:10:33 +0100
From: Javier Carrasco <javier.carrasco.cruz@...il.com>
To: Rob Herring <robh+dt@...nel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
 Conor Dooley <conor+dt@...nel.org>, Jean Delvare <jdelvare@...e.com>, 
 Guenter Roeck <linux@...ck-us.net>, Jonathan Corbet <corbet@....net>, 
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>
Cc: Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org, 
 linux-doc@...r.kernel.org, Javier Carrasco <javier.carrasco.cruz@...il.com>
Subject: [PATCH v4 5/5] hwmon: Add support for Amphenol ChipCap 2

The Amphenol ChipCap 2 is a capacitive polymer humidity and temperature
sensor with an integrated EEPROM and minimum/maximum humidity alarms.

All device variants offer an I2C interface and depending on the part
number, two different output modes:
- CC2D: digital output
- CC2A: analog (PDM) output

This driver adds support for the digital variant (CC2D part numbers),
which includes the following part numbers:
- non-sleep measurement mode (CC2D23, CC2D25, CC2D33, CC2D35)
- sleep measurement mode (CC2D23S, CC2D25S, CC2D33S, CC2D35S)

The Chipcap 2 EEPROM can be accessed to configure a series of parameters
like the minimum/maximum humidity alarm threshold and hysteresis. The
EEPROM is only accessible in the command window after a power-on reset.
The default window lasts 10 ms if no Start_CM command is sent. After the
command window is finished (either after the mentioned timeout of after
a Start_NOM command is sent), the device enters the normal operation
mode and makes a first measurement automatically.

Unfortunately, the device does not provide any hardware or software
reset and therefore the driver must trigger power cycles to enter the
command mode. A dedicated, external regulator is required for that.

This driver keeps the device off until a measurement is required, making
use of the first automatic measurement to avoid different code paths for
sleep and non-sleep devices.

The minimum and maximum humidity alarms are configured with two
registers per alarm: one stores the alarm threshold and the other one
keeps the value that turns off the alarm. Note that the second register
stores an absolute value and not the hysteresis. The hysteresis is
therefore obtained as a subtraction of the two registers.
The alarm signals are only updated when a measurement is carried out.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@...il.com>
---
 Documentation/hwmon/chipcap2.rst |  73 ++++
 Documentation/hwmon/index.rst    |   1 +
 MAINTAINERS                      |   8 +
 drivers/hwmon/Kconfig            |  10 +
 drivers/hwmon/Makefile           |   1 +
 drivers/hwmon/chipcap2.c         | 835 +++++++++++++++++++++++++++++++++++++++
 6 files changed, 928 insertions(+)

diff --git a/Documentation/hwmon/chipcap2.rst b/Documentation/hwmon/chipcap2.rst
new file mode 100644
index 000000000000..dc165becc64c
--- /dev/null
+++ b/Documentation/hwmon/chipcap2.rst
@@ -0,0 +1,73 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver ChipCap2
+======================
+
+Supported chips:
+
+  * Amphenol CC2D23, CC2D23S, CC2D25, CC2D25S, CC2D33, CC2D33S, CC2D35, CC2D35S
+
+    Prefix: 'chipcap2'
+
+    Addresses scanned: -
+
+    Datasheet: https://www.amphenol-sensors.com/en/telaire/humidity/527-humidity-sensors/3095-chipcap-2
+
+Author:
+
+  - Javier Carrasco <javier.carrasco.cruz@...il.com>
+
+Description
+-----------
+
+This driver implements support for the Amphenol ChipCap 2, a humidity and
+temperature chip family. Temperature is measured in milli degrees celsius,
+relative humidity is expressed as a per cent mille. The measurement ranges
+are the following:
+
+  - Relative humidity: 0 to 100000 pcm (14-bit resolution)
+  - Temperature: -40000 to +125000 m°C (14-bit resolution)
+
+The device communicates with the I2C protocol and uses the I2C address 0x28
+by default.
+
+Depending on the hardware configuration, up to two humidity alarms to control
+minimum and maximum values are provided. Their thresholds and hystersis can be
+configured via sysfs.
+
+Thresholds and hysteris must be provided as a per cent mille. These values
+might be truncated to match the 14-bit device resolution (6.1 pcm/LSB)
+
+Known Issues
+------------
+
+The driver does not support I2C address and command window length modification.
+
+sysfs-Interface
+---------------
+
+The following list includes the sysfs attributes that the driver always provides,
+their permissions and a short description:
+
+=============================== ======= ========================================
+Name                            Perm    Description
+=============================== ======= ========================================
+temp1_input:                    RO      temperature input
+humidity1_input:                RO      humidity input
+=============================== ======= ========================================
+
+The following list includes the sysfs attributes that the driver may provide
+depending on the hardware configuration:
+
+=============================== ======= ========================================
+Name                            Perm    Description
+=============================== ======= ========================================
+humidity1_min:                  RW      humidity low limit. Measurements under
+                                        this limit trigger a humidity low alarm
+humidity1_max:                  RW      humidity high limit. Measurements above
+                                        this limit trigger a humidity high alarm
+humidity1_min_hyst:             RW      humidity low hystersis
+humidity1_max_hyst:             RW      humidity high hystersis
+humidity1_min_alarm:            RO      humidity low alarm indicator
+humidity1_max_alarm:            RO      humidity high alarm indicator
+=============================== ======= ========================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 72f4e6065bae..35f7573b4822 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -51,6 +51,7 @@ Hardware Monitoring Kernel Drivers
    bel-pfe
    bpa-rs600
    bt1-pvt
+   chipcap2
    coretemp
    corsair-cpro
    corsair-psu
diff --git a/MAINTAINERS b/MAINTAINERS
index 788be9ab5b73..88eec0adec49 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1086,6 +1086,14 @@ F:	Documentation/devicetree/bindings/perf/amlogic,g12-ddr-pmu.yaml
 F:	drivers/perf/amlogic/
 F:	include/soc/amlogic/
 
+AMPHENOL CHIPCAP 2 HUMIDITY-TEMPERATURE IIO DRIVER
+M:	Javier Carrasco <javier.carrasco.cruz@...il.com>
+L:	linux-hwmon@...r.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml
+F:	Documentation/hwmon/chipcap2.rst
+F:	drivers/hwmon/chipcap2.c
+
 AMPHION VPU CODEC V4L2 DRIVER
 M:	Ming Qian <ming.qian@....com>
 M:	Zhou Peng <eagle.zhou@....com>
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index cf27523eed5a..11b133ef2384 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -452,6 +452,16 @@ config SENSORS_BT1_PVT_ALARMS
 	  the data conversion will be periodically performed and the data will be
 	  saved in the internal driver cache.
 
+config SENSORS_CHIPCAP2
+	tristate "Amphenol ChipCap 2 relative humidity and temperature sensor"
+	depends on I2C
+	help
+	  Say yes here to build support for the Amphenol ChipCap 2
+	  relative humidity and temperature sensor.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called chipcap2.
+
 config SENSORS_CORSAIR_CPRO
 	tristate "Corsair Commander Pro controller"
 	depends on HID
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index e84bd9685b5c..daf0acef1482 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -58,6 +58,7 @@ obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o
 obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o
 obj-$(CONFIG_SENSORS_AXI_FAN_CONTROL) += axi-fan-control.o
 obj-$(CONFIG_SENSORS_BT1_PVT)	+= bt1-pvt.o
+obj-$(CONFIG_SENSORS_CHIPCAP2) += chipcap2.o
 obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
 obj-$(CONFIG_SENSORS_CORSAIR_CPRO) += corsair-cpro.o
 obj-$(CONFIG_SENSORS_CORSAIR_PSU) += corsair-psu.o
diff --git a/drivers/hwmon/chipcap2.c b/drivers/hwmon/chipcap2.c
new file mode 100644
index 000000000000..024d68485898
--- /dev/null
+++ b/drivers/hwmon/chipcap2.c
@@ -0,0 +1,835 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * cc2.c - Support for the Amphenol ChipCap 2 relative humidity, temperature sensor
+ *
+ * Part numbers supported:
+ * CC2D23, CC2D23S, CC2D25, CC2D25S, CC2D33, CC2D33S, CC2D35, CC2D35S
+ *
+ * Author: Javier Carrasco <javier.carrasco.cruz@...il.com>
+ *
+ * Datasheet and application notes:
+ * https://www.amphenol-sensors.com/en/telaire/humidity/527-humidity-sensors/3095-chipcap-2
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bits.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+
+#define CC2_START_CM			0xA0
+#define CC2_START_NOM			0x80
+#define CC2_R_ALARM_H_ON		0x18
+#define CC2_R_ALARM_H_OFF		0x19
+#define CC2_R_ALARM_L_ON		0x1A
+#define CC2_R_ALARM_L_OFF		0x1B
+#define CC2_RW_OFFSET			0x40
+#define CC2_W_ALARM_H_ON		(CC2_R_ALARM_H_ON + CC2_RW_OFFSET)
+#define CC2_W_ALARM_H_OFF		(CC2_R_ALARM_H_OFF + CC2_RW_OFFSET)
+#define CC2_W_ALARM_L_ON		(CC2_R_ALARM_L_ON + CC2_RW_OFFSET)
+#define CC2_W_ALARM_L_OFF		(CC2_R_ALARM_L_OFF + CC2_RW_OFFSET)
+
+#define CC2_STATUS_FIELD		GENMASK(7, 6)
+#define CC2_STATUS_VALID_DATA		0x00
+#define CC2_STATUS_STALE_DATA		0x01
+#define CC2_STATUS_CMD_MODE		0x02
+
+#define CC2_RESPONSE_FIELD		GENMASK(1, 0)
+#define CC2_RESPONSE_BUSY		0x00
+#define CC2_RESPONSE_ACK		0x01
+#define CC2_RESPONSE_NACK		0x02
+
+#define CC2_ERR_CORR_EEPROM		BIT(2)
+#define CC2_ERR_UNCORR_EEPROM		BIT(3)
+#define CC2_ERR_RAM_PARITY		BIT(4)
+#define CC2_ERR_CONFIG_LOAD		BIT(5)
+
+#define CC2_EEPROM_SIZE			10
+#define CC2_EEPROM_DATA_LEN		3
+#define CC2_MEASUREMENT_DATA_LEN	4
+
+#define CC2_RH_DATA_FIELD		GENMASK(13, 0)
+
+/* ensure clean off -> on transitions */
+#define CC2_POWER_CYCLE_MS		80
+
+#define CC2_STARTUP_TO_DATA_MS		55
+#define CC2_RESP_START_CM_US		100
+#define CC2_RESP_EEPROM_R_US		100
+#define CC2_RESP_EEPROM_W_MS		12
+#define CC2_STARTUP_TIME_US		1250
+
+#define CC2_RH_MAX			(100 * 1000U)
+
+#define CC2_CM_RETRIES			5
+
+struct cc2_rh_alarm_info {
+	bool low_alarm;
+	bool high_alarm;
+	bool low_alarm_visible;
+	bool high_alarm_visible;
+};
+
+struct cc2_data {
+	struct cc2_rh_alarm_info rh_alarm;
+	struct mutex alarm_lock; /* alarm status lock */
+	struct completion complete;
+	struct device *hwmon;
+	struct i2c_client *client;
+	struct mutex dev_access_lock; /* device access lock */
+	struct regulator *regulator;
+	const char *name;
+	int irq_ready;
+	int irq_low;
+	int irq_high;
+	bool ignore_irqs;
+};
+
+enum cc2_chan_addr {
+	CC2_CHAN_TEMP = 0,
+	CC2_CHAN_HUMIDITY,
+};
+
+/* %RH as a per cent mille from a register value */
+static long cc2_rh_convert(u16 data)
+{
+	unsigned long tmp = (data & CC2_RH_DATA_FIELD) * CC2_RH_MAX;
+
+	return tmp / ((1 << 14) - 1);
+}
+
+/* convert %RH to a register value */
+static u16 cc2_rh_to_reg(long data)
+{
+	return data * ((1 << 14) - 1) / CC2_RH_MAX;
+}
+
+/* temperature in milli degrees celsius from a register value */
+static long cc2_temp_convert(u16 data)
+{
+	unsigned long tmp = ((data >> 2) * 165 * 1000U) / ((1 << 14) - 1);
+
+	return tmp - 40 * 1000U;
+}
+
+static int cc2_enable(struct cc2_data *data)
+{
+	int ret;
+
+	if (regulator_is_enabled(data->regulator))
+		return 0;
+
+	/* ignore alarms triggered by voltage toggling when powering up */
+	mutex_lock(&data->alarm_lock);
+	data->ignore_irqs = true;
+	mutex_unlock(&data->alarm_lock);
+
+	/* clear any pending completion */
+	try_wait_for_completion(&data->complete);
+
+	ret = regulator_enable(data->regulator);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * TODO: the startup-delay-us property of the regulator might be
+	 * added to the delay (if provided).
+	 * Currently there is no interface to read its value apart from
+	 * a direct access to regulator->rdev->constraints->enable_time,
+	 * which is discouraged like any direct access to the regulator_dev
+	 * structure. This would be relevant in cases where the startup delay
+	 * is in the range of milliseconds.
+	 */
+	usleep_range(CC2_STARTUP_TIME_US, CC2_STARTUP_TIME_US + 125);
+
+	mutex_lock(&data->alarm_lock);
+	data->ignore_irqs = false;
+	mutex_unlock(&data->alarm_lock);
+
+	return 0;
+}
+
+static void cc2_disable(struct cc2_data *data)
+{
+	int err;
+
+	if (regulator_is_enabled(data->regulator)) {
+		err = regulator_disable(data->regulator);
+		if (err)
+			dev_dbg(&data->client->dev, "Failed to disable device");
+	}
+}
+
+static int cc2_cmd_response_diagnostic(struct device *dev, u8 status)
+{
+	int resp;
+
+	if (FIELD_GET(CC2_STATUS_FIELD, status) != CC2_STATUS_CMD_MODE) {
+		dev_dbg(dev, "Command sent out of command window\n");
+		return -ETIMEDOUT;
+	}
+
+	resp = FIELD_GET(CC2_RESPONSE_FIELD, status);
+	switch (resp) {
+	case CC2_RESPONSE_ACK:
+		return 0;
+	case CC2_RESPONSE_BUSY:
+		return -EBUSY;
+	case CC2_RESPONSE_NACK:
+		if (resp & CC2_ERR_CORR_EEPROM)
+			dev_dbg(dev, "Command failed: corrected EEPROM\n");
+		if (resp & CC2_ERR_UNCORR_EEPROM)
+			dev_dbg(dev, "Command failed: uncorrected EEPROM\n");
+		if (resp & CC2_ERR_RAM_PARITY)
+			dev_dbg(dev, "Command failed: RAM parity\n");
+		if (resp & CC2_ERR_RAM_PARITY)
+			dev_dbg(dev, "Command failed: configuration error\n");
+		return -ENODATA;
+	default:
+		dev_dbg(dev, "Unknown command reply\n");
+		return -EINVAL;
+	}
+}
+
+static int cc2_read_command_status(struct i2c_client *client)
+{
+	u8 status;
+	int ret;
+
+	ret = i2c_master_recv(client, &status, 1);
+	if (ret != 1) {
+		ret = ret < 0 ? ret : -EIO;
+		return ret;
+	}
+
+	return cc2_cmd_response_diagnostic(&client->dev, status);
+}
+
+/*
+ * The command mode is only accessible after sending the START_CM command in the
+ * first 10 ms after power-up. Only in case the command window is missed,
+ * CC2_CM_RETRIES retries are attempted before giving up and returning an error.
+ */
+static int cc2_command_mode_start(struct cc2_data *data)
+{
+	unsigned long timeout;
+	int i, ret;
+
+	for (i = 0; i < CC2_CM_RETRIES; i++) {
+		ret = cc2_enable(data);
+		if (ret < 0)
+			return ret;
+
+		ret = i2c_smbus_write_word_data(data->client, CC2_START_CM, 0);
+		if (ret < 0)
+			return ret;
+
+		if (data->irq_ready > 0) {
+			timeout = usecs_to_jiffies(2 * CC2_RESP_START_CM_US);
+			ret = wait_for_completion_timeout(&data->complete,
+							  timeout);
+			if (!ret)
+				return -ETIMEDOUT;
+		} else {
+			usleep_range(CC2_RESP_START_CM_US,
+				     2 * CC2_RESP_START_CM_US);
+		}
+		ret = cc2_read_command_status(data->client);
+		if (ret != -ETIMEDOUT || i == CC2_CM_RETRIES)
+			break;
+
+		/* command window missed, prepare for a retry */
+		cc2_disable(data);
+		msleep(CC2_POWER_CYCLE_MS);
+	}
+
+	return ret;
+}
+
+/* Sending a Start_NOM command finishes the command mode immediately with no
+ * reply and the device enters normal operation mode
+ */
+static int cc2_command_mode_finish(struct cc2_data *data)
+{
+	int ret;
+
+	ret = i2c_smbus_write_word_data(data->client, CC2_START_NOM, 0);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+
+static int cc2_write_reg(struct cc2_data *data, u8 reg, u16 val)
+{
+	unsigned long timeout;
+	int ret;
+
+	ret = cc2_command_mode_start(data);
+	if (ret < 0)
+		goto disable;
+
+	cpu_to_be16s(&val);
+	ret = i2c_smbus_write_word_data(data->client, reg, val);
+	if (ret < 0)
+		goto disable;
+
+	if (data->irq_ready > 0) {
+		timeout = msecs_to_jiffies(2 * CC2_RESP_EEPROM_W_MS);
+		ret = wait_for_completion_timeout(&data->complete, timeout);
+		if (!ret) {
+			ret = -ETIMEDOUT;
+			goto disable;
+		}
+	} else {
+		msleep(CC2_RESP_EEPROM_W_MS);
+	}
+
+	ret = cc2_read_command_status(data->client);
+
+disable:
+	cc2_disable(data);
+
+	return ret;
+}
+
+static int cc2_read_reg(struct cc2_data *data, u8 reg, u16 *val)
+{
+	u8 buf[CC2_EEPROM_DATA_LEN];
+	unsigned long timeout;
+	int ret;
+
+	ret = cc2_command_mode_start(data);
+	if (ret < 0)
+		return ret;
+
+	ret = i2c_smbus_write_word_data(data->client, reg, 0);
+	if (ret < 0)
+		return ret;
+
+	if (data->irq_ready > 0) {
+		timeout = usecs_to_jiffies(2 * CC2_RESP_EEPROM_R_US);
+		ret = wait_for_completion_timeout(&data->complete, timeout);
+		if (!ret)
+			return -ETIMEDOUT;
+
+	} else {
+		usleep_range(CC2_RESP_EEPROM_R_US, CC2_RESP_EEPROM_R_US + 10);
+	}
+	ret = i2c_master_recv(data->client, buf, CC2_EEPROM_DATA_LEN);
+	if (ret != CC2_EEPROM_DATA_LEN)
+		return ret < 0 ? ret : -EIO;
+
+	*val = be16_to_cpup((__be16 *)&buf[1]);
+
+	return cc2_read_command_status(data->client);
+}
+
+static int cc2_get_reg_val(struct cc2_data *data, u8 reg, long *val)
+{
+	u16 reg_val;
+	int ret;
+
+	ret = cc2_read_reg(data, reg, &reg_val);
+	*val = cc2_rh_convert(reg_val);
+	cc2_disable(data);
+
+	return ret;
+}
+
+static int cc2_data_fetch(struct i2c_client *client,
+			  enum hwmon_sensor_types type, long *val)
+{
+	u8 data[CC2_MEASUREMENT_DATA_LEN];
+	u8 status;
+	int ret;
+
+	ret = i2c_master_recv(client, data, CC2_MEASUREMENT_DATA_LEN);
+	if (ret != CC2_MEASUREMENT_DATA_LEN) {
+		ret = ret < 0 ? ret : -EIO;
+		return ret;
+	}
+	status = FIELD_GET(CC2_STATUS_FIELD, data[0]);
+	if (status == CC2_STATUS_STALE_DATA)
+		return -EBUSY;
+
+	if (status != CC2_STATUS_VALID_DATA)
+		return -EIO;
+
+	switch (type) {
+	case hwmon_humidity:
+		*val = cc2_rh_convert(be16_to_cpup((__be16 *)&data[0]));
+		break;
+	case hwmon_temp:
+		*val = cc2_temp_convert(be16_to_cpup((__be16 *)&data[2]));
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int cc2_read_measurement(struct cc2_data *data,
+				enum hwmon_sensor_types type, long *val)
+{
+	unsigned long timeout;
+	int ret;
+
+	if (data->irq_ready > 0) {
+		timeout = msecs_to_jiffies(CC2_STARTUP_TO_DATA_MS * 2);
+		ret = wait_for_completion_timeout(&data->complete, timeout);
+		if (!ret)
+			return -ETIMEDOUT;
+
+	} else {
+		msleep(CC2_STARTUP_TO_DATA_MS);
+	}
+
+	ret = cc2_data_fetch(data->client, type, val);
+
+	return ret;
+}
+
+/*
+ * A measurement requires enabling the device, waiting for the automatic
+ * measurement to finish, reading the measurement data and disabling the device
+ * again.
+ */
+static int cc2_measurement(struct cc2_data *data, enum hwmon_sensor_types type,
+			   long *val)
+{
+	int ret;
+
+	ret = cc2_enable(data);
+	if (ret)
+		return ret;
+
+	ret = cc2_read_measurement(data, type, val);
+
+	cc2_disable(data);
+
+	return ret;
+}
+
+/*
+ * In order to check alarm status, the corresponding ALARM_OFF (hysteresis)
+ * register must be read and a new measurement must be carried out to trigger
+ * the alarm signals. Given that the device carries out a measurement after
+ * exiting the command mode, there is no need to force two power-up sequences.
+ * Instead, a NOM command is sent and the device is disabled after the
+ * measurement is read.
+ */
+static int cc2_read_hyst_and_measure(struct cc2_data *data, u8 reg,
+				     long *hyst, long *measurement)
+{
+	u16 reg_val;
+	int ret;
+
+	ret = cc2_read_reg(data, reg, &reg_val);
+	if (ret)
+		goto disable;
+
+	*hyst = cc2_rh_convert(reg_val);
+
+	ret = cc2_command_mode_finish(data);
+	if (ret)
+		goto disable;
+
+	ret = cc2_read_measurement(data, hwmon_humidity, measurement);
+
+disable:
+	cc2_disable(data);
+
+	return ret;
+}
+
+static umode_t cc2_is_visible(const void *data, enum hwmon_sensor_types type,
+			      u32 attr, int channel)
+{
+	const struct cc2_data *cc2 = data;
+
+	switch (type) {
+	case hwmon_humidity:
+		switch (attr) {
+		case hwmon_humidity_input:
+			return 0444;
+		case hwmon_humidity_min_alarm:
+			return cc2->rh_alarm.low_alarm_visible ? 0444 : 0;
+		case hwmon_humidity_max_alarm:
+			return cc2->rh_alarm.high_alarm_visible ? 0444 : 0;
+		case hwmon_humidity_min:
+		case hwmon_humidity_min_hyst:
+			return cc2->rh_alarm.low_alarm_visible ? 0644 : 0;
+		case hwmon_humidity_max:
+		case hwmon_humidity_max_hyst:
+			return cc2->rh_alarm.high_alarm_visible ? 0644 : 0;
+		default:
+			return 0;
+		}
+	case hwmon_temp:
+		switch (attr) {
+		case hwmon_temp_input:
+			return 0444;
+		default:
+			return 0;
+		}
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+static irqreturn_t cc2_ready_interrupt(int irq, void *data)
+{
+	struct cc2_data *cc2 = data;
+
+	mutex_lock(&cc2->alarm_lock);
+	if (!cc2->ignore_irqs)
+		complete(&cc2->complete);
+	mutex_unlock(&cc2->alarm_lock);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t cc2_low_interrupt(int irq, void *data)
+{
+	struct cc2_data *cc2 = data;
+
+	mutex_lock(&cc2->alarm_lock);
+	if (!cc2->ignore_irqs) {
+		hwmon_notify_event(cc2->hwmon, hwmon_humidity,
+				   hwmon_humidity_min_alarm, CC2_CHAN_HUMIDITY);
+		cc2->rh_alarm.low_alarm = true;
+	}
+	mutex_unlock(&cc2->alarm_lock);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t cc2_high_interrupt(int irq, void *data)
+{
+	struct cc2_data *cc2 = data;
+
+	mutex_lock(&cc2->alarm_lock);
+	if (!cc2->ignore_irqs) {
+		hwmon_notify_event(cc2->hwmon, hwmon_humidity,
+				   hwmon_humidity_max_alarm, CC2_CHAN_HUMIDITY);
+		cc2->rh_alarm.high_alarm = true;
+	}
+	mutex_unlock(&cc2->alarm_lock);
+
+	return IRQ_HANDLED;
+}
+
+static int cc2_humidity_min_alarm_status(struct cc2_data *data, long *val)
+{
+	long measurement, min_hyst;
+	int ret;
+
+	ret = cc2_read_hyst_and_measure(data, CC2_R_ALARM_L_OFF, &min_hyst,
+					&measurement);
+	if (ret < 0)
+		return ret;
+
+	if (data->rh_alarm.low_alarm) {
+		*val = (measurement < min_hyst) ? 1 : 0;
+		data->rh_alarm.low_alarm = *val;
+	} else {
+		*val = 0;
+	}
+
+	return 0;
+}
+
+static int cc2_humidity_max_alarm_status(struct cc2_data *data, long *val)
+{
+	long measurement, max_hyst;
+	int ret;
+
+	ret = cc2_read_hyst_and_measure(data, CC2_R_ALARM_H_OFF, &max_hyst,
+					&measurement);
+	if (ret < 0)
+		return ret;
+
+	if (data->rh_alarm.high_alarm) {
+		*val = (measurement > max_hyst) ? 1 : 0;
+		data->rh_alarm.high_alarm = *val;
+	} else {
+		*val = 0;
+	}
+
+	return 0;
+}
+
+static int cc2_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
+		    int channel, long *val)
+{
+	struct cc2_data *data = dev_get_drvdata(dev);
+	int ret = 0;
+
+	mutex_lock(&data->dev_access_lock);
+
+	switch (type) {
+	case hwmon_temp:
+		ret = cc2_measurement(data, type, val);
+		break;
+	case hwmon_humidity:
+		switch (attr) {
+		case hwmon_humidity_input:
+			ret = cc2_measurement(data, type, val);
+			break;
+		case hwmon_humidity_min:
+			ret = cc2_get_reg_val(data, CC2_R_ALARM_L_ON, val);
+			break;
+		case hwmon_humidity_min_hyst:
+			ret = cc2_get_reg_val(data, CC2_R_ALARM_L_OFF, val);
+			break;
+		case hwmon_humidity_max:
+			ret = cc2_get_reg_val(data, CC2_R_ALARM_H_ON, val);
+			break;
+		case hwmon_humidity_max_hyst:
+			ret = cc2_get_reg_val(data, CC2_R_ALARM_H_OFF, val);
+			break;
+		case hwmon_humidity_min_alarm:
+			ret = cc2_humidity_min_alarm_status(data, val);
+			break;
+		case hwmon_humidity_max_alarm:
+			ret = cc2_humidity_max_alarm_status(data, val);
+			break;
+		default:
+			ret = -EOPNOTSUPP;
+		}
+		break;
+	default:
+		ret = -EOPNOTSUPP;
+	}
+
+	mutex_unlock(&data->dev_access_lock);
+
+	return ret;
+}
+
+static int cc2_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
+		     int channel, long val)
+{
+	struct cc2_data *data = dev_get_drvdata(dev);
+	int ret;
+	u16 arg;
+	u8 cmd;
+
+	if (type != hwmon_humidity)
+		return -EOPNOTSUPP;
+
+	if (val < 0 || val > CC2_RH_MAX)
+		return -EINVAL;
+
+	mutex_lock(&data->dev_access_lock);
+
+	switch (attr) {
+	case hwmon_humidity_min:
+		cmd = CC2_W_ALARM_L_ON;
+		arg = cc2_rh_to_reg(val);
+		ret = cc2_write_reg(data, cmd, arg);
+		break;
+
+	case hwmon_humidity_min_hyst:
+		cmd = CC2_W_ALARM_L_OFF;
+		arg = cc2_rh_to_reg(val);
+		ret = cc2_write_reg(data, cmd, arg);
+		break;
+
+	case hwmon_humidity_max:
+		cmd = CC2_W_ALARM_H_ON;
+		arg = cc2_rh_to_reg(val);
+		ret = cc2_write_reg(data, cmd, arg);
+		break;
+
+	case hwmon_humidity_max_hyst:
+		cmd = CC2_W_ALARM_H_OFF;
+		arg = cc2_rh_to_reg(val);
+		ret = cc2_write_reg(data, cmd, arg);
+		break;
+
+	default:
+		ret = -EOPNOTSUPP;
+		break;
+	}
+
+	mutex_unlock(&data->dev_access_lock);
+
+	return ret;
+}
+
+static int cc2_request_ready_irq(struct cc2_data *data, struct device *dev)
+{
+	int ret = 0;
+
+	data->irq_ready = fwnode_irq_get_byname(dev_fwnode(dev), "ready");
+	if (data->irq_ready > 0) {
+		init_completion(&data->complete);
+		ret = devm_request_threaded_irq(dev, data->irq_ready, NULL,
+						cc2_ready_interrupt,
+						IRQF_ONESHOT |
+						IRQF_TRIGGER_RISING,
+						dev_name(dev), data);
+	}
+
+	return ret;
+}
+
+static int cc2_request_alarm_irqs(struct cc2_data *data, struct device *dev)
+{
+	int ret;
+
+	data->irq_low = fwnode_irq_get_byname(dev_fwnode(dev), "low");
+	if (data->irq_low > 0) {
+		ret = devm_request_threaded_irq(dev, data->irq_low, NULL,
+						cc2_low_interrupt,
+						IRQF_ONESHOT |
+						IRQF_TRIGGER_RISING,
+						dev_name(dev), data);
+		if (!ret)
+			data->rh_alarm.low_alarm_visible = true;
+	}
+
+	data->irq_high = fwnode_irq_get_byname(dev_fwnode(dev), "high");
+	if (data->irq_high > 0) {
+		ret = devm_request_threaded_irq(dev, data->irq_high, NULL,
+						cc2_high_interrupt,
+						IRQF_ONESHOT |
+						IRQF_TRIGGER_RISING,
+						dev_name(dev), data);
+		if (!ret)
+			data->rh_alarm.high_alarm_visible = true;
+	}
+
+	return ret;
+}
+
+static const struct hwmon_channel_info *cc2_info[] = {
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT | HWMON_H_MIN | HWMON_H_MAX |
+			   HWMON_H_MIN_HYST | HWMON_H_MAX_HYST |
+			   HWMON_H_MIN_ALARM | HWMON_H_MAX_ALARM),
+	NULL
+};
+
+static const struct hwmon_ops cc2_hwmon_ops = {
+	.is_visible = cc2_is_visible,
+	.read = cc2_read,
+	.write = cc2_write,
+};
+
+static const struct hwmon_chip_info cc2_chip_info = {
+	.ops = &cc2_hwmon_ops,
+	.info = cc2_info,
+};
+
+static int cc2_probe(struct i2c_client *client)
+{
+	struct cc2_data *data;
+	struct device *dev = &client->dev;
+	int ret;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+		return -EOPNOTSUPP;
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, data);
+
+	mutex_init(&data->dev_access_lock);
+	mutex_init(&data->alarm_lock);
+
+	data->client = client;
+
+	data->regulator = devm_regulator_get_exclusive(dev, "vdd");
+	if (IS_ERR(data->regulator)) {
+		dev_err_probe(dev, PTR_ERR(data->regulator),
+			      "Failed to get regulator\n");
+		return PTR_ERR(data->regulator);
+	}
+
+	ret = cc2_request_ready_irq(data, dev);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to request ready irq\n");
+		return ret;
+	}
+
+	ret = cc2_request_alarm_irqs(data, dev);
+	if (ret) {
+		dev_err_probe(dev, ret, "Failed to request alarm irqs\n");
+		goto disable;
+	}
+
+	data->hwmon = devm_hwmon_device_register_with_info(dev, client->name,
+							   data, &cc2_chip_info,
+							   NULL);
+	if (IS_ERR(data->hwmon)) {
+		dev_err_probe(dev, PTR_ERR(data->hwmon),
+			      "Failed to register hwmon device\n");
+		ret = PTR_ERR(data->hwmon);
+	}
+
+disable:
+	cc2_disable(data);
+
+	return ret;
+}
+
+static void cc2_remove(struct i2c_client *client)
+{
+	struct cc2_data *data = i2c_get_clientdata(client);
+
+	cc2_disable(data);
+}
+
+static const struct i2c_device_id cc2_id[] = {
+	{ "cc2d23" },
+	{ "cc2d23s" },
+	{ "cc2d25" },
+	{ "cc2d25s" },
+	{ "cc2d33" },
+	{ "cc2d33s" },
+	{ "cc2d35" },
+	{ "cc2d35s" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, cc2_id);
+
+static const struct of_device_id cc2_of_match[] = {
+	{ .compatible = "amphenol,cc2d23" },
+	{ .compatible = "amphenol,cc2d23s" },
+	{ .compatible = "amphenol,cc2d25" },
+	{ .compatible = "amphenol,cc2d25s" },
+	{ .compatible = "amphenol,cc2d33" },
+	{ .compatible = "amphenol,cc2d33s" },
+	{ .compatible = "amphenol,cc2d35" },
+	{ .compatible = "amphenol,cc2d35s" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, cc2_of_match);
+
+static struct i2c_driver cc2_driver = {
+	.driver = {
+		.name	= "cc2d23",
+		.of_match_table = cc2_of_match,
+	},
+	.probe		= cc2_probe,
+	.remove		= cc2_remove,
+	.id_table = cc2_id,
+};
+module_i2c_driver(cc2_driver);
+
+MODULE_AUTHOR("Javier Carrasco <javier.carrasco.cruz@...il.com>");
+MODULE_DESCRIPTION("Amphenol ChipCap 2 humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");

-- 
2.39.2

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