iio:pressure: initial zpa2326 barometer support

Introduce driver for Murata ZPA2326 pressure and temperature sensor:
http://www.murata.com/en-us/products/productdetail?partno=ZPA2326-0311A-R

Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 1735 insertions, 0 deletions

diff --git a/drivers/iio/pressure/zpa2326.c b/drivers/iio/pressure/zpa2326.c
new file mode 100644
index 000000000000..19d2eb46fda6
--- /dev/null
+++ b/drivers/iio/pressure/zpa2326.c
@@ -0,0 +1,1735 @@
+/*
+ * Murata ZPA2326 pressure and temperature sensor IIO driver
+ *
+ * Copyright (c) 2016 Parrot S.A.
+ *
+ * Author: Gregor Boirie <gregor.boirie@parrot.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+/**
+ * DOC: ZPA2326 theory of operations
+ *
+ * This driver supports %INDIO_DIRECT_MODE and %INDIO_BUFFER_TRIGGERED IIO
+ * modes.
+ * A internal hardware trigger is also implemented to dispatch registered IIO
+ * trigger consumers upon "sample ready" interrupts.
+ *
+ * ZPA2326 hardware supports 2 sampling mode: one shot and continuous.
+ *
+ * A complete one shot sampling cycle gets device out of low power mode,
+ * performs pressure and temperature measurements, then automatically switches
+ * back to low power mode. It is meant for on demand sampling with optimal power
+ * saving at the cost of lower sampling rate and higher software overhead.
+ * This is a natural candidate for IIO read_raw hook implementation
+ * (%INDIO_DIRECT_MODE). It is also used for triggered buffering support to
+ * ensure explicit synchronization with external trigger events
+ * (%INDIO_BUFFER_TRIGGERED).
+ *
+ * The continuous mode works according to a periodic hardware measurement
+ * process continuously pushing samples into an internal hardware FIFO (for
+ * pressure samples only). Measurement cycle completion may be signaled by a
+ * "sample ready" interrupt.
+ * Typical software sequence of operations :
+ * - get device out of low power mode,
+ * - setup hardware sampling period,
+ * - at end of period, upon data ready interrupt: pop pressure samples out of
+ *   hardware FIFO and fetch temperature sample
+ * - when no longer needed, stop sampling process by putting device into
+ *   low power mode.
+ * This mode is used to implement %INDIO_BUFFER_TRIGGERED mode if device tree
+ * declares a valid interrupt line. In this case, the internal hardware trigger
+ * drives acquisition.
+ *
+ * Note that hardware sampling frequency is taken into account only when
+ * internal hardware trigger is attached as the highest sampling rate seems to
+ * be the most energy efficient.
+ *
+ * TODO:
+ *   preset pressure threshold crossing / IIO events ;
+ *   differential pressure sampling ;
+ *   hardware samples averaging.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/regulator/consumer.h>
+#include <linux/pm_runtime.h>
+#include <linux/regmap.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/trigger.h>
+#include <linux/iio/trigger_consumer.h>
+#include <linux/iio/triggered_buffer.h>
+#include "zpa2326.h"
+
+/* 200 ms should be enough for the longest conversion time in one-shot mode. */
+#define ZPA2326_CONVERSION_JIFFIES (HZ / 5)
+
+/* There should be a 1 ms delay (Tpup) after getting out of reset. */
+#define ZPA2326_TPUP_USEC_MIN      (1000)
+#define ZPA2326_TPUP_USEC_MAX      (2000)
+
+/**
+ * struct zpa2326_frequency - Hardware sampling frequency descriptor
+ * @hz : Frequency in Hertz.
+ * @odr: Output Data Rate word as expected by %ZPA2326_CTRL_REG3_REG.
+ */
+struct zpa2326_frequency {
+	int hz;
+	u16 odr;
+};
+
+/*
+ * Keep these in strict ascending order: last array entry is expected to
+ * correspond to the highest sampling frequency.
+ */
+static const struct zpa2326_frequency zpa2326_sampling_frequencies[] = {
+	{ .hz = 1,  .odr = 1 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+	{ .hz = 5,  .odr = 5 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+	{ .hz = 11, .odr = 6 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+	{ .hz = 23, .odr = 7 << ZPA2326_CTRL_REG3_ODR_SHIFT },
+};
+
+/* Return the highest hardware sampling frequency available. */
+static const struct zpa2326_frequency *zpa2326_highest_frequency(void)
+{
+	return &zpa2326_sampling_frequencies[
+		ARRAY_SIZE(zpa2326_sampling_frequencies) - 1];
+}
+
+/**
+ * struct zpa_private - Per-device internal private state
+ * @timestamp:  Buffered samples ready datum.
+ * @regmap:     Underlying I2C / SPI bus adapter used to abstract slave register
+ *              accesses.
+ * @result:     Allows sampling logic to get completion status of operations
+ *              that interrupt handlers perform asynchronously.
+ * @data_ready: Interrupt handler uses this to wake user context up at sampling
+ *              operation completion.
+ * @trigger:    Optional hardware / interrupt driven trigger used to notify
+ *              external devices a new sample is ready.
+ * @waken:      Flag indicating whether or not device has just been powered on.
+ * @irq:        Optional interrupt line: negative or zero if not declared into
+ *              DT, in which case sampling logic keeps polling status register
+ *              to detect completion.
+ * @frequency:  Current hardware sampling frequency.
+ * @vref:       Power / voltage reference.
+ * @vdd:        Power supply.
+ */
+struct zpa2326_private {
+	s64                             timestamp;
+	struct regmap                  *regmap;
+	int                             result;
+	struct completion               data_ready;
+	struct iio_trigger             *trigger;
+	bool                            waken;
+	int                             irq;
+	const struct zpa2326_frequency *frequency;
+	struct regulator               *vref;
+	struct regulator               *vdd;
+};
+
+#define zpa2326_err(_idev, _format, _arg...) \
+	dev_err(_idev->dev.parent, _format, ##_arg)
+
+#define zpa2326_warn(_idev, _format, _arg...) \
+	dev_warn(_idev->dev.parent, _format, ##_arg)
+
+#ifdef DEBUG
+#define zpa2326_dbg(_idev, _format, _arg...) \
+	dev_dbg(_idev->dev.parent, _format, ##_arg)
+#else
+#define zpa2326_dbg(_idev, _format, _arg...)
+#endif
+
+bool zpa2326_isreg_writeable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case ZPA2326_REF_P_XL_REG:
+	case ZPA2326_REF_P_L_REG:
+	case ZPA2326_REF_P_H_REG:
+	case ZPA2326_RES_CONF_REG:
+	case ZPA2326_CTRL_REG0_REG:
+	case ZPA2326_CTRL_REG1_REG:
+	case ZPA2326_CTRL_REG2_REG:
+	case ZPA2326_CTRL_REG3_REG:
+	case ZPA2326_THS_P_LOW_REG:
+	case ZPA2326_THS_P_HIGH_REG:
+		return true;
+
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(zpa2326_isreg_writeable);
+
+bool zpa2326_isreg_readable(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case ZPA2326_REF_P_XL_REG:
+	case ZPA2326_REF_P_L_REG:
+	case ZPA2326_REF_P_H_REG:
+	case ZPA2326_DEVICE_ID_REG:
+	case ZPA2326_RES_CONF_REG:
+	case ZPA2326_CTRL_REG0_REG:
+	case ZPA2326_CTRL_REG1_REG:
+	case ZPA2326_CTRL_REG2_REG:
+	case ZPA2326_CTRL_REG3_REG:
+	case ZPA2326_INT_SOURCE_REG:
+	case ZPA2326_THS_P_LOW_REG:
+	case ZPA2326_THS_P_HIGH_REG:
+	case ZPA2326_STATUS_REG:
+	case ZPA2326_PRESS_OUT_XL_REG:
+	case ZPA2326_PRESS_OUT_L_REG:
+	case ZPA2326_PRESS_OUT_H_REG:
+	case ZPA2326_TEMP_OUT_L_REG:
+	case ZPA2326_TEMP_OUT_H_REG:
+		return true;
+
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(zpa2326_isreg_readable);
+
+bool zpa2326_isreg_precious(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case ZPA2326_INT_SOURCE_REG:
+	case ZPA2326_PRESS_OUT_H_REG:
+		return true;
+
+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL_GPL(zpa2326_isreg_precious);
+
+/**
+ * zpa2326_enable_device() - Enable device, i.e. get out of low power mode.
+ * @indio_dev: The IIO device associated with the hardware to enable.
+ *
+ * Required to access complete register space and to perform any sampling
+ * or control operations.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_enable_device(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG0_REG, ZPA2326_CTRL_REG0_ENABLE);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to enable device (%d)", err);
+		return err;
+	}
+
+	zpa2326_dbg(indio_dev, "enabled");
+
+	return 0;
+}
+
+/**
+ * zpa2326_sleep() - Disable device, i.e. switch to low power mode.
+ * @indio_dev: The IIO device associated with the hardware to disable.
+ *
+ * Only %ZPA2326_DEVICE_ID_REG and %ZPA2326_CTRL_REG0_REG registers may be
+ * accessed once device is in the disabled state.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_sleep(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG0_REG, 0);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to sleep (%d)", err);
+		return err;
+	}
+
+	zpa2326_dbg(indio_dev, "sleeping");
+
+	return 0;
+}
+
+/**
+ * zpa2326_reset_device() - Reset device to default hardware state.
+ * @indio_dev: The IIO device associated with the hardware to reset.
+ *
+ * Disable sampling and empty hardware FIFO.
+ * Device must be enabled before reset, i.e. not in low power mode.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_reset_device(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG2_REG, ZPA2326_CTRL_REG2_SWRESET);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to reset device (%d)", err);
+		return err;
+	}
+
+	usleep_range(ZPA2326_TPUP_USEC_MIN, ZPA2326_TPUP_USEC_MAX);
+
+	zpa2326_dbg(indio_dev, "reset");
+
+	return 0;
+}
+
+/**
+ * zpa2326_start_oneshot() - Start a single sampling cycle, i.e. in one shot
+ *                           mode.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Device must have been previously enabled and configured for one shot mode.
+ * Device will be switched back to low power mode at end of cycle.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_start_oneshot(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = regmap_write(((struct zpa2326_private *)
+			    iio_priv(indio_dev))->regmap,
+			    ZPA2326_CTRL_REG0_REG,
+			    ZPA2326_CTRL_REG0_ENABLE |
+			    ZPA2326_CTRL_REG0_ONE_SHOT);
+	if (err) {
+		zpa2326_err(indio_dev, "failed to start one shot cycle (%d)",
+			    err);
+		return err;
+	}
+
+	zpa2326_dbg(indio_dev, "one shot cycle started");
+
+	return 0;
+}
+
+/**
+ * zpa2326_power_on() - Power on device to allow subsequent configuration.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ *
+ * Sampling will be disabled, preventing strange things from happening in our
+ * back. Hardware FIFO content will be cleared.
+ * When successful, device will be left in the enabled state to allow further
+ * configuration.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_power_on(const struct iio_dev         *indio_dev,
+			    const struct zpa2326_private *private)
+{
+	int err;
+
+	err = regulator_enable(private->vref);
+	if (err)
+		return err;
+
+	err = regulator_enable(private->vdd);
+	if (err)
+		goto vref;
+
+	zpa2326_dbg(indio_dev, "powered on");
+
+	err = zpa2326_enable_device(indio_dev);
+	if (err)
+		goto vdd;
+
+	err = zpa2326_reset_device(indio_dev);
+	if (err)
+		goto sleep;
+
+	return 0;
+
+sleep:
+	zpa2326_sleep(indio_dev);
+vdd:
+	regulator_disable(private->vdd);
+vref:
+	regulator_disable(private->vref);
+
+	zpa2326_dbg(indio_dev, "powered off");
+
+	return err;
+}
+
+/**
+ * zpa2326_power_off() - Power off device, i.e. disable attached power
+ *                       regulators.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static void zpa2326_power_off(const struct iio_dev         *indio_dev,
+			      const struct zpa2326_private *private)
+{
+	regulator_disable(private->vdd);
+	regulator_disable(private->vref);
+
+	zpa2326_dbg(indio_dev, "powered off");
+}
+
+/**
+ * zpa2326_config_oneshot() - Setup device for one shot / on demand mode.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @irq:       Optional interrupt line the hardware uses to notify new data
+ *             samples are ready. Negative or zero values indicate no interrupts
+ *             are available, meaning polling is required.
+ *
+ * Output Data Rate is configured for the highest possible rate so that
+ * conversion time and power consumption are reduced to a minimum.
+ * Note that hardware internal averaging machinery (not implemented in this
+ * driver) is not applicable in this mode.
+ *
+ * Device must have been previously enabled before calling
+ * zpa2326_config_oneshot().
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_config_oneshot(const struct iio_dev *indio_dev,
+				  int                   irq)
+{
+	struct regmap                  *regs = ((struct zpa2326_private *)
+						iio_priv(indio_dev))->regmap;
+	const struct zpa2326_frequency *freq = zpa2326_highest_frequency();
+	int                             err;
+
+	/* Setup highest available Output Data Rate for one shot mode. */
+	err = regmap_write(regs, ZPA2326_CTRL_REG3_REG, freq->odr);
+	if (err)
+		return err;
+
+	if (irq > 0) {
+		/* Request interrupt when new sample is available. */
+		err = regmap_write(regs, ZPA2326_CTRL_REG1_REG,
+				   (u8)~ZPA2326_CTRL_REG1_MASK_DATA_READY);
+
+		if (err) {
+			dev_err(indio_dev->dev.parent,
+				"failed to setup one shot mode (%d)", err);
+			return err;
+		}
+	}
+
+	zpa2326_dbg(indio_dev, "one shot mode setup @%dHz", freq->hz);
+
+	return 0;
+}
+
+/**
+ * zpa2326_clear_fifo() - Clear remaining entries in hardware FIFO.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @min_count: Number of samples present within hardware FIFO.
+ *
+ * @min_count argument is a hint corresponding to the known minimum number of
+ * samples currently living in the FIFO. This allows to reduce the number of bus
+ * accesses by skipping status register read operation as long as we know for
+ * sure there are still entries left.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_clear_fifo(const struct iio_dev *indio_dev,
+			      unsigned int          min_count)
+{
+	struct regmap *regs = ((struct zpa2326_private *)
+			       iio_priv(indio_dev))->regmap;
+	int            err;
+	unsigned int   val;
+
+	if (!min_count) {
+		/*
+		 * No hint: read status register to determine whether FIFO is
+		 * empty or not.
+		 */
+		err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+
+		if (err < 0)
+			goto err;
+
+		if (val & ZPA2326_STATUS_FIFO_E)
+			/* Fifo is empty: nothing to trash. */
+			return 0;
+	}
+
+	/* Clear FIFO. */
+	do {
+		/*
+		 * A single fetch from pressure MSB register is enough to pop
+		 * values out of FIFO.
+		 */
+		err = regmap_read(regs, ZPA2326_PRESS_OUT_H_REG, &val);
+		if (err < 0)
+			goto err;
+
+		if (min_count) {
+			/*
+			 * We know for sure there are at least min_count entries
+			 * left in FIFO. Skip status register read.
+			 */
+			min_count--;
+			continue;
+		}
+
+		err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+		if (err < 0)
+			goto err;
+
+	} while (!(val & ZPA2326_STATUS_FIFO_E));
+
+	zpa2326_dbg(indio_dev, "FIFO cleared");
+
+	return 0;
+
+err:
+	zpa2326_err(indio_dev, "failed to clear FIFO (%d)", err);
+
+	return err;
+}
+
+/**
+ * zpa2326_dequeue_pressure() - Retrieve the most recent pressure sample from
+ *                              hardware FIFO.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @pressure:  Sampled pressure output.
+ *
+ * Note that ZPA2326 hardware FIFO stores pressure samples only.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_dequeue_pressure(const struct iio_dev *indio_dev,
+				    u32                  *pressure)
+{
+	struct regmap *regs = ((struct zpa2326_private *)
+			       iio_priv(indio_dev))->regmap;
+	unsigned int   val;
+	int            err;
+	int            cleared = -1;
+
+	err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+	if (err < 0)
+		return err;
+
+	*pressure = 0;
+
+	if (val & ZPA2326_STATUS_P_OR) {
+		/*
+		 * Fifo overrun : first sample dequeued from FIFO is the
+		 * newest.
+		 */
+		zpa2326_warn(indio_dev, "FIFO overflow");
+
+		err = regmap_bulk_read(regs, ZPA2326_PRESS_OUT_XL_REG, pressure,
+				       3);
+		if (err)
+			return err;
+
+#define ZPA2326_FIFO_DEPTH (16U)
+		/* Hardware FIFO may hold no more than 16 pressure samples. */
+		return zpa2326_clear_fifo(indio_dev, ZPA2326_FIFO_DEPTH - 1);
+	}
+
+	/*
+	 * Fifo has not overflown : retrieve newest sample. We need to pop
+	 * values out until FIFO is empty : last fetched pressure is the newest.
+	 * In nominal cases, we should find a single queued sample only.
+	 */
+	do {
+		err = regmap_bulk_read(regs, ZPA2326_PRESS_OUT_XL_REG, pressure,
+				       3);
+		if (err)
+			return err;
+
+		err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+		if (err < 0)
+			return err;
+
+		cleared++;
+	} while (!(val & ZPA2326_STATUS_FIFO_E));
+
+	if (cleared)
+		/*
+		 * Samples were pushed by hardware during previous rounds but we
+		 * didn't consume them fast enough: inform user.
+		 */
+		zpa2326_dbg(indio_dev, "cleared %d FIFO entries", cleared);
+
+	return 0;
+}
+
+/**
+ * zpa2326_fill_sample_buffer() - Enqueue new channel samples to IIO buffer.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_fill_sample_buffer(struct iio_dev               *indio_dev,
+				      const struct zpa2326_private *private)
+{
+	struct {
+		u32 pressure;
+		u16 temperature;
+		u64 timestamp;
+	}   sample;
+	int err;
+
+	if (test_bit(0, indio_dev->active_scan_mask)) {
+		/* Get current pressure from hardware FIFO. */
+		err = zpa2326_dequeue_pressure(indio_dev, &sample.pressure);
+		if (err) {
+			zpa2326_warn(indio_dev, "failed to fetch pressure (%d)",
+				     err);
+			return err;
+		}
+	}
+
+	if (test_bit(1, indio_dev->active_scan_mask)) {
+		/* Get current temperature. */
+		err = regmap_bulk_read(private->regmap, ZPA2326_TEMP_OUT_L_REG,
+				       &sample.temperature, 2);
+		if (err) {
+			zpa2326_warn(indio_dev,
+				     "failed to fetch temperature (%d)", err);
+			return err;
+		}
+	}
+
+	/*
+	 * Now push samples using timestamp stored either :
+	 *   - by hardware interrupt handler if interrupt is available: see
+	 *     zpa2326_handle_irq(),
+	 *   - or oneshot completion polling machinery : see
+	 *     zpa2326_trigger_handler().
+	 */
+	zpa2326_dbg(indio_dev, "filling raw samples buffer");
+
+	iio_push_to_buffers_with_timestamp(indio_dev, &sample,
+					   private->timestamp);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int zpa2326_runtime_suspend(struct device *parent)
+{
+	const struct iio_dev *indio_dev = dev_get_drvdata(parent);
+
+	if (pm_runtime_autosuspend_expiration(parent))
+		/* Userspace changed autosuspend delay. */
+		return -EAGAIN;
+
+	zpa2326_power_off(indio_dev, iio_priv(indio_dev));
+
+	return 0;
+}
+
+static int zpa2326_runtime_resume(struct device *parent)
+{
+	const struct iio_dev *indio_dev = dev_get_drvdata(parent);
+
+	return zpa2326_power_on(indio_dev, iio_priv(indio_dev));
+}
+
+const struct dev_pm_ops zpa2326_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+	SET_RUNTIME_PM_OPS(zpa2326_runtime_suspend, zpa2326_runtime_resume,
+			   NULL)
+};
+EXPORT_SYMBOL_GPL(zpa2326_pm_ops);
+
+/**
+ * zpa2326_resume() - Request the PM layer to power supply the device.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Return:
+ *  < 0 - a negative error code meaning failure ;
+ *    0 - success, device has just been powered up ;
+ *    1 - success, device was already powered.
+ */
+static int zpa2326_resume(const struct iio_dev *indio_dev)
+{
+	int err;
+
+	err = pm_runtime_get_sync(indio_dev->dev.parent);
+	if (err < 0)
+		return err;
+
+	if (err > 0) {
+		/*
+		 * Device was already power supplied: get it out of low power
+		 * mode and inform caller.
+		 */
+		zpa2326_enable_device(indio_dev);
+		return 1;
+	}
+
+	/* Inform caller device has just been brought back to life. */
+	return 0;
+}
+
+/**
+ * zpa2326_suspend() - Schedule a power down using autosuspend feature of PM
+ *                     layer.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Device is switched to low power mode at first to save power even when
+ * attached regulator is a "dummy" one.
+ */
+static void zpa2326_suspend(struct iio_dev *indio_dev)
+{
+	struct device *parent = indio_dev->dev.parent;
+
+	zpa2326_sleep(indio_dev);
+
+	pm_runtime_mark_last_busy(parent);
+	pm_runtime_put_autosuspend(parent);
+}
+
+static void zpa2326_init_runtime(struct device *parent)
+{
+	pm_runtime_get_noresume(parent);
+	pm_runtime_set_active(parent);
+	pm_runtime_enable(parent);
+	pm_runtime_set_autosuspend_delay(parent, 1000);
+	pm_runtime_use_autosuspend(parent);
+	pm_runtime_mark_last_busy(parent);
+	pm_runtime_put_autosuspend(parent);
+}
+
+static void zpa2326_fini_runtime(struct device *parent)
+{
+	pm_runtime_disable(parent);
+	pm_runtime_set_suspended(parent);
+}
+#else /* !CONFIG_PM */
+static int zpa2326_resume(const struct iio_dev *indio_dev)
+{
+	zpa2326_enable_device(indio_dev);
+
+	return 0;
+}
+
+static void zpa2326_suspend(struct iio_dev *indio_dev)
+{
+	zpa2326_sleep(indio_dev);
+}
+
+#define zpa2326_init_runtime(_parent)
+#define zpa2326_fini_runtime(_parent)
+#endif /* !CONFIG_PM */
+
+/**
+ * zpa2326_handle_irq() - Process hardware interrupts.
+ * @irq:  Interrupt line the hardware uses to notify new data has arrived.
+ * @data: The IIO device associated with the sampling hardware.
+ *
+ * Timestamp buffered samples as soon as possible then schedule threaded bottom
+ * half.
+ *
+ * Return: Always successful.
+ */
+static irqreturn_t zpa2326_handle_irq(int irq, void *data)
+{
+	struct iio_dev *indio_dev = (struct iio_dev *)data;
+
+	if (iio_buffer_enabled(indio_dev)) {
+		/* Timestamping needed for buffered sampling only. */
+		((struct zpa2326_private *)
+		 iio_priv(indio_dev))->timestamp = iio_get_time_ns(indio_dev);
+	}
+
+	return IRQ_WAKE_THREAD;
+}
+
+/**
+ * zpa2326_handle_threaded_irq() - Interrupt bottom-half handler.
+ * @irq:  Interrupt line the hardware uses to notify new data has arrived.
+ * @data: The IIO device associated with the sampling hardware.
+ *
+ * Mainly ensures interrupt is caused by a real "new sample available"
+ * condition. This relies upon the ability to perform blocking / sleeping bus
+ * accesses to slave's registers. This is why zpa2326_handle_threaded_irq() is
+ * called from within a thread, i.e. not called from hard interrupt context.
+ *
+ * When device is using its own internal hardware trigger in continuous sampling
+ * mode, data are available into hardware FIFO once interrupt has occurred. All
+ * we have to do is to dispatch the trigger, which in turn will fetch data and
+ * fill IIO buffer.
+ *
+ * When not using its own internal hardware trigger, the device has been
+ * configured in one-shot mode either by an external trigger or the IIO read_raw
+ * hook. This means one of the latter is currently waiting for sampling
+ * completion, in which case we must simply wake it up.
+ *
+ * See zpa2326_trigger_handler().
+ *
+ * Return:
+ *   %IRQ_NONE - no consistent interrupt happened ;
+ *   %IRQ_HANDLED - there was new samples available.
+ */
+static irqreturn_t zpa2326_handle_threaded_irq(int irq, void *data)
+{
+	struct iio_dev         *indio_dev = (struct iio_dev *)data;
+	struct zpa2326_private *priv = iio_priv(indio_dev);
+	unsigned int            val;
+	bool                    cont;
+	irqreturn_t             ret = IRQ_NONE;
+
+	/*
+	 * Are we using our own internal trigger in triggered buffer mode, i.e.,
+	 * currently working in continuous sampling mode ?
+	 */
+	cont = (iio_buffer_enabled(indio_dev) &&
+		iio_trigger_using_own(indio_dev));
+
+	/*
+	 * Device works according to a level interrupt scheme: reading interrupt
+	 * status de-asserts interrupt line.
+	 */
+	priv->result = regmap_read(priv->regmap, ZPA2326_INT_SOURCE_REG, &val);
+	if (priv->result < 0) {
+		if (cont)
+			return IRQ_NONE;
+
+		goto complete;
+	}
+
+	/* Data ready is the only interrupt source we requested. */
+	if (!(val & ZPA2326_INT_SOURCE_DATA_READY)) {
+		/*
+		 * Interrupt happened but no new sample available: likely caused
+		 * by spurious interrupts, in which case, returning IRQ_NONE
+		 * allows to benefit from the generic spurious interrupts
+		 * handling.
+		 */
+		zpa2326_warn(indio_dev, "unexpected interrupt status %02x",
+			     val);
+
+		if (cont)
+			return IRQ_NONE;
+
+		priv->result = -ENODATA;
+		goto complete;
+	}
+
+	/* New sample available: dispatch internal trigger consumers. */
+	iio_trigger_poll_chained(priv->trigger);
+
+	if (cont)
+		/*
+		 * Internal hardware trigger has been scheduled above : it will
+		 * fetch data on its own.
+		 */
+		return IRQ_HANDLED;
+
+	ret = IRQ_HANDLED;
+
+complete:
+	/*
+	 * Wake up direct or externaly triggered buffer mode waiters: see
+	 * zpa2326_sample_oneshot() and zpa2326_trigger_handler().
+	 */
+	complete(&priv->data_ready);
+
+	return ret;
+}
+
+/**
+ * zpa2326_wait_oneshot_completion() - Wait for oneshot data ready interrupt.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_wait_oneshot_completion(const struct iio_dev   *indio_dev,
+					   struct zpa2326_private *private)
+{
+	int          ret;
+	unsigned int val;
+
+	zpa2326_dbg(indio_dev, "waiting for one shot completion interrupt");
+
+	ret = wait_for_completion_interruptible_timeout(
+		&private->data_ready, ZPA2326_CONVERSION_JIFFIES);
+	if (ret > 0)
+		/*
+		 * Interrupt handler completed before timeout: return operation
+		 * status.
+		 */
+		return private->result;
+
+	/* Clear all interrupts just to be sure. */
+	regmap_read(private->regmap, ZPA2326_INT_SOURCE_REG, &val);
+
+	if (!ret)
+		/* Timed out. */
+		ret = -ETIME;
+
+	if (ret != -ERESTARTSYS)
+		zpa2326_warn(indio_dev, "no one shot interrupt occurred (%d)",
+			     ret);
+
+	return ret;
+}
+
+static int zpa2326_init_managed_irq(struct device          *parent,
+				    struct iio_dev         *indio_dev,
+				    struct zpa2326_private *private,
+				    int                     irq)
+{
+	int err;
+
+	private->irq = irq;
+
+	if (irq <= 0) {
+		/*
+		 * Platform declared no interrupt line: device will be polled
+		 * for data availability.
+		 */
+		dev_info(parent, "no interrupt found, running in polling mode");
+		return 0;
+	}
+
+	init_completion(&private->data_ready);
+
+	/* Request handler to be scheduled into threaded interrupt context. */
+	err = devm_request_threaded_irq(parent, irq, zpa2326_handle_irq,
+					zpa2326_handle_threaded_irq,
+					IRQF_TRIGGER_RISING | IRQF_ONESHOT,
+					dev_name(parent), indio_dev);
+	if (err) {
+		dev_err(parent, "failed to request interrupt %d (%d)", irq,
+			err);
+		return err;
+	}
+
+	dev_info(parent, "using interrupt %d", irq);
+
+	return 0;
+}
+
+/**
+ * zpa2326_poll_oneshot_completion() - Actively poll for one shot data ready.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Loop over registers content to detect end of sampling cycle. Used when DT
+ * declared no valid interrupt lines.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_poll_oneshot_completion(const struct iio_dev *indio_dev)
+{
+	unsigned long  tmout = jiffies + ZPA2326_CONVERSION_JIFFIES;
+	struct regmap *regs = ((struct zpa2326_private *)
+			       iio_priv(indio_dev))->regmap;
+	unsigned int   val;
+	int            err;
+
+	zpa2326_dbg(indio_dev, "polling for one shot completion");
+
+	/*
+	 * At least, 100 ms is needed for the device to complete its one-shot
+	 * cycle.
+	 */
+	if (msleep_interruptible(100))
+		return -ERESTARTSYS;
+
+	/* Poll for conversion completion in hardware. */
+	while (true) {
+		err = regmap_read(regs, ZPA2326_CTRL_REG0_REG, &val);
+		if (err < 0)
+			goto err;
+
+		if (!(val & ZPA2326_CTRL_REG0_ONE_SHOT))
+			/* One-shot bit self clears at conversion end. */
+			break;
+
+		if (time_after(jiffies, tmout)) {
+			/* Prevent from waiting forever : let's time out. */
+			err = -ETIME;
+			goto err;
+		}
+
+		usleep_range(10000, 20000);
+	}
+
+	/*
+	 * In oneshot mode, pressure sample availability guarantees that
+	 * temperature conversion has also completed : just check pressure
+	 * status bit to keep things simple.
+	 */
+	err = regmap_read(regs, ZPA2326_STATUS_REG, &val);
+	if (err < 0)
+		goto err;
+
+	if (!(val & ZPA2326_STATUS_P_DA)) {
+		/* No sample available. */
+		err = -ENODATA;
+		goto err;
+	}
+
+	return 0;
+
+err:
+	zpa2326_warn(indio_dev, "failed to poll one shot completion (%d)", err);
+
+	return err;
+}
+
+/**
+ * zpa2326_fetch_raw_sample() - Retrieve a raw sample and convert it to CPU
+ *                              endianness.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @type:      Type of measurement / channel to fetch from.
+ * @value:     Sample output.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_fetch_raw_sample(const struct iio_dev *indio_dev,
+				    enum iio_chan_type    type,
+				    int                  *value)
+{
+	struct regmap *regs = ((struct zpa2326_private *)
+			       iio_priv(indio_dev))->regmap;
+	int            err;
+
+	switch (type) {
+	case IIO_PRESSURE:
+		zpa2326_dbg(indio_dev, "fetching raw pressure sample");
+
+		err = regmap_bulk_read(regs, ZPA2326_PRESS_OUT_XL_REG, value,
+				       3);
+		if (err) {
+			zpa2326_warn(indio_dev, "failed to fetch pressure (%d)",
+				     err);
+			return err;
+		}
+
+		/* Pressure is a 24 bits wide little-endian unsigned int. */
+		*value = (((u8 *)value)[2] << 16) | (((u8 *)value)[1] << 8) |
+			 ((u8 *)value)[0];
+
+		return IIO_VAL_INT;
+
+	case IIO_TEMP:
+		zpa2326_dbg(indio_dev, "fetching raw temperature sample");
+
+		err = regmap_bulk_read(regs, ZPA2326_TEMP_OUT_L_REG, value, 2);
+		if (err) {
+			zpa2326_warn(indio_dev,
+				     "failed to fetch temperature (%d)", err);
+			return err;
+		}
+
+		/* Temperature is a 16 bits wide little-endian signed int. */
+		*value = (int)le16_to_cpup((__le16 *)value);
+
+		return IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+/**
+ * zpa2326_sample_oneshot() - Perform a complete one shot sampling cycle.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @type:      Type of measurement / channel to fetch from.
+ * @value:     Sample output.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_sample_oneshot(struct iio_dev     *indio_dev,
+				  enum iio_chan_type  type,
+				  int                *value)
+{
+	int                     ret;
+	struct zpa2326_private *priv;
+
+	ret = iio_device_claim_direct_mode(indio_dev);
+	if (ret)
+		return ret;
+
+	ret = zpa2326_resume(indio_dev);
+	if (ret < 0)
+		goto release;
+
+	priv = iio_priv(indio_dev);
+
+	if (ret > 0) {
+		/*
+		 * We were already power supplied. Just clear hardware FIFO to
+		 * get rid of samples acquired during previous rounds (if any).
+		 * Sampling operation always generates both temperature and
+		 * pressure samples. The latter are always enqueued into
+		 * hardware FIFO. This may lead to situations were pressure
+		 * samples still sit into FIFO when previous cycle(s) fetched
+		 * temperature data only.
+		 * Hence, we need to clear hardware FIFO content to prevent from
+		 * getting outdated values at the end of current cycle.
+		 */
+		if (type == IIO_PRESSURE) {
+			ret = zpa2326_clear_fifo(indio_dev, 0);
+			if (ret)
+				goto suspend;
+		}
+	} else {
+		/*
+		 * We have just been power supplied, i.e. device is in default
+		 * "out of reset" state, meaning we need to reconfigure it
+		 * entirely.
+		 */
+		ret = zpa2326_config_oneshot(indio_dev, priv->irq);
+		if (ret)
+			goto suspend;
+	}
+
+	/* Start a sampling cycle in oneshot mode. */
+	ret = zpa2326_start_oneshot(indio_dev);
+	if (ret)
+		goto suspend;
+
+	/* Wait for sampling cycle to complete. */
+	if (priv->irq > 0)
+		ret = zpa2326_wait_oneshot_completion(indio_dev, priv);
+	else
+		ret = zpa2326_poll_oneshot_completion(indio_dev);
+
+	if (ret)
+		goto suspend;
+
+	/* Retrieve raw sample value and convert it to CPU endianness. */
+	ret = zpa2326_fetch_raw_sample(indio_dev, type, value);
+
+suspend:
+	zpa2326_suspend(indio_dev);
+release:
+	iio_device_release_direct_mode(indio_dev);
+
+	return ret;
+}
+
+/**
+ * zpa2326_trigger_handler() - Perform an IIO buffered sampling round in one
+ *                             shot mode.
+ * @irq:  The software interrupt assigned to @data
+ * @data: The IIO poll function dispatched by external trigger our device is
+ *        attached to.
+ *
+ * Bottom-half handler called by the IIO trigger to which our device is
+ * currently attached. Allows us to synchronize this device buffered sampling
+ * either with external events (such as timer expiration, external device sample
+ * ready, etc...) or with its own interrupt (internal hardware trigger).
+ *
+ * When using an external trigger, basically run the same sequence of operations
+ * as for zpa2326_sample_oneshot() with the following hereafter. Hardware FIFO
+ * is not cleared since already done at buffering enable time and samples
+ * dequeueing always retrieves the most recent value.
+ *
+ * Otherwise, when internal hardware trigger has dispatched us, just fetch data
+ * from hardware FIFO.
+ *
+ * Fetched data will pushed unprocessed to IIO buffer since samples conversion
+ * is delegated to userspace in buffered mode (endianness, etc...).
+ *
+ * Return:
+ *   %IRQ_NONE - no consistent interrupt happened ;
+ *   %IRQ_HANDLED - there was new samples available.
+ */
+static irqreturn_t zpa2326_trigger_handler(int irq, void *data)
+{
+	struct iio_dev         *indio_dev = ((struct iio_poll_func *)
+					     data)->indio_dev;
+	struct zpa2326_private *priv = iio_priv(indio_dev);
+	bool                    cont;
+
+	/*
+	 * We have been dispatched, meaning we are in triggered buffer mode.
+	 * Using our own internal trigger implies we are currently in continuous
+	 * hardware sampling mode.
+	 */
+	cont = iio_trigger_using_own(indio_dev);
+
+	if (!cont) {
+		/* On demand sampling : start a one shot cycle. */
+		if (zpa2326_start_oneshot(indio_dev))
+			goto out;
+
+		/* Wait for sampling cycle to complete. */
+		if (priv->irq <= 0) {
+			/* No interrupt available: poll for completion. */
+			if (zpa2326_poll_oneshot_completion(indio_dev))
+				goto out;
+
+			/* Only timestamp sample once it is ready. */
+			priv->timestamp = iio_get_time_ns(indio_dev);
+		} else {
+			/* Interrupt handlers will timestamp for us. */
+			if (zpa2326_wait_oneshot_completion(indio_dev, priv))
+				goto out;
+		}
+	}
+
+	/* Enqueue to IIO buffer / userspace. */
+	zpa2326_fill_sample_buffer(indio_dev, priv);
+
+out:
+	if (!cont)
+		/* Don't switch to low power if sampling continuously. */
+		zpa2326_sleep(indio_dev);
+
+	/* Inform attached trigger we are done. */
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * zpa2326_preenable_buffer() - Prepare device for configuring triggered
+ *                              sampling
+ * modes.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Basically power up device.
+ * Called with IIO device's lock held.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_preenable_buffer(struct iio_dev *indio_dev)
+{
+	int ret = zpa2326_resume(indio_dev);
+
+	if (ret < 0)
+		return ret;
+
+	/* Tell zpa2326_postenable_buffer() if we have just been powered on. */
+	((struct zpa2326_private *)
+	 iio_priv(indio_dev))->waken = iio_priv(indio_dev);
+
+	return 0;
+}
+
+/**
+ * zpa2326_postenable_buffer() - Configure device for triggered sampling.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ *
+ * Basically setup one-shot mode if plugging external trigger.
+ * Otherwise, let internal trigger configure continuous sampling :
+ * see zpa2326_set_trigger_state().
+ *
+ * If an error is returned, IIO layer will call our postdisable hook for us,
+ * i.e. no need to explicitly power device off here.
+ * Called with IIO device's lock held.
+ *
+ * Called with IIO device's lock held.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_postenable_buffer(struct iio_dev *indio_dev)
+{
+	const struct zpa2326_private *priv = iio_priv(indio_dev);
+	int                           err;
+
+	if (!priv->waken) {
+		/*
+		 * We were already power supplied. Just clear hardware FIFO to
+		 * get rid of samples acquired during previous rounds (if any).
+		 */
+		err = zpa2326_clear_fifo(indio_dev, 0);
+		if (err)
+			goto err;
+	}
+
+	if (!iio_trigger_using_own(indio_dev) && priv->waken) {
+		/*
+		 * We are using an external trigger and we have just been
+		 * powered up: reconfigure one-shot mode.
+		 */
+		err = zpa2326_config_oneshot(indio_dev, priv->irq);
+		if (err)
+			goto err;
+	}
+
+	/* Plug our own trigger event handler. */
+	err = iio_triggered_buffer_postenable(indio_dev);
+	if (err)
+		goto err;
+
+	return 0;
+
+err:
+	zpa2326_err(indio_dev, "failed to enable buffering (%d)", err);
+
+	return err;
+}
+
+static int zpa2326_postdisable_buffer(struct iio_dev *indio_dev)
+{
+	zpa2326_suspend(indio_dev);
+
+	return 0;
+}
+
+static const struct iio_buffer_setup_ops zpa2326_buffer_setup_ops = {
+	.preenable   = zpa2326_preenable_buffer,
+	.postenable  = zpa2326_postenable_buffer,
+	.predisable  = iio_triggered_buffer_predisable,
+	.postdisable = zpa2326_postdisable_buffer
+};
+
+/**
+ * zpa2326_set_trigger_state() - Start / stop continuous sampling.
+ * @trig:  The trigger being attached to IIO device associated with the sampling
+ *         hardware.
+ * @state: Tell whether to start (true) or stop (false)
+ *
+ * Basically enable / disable hardware continuous sampling mode.
+ *
+ * Called with IIO device's lock held at postenable() or predisable() time.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_set_trigger_state(struct iio_trigger *trig, bool state)
+{
+	const struct iio_dev         *indio_dev = dev_get_drvdata(
+							trig->dev.parent);
+	const struct zpa2326_private *priv = iio_priv(indio_dev);
+	int                           err;
+
+	if (!state) {
+		/*
+		 * Switch trigger off : in case of failure, interrupt is left
+		 * disabled in order to prevent handler from accessing released
+		 * resources.
+		 */
+		unsigned int val;
+
+		/*
+		 * As device is working in continuous mode, handlers may be
+		 * accessing resources we are currently freeing...
+		 * Prevent this by disabling interrupt handlers and ensure
+		 * the device will generate no more interrupts unless explicitly
+		 * required to, i.e. by restoring back to default one shot mode.
+		 */
+		disable_irq(priv->irq);
+
+		/*
+		 * Disable continuous sampling mode to restore settings for
+		 * one shot / direct sampling operations.
+		 */
+		err = regmap_write(priv->regmap, ZPA2326_CTRL_REG3_REG,
+				   zpa2326_highest_frequency()->odr);
+		if (err)
+			return err;
+
+		/*
+		 * Now that device won't generate interrupts on its own,
+		 * acknowledge any currently active interrupts (may happen on
+		 * rare occasions while stopping continuous mode).
+		 */
+		err = regmap_read(priv->regmap, ZPA2326_INT_SOURCE_REG, &val);
+		if (err < 0)
+			return err;
+
+		/*
+		 * Re-enable interrupts only if we can guarantee the device will
+		 * generate no more interrupts to prevent handlers from
+		 * accessing released resources.
+		 */
+		enable_irq(priv->irq);
+
+		zpa2326_dbg(indio_dev, "continuous mode stopped");
+	} else {
+		/*
+		 * Switch trigger on : start continuous sampling at required
+		 * frequency.
+		 */
+
+		if (priv->waken) {
+			/* Enable interrupt if getting out of reset. */
+			err = regmap_write(priv->regmap, ZPA2326_CTRL_REG1_REG,
+					   (u8)
+					   ~ZPA2326_CTRL_REG1_MASK_DATA_READY);
+			if (err)
+				return err;
+		}
+
+		/* Enable continuous sampling at specified frequency. */
+		err = regmap_write(priv->regmap, ZPA2326_CTRL_REG3_REG,
+				   ZPA2326_CTRL_REG3_ENABLE_MEAS |
+				   priv->frequency->odr);
+		if (err)
+			return err;
+
+		zpa2326_dbg(indio_dev, "continuous mode setup @%dHz",
+			    priv->frequency->hz);
+	}
+
+	return 0;
+}
+
+static const struct iio_trigger_ops zpa2326_trigger_ops = {
+	.owner             = THIS_MODULE,
+	.set_trigger_state = zpa2326_set_trigger_state,
+};
+
+/**
+ * zpa2326_init_trigger() - Create an interrupt driven / hardware trigger
+ *                          allowing to notify external devices a new sample is
+ *                          ready.
+ * @parent:    Hardware sampling device @indio_dev is a child of.
+ * @indio_dev: The IIO device associated with the sampling hardware.
+ * @private:   Internal private state related to @indio_dev.
+ * @irq:       Optional interrupt line the hardware uses to notify new data
+ *             samples are ready. Negative or zero values indicate no interrupts
+ *             are available, meaning polling is required.
+ *
+ * Only relevant when DT declares a valid interrupt line.
+ *
+ * Return: Zero when successful, a negative error code otherwise.
+ */
+static int zpa2326_init_managed_trigger(struct device          *parent,
+					struct iio_dev         *indio_dev,
+					struct zpa2326_private *private,
+					int                     irq)
+{
+	struct iio_trigger *trigger;
+	int                 ret;
+
+	if (irq <= 0)
+		return 0;
+
+	trigger = devm_iio_trigger_alloc(parent, "%s-dev%d",
+					 indio_dev->name, indio_dev->id);
+	if (!trigger)
+		return -ENOMEM;
+
+	/* Basic setup. */
+	trigger->dev.parent = parent;
+	trigger->ops = &zpa2326_trigger_ops;
+
+	private->trigger = trigger;
+
+	/* Register to triggers space. */
+	ret = devm_iio_trigger_register(parent, trigger);
+	if (ret)
+		dev_err(parent, "failed to register hardware trigger (%d)",
+			ret);
+
+	return ret;
+}
+
+static int zpa2326_get_frequency(const struct iio_dev *indio_dev)
+{
+	return ((struct zpa2326_private *)iio_priv(indio_dev))->frequency->hz;
+}
+
+static int zpa2326_set_frequency(struct iio_dev *indio_dev, int hz)
+{
+	struct zpa2326_private *priv = iio_priv(indio_dev);
+	int                     freq;
+	int                     err;
+
+	/* Check if requested frequency is supported. */
+	for (freq = 0; freq < ARRAY_SIZE(zpa2326_sampling_frequencies); freq++)
+		if (zpa2326_sampling_frequencies[freq].hz == hz)
+			break;
+	if (freq == ARRAY_SIZE(zpa2326_sampling_frequencies))
+		return -EINVAL;
+
+	/* Don't allow changing frequency if buffered sampling is ongoing. */
+	err = iio_device_claim_direct_mode(indio_dev);
+	if (err)
+		return err;
+
+	priv->frequency = &zpa2326_sampling_frequencies[freq];
+
+	iio_device_release_direct_mode(indio_dev);
+
+	return 0;
+}
+
+/* Expose supported hardware sampling frequencies (Hz) through sysfs. */
+static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("1 5 11 23");
+
+static struct attribute *zpa2326_attributes[] = {
+	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
+	NULL
+};
+
+static const struct attribute_group zpa2326_attribute_group = {
+	.attrs = zpa2326_attributes,
+};
+
+static int zpa2326_read_raw(struct iio_dev             *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int                        *val,
+			    int                        *val2,
+			    long                        mask)
+{
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		return zpa2326_sample_oneshot(indio_dev, chan->type, val);
+
+	case IIO_CHAN_INFO_SCALE:
+		switch (chan->type) {
+		case IIO_PRESSURE:
+			/*
+			 * Pressure resolution is 1/64 Pascal. Scale to kPascal
+			 * as required by IIO ABI.
+			 */
+			*val = 1;
+			*val2 = 64000;
+			return IIO_VAL_FRACTIONAL;
+
+		case IIO_TEMP:
+			/*
+			 * Temperature follows the equation:
+			 *     Temp[degC] = Tempcode * 0.00649 - 176.83
+			 * where:
+			 *     Tempcode is composed the raw sampled 16 bits.
+			 *
+			 * Hence, to produce a temperature in milli-degrees
+			 * Celsius according to IIO ABI, we need to apply the
+			 * following equation to raw samples:
+			 *     Temp[milli degC] = (Tempcode + Offset) * Scale
+			 * where:
+			 *     Offset = -176.83 / 0.00649
+			 *     Scale = 0.00649 * 1000
+			 */
+			*val = 6;
+			*val2 = 490000;
+			return IIO_VAL_INT_PLUS_MICRO;
+
+		default:
+			return -EINVAL;
+		}
+
+	case IIO_CHAN_INFO_OFFSET:
+		switch (chan->type) {
+		case IIO_TEMP:
+			*val = -17683000;
+			*val2 = 649;
+			return IIO_VAL_FRACTIONAL;
+
+		default:
+			return -EINVAL;
+		}
+
+	case IIO_CHAN_INFO_SAMP_FREQ:
+		*val = zpa2326_get_frequency(indio_dev);
+		return IIO_VAL_INT;
+
+	default:
+		return -EINVAL;
+	}
+}
+
+static int zpa2326_write_raw(struct iio_dev             *indio_dev,
+			     const struct iio_chan_spec *chan,
+			     int                         val,
+			     int                         val2,
+			     long                        mask)
+{
+	if ((mask != IIO_CHAN_INFO_SAMP_FREQ) || val2)
+		return -EINVAL;
+
+	return zpa2326_set_frequency(indio_dev, val);
+}
+
+static const struct iio_chan_spec zpa2326_channels[] = {
+	[0] = {
+		.type                    = IIO_PRESSURE,
+		.scan_index              = 0,
+		.scan_type               = {
+			.sign                   = 'u',
+			.realbits               = 24,
+			.storagebits            = 32,
+			.endianness             = IIO_LE,
+		},
+		.info_mask_separate      = BIT(IIO_CHAN_INFO_RAW) |
+					   BIT(IIO_CHAN_INFO_SCALE),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+	},
+	[1] = {
+		.type                    = IIO_TEMP,
+		.scan_index              = 1,
+		.scan_type               = {
+			.sign                   = 's',
+			.realbits               = 16,
+			.storagebits            = 16,
+			.endianness             = IIO_LE,
+		},
+		.info_mask_separate      = BIT(IIO_CHAN_INFO_RAW) |
+					   BIT(IIO_CHAN_INFO_SCALE) |
+					   BIT(IIO_CHAN_INFO_OFFSET),
+		.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+	},
+	[2] = IIO_CHAN_SOFT_TIMESTAMP(2),
+};
+
+static const struct iio_info zpa2326_info = {
+	.driver_module = THIS_MODULE,
+	.attrs         = &zpa2326_attribute_group,
+	.read_raw      = zpa2326_read_raw,
+	.write_raw     = zpa2326_write_raw,
+};
+
+static struct iio_dev *zpa2326_create_managed_iiodev(struct device *device,
+						     const char    *name,
+						     struct regmap *regmap)
+{
+	struct iio_dev *indio_dev;
+
+	/* Allocate space to hold IIO device internal state. */
+	indio_dev = devm_iio_device_alloc(device,
+					  sizeof(struct zpa2326_private));
+	if (!indio_dev)
+		return NULL;
+
+	/* Setup for userspace synchronous on demand sampling. */
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->dev.parent = device;
+	indio_dev->channels = zpa2326_channels;
+	indio_dev->num_channels = ARRAY_SIZE(zpa2326_channels);
+	indio_dev->name = name;
+	indio_dev->info = &zpa2326_info;
+
+	return indio_dev;
+}
+
+int zpa2326_probe(struct device *parent,
+		  const char    *name,
+		  int            irq,
+		  unsigned int   hwid,
+		  struct regmap *regmap)
+{
+	struct iio_dev         *indio_dev;
+	struct zpa2326_private *priv;
+	int                     err;
+	unsigned int            id;
+
+	indio_dev = zpa2326_create_managed_iiodev(parent, name, regmap);
+	if (!indio_dev)
+		return -ENOMEM;
+
+	priv = iio_priv(indio_dev);
+
+	priv->vref = devm_regulator_get(parent, "vref");
+	if (IS_ERR(priv->vref))
+		return PTR_ERR(priv->vref);
+
+	priv->vdd = devm_regulator_get(parent, "vdd");
+	if (IS_ERR(priv->vdd))
+		return PTR_ERR(priv->vdd);
+
+	/* Set default hardware sampling frequency to highest rate supported. */
+	priv->frequency = zpa2326_highest_frequency();
+
+	/*
+	 * Plug device's underlying bus abstraction : this MUST be set before
+	 * registering interrupt handlers since an interrupt might happen if
+	 * power up sequence is not properly applied.
+	 */
+	priv->regmap = regmap;
+
+	err = devm_iio_triggered_buffer_setup(parent, indio_dev, NULL,
+					      zpa2326_trigger_handler,
+					      &zpa2326_buffer_setup_ops);
+	if (err)
+		return err;
+
+	err = zpa2326_init_managed_trigger(parent, indio_dev, priv, irq);
+	if (err)
+		return err;
+
+	err = zpa2326_init_managed_irq(parent, indio_dev, priv, irq);
+	if (err)
+		return err;
+
+	/* Power up to check device ID and perform initial hardware setup. */
+	err = zpa2326_power_on(indio_dev, priv);
+	if (err)
+		return err;
+
+	/* Read id register to check we are talking to the right slave. */
+	err = regmap_read(regmap, ZPA2326_DEVICE_ID_REG, &id);
+	if (err)
+		goto sleep;
+
+	if (id != hwid) {
+		dev_err(parent, "found device with unexpected id %02x", id);
+		err = -ENODEV;
+		goto sleep;
+	}
+
+	err = zpa2326_config_oneshot(indio_dev, irq);
+	if (err)
+		goto sleep;
+
+	/* Setup done : go sleeping. Device will be awaken upon user request. */
+	err = zpa2326_sleep(indio_dev);
+	if (err)
+		goto poweroff;
+
+	dev_set_drvdata(parent, indio_dev);
+
+	zpa2326_init_runtime(parent);
+
+	err = iio_device_register(indio_dev);
+	if (err) {
+		zpa2326_fini_runtime(parent);
+		goto poweroff;
+	}
+
+	return 0;
+
+sleep:
+	/* Put to sleep just in case power regulators are "dummy" ones. */
+	zpa2326_sleep(indio_dev);
+poweroff:
+	zpa2326_power_off(indio_dev, priv);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(zpa2326_probe);
+
+void zpa2326_remove(const struct device *parent)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(parent);
+
+	iio_device_unregister(indio_dev);
+	zpa2326_fini_runtime(indio_dev->dev.parent);
+	zpa2326_sleep(indio_dev);
+	zpa2326_power_off(indio_dev, iio_priv(indio_dev));
+}
+EXPORT_SYMBOL_GPL(zpa2326_remove);
+
+MODULE_AUTHOR("Gregor Boirie <gregor.boirie@parrot.com>");
+MODULE_DESCRIPTION("Core driver for Murata ZPA2326 pressure sensor");
+MODULE_LICENSE("GPL v2");