iio: pressure: bmp280: split driver in logical parts

This splits the BMP280 driver in three logical parts: the core driver
bmp280-core that only operated on a struct device * and a struct regmap *,
the regmap driver bmp280-regmap that can be shared between I2C and other
transports and the I2C module driver bmp280-i2c.

Cleverly bake all functionality into a single object bmp280.o so that
we still get the same module binary built for the device in the end,
without any fuzz exporting symbols to the left and right.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 968 insertions, 0 deletions

diff --git a/drivers/iio/pressure/bmp280-core.c b/drivers/iio/pressure/bmp280-core.c
new file mode 100644
index 000000000000..83b96fe71f3b
--- /dev/null
+++ b/drivers/iio/pressure/bmp280-core.c
@@ -0,0 +1,968 @@
+/*
+ * Copyright (c) 2014 Intel Corporation
+ *
+ * Driver for Bosch Sensortec BMP180 and BMP280 digital pressure sensor.
+ *
+ * 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.
+ *
+ * Datasheet:
+ * https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMP180-DS000-121.pdf
+ * https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMP280-DS001-12.pdf
+ * https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME280_DS001-11.pdf
+ */
+
+#define pr_fmt(fmt) "bmp280: " fmt
+
+#include <linux/device.h>
+#include <linux/regmap.h>
+#include <linux/delay.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+#include <linux/gpio/consumer.h>
+#include <linux/regulator/consumer.h>
+
+#include "bmp280.h"
+
+struct bmp280_data {
+	struct device *dev;
+	struct mutex lock;
+	struct regmap *regmap;
+	const struct bmp280_chip_info *chip_info;
+	struct regulator *vddd;
+	struct regulator *vdda;
+	unsigned int start_up_time; /* in milliseconds */
+
+	/* log of base 2 of oversampling rate */
+	u8 oversampling_press;
+	u8 oversampling_temp;
+	u8 oversampling_humid;
+
+	/*
+	 * Carryover value from temperature conversion, used in pressure
+	 * calculation.
+	 */
+	s32 t_fine;
+};
+
+struct bmp280_chip_info {
+	const int *oversampling_temp_avail;
+	int num_oversampling_temp_avail;
+
+	const int *oversampling_press_avail;
+	int num_oversampling_press_avail;
+
+	const int *oversampling_humid_avail;
+	int num_oversampling_humid_avail;
+
+	int (*chip_config)(struct bmp280_data *);
+	int (*read_temp)(struct bmp280_data *, int *);
+	int (*read_press)(struct bmp280_data *, int *, int *);
+	int (*read_humid)(struct bmp280_data *, int *, int *);
+};
+
+/*
+ * These enums are used for indexing into the array of compensation
+ * parameters for BMP280.
+ */
+enum { T1, T2, T3 };
+enum { P1, P2, P3, P4, P5, P6, P7, P8, P9 };
+
+static const struct iio_chan_spec bmp280_channels[] = {
+	{
+		.type = IIO_PRESSURE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+	},
+	{
+		.type = IIO_TEMP,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+	},
+	{
+		.type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+	},
+};
+
+/*
+ * Returns humidity in percent, resolution is 0.01 percent. Output value of
+ * "47445" represents 47445/1024 = 46.333 %RH.
+ *
+ * Taken from BME280 datasheet, Section 4.2.3, "Compensation formula".
+ */
+
+static u32 bmp280_compensate_humidity(struct bmp280_data *data,
+				      s32 adc_humidity)
+{
+	struct device *dev = data->dev;
+	unsigned int H1, H3, tmp;
+	int H2, H4, H5, H6, ret, var;
+
+	ret = regmap_read(data->regmap, BMP280_REG_COMP_H1, &H1);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H1 comp value\n");
+		return ret;
+	}
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H2, &tmp, 2);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H2 comp value\n");
+		return ret;
+	}
+	H2 = sign_extend32(le16_to_cpu(tmp), 15);
+
+	ret = regmap_read(data->regmap, BMP280_REG_COMP_H3, &H3);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H3 comp value\n");
+		return ret;
+	}
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H4, &tmp, 2);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H4 comp value\n");
+		return ret;
+	}
+	H4 = sign_extend32(((be16_to_cpu(tmp) >> 4) & 0xff0) |
+			  (be16_to_cpu(tmp) & 0xf), 11);
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H5, &tmp, 2);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H5 comp value\n");
+		return ret;
+	}
+	H5 = sign_extend32(((le16_to_cpu(tmp) >> 4) & 0xfff), 11);
+
+	ret = regmap_read(data->regmap, BMP280_REG_COMP_H6, &tmp);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H6 comp value\n");
+		return ret;
+	}
+	H6 = sign_extend32(tmp, 7);
+
+	var = ((s32)data->t_fine) - 76800;
+	var = ((((adc_humidity << 14) - (H4 << 20) - (H5 * var)) + 16384) >> 15)
+		* (((((((var * H6) >> 10) * (((var * H3) >> 11) + 32768)) >> 10)
+		+ 2097152) * H2 + 8192) >> 14);
+	var -= ((((var >> 15) * (var >> 15)) >> 7) * H1) >> 4;
+
+	return var >> 12;
+};
+
+/*
+ * Returns temperature in DegC, resolution is 0.01 DegC.  Output value of
+ * "5123" equals 51.23 DegC.  t_fine carries fine temperature as global
+ * value.
+ *
+ * Taken from datasheet, Section 3.11.3, "Compensation formula".
+ */
+static s32 bmp280_compensate_temp(struct bmp280_data *data,
+				  s32 adc_temp)
+{
+	int ret;
+	s32 var1, var2;
+	__le16 buf[BMP280_COMP_TEMP_REG_COUNT / 2];
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
+			       buf, BMP280_COMP_TEMP_REG_COUNT);
+	if (ret < 0) {
+		dev_err(data->dev,
+			"failed to read temperature calibration parameters\n");
+		return ret;
+	}
+
+	/*
+	 * The double casts are necessary because le16_to_cpu returns an
+	 * unsigned 16-bit value.  Casting that value directly to a
+	 * signed 32-bit will not do proper sign extension.
+	 *
+	 * Conversely, T1 and P1 are unsigned values, so they can be
+	 * cast straight to the larger type.
+	 */
+	var1 = (((adc_temp >> 3) - ((s32)le16_to_cpu(buf[T1]) << 1)) *
+		((s32)(s16)le16_to_cpu(buf[T2]))) >> 11;
+	var2 = (((((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1]))) *
+		  ((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1])))) >> 12) *
+		((s32)(s16)le16_to_cpu(buf[T3]))) >> 14;
+	data->t_fine = var1 + var2;
+
+	return (data->t_fine * 5 + 128) >> 8;
+}
+
+/*
+ * Returns pressure in Pa as unsigned 32 bit integer in Q24.8 format (24
+ * integer bits and 8 fractional bits).  Output value of "24674867"
+ * represents 24674867/256 = 96386.2 Pa = 963.862 hPa
+ *
+ * Taken from datasheet, Section 3.11.3, "Compensation formula".
+ */
+static u32 bmp280_compensate_press(struct bmp280_data *data,
+				   s32 adc_press)
+{
+	int ret;
+	s64 var1, var2, p;
+	__le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,
+			       buf, BMP280_COMP_PRESS_REG_COUNT);
+	if (ret < 0) {
+		dev_err(data->dev,
+			"failed to read pressure calibration parameters\n");
+		return ret;
+	}
+
+	var1 = ((s64)data->t_fine) - 128000;
+	var2 = var1 * var1 * (s64)(s16)le16_to_cpu(buf[P6]);
+	var2 += (var1 * (s64)(s16)le16_to_cpu(buf[P5])) << 17;
+	var2 += ((s64)(s16)le16_to_cpu(buf[P4])) << 35;
+	var1 = ((var1 * var1 * (s64)(s16)le16_to_cpu(buf[P3])) >> 8) +
+		((var1 * (s64)(s16)le16_to_cpu(buf[P2])) << 12);
+	var1 = ((((s64)1) << 47) + var1) * ((s64)le16_to_cpu(buf[P1])) >> 33;
+
+	if (var1 == 0)
+		return 0;
+
+	p = ((((s64)1048576 - adc_press) << 31) - var2) * 3125;
+	p = div64_s64(p, var1);
+	var1 = (((s64)(s16)le16_to_cpu(buf[P9])) * (p >> 13) * (p >> 13)) >> 25;
+	var2 = (((s64)(s16)le16_to_cpu(buf[P8])) * p) >> 19;
+	p = ((p + var1 + var2) >> 8) + (((s64)(s16)le16_to_cpu(buf[P7])) << 4);
+
+	return (u32)p;
+}
+
+static int bmp280_read_temp(struct bmp280_data *data,
+			    int *val)
+{
+	int ret;
+	__be32 tmp = 0;
+	s32 adc_temp, comp_temp;
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
+			       (u8 *) &tmp, 3);
+	if (ret < 0) {
+		dev_err(data->dev, "failed to read temperature\n");
+		return ret;
+	}
+
+	adc_temp = be32_to_cpu(tmp) >> 12;
+	comp_temp = bmp280_compensate_temp(data, adc_temp);
+
+	/*
+	 * val might be NULL if we're called by the read_press routine,
+	 * who only cares about the carry over t_fine value.
+	 */
+	if (val) {
+		*val = comp_temp * 10;
+		return IIO_VAL_INT;
+	}
+
+	return 0;
+}
+
+static int bmp280_read_press(struct bmp280_data *data,
+			     int *val, int *val2)
+{
+	int ret;
+	__be32 tmp = 0;
+	s32 adc_press;
+	u32 comp_press;
+
+	/* Read and compensate temperature so we get a reading of t_fine. */
+	ret = bmp280_read_temp(data, NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_PRESS_MSB,
+			       (u8 *) &tmp, 3);
+	if (ret < 0) {
+		dev_err(data->dev, "failed to read pressure\n");
+		return ret;
+	}
+
+	adc_press = be32_to_cpu(tmp) >> 12;
+	comp_press = bmp280_compensate_press(data, adc_press);
+
+	*val = comp_press;
+	*val2 = 256000;
+
+	return IIO_VAL_FRACTIONAL;
+}
+
+static int bmp280_read_humid(struct bmp280_data *data, int *val, int *val2)
+{
+	int ret;
+	__be16 tmp = 0;
+	s32 adc_humidity;
+	u32 comp_humidity;
+
+	/* Read and compensate temperature so we get a reading of t_fine. */
+	ret = bmp280_read_temp(data, NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_HUMIDITY_MSB,
+			       (u8 *) &tmp, 2);
+	if (ret < 0) {
+		dev_err(data->dev, "failed to read humidity\n");
+		return ret;
+	}
+
+	adc_humidity = be16_to_cpu(tmp);
+	comp_humidity = bmp280_compensate_humidity(data, adc_humidity);
+
+	*val = comp_humidity;
+	*val2 = 1024;
+
+	return IIO_VAL_FRACTIONAL;
+}
+
+static int bmp280_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val, int *val2, long mask)
+{
+	int ret;
+	struct bmp280_data *data = iio_priv(indio_dev);
+
+	mutex_lock(&data->lock);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_PROCESSED:
+		switch (chan->type) {
+		case IIO_HUMIDITYRELATIVE:
+			ret = data->chip_info->read_humid(data, val, val2);
+			break;
+		case IIO_PRESSURE:
+			ret = data->chip_info->read_press(data, val, val2);
+			break;
+		case IIO_TEMP:
+			ret = data->chip_info->read_temp(data, val);
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		break;
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		switch (chan->type) {
+		case IIO_HUMIDITYRELATIVE:
+			*val = 1 << data->oversampling_humid;
+			ret = IIO_VAL_INT;
+			break;
+		case IIO_PRESSURE:
+			*val = 1 << data->oversampling_press;
+			ret = IIO_VAL_INT;
+			break;
+		case IIO_TEMP:
+			*val = 1 << data->oversampling_temp;
+			ret = IIO_VAL_INT;
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+
+	mutex_unlock(&data->lock);
+
+	return ret;
+}
+
+static int bmp280_write_oversampling_ratio_humid(struct bmp280_data *data,
+					       int val)
+{
+	int i;
+	const int *avail = data->chip_info->oversampling_humid_avail;
+	const int n = data->chip_info->num_oversampling_humid_avail;
+
+	for (i = 0; i < n; i++) {
+		if (avail[i] == val) {
+			data->oversampling_humid = ilog2(val);
+
+			return data->chip_info->chip_config(data);
+		}
+	}
+	return -EINVAL;
+}
+
+static int bmp280_write_oversampling_ratio_temp(struct bmp280_data *data,
+					       int val)
+{
+	int i;
+	const int *avail = data->chip_info->oversampling_temp_avail;
+	const int n = data->chip_info->num_oversampling_temp_avail;
+
+	for (i = 0; i < n; i++) {
+		if (avail[i] == val) {
+			data->oversampling_temp = ilog2(val);
+
+			return data->chip_info->chip_config(data);
+		}
+	}
+	return -EINVAL;
+}
+
+static int bmp280_write_oversampling_ratio_press(struct bmp280_data *data,
+					       int val)
+{
+	int i;
+	const int *avail = data->chip_info->oversampling_press_avail;
+	const int n = data->chip_info->num_oversampling_press_avail;
+
+	for (i = 0; i < n; i++) {
+		if (avail[i] == val) {
+			data->oversampling_press = ilog2(val);
+
+			return data->chip_info->chip_config(data);
+		}
+	}
+	return -EINVAL;
+}
+
+static int bmp280_write_raw(struct iio_dev *indio_dev,
+			    struct iio_chan_spec const *chan,
+			    int val, int val2, long mask)
+{
+	int ret = 0;
+	struct bmp280_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+		mutex_lock(&data->lock);
+		switch (chan->type) {
+		case IIO_HUMIDITYRELATIVE:
+			ret = bmp280_write_oversampling_ratio_humid(data, val);
+			break;
+		case IIO_PRESSURE:
+			ret = bmp280_write_oversampling_ratio_press(data, val);
+			break;
+		case IIO_TEMP:
+			ret = bmp280_write_oversampling_ratio_temp(data, val);
+			break;
+		default:
+			ret = -EINVAL;
+			break;
+		}
+		mutex_unlock(&data->lock);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static ssize_t bmp280_show_avail(char *buf, const int *vals, const int n)
+{
+	size_t len = 0;
+	int i;
+
+	for (i = 0; i < n; i++)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "%d ", vals[i]);
+
+	buf[len - 1] = '\n';
+
+	return len;
+}
+
+static ssize_t bmp280_show_temp_oversampling_avail(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct bmp280_data *data = iio_priv(dev_to_iio_dev(dev));
+
+	return bmp280_show_avail(buf, data->chip_info->oversampling_temp_avail,
+				 data->chip_info->num_oversampling_temp_avail);
+}
+
+static ssize_t bmp280_show_press_oversampling_avail(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct bmp280_data *data = iio_priv(dev_to_iio_dev(dev));
+
+	return bmp280_show_avail(buf, data->chip_info->oversampling_press_avail,
+				 data->chip_info->num_oversampling_press_avail);
+}
+
+static IIO_DEVICE_ATTR(in_temp_oversampling_ratio_available,
+	S_IRUGO, bmp280_show_temp_oversampling_avail, NULL, 0);
+
+static IIO_DEVICE_ATTR(in_pressure_oversampling_ratio_available,
+	S_IRUGO, bmp280_show_press_oversampling_avail, NULL, 0);
+
+static struct attribute *bmp280_attributes[] = {
+	&iio_dev_attr_in_temp_oversampling_ratio_available.dev_attr.attr,
+	&iio_dev_attr_in_pressure_oversampling_ratio_available.dev_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group bmp280_attrs_group = {
+	.attrs = bmp280_attributes,
+};
+
+static const struct iio_info bmp280_info = {
+	.driver_module = THIS_MODULE,
+	.read_raw = &bmp280_read_raw,
+	.write_raw = &bmp280_write_raw,
+	.attrs = &bmp280_attrs_group,
+};
+
+static int bmp280_chip_config(struct bmp280_data *data)
+{
+	int ret;
+	u8 osrs = BMP280_OSRS_TEMP_X(data->oversampling_temp + 1) |
+		  BMP280_OSRS_PRESS_X(data->oversampling_press + 1);
+
+	ret = regmap_update_bits(data->regmap, BMP280_REG_CTRL_MEAS,
+				 BMP280_OSRS_TEMP_MASK |
+				 BMP280_OSRS_PRESS_MASK |
+				 BMP280_MODE_MASK,
+				 osrs | BMP280_MODE_NORMAL);
+	if (ret < 0) {
+		dev_err(data->dev,
+			"failed to write ctrl_meas register\n");
+		return ret;
+	}
+
+	ret = regmap_update_bits(data->regmap, BMP280_REG_CONFIG,
+				 BMP280_FILTER_MASK,
+				 BMP280_FILTER_4X);
+	if (ret < 0) {
+		dev_err(data->dev,
+			"failed to write config register\n");
+		return ret;
+	}
+
+	return ret;
+}
+
+static const int bmp280_oversampling_avail[] = { 1, 2, 4, 8, 16 };
+
+static const struct bmp280_chip_info bmp280_chip_info = {
+	.oversampling_temp_avail = bmp280_oversampling_avail,
+	.num_oversampling_temp_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.oversampling_press_avail = bmp280_oversampling_avail,
+	.num_oversampling_press_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.chip_config = bmp280_chip_config,
+	.read_temp = bmp280_read_temp,
+	.read_press = bmp280_read_press,
+};
+
+static int bme280_chip_config(struct bmp280_data *data)
+{
+	int ret = bmp280_chip_config(data);
+	u8 osrs = BMP280_OSRS_HUMIDITIY_X(data->oversampling_humid + 1);
+
+	if (ret < 0)
+		return ret;
+
+	return regmap_update_bits(data->regmap, BMP280_REG_CTRL_HUMIDITY,
+				  BMP280_OSRS_HUMIDITY_MASK, osrs);
+}
+
+static const struct bmp280_chip_info bme280_chip_info = {
+	.oversampling_temp_avail = bmp280_oversampling_avail,
+	.num_oversampling_temp_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.oversampling_press_avail = bmp280_oversampling_avail,
+	.num_oversampling_press_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.oversampling_humid_avail = bmp280_oversampling_avail,
+	.num_oversampling_humid_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.chip_config = bme280_chip_config,
+	.read_temp = bmp280_read_temp,
+	.read_press = bmp280_read_press,
+	.read_humid = bmp280_read_humid,
+};
+
+static int bmp180_measure(struct bmp280_data *data, u8 ctrl_meas)
+{
+	int ret;
+	const int conversion_time_max[] = { 4500, 7500, 13500, 25500 };
+	unsigned int delay_us;
+	unsigned int ctrl;
+
+	ret = regmap_write(data->regmap, BMP280_REG_CTRL_MEAS, ctrl_meas);
+	if (ret)
+		return ret;
+
+	if (ctrl_meas == BMP180_MEAS_TEMP)
+		delay_us = 4500;
+	else
+		delay_us = conversion_time_max[data->oversampling_press];
+
+	usleep_range(delay_us, delay_us + 1000);
+
+	ret = regmap_read(data->regmap, BMP280_REG_CTRL_MEAS, &ctrl);
+	if (ret)
+		return ret;
+
+	/* The value of this bit reset to "0" after conversion is complete */
+	if (ctrl & BMP180_MEAS_SCO)
+		return -EIO;
+
+	return 0;
+}
+
+static int bmp180_read_adc_temp(struct bmp280_data *data, int *val)
+{
+	int ret;
+	__be16 tmp = 0;
+
+	ret = bmp180_measure(data, BMP180_MEAS_TEMP);
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, BMP180_REG_OUT_MSB, (u8 *)&tmp, 2);
+	if (ret)
+		return ret;
+
+	*val = be16_to_cpu(tmp);
+
+	return 0;
+}
+
+/*
+ * These enums are used for indexing into the array of calibration
+ * coefficients for BMP180.
+ */
+enum { AC1, AC2, AC3, AC4, AC5, AC6, B1, B2, MB, MC, MD };
+
+struct bmp180_calib {
+	s16 AC1;
+	s16 AC2;
+	s16 AC3;
+	u16 AC4;
+	u16 AC5;
+	u16 AC6;
+	s16 B1;
+	s16 B2;
+	s16 MB;
+	s16 MC;
+	s16 MD;
+};
+
+static int bmp180_read_calib(struct bmp280_data *data,
+			     struct bmp180_calib *calib)
+{
+	int ret;
+	int i;
+	__be16 buf[BMP180_REG_CALIB_COUNT / 2];
+
+	ret = regmap_bulk_read(data->regmap, BMP180_REG_CALIB_START, buf,
+			       sizeof(buf));
+
+	if (ret < 0)
+		return ret;
+
+	/* None of the words has the value 0 or 0xFFFF */
+	for (i = 0; i < ARRAY_SIZE(buf); i++) {
+		if (buf[i] == cpu_to_be16(0) || buf[i] == cpu_to_be16(0xffff))
+			return -EIO;
+	}
+
+	calib->AC1 = be16_to_cpu(buf[AC1]);
+	calib->AC2 = be16_to_cpu(buf[AC2]);
+	calib->AC3 = be16_to_cpu(buf[AC3]);
+	calib->AC4 = be16_to_cpu(buf[AC4]);
+	calib->AC5 = be16_to_cpu(buf[AC5]);
+	calib->AC6 = be16_to_cpu(buf[AC6]);
+	calib->B1 = be16_to_cpu(buf[B1]);
+	calib->B2 = be16_to_cpu(buf[B2]);
+	calib->MB = be16_to_cpu(buf[MB]);
+	calib->MC = be16_to_cpu(buf[MC]);
+	calib->MD = be16_to_cpu(buf[MD]);
+
+	return 0;
+}
+
+/*
+ * Returns temperature in DegC, resolution is 0.1 DegC.
+ * t_fine carries fine temperature as global value.
+ *
+ * Taken from datasheet, Section 3.5, "Calculating pressure and temperature".
+ */
+static s32 bmp180_compensate_temp(struct bmp280_data *data, s32 adc_temp)
+{
+	int ret;
+	s32 x1, x2;
+	struct bmp180_calib calib;
+
+	ret = bmp180_read_calib(data, &calib);
+	if (ret < 0) {
+		dev_err(data->dev,
+			"failed to read calibration coefficients\n");
+		return ret;
+	}
+
+	x1 = ((adc_temp - calib.AC6) * calib.AC5) >> 15;
+	x2 = (calib.MC << 11) / (x1 + calib.MD);
+	data->t_fine = x1 + x2;
+
+	return (data->t_fine + 8) >> 4;
+}
+
+static int bmp180_read_temp(struct bmp280_data *data, int *val)
+{
+	int ret;
+	s32 adc_temp, comp_temp;
+
+	ret = bmp180_read_adc_temp(data, &adc_temp);
+	if (ret)
+		return ret;
+
+	comp_temp = bmp180_compensate_temp(data, adc_temp);
+
+	/*
+	 * val might be NULL if we're called by the read_press routine,
+	 * who only cares about the carry over t_fine value.
+	 */
+	if (val) {
+		*val = comp_temp * 100;
+		return IIO_VAL_INT;
+	}
+
+	return 0;
+}
+
+static int bmp180_read_adc_press(struct bmp280_data *data, int *val)
+{
+	int ret;
+	__be32 tmp = 0;
+	u8 oss = data->oversampling_press;
+
+	ret = bmp180_measure(data, BMP180_MEAS_PRESS_X(oss));
+	if (ret)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, BMP180_REG_OUT_MSB, (u8 *)&tmp, 3);
+	if (ret)
+		return ret;
+
+	*val = (be32_to_cpu(tmp) >> 8) >> (8 - oss);
+
+	return 0;
+}
+
+/*
+ * Returns pressure in Pa, resolution is 1 Pa.
+ *
+ * Taken from datasheet, Section 3.5, "Calculating pressure and temperature".
+ */
+static u32 bmp180_compensate_press(struct bmp280_data *data, s32 adc_press)
+{
+	int ret;
+	s32 x1, x2, x3, p;
+	s32 b3, b6;
+	u32 b4, b7;
+	s32 oss = data->oversampling_press;
+	struct bmp180_calib calib;
+
+	ret = bmp180_read_calib(data, &calib);
+	if (ret < 0) {
+		dev_err(data->dev,
+			"failed to read calibration coefficients\n");
+		return ret;
+	}
+
+	b6 = data->t_fine - 4000;
+	x1 = (calib.B2 * (b6 * b6 >> 12)) >> 11;
+	x2 = calib.AC2 * b6 >> 11;
+	x3 = x1 + x2;
+	b3 = ((((s32)calib.AC1 * 4 + x3) << oss) + 2) / 4;
+	x1 = calib.AC3 * b6 >> 13;
+	x2 = (calib.B1 * ((b6 * b6) >> 12)) >> 16;
+	x3 = (x1 + x2 + 2) >> 2;
+	b4 = calib.AC4 * (u32)(x3 + 32768) >> 15;
+	b7 = ((u32)adc_press - b3) * (50000 >> oss);
+	if (b7 < 0x80000000)
+		p = (b7 * 2) / b4;
+	else
+		p = (b7 / b4) * 2;
+
+	x1 = (p >> 8) * (p >> 8);
+	x1 = (x1 * 3038) >> 16;
+	x2 = (-7357 * p) >> 16;
+
+	return p + ((x1 + x2 + 3791) >> 4);
+}
+
+static int bmp180_read_press(struct bmp280_data *data,
+			     int *val, int *val2)
+{
+	int ret;
+	s32 adc_press;
+	u32 comp_press;
+
+	/* Read and compensate temperature so we get a reading of t_fine. */
+	ret = bmp180_read_temp(data, NULL);
+	if (ret)
+		return ret;
+
+	ret = bmp180_read_adc_press(data, &adc_press);
+	if (ret)
+		return ret;
+
+	comp_press = bmp180_compensate_press(data, adc_press);
+
+	*val = comp_press;
+	*val2 = 1000;
+
+	return IIO_VAL_FRACTIONAL;
+}
+
+static int bmp180_chip_config(struct bmp280_data *data)
+{
+	return 0;
+}
+
+static const int bmp180_oversampling_temp_avail[] = { 1 };
+static const int bmp180_oversampling_press_avail[] = { 1, 2, 4, 8 };
+
+static const struct bmp280_chip_info bmp180_chip_info = {
+	.oversampling_temp_avail = bmp180_oversampling_temp_avail,
+	.num_oversampling_temp_avail =
+		ARRAY_SIZE(bmp180_oversampling_temp_avail),
+
+	.oversampling_press_avail = bmp180_oversampling_press_avail,
+	.num_oversampling_press_avail =
+		ARRAY_SIZE(bmp180_oversampling_press_avail),
+
+	.chip_config = bmp180_chip_config,
+	.read_temp = bmp180_read_temp,
+	.read_press = bmp180_read_press,
+};
+
+int bmp280_common_probe(struct device *dev,
+			struct regmap *regmap,
+			unsigned int chip,
+			const char *name)
+{
+	int ret;
+	struct iio_dev *indio_dev;
+	struct bmp280_data *data;
+	unsigned int chip_id;
+	struct gpio_desc *gpiod;
+
+	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	data = iio_priv(indio_dev);
+	mutex_init(&data->lock);
+	data->dev = dev;
+
+	indio_dev->dev.parent = dev;
+	indio_dev->name = name;
+	indio_dev->channels = bmp280_channels;
+	indio_dev->info = &bmp280_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+
+	switch (chip) {
+	case BMP180_CHIP_ID:
+		indio_dev->num_channels = 2;
+		data->chip_info = &bmp180_chip_info;
+		data->oversampling_press = ilog2(8);
+		data->oversampling_temp = ilog2(1);
+		data->start_up_time = 10;
+		break;
+	case BMP280_CHIP_ID:
+		indio_dev->num_channels = 2;
+		data->chip_info = &bmp280_chip_info;
+		data->oversampling_press = ilog2(16);
+		data->oversampling_temp = ilog2(2);
+		data->start_up_time = 2;
+		break;
+	case BME280_CHIP_ID:
+		indio_dev->num_channels = 3;
+		data->chip_info = &bme280_chip_info;
+		data->oversampling_press = ilog2(16);
+		data->oversampling_humid = ilog2(16);
+		data->oversampling_temp = ilog2(2);
+		data->start_up_time = 2;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* Bring up regulators */
+	data->vddd = devm_regulator_get(dev, "vddd");
+	if (IS_ERR(data->vddd)) {
+		dev_err(dev, "failed to get VDDD regulator\n");
+		return PTR_ERR(data->vddd);
+	}
+	ret = regulator_enable(data->vddd);
+	if (ret) {
+		dev_err(dev, "failed to enable VDDD regulator\n");
+		return ret;
+	}
+	data->vdda = devm_regulator_get(dev, "vdda");
+	if (IS_ERR(data->vdda)) {
+		dev_err(dev, "failed to get VDDA regulator\n");
+		ret = PTR_ERR(data->vddd);
+		goto out_disable_vddd;
+	}
+	ret = regulator_enable(data->vdda);
+	if (ret) {
+		dev_err(dev, "failed to enable VDDA regulator\n");
+		goto out_disable_vddd;
+	}
+	/* Wait to make sure we started up properly */
+	mdelay(data->start_up_time);
+
+	/* Bring chip out of reset if there is an assigned GPIO line */
+	gpiod = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	/* Deassert the signal */
+	if (!IS_ERR(gpiod)) {
+		dev_info(dev, "release reset\n");
+		gpiod_set_value(gpiod, 0);
+	}
+
+	data->regmap = regmap;
+	ret = regmap_read(regmap, BMP280_REG_ID, &chip_id);
+	if (ret < 0)
+		goto out_disable_vdda;
+	if (chip_id != chip) {
+		dev_err(dev, "bad chip id: expected %x got %x\n",
+			chip, chip_id);
+		ret = -EINVAL;
+		goto out_disable_vdda;
+	}
+
+	ret = data->chip_info->chip_config(data);
+	if (ret < 0)
+		goto out_disable_vdda;
+
+	dev_set_drvdata(dev, indio_dev);
+
+	ret = iio_device_register(indio_dev);
+	if (ret)
+		goto out_disable_vdda;
+
+	return 0;
+
+out_disable_vdda:
+	regulator_disable(data->vdda);
+out_disable_vddd:
+	regulator_disable(data->vddd);
+	return ret;
+}
+
+int bmp280_common_remove(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct bmp280_data *data = iio_priv(indio_dev);
+
+	iio_device_unregister(indio_dev);
+	regulator_disable(data->vdda);
+	regulator_disable(data->vddd);
+	return 0;
+}