drivers/iio/pressure/bmp280.c - kernel/msm-4.9 - Gitiles

 /*
  * Copyright (c) 2014 Intel Corporation
  *
  * Driver for Bosch Sensortec 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.
  *
  */

 #define pr_fmt(fmt) "bmp280: " fmt

 #include <linux/module.h>
 #include <linux/i2c.h>
 #include <linux/acpi.h>
 #include <linux/regmap.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>

 #define BMP280_REG_TEMP_XLSB		0xFC
 #define BMP280_REG_TEMP_LSB		0xFB
 #define BMP280_REG_TEMP_MSB		0xFA
 #define BMP280_REG_PRESS_XLSB		0xF9
 #define BMP280_REG_PRESS_LSB		0xF8
 #define BMP280_REG_PRESS_MSB		0xF7

 #define BMP280_REG_CONFIG		0xF5
 #define BMP280_REG_CTRL_MEAS		0xF4
 #define BMP280_REG_STATUS		0xF3
 #define BMP280_REG_RESET		0xE0
 #define BMP280_REG_ID			0xD0

 #define BMP280_REG_COMP_TEMP_START	0x88
 #define BMP280_COMP_TEMP_REG_COUNT	6

 #define BMP280_REG_COMP_PRESS_START	0x8E
 #define BMP280_COMP_PRESS_REG_COUNT	18

 #define BMP280_FILTER_MASK		(BIT(4) | BIT(3) | BIT(2))
 #define BMP280_FILTER_OFF		0
 #define BMP280_FILTER_2X		BIT(2)
 #define BMP280_FILTER_4X		BIT(3)
 #define BMP280_FILTER_8X		(BIT(3) | BIT(2))
 #define BMP280_FILTER_16X		BIT(4)

 #define BMP280_OSRS_TEMP_MASK		(BIT(7) | BIT(6) | BIT(5))
 #define BMP280_OSRS_TEMP_SKIP		0
 #define BMP280_OSRS_TEMP_1X		BIT(5)
 #define BMP280_OSRS_TEMP_2X		BIT(6)
 #define BMP280_OSRS_TEMP_4X		(BIT(6) | BIT(5))
 #define BMP280_OSRS_TEMP_8X		BIT(7)
 #define BMP280_OSRS_TEMP_16X		(BIT(7) | BIT(5))

 #define BMP280_OSRS_PRESS_MASK		(BIT(4) | BIT(3) | BIT(2))
 #define BMP280_OSRS_PRESS_SKIP		0
 #define BMP280_OSRS_PRESS_1X		BIT(2)
 #define BMP280_OSRS_PRESS_2X		BIT(3)
 #define BMP280_OSRS_PRESS_4X		(BIT(3) | BIT(2))
 #define BMP280_OSRS_PRESS_8X		BIT(4)
 #define BMP280_OSRS_PRESS_16X		(BIT(4) | BIT(2))

 #define BMP280_MODE_MASK		(BIT(1) | BIT(0))
 #define BMP280_MODE_SLEEP		0
 #define BMP280_MODE_FORCED		BIT(0)
 #define BMP280_MODE_NORMAL		(BIT(1) | BIT(0))

 #define BMP280_CHIP_ID			0x58
 #define BMP280_SOFT_RESET_VAL		0xB6

 struct bmp280_data {
 	struct i2c_client *client;
 	struct mutex lock;
 	struct regmap *regmap;

 	/*
 	 * Carryover value from temperature conversion, used in pressure
 	 * calculation.
 	 */
 	s32 t_fine;
 };

 /* Compensation parameters. */
 struct bmp280_comp_temp {
 	u16 dig_t1;
 	s16 dig_t2, dig_t3;
 };

 struct bmp280_comp_press {
 	u16 dig_p1;
 	s16 dig_p2, dig_p3, dig_p4, dig_p5, dig_p6, dig_p7, dig_p8, dig_p9;
 };

 static const struct iio_chan_spec bmp280_channels[] = {
 	{
 		.type = IIO_PRESSURE,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
 	},
 	{
 		.type = IIO_TEMP,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
 	},
 };

 static bool bmp280_is_writeable_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
 	case BMP280_REG_CONFIG:
 	case BMP280_REG_CTRL_MEAS:
 	case BMP280_REG_RESET:
 		return true;
 	default:
 		return false;
 	};
 }

 static bool bmp280_is_volatile_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
 	case BMP280_REG_TEMP_XLSB:
 	case BMP280_REG_TEMP_LSB:
 	case BMP280_REG_TEMP_MSB:
 	case BMP280_REG_PRESS_XLSB:
 	case BMP280_REG_PRESS_LSB:
 	case BMP280_REG_PRESS_MSB:
 	case BMP280_REG_STATUS:
 		return true;
 	default:
 		return false;
 	}
 }

 static const struct regmap_config bmp280_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,

 	.max_register = BMP280_REG_TEMP_XLSB,
 	.cache_type = REGCACHE_RBTREE,

 	.writeable_reg = bmp280_is_writeable_reg,
 	.volatile_reg = bmp280_is_volatile_reg,
 };

 static int bmp280_read_compensation_temp(struct bmp280_data *data,
 					 struct bmp280_comp_temp *comp)
 {
 	int ret;
 	__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->client->dev,
 			"failed to read temperature calibration parameters\n");
 		return ret;
 	}

 	comp->dig_t1 = (u16) le16_to_cpu(buf[0]);
 	comp->dig_t2 = (s16) le16_to_cpu(buf[1]);
 	comp->dig_t3 = (s16) le16_to_cpu(buf[2]);

 	return 0;
 }

 static int bmp280_read_compensation_press(struct bmp280_data *data,
 					  struct bmp280_comp_press *comp)
 {
 	int ret;
 	__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->client->dev,
 			"failed to read pressure calibration parameters\n");
 		return ret;
 	}

 	comp->dig_p1 = (u16) le16_to_cpu(buf[0]);
 	comp->dig_p2 = (s16) le16_to_cpu(buf[1]);
 	comp->dig_p3 = (s16) le16_to_cpu(buf[2]);
 	comp->dig_p4 = (s16) le16_to_cpu(buf[3]);
 	comp->dig_p5 = (s16) le16_to_cpu(buf[4]);
 	comp->dig_p6 = (s16) le16_to_cpu(buf[5]);
 	comp->dig_p7 = (s16) le16_to_cpu(buf[6]);
 	comp->dig_p8 = (s16) le16_to_cpu(buf[7]);
 	comp->dig_p9 = (s16) le16_to_cpu(buf[8]);

 	return 0;
 }

 /*
  * 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,
 				  struct bmp280_comp_temp *comp,
 				  s32 adc_temp)
 {
 	s32 var1, var2, t;

 	var1 = (((adc_temp >> 3) - ((s32) comp->dig_t1 << 1)) *
 		((s32) comp->dig_t2)) >> 11;
 	var2 = (((((adc_temp >> 4) - ((s32) comp->dig_t1)) *
 		  ((adc_temp >> 4) - ((s32) comp->dig_t1))) >> 12) *
 		((s32) comp->dig_t3)) >> 14;

 	data->t_fine = var1 + var2;
 	t = (data->t_fine * 5 + 128) >> 8;

 	return t;
 }

 /*
  * 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,
 				   struct bmp280_comp_press *comp,
 				   s32 adc_press)
 {
 	s64 var1, var2, p;

 	var1 = ((s64) data->t_fine) - 128000;
 	var2 = var1 * var1 * (s64) comp->dig_p6;
 	var2 = var2 + ((var1 * (s64) comp->dig_p5) << 17);
 	var2 = var2 + (((s64) comp->dig_p4) << 35);
 	var1 = ((var1 * var1 * (s64) comp->dig_p3) >> 8) +
 		((var1 * (s64) comp->dig_p2) << 12);
 	var1 = (((((s64) 1) << 47) + var1)) * ((s64) comp->dig_p1) >> 33;

 	if (var1 == 0)
 		return 0;

 	p = ((((s64) 1048576 - adc_press) << 31) - var2) * 3125;
 	p = div64_s64(p, var1);
 	var1 = (((s64) comp->dig_p9) * (p >> 13) * (p >> 13)) >> 25;
 	var2 = (((s64) comp->dig_p8) * p) >> 19;
 	p = ((p + var1 + var2) >> 8) + (((s64) comp->dig_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;
 	struct bmp280_comp_temp comp;

 	ret = bmp280_read_compensation_temp(data, &comp);
 	if (ret < 0)
 		return ret;

 	ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
 			       (u8 *) &tmp, 3);
 	if (ret < 0) {
 		dev_err(&data->client->dev, "failed to read temperature\n");
 		return ret;
 	}

 	adc_temp = be32_to_cpu(tmp) >> 12;
 	comp_temp = bmp280_compensate_temp(data, &comp, 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;
 	struct bmp280_comp_press comp;

 	ret = bmp280_read_compensation_press(data, &comp);
 	if (ret < 0)
 		return ret;

 	/* 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->client->dev, "failed to read pressure\n");
 		return ret;
 	}

 	adc_press = be32_to_cpu(tmp) >> 12;
 	comp_press = bmp280_compensate_press(data, &comp, adc_press);

 	*val = comp_press;
 	*val2 = 256000;

 	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_PRESSURE:
 			ret = bmp280_read_press(data, val, val2);
 			break;
 		case IIO_TEMP:
 			ret = bmp280_read_temp(data, val);
 			break;
 		default:
 			ret = -EINVAL;
 			break;
 		}
 		break;
 	default:
 		ret = -EINVAL;
 		break;
 	}

 	mutex_unlock(&data->lock);

 	return ret;
 }

 static const struct iio_info bmp280_info = {
 	.driver_module = THIS_MODULE,
 	.read_raw = &bmp280_read_raw,
 };

 static int bmp280_chip_init(struct bmp280_data *data)
 {
 	int ret;

 	ret = regmap_update_bits(data->regmap, BMP280_REG_CTRL_MEAS,
 				 BMP280_OSRS_TEMP_MASK |
 				 BMP280_OSRS_PRESS_MASK |
 				 BMP280_MODE_MASK,
 				 BMP280_OSRS_TEMP_2X |
 				 BMP280_OSRS_PRESS_16X |
 				 BMP280_MODE_NORMAL);
 	if (ret < 0) {
 		dev_err(&data->client->dev,
 			"failed to write config 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->client->dev,
 			"failed to write config register\n");
 		return ret;
 	}

 	return ret;
 }

 static int bmp280_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
 	int ret;
 	struct iio_dev *indio_dev;
 	struct bmp280_data *data;
 	unsigned int chip_id;

 	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
 	if (!indio_dev)
 		return -ENOMEM;

 	i2c_set_clientdata(client, indio_dev);
 	data = iio_priv(indio_dev);
 	mutex_init(&data->lock);
 	data->client = client;

 	indio_dev->dev.parent = &client->dev;
 	indio_dev->name = id->name;
 	indio_dev->channels = bmp280_channels;
 	indio_dev->num_channels = ARRAY_SIZE(bmp280_channels);
 	indio_dev->info = &bmp280_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;

 	data->regmap = devm_regmap_init_i2c(client, &bmp280_regmap_config);
 	if (IS_ERR(data->regmap)) {
 		dev_err(&client->dev, "failed to allocate register map\n");
 		return PTR_ERR(data->regmap);
 	}

 	ret = regmap_read(data->regmap, BMP280_REG_ID, &chip_id);
 	if (ret < 0)
 		return ret;
 	if (chip_id != BMP280_CHIP_ID) {
 		dev_err(&client->dev, "bad chip id.  expected %x got %x\n",
 			BMP280_CHIP_ID, chip_id);
 		return -EINVAL;
 	}

 	ret = bmp280_chip_init(data);
 	if (ret < 0)
 		return ret;

 	return devm_iio_device_register(&client->dev, indio_dev);
 }

 static const struct acpi_device_id bmp280_acpi_match[] = {
 	{"BMP0280", 0},
 	{ },
 };
 MODULE_DEVICE_TABLE(acpi, bmp280_acpi_match);

 static const struct i2c_device_id bmp280_id[] = {
 	{"bmp280", 0},
 	{ },
 };
 MODULE_DEVICE_TABLE(i2c, bmp280_id);

 static struct i2c_driver bmp280_driver = {
 	.driver = {
 		.name	= "bmp280",
 		.acpi_match_table = ACPI_PTR(bmp280_acpi_match),
 	},
 	.probe		= bmp280_probe,
 	.id_table	= bmp280_id,
 };
 module_i2c_driver(bmp280_driver);

 MODULE_AUTHOR("Vlad Dogaru <vlad.dogaru@intel.com>");
 MODULE_DESCRIPTION("Driver for Bosch Sensortec BMP280 pressure and temperature sensor");
 MODULE_LICENSE("GPL v2");
	/*
	* Copyright (c) 2014 Intel Corporation
	*
	* Driver for Bosch Sensortec 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.
	*
	*/

	#define pr_fmt(fmt) "bmp280: " fmt

	#include <linux/module.h>
	#include <linux/i2c.h>
	#include <linux/acpi.h>
	#include <linux/regmap.h>
	#include <linux/iio/iio.h>
	#include <linux/iio/sysfs.h>

	#define BMP280_REG_TEMP_XLSB 0xFC
	#define BMP280_REG_TEMP_LSB 0xFB
	#define BMP280_REG_TEMP_MSB 0xFA
	#define BMP280_REG_PRESS_XLSB 0xF9
	#define BMP280_REG_PRESS_LSB 0xF8
	#define BMP280_REG_PRESS_MSB 0xF7

	#define BMP280_REG_CONFIG 0xF5
	#define BMP280_REG_CTRL_MEAS 0xF4
	#define BMP280_REG_STATUS 0xF3
	#define BMP280_REG_RESET 0xE0
	#define BMP280_REG_ID 0xD0

	#define BMP280_REG_COMP_TEMP_START 0x88
	#define BMP280_COMP_TEMP_REG_COUNT 6

	#define BMP280_REG_COMP_PRESS_START 0x8E
	#define BMP280_COMP_PRESS_REG_COUNT 18

	#define BMP280_FILTER_MASK (BIT(4) \| BIT(3) \| BIT(2))
	#define BMP280_FILTER_OFF 0
	#define BMP280_FILTER_2X BIT(2)
	#define BMP280_FILTER_4X BIT(3)
	#define BMP280_FILTER_8X (BIT(3) \| BIT(2))
	#define BMP280_FILTER_16X BIT(4)

	#define BMP280_OSRS_TEMP_MASK (BIT(7) \| BIT(6) \| BIT(5))
	#define BMP280_OSRS_TEMP_SKIP 0
	#define BMP280_OSRS_TEMP_1X BIT(5)
	#define BMP280_OSRS_TEMP_2X BIT(6)
	#define BMP280_OSRS_TEMP_4X (BIT(6) \| BIT(5))
	#define BMP280_OSRS_TEMP_8X BIT(7)
	#define BMP280_OSRS_TEMP_16X (BIT(7) \| BIT(5))

	#define BMP280_OSRS_PRESS_MASK (BIT(4) \| BIT(3) \| BIT(2))
	#define BMP280_OSRS_PRESS_SKIP 0
	#define BMP280_OSRS_PRESS_1X BIT(2)
	#define BMP280_OSRS_PRESS_2X BIT(3)
	#define BMP280_OSRS_PRESS_4X (BIT(3) \| BIT(2))
	#define BMP280_OSRS_PRESS_8X BIT(4)
	#define BMP280_OSRS_PRESS_16X (BIT(4) \| BIT(2))

	#define BMP280_MODE_MASK (BIT(1) \| BIT(0))
	#define BMP280_MODE_SLEEP 0
	#define BMP280_MODE_FORCED BIT(0)
	#define BMP280_MODE_NORMAL (BIT(1) \| BIT(0))

	#define BMP280_CHIP_ID 0x58
	#define BMP280_SOFT_RESET_VAL 0xB6

	struct bmp280_data {
	struct i2c_client *client;
	struct mutex lock;
	struct regmap *regmap;

	/*
	* Carryover value from temperature conversion, used in pressure
	* calculation.
	*/
	s32 t_fine;
	};

	/* Compensation parameters. */
	struct bmp280_comp_temp {
	u16 dig_t1;
	s16 dig_t2, dig_t3;
	};

	struct bmp280_comp_press {
	u16 dig_p1;
	s16 dig_p2, dig_p3, dig_p4, dig_p5, dig_p6, dig_p7, dig_p8, dig_p9;
	};

	static const struct iio_chan_spec bmp280_channels[] = {
	{
	.type = IIO_PRESSURE,
	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
	},
	{
	.type = IIO_TEMP,
	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
	},
	};

	static bool bmp280_is_writeable_reg(struct device *dev, unsigned int reg)
	{
	switch (reg) {
	case BMP280_REG_CONFIG:
	case BMP280_REG_CTRL_MEAS:
	case BMP280_REG_RESET:
	return true;
	default:
	return false;
	};
	}

	static bool bmp280_is_volatile_reg(struct device *dev, unsigned int reg)
	{
	switch (reg) {
	case BMP280_REG_TEMP_XLSB:
	case BMP280_REG_TEMP_LSB:
	case BMP280_REG_TEMP_MSB:
	case BMP280_REG_PRESS_XLSB:
	case BMP280_REG_PRESS_LSB:
	case BMP280_REG_PRESS_MSB:
	case BMP280_REG_STATUS:
	return true;
	default:
	return false;
	}
	}

	static const struct regmap_config bmp280_regmap_config = {
	.reg_bits = 8,
	.val_bits = 8,

	.max_register = BMP280_REG_TEMP_XLSB,
	.cache_type = REGCACHE_RBTREE,

	.writeable_reg = bmp280_is_writeable_reg,
	.volatile_reg = bmp280_is_volatile_reg,
	};

	static int bmp280_read_compensation_temp(struct bmp280_data *data,
	struct bmp280_comp_temp *comp)
	{
	int ret;
	__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->client->dev,
	"failed to read temperature calibration parameters\n");
	return ret;
	}

	comp->dig_t1 = (u16) le16_to_cpu(buf[0]);
	comp->dig_t2 = (s16) le16_to_cpu(buf[1]);
	comp->dig_t3 = (s16) le16_to_cpu(buf[2]);

	return 0;
	}

	static int bmp280_read_compensation_press(struct bmp280_data *data,
	struct bmp280_comp_press *comp)
	{
	int ret;
	__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->client->dev,
	"failed to read pressure calibration parameters\n");
	return ret;
	}

	comp->dig_p1 = (u16) le16_to_cpu(buf[0]);
	comp->dig_p2 = (s16) le16_to_cpu(buf[1]);
	comp->dig_p3 = (s16) le16_to_cpu(buf[2]);
	comp->dig_p4 = (s16) le16_to_cpu(buf[3]);
	comp->dig_p5 = (s16) le16_to_cpu(buf[4]);
	comp->dig_p6 = (s16) le16_to_cpu(buf[5]);
	comp->dig_p7 = (s16) le16_to_cpu(buf[6]);
	comp->dig_p8 = (s16) le16_to_cpu(buf[7]);
	comp->dig_p9 = (s16) le16_to_cpu(buf[8]);

	return 0;
	}

	/*
	* 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,
	struct bmp280_comp_temp *comp,
	s32 adc_temp)
	{
	s32 var1, var2, t;

	var1 = (((adc_temp >> 3) - ((s32) comp->dig_t1 << 1)) *
	((s32) comp->dig_t2)) >> 11;
	var2 = (((((adc_temp >> 4) - ((s32) comp->dig_t1)) *
	((adc_temp >> 4) - ((s32) comp->dig_t1))) >> 12) *
	((s32) comp->dig_t3)) >> 14;

	data->t_fine = var1 + var2;
	t = (data->t_fine * 5 + 128) >> 8;

	return t;
	}

	/*
	* 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,
	struct bmp280_comp_press *comp,
	s32 adc_press)
	{
	s64 var1, var2, p;

	var1 = ((s64) data->t_fine) - 128000;
	var2 = var1 * var1 * (s64) comp->dig_p6;
	var2 = var2 + ((var1 * (s64) comp->dig_p5) << 17);
	var2 = var2 + (((s64) comp->dig_p4) << 35);
	var1 = ((var1 * var1 * (s64) comp->dig_p3) >> 8) +
	((var1 * (s64) comp->dig_p2) << 12);
	var1 = (((((s64) 1) << 47) + var1)) * ((s64) comp->dig_p1) >> 33;

	if (var1 == 0)
	return 0;

	p = ((((s64) 1048576 - adc_press) << 31) - var2) * 3125;
	p = div64_s64(p, var1);
	var1 = (((s64) comp->dig_p9) * (p >> 13) * (p >> 13)) >> 25;
	var2 = (((s64) comp->dig_p8) * p) >> 19;
	p = ((p + var1 + var2) >> 8) + (((s64) comp->dig_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;
	struct bmp280_comp_temp comp;

	ret = bmp280_read_compensation_temp(data, &comp);
	if (ret < 0)
	return ret;

	ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
	(u8 *) &tmp, 3);
	if (ret < 0) {
	dev_err(&data->client->dev, "failed to read temperature\n");
	return ret;
	}

	adc_temp = be32_to_cpu(tmp) >> 12;
	comp_temp = bmp280_compensate_temp(data, &comp, 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;
	struct bmp280_comp_press comp;

	ret = bmp280_read_compensation_press(data, &comp);
	if (ret < 0)
	return ret;

	/* 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->client->dev, "failed to read pressure\n");
	return ret;
	}

	adc_press = be32_to_cpu(tmp) >> 12;
	comp_press = bmp280_compensate_press(data, &comp, adc_press);

	*val = comp_press;
	*val2 = 256000;

	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_PRESSURE:
	ret = bmp280_read_press(data, val, val2);
	break;
	case IIO_TEMP:
	ret = bmp280_read_temp(data, val);
	break;
	default:
	ret = -EINVAL;
	break;
	}
	break;
	default:
	ret = -EINVAL;
	break;
	}

	mutex_unlock(&data->lock);

	return ret;
	}

	static const struct iio_info bmp280_info = {
	.driver_module = THIS_MODULE,
	.read_raw = &bmp280_read_raw,
	};

	static int bmp280_chip_init(struct bmp280_data *data)
	{
	int ret;

	ret = regmap_update_bits(data->regmap, BMP280_REG_CTRL_MEAS,
	BMP280_OSRS_TEMP_MASK \|
	BMP280_OSRS_PRESS_MASK \|
	BMP280_MODE_MASK,
	BMP280_OSRS_TEMP_2X \|
	BMP280_OSRS_PRESS_16X \|
	BMP280_MODE_NORMAL);
	if (ret < 0) {
	dev_err(&data->client->dev,
	"failed to write config 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->client->dev,
	"failed to write config register\n");
	return ret;
	}

	return ret;
	}

	static int bmp280_probe(struct i2c_client *client,
	const struct i2c_device_id *id)
	{
	int ret;
	struct iio_dev *indio_dev;
	struct bmp280_data *data;
	unsigned int chip_id;

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
	if (!indio_dev)
	return -ENOMEM;

	i2c_set_clientdata(client, indio_dev);
	data = iio_priv(indio_dev);
	mutex_init(&data->lock);
	data->client = client;

	indio_dev->dev.parent = &client->dev;
	indio_dev->name = id->name;
	indio_dev->channels = bmp280_channels;
	indio_dev->num_channels = ARRAY_SIZE(bmp280_channels);
	indio_dev->info = &bmp280_info;
	indio_dev->modes = INDIO_DIRECT_MODE;

	data->regmap = devm_regmap_init_i2c(client, &bmp280_regmap_config);
	if (IS_ERR(data->regmap)) {
	dev_err(&client->dev, "failed to allocate register map\n");
	return PTR_ERR(data->regmap);
	}

	ret = regmap_read(data->regmap, BMP280_REG_ID, &chip_id);
	if (ret < 0)
	return ret;
	if (chip_id != BMP280_CHIP_ID) {
	dev_err(&client->dev, "bad chip id. expected %x got %x\n",
	BMP280_CHIP_ID, chip_id);
	return -EINVAL;
	}

	ret = bmp280_chip_init(data);
	if (ret < 0)
	return ret;

	return devm_iio_device_register(&client->dev, indio_dev);
	}

	static const struct acpi_device_id bmp280_acpi_match[] = {
	{"BMP0280", 0},
	{ },
	};
	MODULE_DEVICE_TABLE(acpi, bmp280_acpi_match);

	static const struct i2c_device_id bmp280_id[] = {
	{"bmp280", 0},
	{ },
	};
	MODULE_DEVICE_TABLE(i2c, bmp280_id);

	static struct i2c_driver bmp280_driver = {
	.driver = {
	.name = "bmp280",
	.acpi_match_table = ACPI_PTR(bmp280_acpi_match),
	},
	.probe = bmp280_probe,
	.id_table = bmp280_id,
	};
	module_i2c_driver(bmp280_driver);

	MODULE_AUTHOR("Vlad Dogaru <vlad.dogaru@intel.com>");
	MODULE_DESCRIPTION("Driver for Bosch Sensortec BMP280 pressure and temperature sensor");
	MODULE_LICENSE("GPL v2");