drivers/misc/bmp085.c

/*  Copyright (c) 2010  Christoph Mair <christoph.mair@gmail.com>
 *  Copyright (c) 2012  Bosch Sensortec GmbH
 *  Copyright (c) 2012  Unixphere AB
 *
 *  This driver supports the bmp085 digital barometric pressure
 *  and temperature sensor from Bosch Sensortec. The datasheet
 *  is available from their website:
 *  http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf
 *
 *  A pressure measurement is issued by reading from pressure0_input.
 *  The return value ranges from 30000 to 110000 pascal with a resulution
 *  of 1 pascal (0.01 millibar) which enables measurements from 9000m above
 *  to 500m below sea level.
 *
 *  The temperature can be read from temp0_input. Values range from
 *  -400 to 850 representing the ambient temperature in degree celsius
 *  multiplied by 10.The resolution is 0.1 celsius.
 *
 *  Because ambient pressure is temperature dependent, a temperature
 *  measurement will be executed automatically even if the user is reading
 *  from pressure0_input. This happens if the last temperature measurement
 *  has been executed more then one second ago.
 *
 *  To decrease RMS noise from pressure measurements, the bmp085 can
 *  autonomously calculate the average of up to eight samples. This is
 *  set up by writing to the oversampling sysfs file. Accepted values
 *  are 0, 1, 2 and 3. 2^x when x is the value written to this file
 *  specifies the number of samples used to calculate the ambient pressure.
 *  RMS noise is specified with six pascal (without averaging) and decreases
 *  down to 3 pascal when using an oversampling setting of 3.
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/module.h>
#include <linux/device.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/delay.h>

#define BMP085_NAME			"bmp085"
#define BMP085_I2C_ADDRESS		0x77
#define BMP085_CHIP_ID			0x55

#define BMP085_CALIBRATION_DATA_START	0xAA
#define BMP085_CALIBRATION_DATA_LENGTH	11	/* 16 bit values */
#define BMP085_CHIP_ID_REG		0xD0
#define BMP085_CTRL_REG			0xF4
#define BMP085_TEMP_MEASUREMENT		0x2E
#define BMP085_PRESSURE_MEASUREMENT	0x34
#define BMP085_CONVERSION_REGISTER_MSB	0xF6
#define BMP085_CONVERSION_REGISTER_LSB	0xF7
#define BMP085_CONVERSION_REGISTER_XLSB	0xF8
#define BMP085_TEMP_CONVERSION_TIME	5

static const unsigned short normal_i2c[] = { BMP085_I2C_ADDRESS,
							I2C_CLIENT_END };

struct bmp085_calibration_data {
	s16 AC1, AC2, AC3;
	u16 AC4, AC5, AC6;
	s16 B1, B2;
	s16 MB, MC, MD;
};

struct bmp085_data {
	struct	i2c_client *client;
	struct	mutex lock;
	struct	bmp085_calibration_data calibration;
	u8	oversampling_setting;
	u32	raw_temperature;
	u32	raw_pressure;
	u32	temp_measurement_period;
	unsigned long last_temp_measurement;
	s32	b6; /* calculated temperature correction coefficient */
};

static s32 bmp085_read_calibration_data(struct i2c_client *client)
{
	u16 tmp[BMP085_CALIBRATION_DATA_LENGTH];
	struct bmp085_data *data = i2c_get_clientdata(client);
	struct bmp085_calibration_data *cali = &(data->calibration);
	s32 status = i2c_smbus_read_i2c_block_data(client,
				BMP085_CALIBRATION_DATA_START,
				(BMP085_CALIBRATION_DATA_LENGTH << 1),
				(u8 *)tmp);
	if (status < 0)
		return status;

	if (status != (BMP085_CALIBRATION_DATA_LENGTH << 1))
		return -EIO;

	cali->AC1 =  be16_to_cpu(tmp[0]);
	cali->AC2 =  be16_to_cpu(tmp[1]);
	cali->AC3 =  be16_to_cpu(tmp[2]);
	cali->AC4 =  be16_to_cpu(tmp[3]);
	cali->AC5 =  be16_to_cpu(tmp[4]);
	cali->AC6 = be16_to_cpu(tmp[5]);
	cali->B1 = be16_to_cpu(tmp[6]);
	cali->B2 = be16_to_cpu(tmp[7]);
	cali->MB = be16_to_cpu(tmp[8]);
	cali->MC = be16_to_cpu(tmp[9]);
	cali->MD = be16_to_cpu(tmp[10]);
	return 0;
}

static s32 bmp085_update_raw_temperature(struct bmp085_data *data)
{
	u16 tmp;
	s32 status;

	mutex_lock(&data->lock);
	status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG,
						BMP085_TEMP_MEASUREMENT);
	if (status < 0) {
		dev_err(&data->client->dev,
			"Error while requesting temperature measurement.\n");
		goto exit;
	}
	msleep(BMP085_TEMP_CONVERSION_TIME);

	status = i2c_smbus_read_i2c_block_data(data->client,
		BMP085_CONVERSION_REGISTER_MSB, sizeof(tmp), (u8 *)&tmp);
	if (status < 0)
		goto exit;
	if (status != sizeof(tmp)) {
		dev_err(&data->client->dev,
			"Error while reading temperature measurement result\n");
		status = -EIO;
		goto exit;
	}
	data->raw_temperature = be16_to_cpu(tmp);
	data->last_temp_measurement = jiffies;
	status = 0;	/* everything ok, return 0 */

exit:
	mutex_unlock(&data->lock);
	return status;
}

static s32 bmp085_update_raw_pressure(struct bmp085_data *data)
{
	u32 tmp = 0;
	s32 status;

	mutex_lock(&data->lock);
	status = i2c_smbus_write_byte_data(data->client, BMP085_CTRL_REG,
			BMP085_PRESSURE_MEASUREMENT +
			(data->oversampling_setting << 6));
	if (status < 0) {
		dev_err(&data->client->dev,
			"Error while requesting pressure measurement.\n");
		goto exit;
	}

	/* wait for the end of conversion */
	msleep(2+(3 << data->oversampling_setting));

	/* copy data into a u32 (4 bytes), but skip the first byte. */
	status = i2c_smbus_read_i2c_block_data(data->client,
			BMP085_CONVERSION_REGISTER_MSB, 3, ((u8 *)&tmp)+1);
	if (status < 0)
		goto exit;
	if (status != 3) {
		dev_err(&data->client->dev,
			"Error while reading pressure measurement results\n");
		status = -EIO;
		goto exit;
	}
	data->raw_pressure = be32_to_cpu((tmp));
	data->raw_pressure >>= (8-data->oversampling_setting);
	status = 0;	/* everything ok, return 0 */

exit:
	mutex_unlock(&data->lock);
	return status;
}

/*
 * This function starts the temperature measurement and returns the value
 * in tenth of a degree celsius.
 */
static s32 bmp085_get_temperature(struct bmp085_data *data, int *temperature)
{
	struct bmp085_calibration_data *cali = &data->calibration;
	long x1, x2;
	int status;

	status = bmp085_update_raw_temperature(data);
	if (status < 0)
		goto exit;

	x1 = ((data->raw_temperature - cali->AC6) * cali->AC5) >> 15;
	x2 = (cali->MC << 11) / (x1 + cali->MD);
	data->b6 = x1 + x2 - 4000;
	/* if NULL just update b6. Used for pressure only measurements */
	if (temperature != NULL)
		*temperature = (x1+x2+8) >> 4;

exit:
	return status;
}

/*
 * This function starts the pressure measurement and returns the value
 * in millibar. Since the pressure depends on the ambient temperature,
 * a temperature measurement is executed according to the given temperature
 * measurement period (default is 1 sec boundary). This period could vary
 * and needs to be adjusted according to the sensor environment, i.e. if big
 * temperature variations then the temperature needs to be read out often.
 */
static s32 bmp085_get_pressure(struct bmp085_data *data, int *pressure)
{
	struct bmp085_calibration_data *cali = &data->calibration;
	s32 x1, x2, x3, b3;
	u32 b4, b7;
	s32 p;
	int status;

	/* alt least every second force an update of the ambient temperature */
	if ((data->last_temp_measurement == 0) ||
	    time_is_before_jiffies(data->last_temp_measurement + 1*HZ)) {
		status = bmp085_get_temperature(data, NULL);
		if (status < 0)
			return status;
	}

	status = bmp085_update_raw_pressure(data);
	if (status < 0)
		return status;

	x1 = (data->b6 * data->b6) >> 12;
	x1 *= cali->B2;
	x1 >>= 11;

	x2 = cali->AC2 * data->b6;
	x2 >>= 11;

	x3 = x1 + x2;

	b3 = (((((s32)cali->AC1) * 4 + x3) << data->oversampling_setting) + 2);
	b3 >>= 2;

	x1 = (cali->AC3 * data->b6) >> 13;
	x2 = (cali->B1 * ((data->b6 * data->b6) >> 12)) >> 16;
	x3 = (x1 + x2 + 2) >> 2;
	b4 = (cali->AC4 * (u32)(x3 + 32768)) >> 15;

	b7 = ((u32)data->raw_pressure - b3) *
					(50000 >> data->oversampling_setting);
	p = ((b7 < 0x80000000) ? ((b7 << 1) / b4) : ((b7 / b4) * 2));

	x1 = p >> 8;
	x1 *= x1;
	x1 = (x1 * 3038) >> 16;
	x2 = (-7357 * p) >> 16;
	p += (x1 + x2 + 3791) >> 4;

	*pressure = p;

	return 0;
}

/*
 * This function sets the chip-internal oversampling. Valid values are 0..3.
 * The chip will use 2^oversampling samples for internal averaging.
 * This influences the measurement time and the accuracy; larger values
 * increase both. The datasheet gives an overview on how measurement time,
 * accuracy and noise correlate.
 */
static void bmp085_set_oversampling(struct bmp085_data *data,
						unsigned char oversampling)
{
	if (oversampling > 3)
		oversampling = 3;
	data->oversampling_setting = oversampling;
}

/*
 * Returns the currently selected oversampling. Range: 0..3
 */
static unsigned char bmp085_get_oversampling(struct bmp085_data *data)
{
	return data->oversampling_setting;
}

/* sysfs callbacks */
static ssize_t set_oversampling(struct device *dev,
				struct device_attribute *attr,
				const char *buf, size_t count)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct bmp085_data *data = i2c_get_clientdata(client);
	unsigned long oversampling;
	int err = kstrtoul(buf, 10, &oversampling);

	if (err == 0) {
		mutex_lock(&data->lock);
		bmp085_set_oversampling(data, oversampling);
		mutex_unlock(&data->lock);
		return count;
	}

	return err;
}

static ssize_t show_oversampling(struct device *dev,
				 struct device_attribute *attr, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	struct bmp085_data *data = i2c_get_clientdata(client);

	return sprintf(buf, "%u\n", bmp085_get_oversampling(data));
}
static DEVICE_ATTR(oversampling, S_IWUSR | S_IRUGO,
					show_oversampling, set_oversampling);


static ssize_t show_temperature(struct device *dev,
				struct device_attribute *attr, char *buf)
{
	int temperature;
	int status;
	struct i2c_client *client = to_i2c_client(dev);
	struct bmp085_data *data = i2c_get_clientdata(client);

	status = bmp085_get_temperature(data, &temperature);
	if (status < 0)
		return status;
	else
		return sprintf(buf, "%d\n", temperature);
}
static DEVICE_ATTR(temp0_input, S_IRUGO, show_temperature, NULL);


static ssize_t show_pressure(struct device *dev,
			     struct device_attribute *attr, char *buf)
{
	int pressure;
	int status;
	struct i2c_client *client = to_i2c_client(dev);
	struct bmp085_data *data = i2c_get_clientdata(client);

	status = bmp085_get_pressure(data, &pressure);
	if (status < 0)
		return status;
	else
		return sprintf(buf, "%d\n", pressure);
}
static DEVICE_ATTR(pressure0_input, S_IRUGO, show_pressure, NULL);


static struct attribute *bmp085_attributes[] = {
	&dev_attr_temp0_input.attr,
	&dev_attr_pressure0_input.attr,
	&dev_attr_oversampling.attr,
	NULL
};

static const struct attribute_group bmp085_attr_group = {
	.attrs = bmp085_attributes,
};

static int bmp085_detect(struct i2c_client *client, struct i2c_board_info *info)
{
	if (client->addr != BMP085_I2C_ADDRESS)
		return -ENODEV;

	if (i2c_smbus_read_byte_data(client, BMP085_CHIP_ID_REG) != BMP085_CHIP_ID)
		return -ENODEV;

	return 0;
}

static int bmp085_init_client(struct i2c_client *client)
{
	struct bmp085_data *data = i2c_get_clientdata(client);
	int status = bmp085_read_calibration_data(client);

	if (status < 0)
		return status;

	data->client = client;
	data->last_temp_measurement = 0;
	data->temp_measurement_period = 1*HZ;
	data->oversampling_setting = 3;
	mutex_init(&data->lock);

	return 0;
}

static int __devinit bmp085_probe(struct i2c_client *client,
			const struct i2c_device_id *id)
{
	struct bmp085_data *data;
	int err = 0;

	data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL);
	if (!data) {
		err = -ENOMEM;
		goto exit;
	}

	i2c_set_clientdata(client, data);

	/* Initialize the BMP085 chip */
	err = bmp085_init_client(client);
	if (err < 0)
		goto exit_free;

	/* Register sysfs hooks */
	err = sysfs_create_group(&client->dev.kobj, &bmp085_attr_group);
	if (err)
		goto exit_free;

	dev_info(&client->dev, "Successfully initialized %s!\n", BMP085_NAME);

	return 0;

exit_free:
	kfree(data);
exit:
	return err;
}

static int __devexit bmp085_remove(struct i2c_client *client)
{
	struct bmp085_data *data = i2c_get_clientdata(client);

	sysfs_remove_group(&client->dev.kobj, &bmp085_attr_group);
	kfree(data);

	return 0;
}

static const struct i2c_device_id bmp085_id[] = {
	{ BMP085_NAME, 0 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, bmp085_id);

static struct i2c_driver bmp085_driver = {
	.driver = {
		.owner = THIS_MODULE,
		.name	= BMP085_NAME
	},
	.id_table	= bmp085_id,
	.probe		= bmp085_probe,
	.remove		= __devexit_p(bmp085_remove),

	.detect		= bmp085_detect,
	.address_list	= normal_i2c
};

module_i2c_driver(bmp085_driver);

MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com>");
MODULE_DESCRIPTION("BMP085 driver");
MODULE_LICENSE("GPL");