--- /dev/null
+/* Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com>
+
+ This driver supports the bmp085 digital barometric pressure
+ and temperature sensor from Bosch Sensortec. The datasheet
+ is avaliable 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/init.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+
+
+#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_VERSION_REG 0xD1
+#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
+
+#define BMP085_CLIENT_NAME "bmp085"
+
+
+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;
+};
+
+
+/* Each client has this additional data */
+struct bmp085_data {
+ struct i2c_client *client;
+ struct mutex lock;
+ struct bmp085_calibration_data calibration;
+ u32 raw_temperature;
+ u32 raw_pressure;
+ unsigned char oversampling_setting;
+ u32 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*sizeof(u16),
+ (u8 *)tmp);
+ if (status < 0)
+ return status;
+
+ if (status != BMP085_CALIBRATION_DATA_LENGTH*sizeof(u16))
+ 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 if the last known value is older
+ * than one second.
+ */
+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 + 1*HZ < jiffies) {
+ status = bmp085_get_temperature(data, NULL);
+ if (status != 0)
+ goto exit;
+ }
+
+ status = bmp085_update_raw_pressure(data);
+ if (status != 0)
+ goto exit;
+
+ 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;
+
+exit:
+ return status;
+}
+
+/*
+ * 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 on 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 success = strict_strtoul(buf, 10, &oversampling);
+ if (success == 0) {
+ bmp085_set_oversampling(data, oversampling);
+ return count;
+ }
+ return success;
+}
+
+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)
+{
+ unsigned char version;
+ int status;
+ struct bmp085_data *data = i2c_get_clientdata(client);
+ data->client = client;
+ status = bmp085_read_calibration_data(client);
+ if (status != 0)
+ goto exit;
+ version = i2c_smbus_read_byte_data(client, BMP085_VERSION_REG);
+ data->last_temp_measurement = 0;
+ data->oversampling_setting = 3;
+ mutex_init(&data->lock);
+ dev_info(&data->client->dev, "BMP085 ver. %d.%d found.\n",
+ (version & 0x0F), (version & 0xF0) >> 4);
+exit:
+ return status;
+}
+
+static int 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;
+ }
+
+ /* default settings after POR */
+ data->oversampling_setting = 0x00;
+
+ 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(&data->client->dev, "Succesfully initialized bmp085!\n");
+ goto exit;
+
+exit_free:
+ kfree(data);
+exit:
+ return err;
+}
+
+static int bmp085_remove(struct i2c_client *client)
+{
+ sysfs_remove_group(&client->dev.kobj, &bmp085_attr_group);
+ kfree(i2c_get_clientdata(client));
+ return 0;
+}
+
+static const struct i2c_device_id bmp085_id[] = {
+ { "bmp085", 0 },
+ { }
+};
+
+static struct i2c_driver bmp085_driver = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "bmp085"
+ },
+ .id_table = bmp085_id,
+ .probe = bmp085_probe,
+ .remove = bmp085_remove,
+
+ .detect = bmp085_detect,
+ .address_list = normal_i2c
+};
+
+static int __init bmp085_init(void)
+{
+ return i2c_add_driver(&bmp085_driver);
+}
+
+static void __exit bmp085_exit(void)
+{
+ i2c_del_driver(&bmp085_driver);
+}
+
+
+MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com");
+MODULE_DESCRIPTION("BMP085 driver");
+MODULE_LICENSE("GPL");
+
+module_init(bmp085_init);
+module_exit(bmp085_exit);
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