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Date: Mon, 21 Jun 2010 12:15:02 +0530
From: "Datta, Shubhrajyoti" <shubhrajyoti@...com>
To: Christoph Mair <christoph.mair@...il.com>,
Jonathan Cameron <kernel@...23.retrosnub.co.uk>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Stefan Schmidt <stefan@...enfreihafen.org>
Subject: RE: [PATCH] Support for the pressure sensor BMP085 from Bosch
Sensortec.
> -----Original Message-----
> From: Christoph Mair [mailto:christoph.mair@...il.com]
> Sent: Monday, June 21, 2010 2:21 AM
> To: Jonathan Cameron
> Cc: linux-kernel@...r.kernel.org; Andrew Morton; Stefan Schmidt; Datta,
> Shubhrajyoti; Christoph Mair
> Subject: [PATCH] Support for the pressure sensor BMP085 from Bosch
> Sensortec.
>
> This driver adds support for the BMP085 digital pressure sensor
> from Bosch Sensortec. It exposes a sysfs api to userspace where
> pressure and temperature measurement results can be read from the
> pressure0_input and temp0_input file. The chip is able to calculate
> the average of up to eight samples to increase the accuracy.
> This feature can be controlled by writing to the oversampling file.
>
> Signed-off-by: Christoph Mair <christoph.mair@...il.com>
> Acked-by: Jonathan Cameron <jic23@....ac.uk>
> ---
> drivers/misc/Kconfig | 10 +
> drivers/misc/Makefile | 1 +
> drivers/misc/bmp085.c | 455
> +++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 466 insertions(+), 0 deletions(-)
> create mode 100644 drivers/misc/bmp085.c
>
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 26386a9..9df8d3e 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -353,6 +353,16 @@ config VMWARE_BALLOON
> To compile this driver as a module, choose M here: the
> module will be called vmware_balloon.
>
> +config BMP085
> + tristate "BMP085 digital pressure sensor"
> + depends on I2C && SYSFS
> + help
> + If you say yes here you get support for the Bosch Sensortec
> + BMP086 digital pressure sensor.
> +
> + To compile this driver as a module, choose M here: the
> + module will be called bmp085.
> +
> source "drivers/misc/c2port/Kconfig"
> source "drivers/misc/eeprom/Kconfig"
> source "drivers/misc/cb710/Kconfig"
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 6ed06a1..5623c54 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -31,3 +31,4 @@ obj-$(CONFIG_IWMC3200TOP) += iwmc3200top/
> obj-y += eeprom/
> obj-y += cb710/
> obj-$(CONFIG_VMWARE_BALLOON) += vmware_balloon.o
> +obj-$(CONFIG_BMP085) += bmp085.o
> diff --git a/drivers/misc/bmp085.c b/drivers/misc/bmp085.c
> new file mode 100644
> index 0000000..16a2b2c
> --- /dev/null
> +++ b/drivers/misc/bmp085.c
> @@ -0,0 +1,455 @@
> +/* Copyright (c) 2010 Christoph Mair <christoph.mair@...il.com>
> +
> + 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;
> + unsigned long last_temp_measurement;
The size of long is arch dependent so using something like s32 etc may be used.
> + 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<<1));
> +
> + /* 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 interlan 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@...il.com");
> +MODULE_DESCRIPTION("BMP085 driver");
> +MODULE_LICENSE("GPL");
> +
> +module_init(bmp085_init);
> +module_exit(bmp085_exit);
> --
> 1.7.1
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