Date:	Mon, 21 Jun 2010 14:22:50 +0530
From:	"Datta, Shubhrajyoti" <shubhrajyoti@...com>
To:	"Datta, Shubhrajyoti" <shubhrajyoti@...com>,
	Christoph Mair <christoph.mair@...il.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stefan Schmidt <stefan@...enfreihafen.org>,
	Jonathan Cameron <kernel@...23.retrosnub.co.uk>
Subject: RE: [PATCH] Support for the pressure sensor BMP085 from Bosch
 Sensortec.



> -----Original Message-----
> From: Datta, Shubhrajyoti
> Sent: Monday, June 21, 2010 12:15 PM
> To: 'Christoph Mair'; Jonathan Cameron
> Cc: linux-kernel@...r.kernel.org; Andrew Morton; Stefan Schmidt
> 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));

/*From the Datasheet
* Oversampling  (osrs)
* Measurement           | Control register      | conversion time[ms]
* Pressure (osrs 0 )    |0x34                   |4.5
* Pressure (osrs 1)     |0x74                   |7.5
* Pressure (osrs 2)     |0xB4                   |13.5
* Pressure (osrs 3)     |0xF4                   |25.5
*/

So I think (2+(3 << data->oversampling_setting)) should also work.


> > +
> > +   /* 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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