507 lines
13 KiB
C
507 lines
13 KiB
C
/* Copyright (c) 2010 Christoph Mair <christoph.mair@gmail.com>
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* Copyright (c) 2012 Bosch Sensortec GmbH
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* Copyright (c) 2012 Unixphere AB
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*
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* This driver supports the bmp085 and bmp18x digital barometric pressure
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* and temperature sensors from Bosch Sensortec. The datasheets
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* are available from their website:
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* http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf
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* http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP180-DS000-07.pdf
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*
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* A pressure measurement is issued by reading from pressure0_input.
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* The return value ranges from 30000 to 110000 pascal with a resulution
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* of 1 pascal (0.01 millibar) which enables measurements from 9000m above
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* to 500m below sea level.
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*
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* The temperature can be read from temp0_input. Values range from
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* -400 to 850 representing the ambient temperature in degree celsius
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* multiplied by 10.The resolution is 0.1 celsius.
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*
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* Because ambient pressure is temperature dependent, a temperature
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* measurement will be executed automatically even if the user is reading
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* from pressure0_input. This happens if the last temperature measurement
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* has been executed more then one second ago.
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*
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* To decrease RMS noise from pressure measurements, the bmp085 can
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* autonomously calculate the average of up to eight samples. This is
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* set up by writing to the oversampling sysfs file. Accepted values
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* are 0, 1, 2 and 3. 2^x when x is the value written to this file
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* specifies the number of samples used to calculate the ambient pressure.
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* RMS noise is specified with six pascal (without averaging) and decreases
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* down to 3 pascal when using an oversampling setting of 3.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/slab.h>
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#include <linux/of.h>
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#include "bmp085.h"
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#include <linux/interrupt.h>
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#include <linux/completion.h>
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#include <linux/gpio.h>
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#define BMP085_CHIP_ID 0x55
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#define BMP085_CALIBRATION_DATA_START 0xAA
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#define BMP085_CALIBRATION_DATA_LENGTH 11 /* 16 bit values */
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#define BMP085_CHIP_ID_REG 0xD0
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#define BMP085_CTRL_REG 0xF4
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#define BMP085_TEMP_MEASUREMENT 0x2E
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#define BMP085_PRESSURE_MEASUREMENT 0x34
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#define BMP085_CONVERSION_REGISTER_MSB 0xF6
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#define BMP085_CONVERSION_REGISTER_LSB 0xF7
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#define BMP085_CONVERSION_REGISTER_XLSB 0xF8
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#define BMP085_TEMP_CONVERSION_TIME 5
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struct bmp085_calibration_data {
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s16 AC1, AC2, AC3;
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u16 AC4, AC5, AC6;
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s16 B1, B2;
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s16 MB, MC, MD;
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};
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struct bmp085_data {
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struct device *dev;
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struct regmap *regmap;
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struct mutex lock;
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struct bmp085_calibration_data calibration;
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u8 oversampling_setting;
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u32 raw_temperature;
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u32 raw_pressure;
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u32 temp_measurement_period;
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unsigned long last_temp_measurement;
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u8 chip_id;
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s32 b6; /* calculated temperature correction coefficient */
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int irq;
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struct completion done;
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};
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static irqreturn_t bmp085_eoc_isr(int irq, void *devid)
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{
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struct bmp085_data *data = devid;
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complete(&data->done);
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return IRQ_HANDLED;
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}
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static s32 bmp085_read_calibration_data(struct bmp085_data *data)
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{
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u16 tmp[BMP085_CALIBRATION_DATA_LENGTH];
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struct bmp085_calibration_data *cali = &(data->calibration);
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s32 status = regmap_bulk_read(data->regmap,
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BMP085_CALIBRATION_DATA_START, (u8 *)tmp,
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(BMP085_CALIBRATION_DATA_LENGTH << 1));
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if (status < 0)
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return status;
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cali->AC1 = be16_to_cpu(tmp[0]);
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cali->AC2 = be16_to_cpu(tmp[1]);
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cali->AC3 = be16_to_cpu(tmp[2]);
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cali->AC4 = be16_to_cpu(tmp[3]);
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cali->AC5 = be16_to_cpu(tmp[4]);
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cali->AC6 = be16_to_cpu(tmp[5]);
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cali->B1 = be16_to_cpu(tmp[6]);
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cali->B2 = be16_to_cpu(tmp[7]);
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cali->MB = be16_to_cpu(tmp[8]);
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cali->MC = be16_to_cpu(tmp[9]);
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cali->MD = be16_to_cpu(tmp[10]);
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return 0;
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}
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static s32 bmp085_update_raw_temperature(struct bmp085_data *data)
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{
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u16 tmp;
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s32 status;
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mutex_lock(&data->lock);
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init_completion(&data->done);
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status = regmap_write(data->regmap, BMP085_CTRL_REG,
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BMP085_TEMP_MEASUREMENT);
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if (status < 0) {
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dev_err(data->dev,
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"Error while requesting temperature measurement.\n");
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goto exit;
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}
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wait_for_completion_timeout(&data->done, 1 + msecs_to_jiffies(
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BMP085_TEMP_CONVERSION_TIME));
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status = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB,
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&tmp, sizeof(tmp));
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if (status < 0) {
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dev_err(data->dev,
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"Error while reading temperature measurement result\n");
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goto exit;
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}
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data->raw_temperature = be16_to_cpu(tmp);
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data->last_temp_measurement = jiffies;
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status = 0; /* everything ok, return 0 */
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exit:
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mutex_unlock(&data->lock);
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return status;
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}
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static s32 bmp085_update_raw_pressure(struct bmp085_data *data)
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{
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u32 tmp = 0;
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s32 status;
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mutex_lock(&data->lock);
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init_completion(&data->done);
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status = regmap_write(data->regmap, BMP085_CTRL_REG,
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BMP085_PRESSURE_MEASUREMENT +
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(data->oversampling_setting << 6));
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if (status < 0) {
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dev_err(data->dev,
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"Error while requesting pressure measurement.\n");
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goto exit;
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}
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/* wait for the end of conversion */
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wait_for_completion_timeout(&data->done, 1 + msecs_to_jiffies(
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2+(3 << data->oversampling_setting)));
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/* copy data into a u32 (4 bytes), but skip the first byte. */
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status = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB,
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((u8 *)&tmp)+1, 3);
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if (status < 0) {
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dev_err(data->dev,
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"Error while reading pressure measurement results\n");
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goto exit;
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}
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data->raw_pressure = be32_to_cpu((tmp));
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data->raw_pressure >>= (8-data->oversampling_setting);
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status = 0; /* everything ok, return 0 */
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exit:
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mutex_unlock(&data->lock);
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return status;
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}
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/*
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* This function starts the temperature measurement and returns the value
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* in tenth of a degree celsius.
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*/
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static s32 bmp085_get_temperature(struct bmp085_data *data, int *temperature)
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{
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struct bmp085_calibration_data *cali = &data->calibration;
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long x1, x2;
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int status;
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status = bmp085_update_raw_temperature(data);
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if (status < 0)
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goto exit;
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x1 = ((data->raw_temperature - cali->AC6) * cali->AC5) >> 15;
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x2 = (cali->MC << 11) / (x1 + cali->MD);
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data->b6 = x1 + x2 - 4000;
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/* if NULL just update b6. Used for pressure only measurements */
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if (temperature != NULL)
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*temperature = (x1+x2+8) >> 4;
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exit:
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return status;
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}
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/*
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* This function starts the pressure measurement and returns the value
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* in millibar. Since the pressure depends on the ambient temperature,
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* a temperature measurement is executed according to the given temperature
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* measurement period (default is 1 sec boundary). This period could vary
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* and needs to be adjusted according to the sensor environment, i.e. if big
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* temperature variations then the temperature needs to be read out often.
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*/
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static s32 bmp085_get_pressure(struct bmp085_data *data, int *pressure)
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{
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struct bmp085_calibration_data *cali = &data->calibration;
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s32 x1, x2, x3, b3;
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u32 b4, b7;
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s32 p;
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int status;
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/* alt least every second force an update of the ambient temperature */
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if ((data->last_temp_measurement == 0) ||
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time_is_before_jiffies(data->last_temp_measurement + 1*HZ)) {
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status = bmp085_get_temperature(data, NULL);
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if (status < 0)
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return status;
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}
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status = bmp085_update_raw_pressure(data);
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if (status < 0)
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return status;
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x1 = (data->b6 * data->b6) >> 12;
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x1 *= cali->B2;
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x1 >>= 11;
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x2 = cali->AC2 * data->b6;
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x2 >>= 11;
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x3 = x1 + x2;
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b3 = (((((s32)cali->AC1) * 4 + x3) << data->oversampling_setting) + 2);
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b3 >>= 2;
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x1 = (cali->AC3 * data->b6) >> 13;
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x2 = (cali->B1 * ((data->b6 * data->b6) >> 12)) >> 16;
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x3 = (x1 + x2 + 2) >> 2;
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b4 = (cali->AC4 * (u32)(x3 + 32768)) >> 15;
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b7 = ((u32)data->raw_pressure - b3) *
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(50000 >> data->oversampling_setting);
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p = ((b7 < 0x80000000) ? ((b7 << 1) / b4) : ((b7 / b4) * 2));
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x1 = p >> 8;
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x1 *= x1;
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x1 = (x1 * 3038) >> 16;
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x2 = (-7357 * p) >> 16;
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p += (x1 + x2 + 3791) >> 4;
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*pressure = p;
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return 0;
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}
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/*
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* This function sets the chip-internal oversampling. Valid values are 0..3.
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* The chip will use 2^oversampling samples for internal averaging.
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* This influences the measurement time and the accuracy; larger values
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* increase both. The datasheet gives an overview on how measurement time,
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* accuracy and noise correlate.
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*/
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static void bmp085_set_oversampling(struct bmp085_data *data,
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unsigned char oversampling)
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{
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if (oversampling > 3)
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oversampling = 3;
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data->oversampling_setting = oversampling;
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}
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/*
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* Returns the currently selected oversampling. Range: 0..3
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*/
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static unsigned char bmp085_get_oversampling(struct bmp085_data *data)
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{
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return data->oversampling_setting;
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}
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/* sysfs callbacks */
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static ssize_t set_oversampling(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct bmp085_data *data = dev_get_drvdata(dev);
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unsigned long oversampling;
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int err = kstrtoul(buf, 10, &oversampling);
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if (err == 0) {
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mutex_lock(&data->lock);
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bmp085_set_oversampling(data, oversampling);
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mutex_unlock(&data->lock);
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return count;
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}
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return err;
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}
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static ssize_t show_oversampling(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct bmp085_data *data = dev_get_drvdata(dev);
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return sprintf(buf, "%u\n", bmp085_get_oversampling(data));
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}
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static DEVICE_ATTR(oversampling, S_IWUSR | S_IRUGO,
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show_oversampling, set_oversampling);
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static ssize_t show_temperature(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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int temperature;
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int status;
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struct bmp085_data *data = dev_get_drvdata(dev);
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status = bmp085_get_temperature(data, &temperature);
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if (status < 0)
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return status;
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else
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return sprintf(buf, "%d\n", temperature);
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}
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static DEVICE_ATTR(temp0_input, S_IRUGO, show_temperature, NULL);
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static ssize_t show_pressure(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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int pressure;
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int status;
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struct bmp085_data *data = dev_get_drvdata(dev);
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status = bmp085_get_pressure(data, &pressure);
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if (status < 0)
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return status;
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else
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return sprintf(buf, "%d\n", pressure);
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}
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static DEVICE_ATTR(pressure0_input, S_IRUGO, show_pressure, NULL);
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static struct attribute *bmp085_attributes[] = {
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&dev_attr_temp0_input.attr,
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&dev_attr_pressure0_input.attr,
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&dev_attr_oversampling.attr,
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NULL
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};
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static const struct attribute_group bmp085_attr_group = {
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.attrs = bmp085_attributes,
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};
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int bmp085_detect(struct device *dev)
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{
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struct bmp085_data *data = dev_get_drvdata(dev);
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unsigned int id;
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int ret;
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ret = regmap_read(data->regmap, BMP085_CHIP_ID_REG, &id);
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if (ret < 0)
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return ret;
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if (id != data->chip_id)
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return -ENODEV;
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return 0;
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}
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EXPORT_SYMBOL_GPL(bmp085_detect);
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static void bmp085_get_of_properties(struct bmp085_data *data)
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{
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#ifdef CONFIG_OF
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struct device_node *np = data->dev->of_node;
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u32 prop;
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if (!np)
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return;
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if (!of_property_read_u32(np, "chip-id", &prop))
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data->chip_id = prop & 0xff;
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if (!of_property_read_u32(np, "temp-measurement-period", &prop))
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data->temp_measurement_period = (prop/100)*HZ;
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if (!of_property_read_u32(np, "default-oversampling", &prop))
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data->oversampling_setting = prop & 0xff;
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#endif
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}
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static int bmp085_init_client(struct bmp085_data *data)
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{
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int status = bmp085_read_calibration_data(data);
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if (status < 0)
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return status;
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/* default settings */
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data->chip_id = BMP085_CHIP_ID;
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data->last_temp_measurement = 0;
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data->temp_measurement_period = 1*HZ;
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data->oversampling_setting = 3;
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bmp085_get_of_properties(data);
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mutex_init(&data->lock);
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return 0;
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}
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struct regmap_config bmp085_regmap_config = {
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.reg_bits = 8,
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.val_bits = 8
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};
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EXPORT_SYMBOL_GPL(bmp085_regmap_config);
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int bmp085_probe(struct device *dev, struct regmap *regmap, int irq)
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{
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struct bmp085_data *data;
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int err = 0;
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data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL);
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if (!data) {
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err = -ENOMEM;
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goto exit;
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}
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dev_set_drvdata(dev, data);
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data->dev = dev;
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data->regmap = regmap;
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data->irq = irq;
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if (data->irq > 0) {
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err = devm_request_irq(dev, data->irq, bmp085_eoc_isr,
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IRQF_TRIGGER_RISING, "bmp085",
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data);
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if (err < 0)
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goto exit_free;
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}
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/* Initialize the BMP085 chip */
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err = bmp085_init_client(data);
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if (err < 0)
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goto exit_free;
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err = bmp085_detect(dev);
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if (err < 0) {
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dev_err(dev, "%s: chip_id failed!\n", BMP085_NAME);
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goto exit_free;
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}
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/* Register sysfs hooks */
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err = sysfs_create_group(&dev->kobj, &bmp085_attr_group);
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if (err)
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goto exit_free;
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dev_info(dev, "Successfully initialized %s!\n", BMP085_NAME);
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return 0;
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exit_free:
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kfree(data);
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exit:
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return err;
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}
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EXPORT_SYMBOL_GPL(bmp085_probe);
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int bmp085_remove(struct device *dev)
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{
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struct bmp085_data *data = dev_get_drvdata(dev);
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sysfs_remove_group(&data->dev->kobj, &bmp085_attr_group);
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kfree(data);
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return 0;
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}
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EXPORT_SYMBOL_GPL(bmp085_remove);
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MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com>");
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MODULE_DESCRIPTION("BMP085 driver");
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MODULE_LICENSE("GPL");
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