linux中bmp085驱动移植

其实，linux内核中默认是包含气压传感器bmp085驱动的，只需该驱动没有选上。现在介绍如何才能让bmp085驱动起来。

首先，进入内核，运行make menuconfig, 进入Device Drivers------->Misc devices,按空格将BMP085 digital pressure sensor

这个选项选上即可。如果你不知道内核的某一项在那个位置可以配置，只需在make menuconfig里面按键盘的"/"键，在搜索

框中输入关键字，按"ENTER"键即可搜索，如下图。Location即你要先进入到该路径下，Prompt的内容为xxxxxxxxxxxxxxxx的

这一项就是你需要配置的一项。



下面为bmp085的驱动源码

/*  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 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/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 __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;
}

/* 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, "Successfully initialized bmp085!\n");
goto exit;

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

static int __devexit 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 },
{ }
};
MODULE_DEVICE_TABLE(i2c, bmp085_id);

static struct i2c_driver bmp085_driver = {
.driver = {
.owner = THIS_MODULE,
.name	= "bmp085"
},
.id_table	= bmp085_id,
.probe		= bmp085_probe,
.remove		= __devexit_p(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);

这时，我们进入板级文件，一般为kernel/arm/arm/mack-xxx/board-xxxx-xxx.c,现在将bmp085挂在第一路i2c上，

找到该路i2c注册函数i2c_register_board_info(0, i2c0_info, ARRAY_SIZE(i2c0_info))对应的数组，添加bmp085的信息即可。

static struct i2c_board_info __initdata i2c0_info[] = {

{

.type = "bmp085",

.addr = 0x77,

.flags = 0,

},

type就是外设的名字。在驱动文件中.name = "bmp085，故这里为bmp085

add即外设的地址(7位地址，本来的8位地址需要转换成7位，内核会自动转换成8位地址进行发送)，

因为用了8位地址，导致了driver和deives匹配不上，没有触发probe函数，花费了一定的时间。

具体的匹配规则见
http://blog.csdn.net/angle_birds/article/details/8028919 http://blog.csdn.net/lanmanck/article/details/7833546

root@rkpx3:/sys/bus/i2c/drivers/bmp085 # ll
lrwxrwxrwx root     root              2011-01-01 20:07 0-0077 -> ../../../../devices/platform/rk30_i2c.0/i2c-0/0-0077
--w------- root     root         4096 2011-01-01 20:07 bind
--w------- root     root         4096 2011-01-01 20:07 uevent
--w------- root     root         4096 2011-01-01 20:07 unbind

如果要快速验证该驱动是否工作正常，只需

adb root 获取权限来查找文件

adb shell busybox find -name pressure0_input查找pressure0_input这个节点的位置

adb shell busybox  find -name pressure0_input
./sys/devices/platform/rk30_i2c.0/i2c-0/0-0077/pressure0_input
进入该路径后，cat pressure0_input查看气压值cat temp0_input查看温度值。
root@rkpx3:/sys/devices/platform/rk30_i2c.0/i2c-0/0-0077 # ls
driver
modalias
name
oversampling
power
pressure0_input
subsystem
temp0_input
uevent  
或者直接查看温度                                                                                                                                                                                                                                                                              
root@hero:~# adb shell cat /sys/devices/platform/rk30_i2c.0/i2c-0/0-0077/pressure0_input
101752
root@hero:~# adb shell cat /sys/devices/platform/rk30_i2c.0/i2c-0/0-0077/temp0_input
284