486 lines
12 KiB
C
486 lines
12 KiB
C
/*
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* A sensor driver for the magnetometer AK8975.
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*
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* Magnetic compass sensor driver for monitoring magnetic flux information.
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*
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* Copyright (c) 2010, NVIDIA Corporation.
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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, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/i2c.h>
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#include <linux/err.h>
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#include <linux/mutex.h>
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#include <linux/delay.h>
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#include <linux/gpio.h>
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#include <linux/iio/iio.h>
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#include <linux/iio/sysfs.h>
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/*
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* Register definitions, as well as various shifts and masks to get at the
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* individual fields of the registers.
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*/
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#define AK8975_REG_WIA 0x00
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#define AK8975_DEVICE_ID 0x48
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#define AK8975_REG_INFO 0x01
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#define AK8975_REG_ST1 0x02
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#define AK8975_REG_ST1_DRDY_SHIFT 0
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#define AK8975_REG_ST1_DRDY_MASK (1 << AK8975_REG_ST1_DRDY_SHIFT)
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#define AK8975_REG_HXL 0x03
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#define AK8975_REG_HXH 0x04
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#define AK8975_REG_HYL 0x05
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#define AK8975_REG_HYH 0x06
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#define AK8975_REG_HZL 0x07
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#define AK8975_REG_HZH 0x08
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#define AK8975_REG_ST2 0x09
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#define AK8975_REG_ST2_DERR_SHIFT 2
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#define AK8975_REG_ST2_DERR_MASK (1 << AK8975_REG_ST2_DERR_SHIFT)
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#define AK8975_REG_ST2_HOFL_SHIFT 3
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#define AK8975_REG_ST2_HOFL_MASK (1 << AK8975_REG_ST2_HOFL_SHIFT)
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#define AK8975_REG_CNTL 0x0A
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#define AK8975_REG_CNTL_MODE_SHIFT 0
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#define AK8975_REG_CNTL_MODE_MASK (0xF << AK8975_REG_CNTL_MODE_SHIFT)
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#define AK8975_REG_CNTL_MODE_POWER_DOWN 0
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#define AK8975_REG_CNTL_MODE_ONCE 1
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#define AK8975_REG_CNTL_MODE_SELF_TEST 8
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#define AK8975_REG_CNTL_MODE_FUSE_ROM 0xF
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#define AK8975_REG_RSVC 0x0B
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#define AK8975_REG_ASTC 0x0C
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#define AK8975_REG_TS1 0x0D
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#define AK8975_REG_TS2 0x0E
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#define AK8975_REG_I2CDIS 0x0F
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#define AK8975_REG_ASAX 0x10
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#define AK8975_REG_ASAY 0x11
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#define AK8975_REG_ASAZ 0x12
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#define AK8975_MAX_REGS AK8975_REG_ASAZ
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/*
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* Miscellaneous values.
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*/
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#define AK8975_MAX_CONVERSION_TIMEOUT 500
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#define AK8975_CONVERSION_DONE_POLL_TIME 10
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/*
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* Per-instance context data for the device.
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*/
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struct ak8975_data {
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struct i2c_client *client;
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struct attribute_group attrs;
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struct mutex lock;
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u8 asa[3];
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long raw_to_gauss[3];
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u8 reg_cache[AK8975_MAX_REGS];
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int eoc_gpio;
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};
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static const int ak8975_index_to_reg[] = {
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AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
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};
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/*
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* Helper function to write to the I2C device's registers.
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*/
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static int ak8975_write_data(struct i2c_client *client,
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u8 reg, u8 val, u8 mask, u8 shift)
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{
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struct iio_dev *indio_dev = i2c_get_clientdata(client);
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struct ak8975_data *data = iio_priv(indio_dev);
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u8 regval;
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int ret;
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regval = (data->reg_cache[reg] & ~mask) | (val << shift);
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ret = i2c_smbus_write_byte_data(client, reg, regval);
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if (ret < 0) {
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dev_err(&client->dev, "Write to device fails status %x\n", ret);
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return ret;
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}
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data->reg_cache[reg] = regval;
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return 0;
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}
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/*
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* Perform some start-of-day setup, including reading the asa calibration
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* values and caching them.
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*/
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static int ak8975_setup(struct i2c_client *client)
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{
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struct iio_dev *indio_dev = i2c_get_clientdata(client);
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struct ak8975_data *data = iio_priv(indio_dev);
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u8 device_id;
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int ret;
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/* Confirm that the device we're talking to is really an AK8975. */
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ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
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if (ret < 0) {
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dev_err(&client->dev, "Error reading WIA\n");
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return ret;
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}
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device_id = ret;
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if (device_id != AK8975_DEVICE_ID) {
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dev_err(&client->dev, "Device ak8975 not found\n");
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return -ENODEV;
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}
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/* Write the fused rom access mode. */
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ret = ak8975_write_data(client,
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AK8975_REG_CNTL,
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AK8975_REG_CNTL_MODE_FUSE_ROM,
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AK8975_REG_CNTL_MODE_MASK,
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AK8975_REG_CNTL_MODE_SHIFT);
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if (ret < 0) {
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dev_err(&client->dev, "Error in setting fuse access mode\n");
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return ret;
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}
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/* Get asa data and store in the device data. */
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ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
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3, data->asa);
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if (ret < 0) {
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dev_err(&client->dev, "Not able to read asa data\n");
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return ret;
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}
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/* After reading fuse ROM data set power-down mode */
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ret = ak8975_write_data(client,
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AK8975_REG_CNTL,
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AK8975_REG_CNTL_MODE_POWER_DOWN,
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AK8975_REG_CNTL_MODE_MASK,
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AK8975_REG_CNTL_MODE_SHIFT);
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if (ret < 0) {
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dev_err(&client->dev, "Error in setting power-down mode\n");
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return ret;
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}
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/*
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* Precalculate scale factor (in Gauss units) for each axis and
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* store in the device data.
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*
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* This scale factor is axis-dependent, and is derived from 3 calibration
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* factors ASA(x), ASA(y), and ASA(z).
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*
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* These ASA values are read from the sensor device at start of day, and
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* cached in the device context struct.
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*
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* Adjusting the flux value with the sensitivity adjustment value should be
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* done via the following formula:
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*
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* Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
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*
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* where H is the raw value, ASA is the sensitivity adjustment, and Hadj
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* is the resultant adjusted value.
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*
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* We reduce the formula to:
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*
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* Hadj = H * (ASA + 128) / 256
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*
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* H is in the range of -4096 to 4095. The magnetometer has a range of
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* +-1229uT. To go from the raw value to uT is:
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*
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* HuT = H * 1229/4096, or roughly, 3/10.
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*
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* Since 1uT = 100 gauss, our final scale factor becomes:
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*
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* Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
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* Hadj = H * ((ASA + 128) * 30 / 256
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*
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* Since ASA doesn't change, we cache the resultant scale factor into the
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* device context in ak8975_setup().
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*/
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data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
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data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
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data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
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return 0;
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}
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static int wait_conversion_complete_gpio(struct ak8975_data *data)
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{
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struct i2c_client *client = data->client;
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u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
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int ret;
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/* Wait for the conversion to complete. */
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while (timeout_ms) {
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msleep(AK8975_CONVERSION_DONE_POLL_TIME);
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if (gpio_get_value(data->eoc_gpio))
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break;
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timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
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}
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if (!timeout_ms) {
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dev_err(&client->dev, "Conversion timeout happened\n");
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return -EINVAL;
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}
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ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
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if (ret < 0)
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dev_err(&client->dev, "Error in reading ST1\n");
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return ret;
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}
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static int wait_conversion_complete_polled(struct ak8975_data *data)
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{
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struct i2c_client *client = data->client;
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u8 read_status;
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u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
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int ret;
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/* Wait for the conversion to complete. */
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while (timeout_ms) {
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msleep(AK8975_CONVERSION_DONE_POLL_TIME);
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ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
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if (ret < 0) {
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dev_err(&client->dev, "Error in reading ST1\n");
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return ret;
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}
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read_status = ret;
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if (read_status)
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break;
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timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
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}
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if (!timeout_ms) {
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dev_err(&client->dev, "Conversion timeout happened\n");
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return -EINVAL;
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}
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return read_status;
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}
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/*
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* Emits the raw flux value for the x, y, or z axis.
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*/
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static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
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{
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struct ak8975_data *data = iio_priv(indio_dev);
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struct i2c_client *client = data->client;
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u16 meas_reg;
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s16 raw;
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int ret;
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mutex_lock(&data->lock);
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/* Set up the device for taking a sample. */
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ret = ak8975_write_data(client,
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AK8975_REG_CNTL,
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AK8975_REG_CNTL_MODE_ONCE,
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AK8975_REG_CNTL_MODE_MASK,
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AK8975_REG_CNTL_MODE_SHIFT);
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if (ret < 0) {
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dev_err(&client->dev, "Error in setting operating mode\n");
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goto exit;
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}
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/* Wait for the conversion to complete. */
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if (gpio_is_valid(data->eoc_gpio))
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ret = wait_conversion_complete_gpio(data);
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else
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ret = wait_conversion_complete_polled(data);
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if (ret < 0)
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goto exit;
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if (ret & AK8975_REG_ST1_DRDY_MASK) {
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ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
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if (ret < 0) {
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dev_err(&client->dev, "Error in reading ST2\n");
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goto exit;
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}
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if (ret & (AK8975_REG_ST2_DERR_MASK |
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AK8975_REG_ST2_HOFL_MASK)) {
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dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
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ret = -EINVAL;
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goto exit;
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}
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}
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/* Read the flux value from the appropriate register
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(the register is specified in the iio device attributes). */
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ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
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if (ret < 0) {
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dev_err(&client->dev, "Read axis data fails\n");
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goto exit;
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}
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meas_reg = ret;
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mutex_unlock(&data->lock);
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/* Endian conversion of the measured values. */
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raw = (s16) (le16_to_cpu(meas_reg));
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/* Clamp to valid range. */
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raw = clamp_t(s16, raw, -4096, 4095);
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*val = raw;
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return IIO_VAL_INT;
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exit:
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mutex_unlock(&data->lock);
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return ret;
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}
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static int ak8975_read_raw(struct iio_dev *indio_dev,
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struct iio_chan_spec const *chan,
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int *val, int *val2,
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long mask)
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{
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struct ak8975_data *data = iio_priv(indio_dev);
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switch (mask) {
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case IIO_CHAN_INFO_RAW:
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return ak8975_read_axis(indio_dev, chan->address, val);
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case IIO_CHAN_INFO_SCALE:
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*val = data->raw_to_gauss[chan->address];
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return IIO_VAL_INT;
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}
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return -EINVAL;
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}
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#define AK8975_CHANNEL(axis, index) \
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{ \
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.type = IIO_MAGN, \
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.modified = 1, \
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.channel2 = IIO_MOD_##axis, \
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.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
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BIT(IIO_CHAN_INFO_SCALE), \
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.address = index, \
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}
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static const struct iio_chan_spec ak8975_channels[] = {
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AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
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};
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static const struct iio_info ak8975_info = {
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.read_raw = &ak8975_read_raw,
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.driver_module = THIS_MODULE,
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};
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static int ak8975_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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struct ak8975_data *data;
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struct iio_dev *indio_dev;
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int eoc_gpio;
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int err;
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/* Grab and set up the supplied GPIO. */
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if (client->dev.platform_data == NULL)
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eoc_gpio = -1;
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else
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eoc_gpio = *(int *)(client->dev.platform_data);
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/* We may not have a GPIO based IRQ to scan, that is fine, we will
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poll if so */
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if (gpio_is_valid(eoc_gpio)) {
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err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
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if (err < 0) {
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dev_err(&client->dev,
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"failed to request GPIO %d, error %d\n",
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eoc_gpio, err);
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goto exit;
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}
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}
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/* Register with IIO */
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indio_dev = iio_device_alloc(sizeof(*data));
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if (indio_dev == NULL) {
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err = -ENOMEM;
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goto exit_gpio;
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}
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data = iio_priv(indio_dev);
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i2c_set_clientdata(client, indio_dev);
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/* Perform some basic start-of-day setup of the device. */
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err = ak8975_setup(client);
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if (err < 0) {
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dev_err(&client->dev, "AK8975 initialization fails\n");
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goto exit_free_iio;
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}
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data->client = client;
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mutex_init(&data->lock);
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data->eoc_gpio = eoc_gpio;
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indio_dev->dev.parent = &client->dev;
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indio_dev->channels = ak8975_channels;
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indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
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indio_dev->info = &ak8975_info;
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indio_dev->modes = INDIO_DIRECT_MODE;
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err = iio_device_register(indio_dev);
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if (err < 0)
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goto exit_free_iio;
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return 0;
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exit_free_iio:
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iio_device_free(indio_dev);
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exit_gpio:
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if (gpio_is_valid(eoc_gpio))
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gpio_free(eoc_gpio);
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exit:
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return err;
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}
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static int ak8975_remove(struct i2c_client *client)
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{
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struct iio_dev *indio_dev = i2c_get_clientdata(client);
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struct ak8975_data *data = iio_priv(indio_dev);
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iio_device_unregister(indio_dev);
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if (gpio_is_valid(data->eoc_gpio))
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gpio_free(data->eoc_gpio);
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iio_device_free(indio_dev);
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return 0;
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}
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static const struct i2c_device_id ak8975_id[] = {
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{"ak8975", 0},
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{}
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};
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MODULE_DEVICE_TABLE(i2c, ak8975_id);
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static const struct of_device_id ak8975_of_match[] = {
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{ .compatible = "asahi-kasei,ak8975", },
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{ .compatible = "ak8975", },
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{ }
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};
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MODULE_DEVICE_TABLE(of, ak8975_of_match);
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static struct i2c_driver ak8975_driver = {
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.driver = {
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.name = "ak8975",
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.of_match_table = ak8975_of_match,
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},
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.probe = ak8975_probe,
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.remove = ak8975_remove,
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.id_table = ak8975_id,
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};
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module_i2c_driver(ak8975_driver);
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MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
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MODULE_DESCRIPTION("AK8975 magnetometer driver");
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MODULE_LICENSE("GPL");
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