On 02/09/2013 04:55 PM, Jonathan Cameron wrote:
> This driver has been clean and correct for quite some time.
> It is simple and uses only straight forward standard
> interfaces.
>
I'm starting this branch of the thread to ask about the weird
manging of i2c in the read function.
...
> +/*
> + * Helper function to write to the I2C device's registers.
> + */
> +static int ak8975_write_data(struct i2c_client *client,
> + u8 reg, u8 val, u8 mask, u8 shift)
> +{
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> + struct ak8975_data *data = iio_priv(indio_dev);
> + u8 regval;
> + int ret;
> +
> + regval = (data->reg_cache[reg] & ~mask) | (val << shift);
> + ret = i2c_smbus_write_byte_data(client, reg, regval);
> + if (ret < 0) {
> + dev_err(&client->dev, "Write to device fails status %x\n", ret);
> + return ret;
> + }
> + data->reg_cache[reg] = regval;
> +
> + return 0;
> +}
> +
> +/*
> + * Helper function to read a contiguous set of the I2C device's registers.
> + */
> +static int ak8975_read_data(struct i2c_client *client,
> + u8 reg, u8 length, u8 *buffer)
> +{
> + int ret;
> + struct i2c_msg msg[2] = {
> + {
> + .addr = client->addr,
> + .flags = I2C_M_NOSTART,
This is 'unusual'. The result as I read it is that we get
something like
START REG [ACK] START ADDR [DATA] STOP
(where [] denotes from device)
The i2c docs specifically tell you that having this flag in the
first msg is a bad idea.
> Flag I2C_M_NOSTART:
> In a combined transaction, no 'S Addr Wr/Rd [A]' is generated at some
> point. For example, setting I2C_M_NOSTART on the second partial message
> generates something like:
> S Addr Rd [A] [Data] NA Data [A] P
> If you set the I2C_M_NOSTART variable for the first partial message,
> we do not generate Addr, but we do generate the startbit S. This will
> probably confuse all other clients on your bus, so don't try this.
>
> This is often used to gather transmits from multiple data buffers in
> system memory into something that appears as a single transfer to the
> I2C device but may also be used between direction changes by some
> rare devices.
A far as I can tell this function as it stands doesn't make sense for either
of the AK8975 read protocols.
> + .len = 1,
> + .buf = ®,
> + }, {
> + .addr = client->addr,
> + .flags = I2C_M_RD,
> + .len = length,
> + .buf = buffer,
> + }
> + };
> +
> + ret = i2c_transfer(client->adapter, msg, 2);
> + if (ret < 0) {
> + dev_err(&client->dev, "Read from device fails\n");
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * Perform some start-of-day setup, including reading the asa calibration
> + * values and caching them.
> + */
> +static int ak8975_setup(struct i2c_client *client)
> +{
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> + struct ak8975_data *data = iio_priv(indio_dev);
> + u8 device_id;
> + int ret;
> +
> + /* Confirm that the device we're talking to is really an AK8975. */
> + ret = ak8975_read_data(client, AK8975_REG_WIA, 1, &device_id);
> + if (ret < 0) {
> + dev_err(&client->dev, "Error reading WIA\n");
> + return ret;
> + }
> + if (device_id != AK8975_DEVICE_ID) {
> + dev_err(&client->dev, "Device ak8975 not found\n");
> + return -ENODEV;
> + }
> +
> + /* Write the fused rom access mode. */
> + ret = ak8975_write_data(client,
> + AK8975_REG_CNTL,
> + AK8975_REG_CNTL_MODE_FUSE_ROM,
> + AK8975_REG_CNTL_MODE_MASK,
> + AK8975_REG_CNTL_MODE_SHIFT);
> + if (ret < 0) {
> + dev_err(&client->dev, "Error in setting fuse access mode\n");
> + return ret;
> + }
> +
> + /* Get asa data and store in the device data. */
> + ret = ak8975_read_data(client, AK8975_REG_ASAX, 3, data->asa);
> + if (ret < 0) {
> + dev_err(&client->dev, "Not able to read asa data\n");
> + return ret;
> + }
> +
> + /* After reading fuse ROM data set power-down mode */
> + ret = ak8975_write_data(client,
> + AK8975_REG_CNTL,
> + AK8975_REG_CNTL_MODE_POWER_DOWN,
> + AK8975_REG_CNTL_MODE_MASK,
> + AK8975_REG_CNTL_MODE_SHIFT);
> + if (ret < 0) {
> + dev_err(&client->dev, "Error in setting power-down mode\n");
> + return ret;
> + }
> +
> +/*
> + * Precalculate scale factor (in Gauss units) for each axis and
> + * store in the device data.
> + *
> + * This scale factor is axis-dependent, and is derived from 3 calibration
> + * factors ASA(x), ASA(y), and ASA(z).
> + *
> + * These ASA values are read from the sensor device at start of day, and
> + * cached in the device context struct.
> + *
> + * Adjusting the flux value with the sensitivity adjustment value should be
> + * done via the following formula:
> + *
> + * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
> + *
> + * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
> + * is the resultant adjusted value.
> + *
> + * We reduce the formula to:
> + *
> + * Hadj = H * (ASA + 128) / 256
> + *
> + * H is in the range of -4096 to 4095. The magnetometer has a range of
> + * +-1229uT. To go from the raw value to uT is:
> + *
> + * HuT = H * 1229/4096, or roughly, 3/10.
> + *
> + * Since 1uT = 100 gauss, our final scale factor becomes:
> + *
> + * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
> + * Hadj = H * ((ASA + 128) * 30 / 256
> + *
> + * Since ASA doesn't change, we cache the resultant scale factor into the
> + * device context in ak8975_setup().
> + */
> + data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
> + data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
> + data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
> +
> + return 0;
> +}
> +
> +static int wait_conversion_complete_gpio(struct ak8975_data *data)
> +{
> + struct i2c_client *client = data->client;
> + u8 read_status;
> + u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
> + int ret;
> +
> + /* Wait for the conversion to complete. */
> + while (timeout_ms) {
> + msleep(AK8975_CONVERSION_DONE_POLL_TIME);
> + if (gpio_get_value(data->eoc_gpio))
> + break;
> + timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
> + }
> + if (!timeout_ms) {
> + dev_err(&client->dev, "Conversion timeout happened\n");
> + return -EINVAL;
> + }
> +
> + ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
> + if (ret < 0) {
> + dev_err(&client->dev, "Error in reading ST1\n");
> + return ret;
> + }
> + return read_status;
> +}
> +
> +static int wait_conversion_complete_polled(struct ak8975_data *data)
> +{
> + struct i2c_client *client = data->client;
> + u8 read_status;
> + u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
> + int ret;
> +
> + /* Wait for the conversion to complete. */
> + while (timeout_ms) {
> + msleep(AK8975_CONVERSION_DONE_POLL_TIME);
> + ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
> + if (ret < 0) {
> + dev_err(&client->dev, "Error in reading ST1\n");
> + return ret;
> + }
> + if (read_status)
> + break;
> + timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
> + }
> + if (!timeout_ms) {
> + dev_err(&client->dev, "Conversion timeout happened\n");
> + return -EINVAL;
> + }
> + return read_status;
> +}
> +
> +/*
> + * Emits the raw flux value for the x, y, or z axis.
> + */
> +static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
> +{
> + struct ak8975_data *data = iio_priv(indio_dev);
> + struct i2c_client *client = data->client;
> + u16 meas_reg;
> + s16 raw;
> + u8 read_status;
> + int ret;
> +
> + mutex_lock(&data->lock);
> +
> + /* Set up the device for taking a sample. */
> + ret = ak8975_write_data(client,
> + AK8975_REG_CNTL,
> + AK8975_REG_CNTL_MODE_ONCE,
> + AK8975_REG_CNTL_MODE_MASK,
> + AK8975_REG_CNTL_MODE_SHIFT);
> + if (ret < 0) {
> + dev_err(&client->dev, "Error in setting operating mode\n");
> + goto exit;
> + }
> +
> + /* Wait for the conversion to complete. */
> + if (gpio_is_valid(data->eoc_gpio))
> + ret = wait_conversion_complete_gpio(data);
> + else
> + ret = wait_conversion_complete_polled(data);
> + if (ret < 0)
> + goto exit;
> +
> + read_status = ret;
> +
> + if (read_status & AK8975_REG_ST1_DRDY_MASK) {
> + ret = ak8975_read_data(client, AK8975_REG_ST2, 1, &read_status);
> + if (ret < 0) {
> + dev_err(&client->dev, "Error in reading ST2\n");
> + goto exit;
> + }
> + if (read_status & (AK8975_REG_ST2_DERR_MASK |
> + AK8975_REG_ST2_HOFL_MASK)) {
> + dev_err(&client->dev, "ST2 status error 0x%x\n",
> + read_status);
> + ret = -EINVAL;
> + goto exit;
> + }
> + }
> +
> + /* Read the flux value from the appropriate register
> + (the register is specified in the iio device attributes). */
> + ret = ak8975_read_data(client, ak8975_index_to_reg[index],
> + 2, (u8 *)&meas_reg);
> + if (ret < 0) {
> + dev_err(&client->dev, "Read axis data fails\n");
> + goto exit;
> + }
> +
> + mutex_unlock(&data->lock);
> +
> + /* Endian conversion of the measured values. */
> + raw = (s16) (le16_to_cpu(meas_reg));
> +
> + /* Clamp to valid range. */
> + raw = clamp_t(s16, raw, -4096, 4095);
> + *val = raw;
> + return IIO_VAL_INT;
> +
> +exit:
> + mutex_unlock(&data->lock);
> + return ret;
> +}
> +
> +static int ak8975_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2,
> + long mask)
> +{
> + struct ak8975_data *data = iio_priv(indio_dev);
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + return ak8975_read_axis(indio_dev, chan->address, val);
> + case IIO_CHAN_INFO_SCALE:
> + *val = data->raw_to_gauss[chan->address];
> + return IIO_VAL_INT;
> + }
> + return -EINVAL;
> +}
> +
> +#define AK8975_CHANNEL(axis, index) \
> + { \
> + .type = IIO_MAGN, \
> + .modified = 1, \
> + .channel2 = IIO_MOD_##axis, \
> + .info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT | \
> + IIO_CHAN_INFO_SCALE_SEPARATE_BIT, \
> + .address = index, \
> + }
> +
> +static const struct iio_chan_spec ak8975_channels[] = {
> + AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
> +};
> +
> +static const struct iio_info ak8975_info = {
> + .read_raw = &ak8975_read_raw,
> + .driver_module = THIS_MODULE,
> +};
> +
> +static int ak8975_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct ak8975_data *data;
> + struct iio_dev *indio_dev;
> + int eoc_gpio;
> + int err;
> +
> + /* Grab and set up the supplied GPIO. */
> + if (client->dev.platform_data == NULL)
> + eoc_gpio = -1;
> + else
> + eoc_gpio = *(int *)(client->dev.platform_data);
> +
> + /* We may not have a GPIO based IRQ to scan, that is fine, we will
> + poll if so */
> + if (gpio_is_valid(eoc_gpio)) {
> + err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
> + if (err < 0) {
> + dev_err(&client->dev,
> + "failed to request GPIO %d, error %d\n",
> + eoc_gpio, err);
> + goto exit;
> + }
> + }
> +
> + /* Register with IIO */
> + indio_dev = iio_device_alloc(sizeof(*data));
> + if (indio_dev == NULL) {
> + err = -ENOMEM;
> + goto exit_gpio;
> + }
> + data = iio_priv(indio_dev);
> + i2c_set_clientdata(client, indio_dev);
> + /* Perform some basic start-of-day setup of the device. */
> + err = ak8975_setup(client);
> + if (err < 0) {
> + dev_err(&client->dev, "AK8975 initialization fails\n");
> + goto exit_free_iio;
> + }
> +
> + data->client = client;
> + mutex_init(&data->lock);
> + data->eoc_irq = client->irq;
> + data->eoc_gpio = eoc_gpio;
> + indio_dev->dev.parent = &client->dev;
> + indio_dev->channels = ak8975_channels;
> + indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
> + indio_dev->info = &ak8975_info;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> +
> + err = iio_device_register(indio_dev);
> + if (err < 0)
> + goto exit_free_iio;
> +
> + return 0;
> +
> +exit_free_iio:
> + iio_device_free(indio_dev);
> +exit_gpio:
> + if (gpio_is_valid(eoc_gpio))
> + gpio_free(eoc_gpio);
> +exit:
> + return err;
> +}
> +
> +static int ak8975_remove(struct i2c_client *client)
> +{
> + struct iio_dev *indio_dev = i2c_get_clientdata(client);
> + struct ak8975_data *data = iio_priv(indio_dev);
> +
> + iio_device_unregister(indio_dev);
> +
> + if (gpio_is_valid(data->eoc_gpio))
> + gpio_free(data->eoc_gpio);
> +
> + iio_device_free(indio_dev);
> +
> + return 0;
> +}
> +
> +static const struct i2c_device_id ak8975_id[] = {
> + {"ak8975", 0},
> + {}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, ak8975_id);
> +
> +static const struct of_device_id ak8975_of_match[] = {
> + { .compatible = "asahi-kasei,ak8975", },
> + { .compatible = "ak8975", },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, ak8975_of_match);
> +
> +static struct i2c_driver ak8975_driver = {
> + .driver = {
> + .name = "ak8975",
> + .of_match_table = ak8975_of_match,
> + },
> + .probe = ak8975_probe,
> + .remove = ak8975_remove,
> + .id_table = ak8975_id,
> +};
> +module_i2c_driver(ak8975_driver);
> +
> +MODULE_AUTHOR("Laxman Dewangan <ldewangan@xxxxxxxxxx>");
> +MODULE_DESCRIPTION("AK8975 magnetometer driver");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/staging/iio/magnetometer/Kconfig b/drivers/staging/iio/magnetometer/Kconfig
> index df5e0d4..a3ea69e 100644
> --- a/drivers/staging/iio/magnetometer/Kconfig
> +++ b/drivers/staging/iio/magnetometer/Kconfig
> @@ -3,17 +3,6 @@
> #
> menu "Magnetometer sensors"
>
> -config SENSORS_AK8975
> - tristate "Asahi Kasei AK8975 3-Axis Magnetometer"
> - depends on I2C
> - depends on GPIOLIB
> - help
> - Say yes here to build support for Asahi Kasei AK8975 3-Axis
> - Magnetometer.
> -
> - To compile this driver as a module, choose M here: the module
> - will be called ak8975.
> -
> config SENSORS_HMC5843
> tristate "Honeywell HMC5843/5883/5883L 3-Axis Magnetometer"
> depends on I2C
> diff --git a/drivers/staging/iio/magnetometer/Makefile b/drivers/staging/iio/magnetometer/Makefile
> index f2a753f..f9bfb2e 100644
> --- a/drivers/staging/iio/magnetometer/Makefile
> +++ b/drivers/staging/iio/magnetometer/Makefile
> @@ -2,5 +2,4 @@
> # Makefile for industrial I/O Magnetometer sensors
> #
>
> -obj-$(CONFIG_SENSORS_AK8975) += ak8975.o
> obj-$(CONFIG_SENSORS_HMC5843) += hmc5843.o
> diff --git a/drivers/staging/iio/magnetometer/ak8975.c b/drivers/staging/iio/magnetometer/ak8975.c
> deleted file mode 100644
> index 28f080e..0000000
> --- a/drivers/staging/iio/magnetometer/ak8975.c
> +++ /dev/null
> @@ -1,520 +0,0 @@
> -/*
> - * A sensor driver for the magnetometer AK8975.
> - *
> - * Magnetic compass sensor driver for monitoring magnetic flux information.
> - *
> - * Copyright (c) 2010, NVIDIA Corporation.
> - *
> - * 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.,
> - * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
> - */
> -
> -#include <linux/module.h>
> -#include <linux/kernel.h>
> -#include <linux/slab.h>
> -#include <linux/i2c.h>
> -#include <linux/err.h>
> -#include <linux/mutex.h>
> -#include <linux/delay.h>
> -
> -#include <linux/gpio.h>
> -
> -#include <linux/iio/iio.h>
> -#include <linux/iio/sysfs.h>
> -/*
> - * Register definitions, as well as various shifts and masks to get at the
> - * individual fields of the registers.
> - */
> -#define AK8975_REG_WIA 0x00
> -#define AK8975_DEVICE_ID 0x48
> -
> -#define AK8975_REG_INFO 0x01
> -
> -#define AK8975_REG_ST1 0x02
> -#define AK8975_REG_ST1_DRDY_SHIFT 0
> -#define AK8975_REG_ST1_DRDY_MASK (1 << AK8975_REG_ST1_DRDY_SHIFT)
> -
> -#define AK8975_REG_HXL 0x03
> -#define AK8975_REG_HXH 0x04
> -#define AK8975_REG_HYL 0x05
> -#define AK8975_REG_HYH 0x06
> -#define AK8975_REG_HZL 0x07
> -#define AK8975_REG_HZH 0x08
> -#define AK8975_REG_ST2 0x09
> -#define AK8975_REG_ST2_DERR_SHIFT 2
> -#define AK8975_REG_ST2_DERR_MASK (1 << AK8975_REG_ST2_DERR_SHIFT)
> -
> -#define AK8975_REG_ST2_HOFL_SHIFT 3
> -#define AK8975_REG_ST2_HOFL_MASK (1 << AK8975_REG_ST2_HOFL_SHIFT)
> -
> -#define AK8975_REG_CNTL 0x0A
> -#define AK8975_REG_CNTL_MODE_SHIFT 0
> -#define AK8975_REG_CNTL_MODE_MASK (0xF << AK8975_REG_CNTL_MODE_SHIFT)
> -#define AK8975_REG_CNTL_MODE_POWER_DOWN 0
> -#define AK8975_REG_CNTL_MODE_ONCE 1
> -#define AK8975_REG_CNTL_MODE_SELF_TEST 8
> -#define AK8975_REG_CNTL_MODE_FUSE_ROM 0xF
> -
> -#define AK8975_REG_RSVC 0x0B
> -#define AK8975_REG_ASTC 0x0C
> -#define AK8975_REG_TS1 0x0D
> -#define AK8975_REG_TS2 0x0E
> -#define AK8975_REG_I2CDIS 0x0F
> -#define AK8975_REG_ASAX 0x10
> -#define AK8975_REG_ASAY 0x11
> -#define AK8975_REG_ASAZ 0x12
> -
> -#define AK8975_MAX_REGS AK8975_REG_ASAZ
> -
> -/*
> - * Miscellaneous values.
> - */
> -#define AK8975_MAX_CONVERSION_TIMEOUT 500
> -#define AK8975_CONVERSION_DONE_POLL_TIME 10
> -
> -/*
> - * Per-instance context data for the device.
> - */
> -struct ak8975_data {
> - struct i2c_client *client;
> - struct attribute_group attrs;
> - struct mutex lock;
> - u8 asa[3];
> - long raw_to_gauss[3];
> - u8 reg_cache[AK8975_MAX_REGS];
> - int eoc_gpio;
> - int eoc_irq;
> -};
> -
> -static const int ak8975_index_to_reg[] = {
> - AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
> -};
> -
> -/*
> - * Helper function to write to the I2C device's registers.
> - */
> -static int ak8975_write_data(struct i2c_client *client,
> - u8 reg, u8 val, u8 mask, u8 shift)
> -{
> - struct iio_dev *indio_dev = i2c_get_clientdata(client);
> - struct ak8975_data *data = iio_priv(indio_dev);
> - u8 regval;
> - int ret;
> -
> - regval = (data->reg_cache[reg] & ~mask) | (val << shift);
> - ret = i2c_smbus_write_byte_data(client, reg, regval);
> - if (ret < 0) {
> - dev_err(&client->dev, "Write to device fails status %x\n", ret);
> - return ret;
> - }
> - data->reg_cache[reg] = regval;
> -
> - return 0;
> -}
> -
> -/*
> - * Helper function to read a contiguous set of the I2C device's registers.
> - */
> -static int ak8975_read_data(struct i2c_client *client,
> - u8 reg, u8 length, u8 *buffer)
> -{
> - int ret;
> - struct i2c_msg msg[2] = {
> - {
> - .addr = client->addr,
> - .flags = I2C_M_NOSTART,
> - .len = 1,
> - .buf = ®,
> - }, {
> - .addr = client->addr,
> - .flags = I2C_M_RD,
> - .len = length,
> - .buf = buffer,
> - }
> - };
> -
> - ret = i2c_transfer(client->adapter, msg, 2);
> - if (ret < 0) {
> - dev_err(&client->dev, "Read from device fails\n");
> - return ret;
> - }
> -
> - return 0;
> -}
> -
> -/*
> - * Perform some start-of-day setup, including reading the asa calibration
> - * values and caching them.
> - */
> -static int ak8975_setup(struct i2c_client *client)
> -{
> - struct iio_dev *indio_dev = i2c_get_clientdata(client);
> - struct ak8975_data *data = iio_priv(indio_dev);
> - u8 device_id;
> - int ret;
> -
> - /* Confirm that the device we're talking to is really an AK8975. */
> - ret = ak8975_read_data(client, AK8975_REG_WIA, 1, &device_id);
> - if (ret < 0) {
> - dev_err(&client->dev, "Error reading WIA\n");
> - return ret;
> - }
> - if (device_id != AK8975_DEVICE_ID) {
> - dev_err(&client->dev, "Device ak8975 not found\n");
> - return -ENODEV;
> - }
> -
> - /* Write the fused rom access mode. */
> - ret = ak8975_write_data(client,
> - AK8975_REG_CNTL,
> - AK8975_REG_CNTL_MODE_FUSE_ROM,
> - AK8975_REG_CNTL_MODE_MASK,
> - AK8975_REG_CNTL_MODE_SHIFT);
> - if (ret < 0) {
> - dev_err(&client->dev, "Error in setting fuse access mode\n");
> - return ret;
> - }
> -
> - /* Get asa data and store in the device data. */
> - ret = ak8975_read_data(client, AK8975_REG_ASAX, 3, data->asa);
> - if (ret < 0) {
> - dev_err(&client->dev, "Not able to read asa data\n");
> - return ret;
> - }
> -
> - /* After reading fuse ROM data set power-down mode */
> - ret = ak8975_write_data(client,
> - AK8975_REG_CNTL,
> - AK8975_REG_CNTL_MODE_POWER_DOWN,
> - AK8975_REG_CNTL_MODE_MASK,
> - AK8975_REG_CNTL_MODE_SHIFT);
> - if (ret < 0) {
> - dev_err(&client->dev, "Error in setting power-down mode\n");
> - return ret;
> - }
> -
> -/*
> - * Precalculate scale factor (in Gauss units) for each axis and
> - * store in the device data.
> - *
> - * This scale factor is axis-dependent, and is derived from 3 calibration
> - * factors ASA(x), ASA(y), and ASA(z).
> - *
> - * These ASA values are read from the sensor device at start of day, and
> - * cached in the device context struct.
> - *
> - * Adjusting the flux value with the sensitivity adjustment value should be
> - * done via the following formula:
> - *
> - * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
> - *
> - * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
> - * is the resultant adjusted value.
> - *
> - * We reduce the formula to:
> - *
> - * Hadj = H * (ASA + 128) / 256
> - *
> - * H is in the range of -4096 to 4095. The magnetometer has a range of
> - * +-1229uT. To go from the raw value to uT is:
> - *
> - * HuT = H * 1229/4096, or roughly, 3/10.
> - *
> - * Since 1uT = 100 gauss, our final scale factor becomes:
> - *
> - * Hadj = H * ((ASA + 128) / 256) * 3/10 * 100
> - * Hadj = H * ((ASA + 128) * 30 / 256
> - *
> - * Since ASA doesn't change, we cache the resultant scale factor into the
> - * device context in ak8975_setup().
> - */
> - data->raw_to_gauss[0] = ((data->asa[0] + 128) * 30) >> 8;
> - data->raw_to_gauss[1] = ((data->asa[1] + 128) * 30) >> 8;
> - data->raw_to_gauss[2] = ((data->asa[2] + 128) * 30) >> 8;
> -
> - return 0;
> -}
> -
> -static int wait_conversion_complete_gpio(struct ak8975_data *data)
> -{
> - struct i2c_client *client = data->client;
> - u8 read_status;
> - u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
> - int ret;
> -
> - /* Wait for the conversion to complete. */
> - while (timeout_ms) {
> - msleep(AK8975_CONVERSION_DONE_POLL_TIME);
> - if (gpio_get_value(data->eoc_gpio))
> - break;
> - timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
> - }
> - if (!timeout_ms) {
> - dev_err(&client->dev, "Conversion timeout happened\n");
> - return -EINVAL;
> - }
> -
> - ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
> - if (ret < 0) {
> - dev_err(&client->dev, "Error in reading ST1\n");
> - return ret;
> - }
> - return read_status;
> -}
> -
> -static int wait_conversion_complete_polled(struct ak8975_data *data)
> -{
> - struct i2c_client *client = data->client;
> - u8 read_status;
> - u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
> - int ret;
> -
> - /* Wait for the conversion to complete. */
> - while (timeout_ms) {
> - msleep(AK8975_CONVERSION_DONE_POLL_TIME);
> - ret = ak8975_read_data(client, AK8975_REG_ST1, 1, &read_status);
> - if (ret < 0) {
> - dev_err(&client->dev, "Error in reading ST1\n");
> - return ret;
> - }
> - if (read_status)
> - break;
> - timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
> - }
> - if (!timeout_ms) {
> - dev_err(&client->dev, "Conversion timeout happened\n");
> - return -EINVAL;
> - }
> - return read_status;
> -}
> -
> -/*
> - * Emits the raw flux value for the x, y, or z axis.
> - */
> -static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
> -{
> - struct ak8975_data *data = iio_priv(indio_dev);
> - struct i2c_client *client = data->client;
> - u16 meas_reg;
> - s16 raw;
> - u8 read_status;
> - int ret;
> -
> - mutex_lock(&data->lock);
> -
> - /* Set up the device for taking a sample. */
> - ret = ak8975_write_data(client,
> - AK8975_REG_CNTL,
> - AK8975_REG_CNTL_MODE_ONCE,
> - AK8975_REG_CNTL_MODE_MASK,
> - AK8975_REG_CNTL_MODE_SHIFT);
> - if (ret < 0) {
> - dev_err(&client->dev, "Error in setting operating mode\n");
> - goto exit;
> - }
> -
> - /* Wait for the conversion to complete. */
> - if (gpio_is_valid(data->eoc_gpio))
> - ret = wait_conversion_complete_gpio(data);
> - else
> - ret = wait_conversion_complete_polled(data);
> - if (ret < 0)
> - goto exit;
> -
> - read_status = ret;
> -
> - if (read_status & AK8975_REG_ST1_DRDY_MASK) {
> - ret = ak8975_read_data(client, AK8975_REG_ST2, 1, &read_status);
> - if (ret < 0) {
> - dev_err(&client->dev, "Error in reading ST2\n");
> - goto exit;
> - }
> - if (read_status & (AK8975_REG_ST2_DERR_MASK |
> - AK8975_REG_ST2_HOFL_MASK)) {
> - dev_err(&client->dev, "ST2 status error 0x%x\n",
> - read_status);
> - ret = -EINVAL;
> - goto exit;
> - }
> - }
> -
> - /* Read the flux value from the appropriate register
> - (the register is specified in the iio device attributes). */
> - ret = ak8975_read_data(client, ak8975_index_to_reg[index],
> - 2, (u8 *)&meas_reg);
> - if (ret < 0) {
> - dev_err(&client->dev, "Read axis data fails\n");
> - goto exit;
> - }
> -
> - mutex_unlock(&data->lock);
> -
> - /* Endian conversion of the measured values. */
> - raw = (s16) (le16_to_cpu(meas_reg));
> -
> - /* Clamp to valid range. */
> - raw = clamp_t(s16, raw, -4096, 4095);
> - *val = raw;
> - return IIO_VAL_INT;
> -
> -exit:
> - mutex_unlock(&data->lock);
> - return ret;
> -}
> -
> -static int ak8975_read_raw(struct iio_dev *indio_dev,
> - struct iio_chan_spec const *chan,
> - int *val, int *val2,
> - long mask)
> -{
> - struct ak8975_data *data = iio_priv(indio_dev);
> -
> - switch (mask) {
> - case IIO_CHAN_INFO_RAW:
> - return ak8975_read_axis(indio_dev, chan->address, val);
> - case IIO_CHAN_INFO_SCALE:
> - *val = data->raw_to_gauss[chan->address];
> - return IIO_VAL_INT;
> - }
> - return -EINVAL;
> -}
> -
> -#define AK8975_CHANNEL(axis, index) \
> - { \
> - .type = IIO_MAGN, \
> - .modified = 1, \
> - .channel2 = IIO_MOD_##axis, \
> - .info_mask = IIO_CHAN_INFO_RAW_SEPARATE_BIT | \
> - IIO_CHAN_INFO_SCALE_SEPARATE_BIT, \
> - .address = index, \
> - }
> -
> -static const struct iio_chan_spec ak8975_channels[] = {
> - AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
> -};
> -
> -static const struct iio_info ak8975_info = {
> - .read_raw = &ak8975_read_raw,
> - .driver_module = THIS_MODULE,
> -};
> -
> -static int ak8975_probe(struct i2c_client *client,
> - const struct i2c_device_id *id)
> -{
> - struct ak8975_data *data;
> - struct iio_dev *indio_dev;
> - int eoc_gpio;
> - int err;
> -
> - /* Grab and set up the supplied GPIO. */
> - if (client->dev.platform_data == NULL)
> - eoc_gpio = -1;
> - else
> - eoc_gpio = *(int *)(client->dev.platform_data);
> -
> - /* We may not have a GPIO based IRQ to scan, that is fine, we will
> - poll if so */
> - if (gpio_is_valid(eoc_gpio)) {
> - err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
> - if (err < 0) {
> - dev_err(&client->dev,
> - "failed to request GPIO %d, error %d\n",
> - eoc_gpio, err);
> - goto exit;
> - }
> - }
> -
> - /* Register with IIO */
> - indio_dev = iio_device_alloc(sizeof(*data));
> - if (indio_dev == NULL) {
> - err = -ENOMEM;
> - goto exit_gpio;
> - }
> - data = iio_priv(indio_dev);
> - i2c_set_clientdata(client, indio_dev);
> - /* Perform some basic start-of-day setup of the device. */
> - err = ak8975_setup(client);
> - if (err < 0) {
> - dev_err(&client->dev, "AK8975 initialization fails\n");
> - goto exit_free_iio;
> - }
> -
> - data->client = client;
> - mutex_init(&data->lock);
> - data->eoc_irq = client->irq;
> - data->eoc_gpio = eoc_gpio;
> - indio_dev->dev.parent = &client->dev;
> - indio_dev->channels = ak8975_channels;
> - indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
> - indio_dev->info = &ak8975_info;
> - indio_dev->modes = INDIO_DIRECT_MODE;
> -
> - err = iio_device_register(indio_dev);
> - if (err < 0)
> - goto exit_free_iio;
> -
> - return 0;
> -
> -exit_free_iio:
> - iio_device_free(indio_dev);
> -exit_gpio:
> - if (gpio_is_valid(eoc_gpio))
> - gpio_free(eoc_gpio);
> -exit:
> - return err;
> -}
> -
> -static int ak8975_remove(struct i2c_client *client)
> -{
> - struct iio_dev *indio_dev = i2c_get_clientdata(client);
> - struct ak8975_data *data = iio_priv(indio_dev);
> -
> - iio_device_unregister(indio_dev);
> -
> - if (gpio_is_valid(data->eoc_gpio))
> - gpio_free(data->eoc_gpio);
> -
> - iio_device_free(indio_dev);
> -
> - return 0;
> -}
> -
> -static const struct i2c_device_id ak8975_id[] = {
> - {"ak8975", 0},
> - {}
> -};
> -
> -MODULE_DEVICE_TABLE(i2c, ak8975_id);
> -
> -static const struct of_device_id ak8975_of_match[] = {
> - { .compatible = "asahi-kasei,ak8975", },
> - { .compatible = "ak8975", },
> - { }
> -};
> -MODULE_DEVICE_TABLE(of, ak8975_of_match);
> -
> -static struct i2c_driver ak8975_driver = {
> - .driver = {
> - .name = "ak8975",
> - .of_match_table = ak8975_of_match,
> - },
> - .probe = ak8975_probe,
> - .remove = ak8975_remove,
> - .id_table = ak8975_id,
> -};
> -module_i2c_driver(ak8975_driver);
> -
> -MODULE_AUTHOR("Laxman Dewangan <ldewangan@xxxxxxxxxx>");
> -MODULE_DESCRIPTION("AK8975 magnetometer driver");
> -MODULE_LICENSE("GPL");
>
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