Re: [PATCH 2/2] iio: magnetometer: Add driver support for PNI RM3100

From: Himanshu Jha
Date: Tue Sep 25 2018 - 13:50:31 EST

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On Tue, Sep 25, 2018 at 11:17:24AM +0800, Song Qiang wrote:
> PNI RM3100 is a high resolution, large signal immunity magnetometer,
> composed of 3 single sensors and a processing chip with MagI2C Interface.
>
> Following functions are available:
> - Single-shot measurement from
> /sys/bus/iio/devices/iio:deviceX/in_magn_{axis}_raw
> - Triggerd buffer measurement.
> - Both i2c and spi interface are supported.
> - Both interrupt and polling measurement is supported, depands on if
depends

> the 'interrupts' in DT is declared.
>
> Signed-off-by: Song Qiang <songqiang1304521@xxxxxxxxx>
> ---
> Changes in v2:
> - Add scale channel.
> - Add EXPORT_SYMBOL_GPL() to export regmap confuguration
> structures.
> - Add sampling frequency available attribute.
> - Clean up headers and License declarations.
> - Change axis number to 3.
> - Remove bus specific part in compatible string.
> - Remove le32_to_cpu().
> - Check cycle count registers at *_probe().
> - Format comments.
> - Spell check.
> - Change prefix from RM_* to RM3100_*.
> - Check all error return paths.
> - Add devm_add_action() to avoid race condition when remove.
>
> MAINTAINERS | 7 +
> drivers/iio/magnetometer/Kconfig | 29 ++
> drivers/iio/magnetometer/Makefile | 4 +
> drivers/iio/magnetometer/rm3100-core.c | 470 +++++++++++++++++++++++++
> drivers/iio/magnetometer/rm3100-i2c.c | 58 +++
> drivers/iio/magnetometer/rm3100-spi.c | 64 ++++
> drivers/iio/magnetometer/rm3100.h | 73 ++++
> 7 files changed, 705 insertions(+)
> create mode 100644 drivers/iio/magnetometer/rm3100-core.c
> create mode 100644 drivers/iio/magnetometer/rm3100-i2c.c
> create mode 100644 drivers/iio/magnetometer/rm3100-spi.c
> create mode 100644 drivers/iio/magnetometer/rm3100.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 967ce8cdd1cc..14eeeb072403 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11393,6 +11393,13 @@ M: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
> S: Maintained
> F: drivers/pnp/
>
> +PNI RM3100 IIO DRIVER
> +M: Song Qiang <songqiang1304521@xxxxxxxxx>
> +L: linux-iio@xxxxxxxxxxxxxxx
> +S: Maintained
> +F: drivers/iio/magnetometer/rm3100*
> +F: Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
> +
> POSIX CLOCKS and TIMERS
> M: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> L: linux-kernel@xxxxxxxxxxxxxxx
> diff --git a/drivers/iio/magnetometer/Kconfig b/drivers/iio/magnetometer/Kconfig
> index ed9d776d01af..f130b866a4fc 100644
> --- a/drivers/iio/magnetometer/Kconfig
> +++ b/drivers/iio/magnetometer/Kconfig
> @@ -175,4 +175,33 @@ config SENSORS_HMC5843_SPI
> - hmc5843_core (core functions)
> - hmc5843_spi (support for HMC5983)
>
> +config SENSORS_RM3100
> + tristate
> + select IIO_BUFFER
> + select IIO_TRIGGERED_BUFFER
> +
> +config SENSORS_RM3100_I2C
> + tristate "PNI RM3100 9-Axis Magnetometer (I2C)"
> + depends on I2C
> + select SENSORS_RM3100
> + select REGMAP_I2C
> + help
> + Say Y here to add support for the PNI RM3100 9-Axis Magnetometer.
> +
> + This driver can also be compiled as a module.
> + To compile this driver as a module, choose M here: the module
> + will be called rm3100-i2c.
> +
> +config SENSORS_RM3100_SPI
> + tristate "PNI RM3100 9-Axis Magnetometer (SPI)"
> + depends on SPI_MASTER
> + select SENSORS_RM3100
> + select REGMAP_SPI
> + help
> + Say Y here to add support for the PNI RM3100 9-Axis Magnetometer.
> +
> + This driver can also be compiled as a module.
> + To compile this driver as a module, choose M here: the module
> + will be called rm3100-spi.

Look at drivers/iio/chemical/Kconfig and do it similarly as done for
BME680.

> endmenu
> diff --git a/drivers/iio/magnetometer/Makefile b/drivers/iio/magnetometer/Makefile
> index 664b2f866472..ba1bc34b82fa 100644
> --- a/drivers/iio/magnetometer/Makefile
> +++ b/drivers/iio/magnetometer/Makefile
> @@ -24,3 +24,7 @@ obj-$(CONFIG_IIO_ST_MAGN_SPI_3AXIS) += st_magn_spi.o
> obj-$(CONFIG_SENSORS_HMC5843) += hmc5843_core.o
> obj-$(CONFIG_SENSORS_HMC5843_I2C) += hmc5843_i2c.o
> obj-$(CONFIG_SENSORS_HMC5843_SPI) += hmc5843_spi.o
> +
> +obj-$(CONFIG_SENSORS_RM3100) += rm3100-core.o
> +obj-$(CONFIG_SENSORS_RM3100_I2C) += rm3100-i2c.o
> +obj-$(CONFIG_SENSORS_RM3100_SPI) += rm3100-spi.o
> diff --git a/drivers/iio/magnetometer/rm3100-core.c b/drivers/iio/magnetometer/rm3100-core.c
> new file mode 100644
> index 000000000000..5d28b53b7a04
> --- /dev/null
> +++ b/drivers/iio/magnetometer/rm3100-core.c
> @@ -0,0 +1,470 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * PNI RM3100 3-axis geomagnetic sensor driver core.
> + *
> + * Copyright (C) 2018 Song Qiang <songqiang1304521@xxxxxxxxx>
> + *
> + * User Manual available at
> + * <https://www.pnicorp.com/download/rm3100-user-manual/>
> + *
> + * TODO: event generaton, pm.
generation

> +#include <linux/module.h>
> +#include <linux/delay.h>
> +#include <linux/interrupt.h>
> +#include <linux/slab.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/kfifo_buf.h>
> +
> +#include "rm3100.h"
> +
> +static const struct regmap_range rm3100_readable_ranges[] = {
> + regmap_reg_range(RM3100_W_REG_START, RM3100_W_REG_END),
> +};
> +
> +const struct regmap_access_table rm3100_readable_table = {
> + .yes_ranges = rm3100_readable_ranges,
> + .n_yes_ranges = ARRAY_SIZE(rm3100_readable_ranges),
> +};
> +EXPORT_SYMBOL_GPL(rm3100_readable_table);
> +
> +static const struct regmap_range rm3100_writable_ranges[] = {
> + regmap_reg_range(RM3100_R_REG_START, RM3100_R_REG_END),
> +};
> +
> +const struct regmap_access_table rm3100_writable_table = {
> + .yes_ranges = rm3100_writable_ranges,
> + .n_yes_ranges = ARRAY_SIZE(rm3100_writable_ranges),
> +};
> +EXPORT_SYMBOL_GPL(rm3100_writable_table);
> +
> +static const struct regmap_range rm3100_volatile_ranges[] = {
> + regmap_reg_range(RM3100_V_REG_START, RM3100_V_REG_END),
> +};
> +
> +const struct regmap_access_table rm3100_volatile_table = {
> + .yes_ranges = rm3100_volatile_ranges,
> + .n_yes_ranges = ARRAY_SIZE(rm3100_volatile_ranges),
> +};
> +EXPORT_SYMBOL_GPL(rm3100_volatile_table);
> +
> +static irqreturn_t rm3100_irq_handler(int irq, void *d)
> +{
> + struct rm3100_data *data = d;
> +
> + complete(&data->measuring_done);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int rm3100_wait_measurement(struct rm3100_data *data)
> +{
> + struct regmap *regmap = data->regmap;
> + unsigned int val;
> + int tries = 20;
> + int ret;
> +
> + /*
> + * A read cycle of 400kbits i2c; bus is about 20us, plus the time
; was mistakenly added ?

> + * used for scheduling, a read cycle of fast mode of this device
> + * can reach 1.7ms, it may be possible for data to arrive just
> + * after we check the RM3100_REG_STATUS. In this case, irq_handler is
> + * called before measuring_done is reinitialized, it will wait
> + * forever for data that has already been ready.
> + * Reinitialize measuring_done before looking up makes sure we
> + * will always capture interrupt no matter when it happened.
> + */
> + if (data->use_interrupt)
> + reinit_completion(&data->measuring_done);
> +
> + ret = regmap_read(regmap, RM3100_REG_STATUS, &val);
> + if (ret < 0)
> + return ret;
> +
> + if ((val & RM3100_STATUS_DRDY) != RM3100_STATUS_DRDY) {
> + if (data->use_interrupt) {
> + ret = wait_for_completion_timeout(&data->measuring_done,
> + msecs_to_jiffies(data->conversion_time));
> + if (ret < 0)
> + return -ETIMEDOUT;
> + } else {
> + do {
> + usleep_range(1000, 5000);
> +
> + ret = regmap_read(regmap, RM3100_REG_STATUS,
> + &val);
> + if (ret < 0)
> + return ret;
> +
> + if (val & RM3100_STATUS_DRDY)
> + break;
> + } while (--tries);
> + if (!tries)
> + return -ETIMEDOUT;
> + }
> + }
> + return 0;
> +}
> +
> +static int rm3100_read_mag(struct rm3100_data *data, int idx, int *val)
> +{
> + struct regmap *regmap = data->regmap;
> + u8 buffer[3];
> + int ret;
> +
> + mutex_lock(&data->lock);
> + ret = rm3100_wait_measurement(data);
> + if (ret < 0) {
> + mutex_unlock(&data->lock);
> + return ret;
> + }
> +
> + ret = regmap_bulk_read(regmap, RM3100_REG_MX2 + 3 * idx, buffer, 3);
> + mutex_unlock(&data->lock);
> + if (ret < 0)
> + return ret;
> +
> + *val = sign_extend32((buffer[0] << 16) | (buffer[1] << 8) | buffer[2],
> + 23);
> +
> + return IIO_VAL_INT;
> +}
> +
> +#define RM3100_CHANNEL(axis, idx) \
> + { \
> + .type = IIO_MAGN, \
> + .modified = 1, \
> + .channel2 = IIO_MOD_##axis, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | \
> + BIT(IIO_CHAN_INFO_SAMP_FREQ), \
> + .scan_index = idx, \
> + .scan_type = { \
> + .sign = 's', \
> + .realbits = 24, \
> + .storagebits = 32, \
> + .shift = 8, \
> + .endianness = IIO_LE, \
> + }, \
> + }
> +
> +static const struct iio_chan_spec rm3100_channels[] = {
> + RM3100_CHANNEL(X, 0),
> + RM3100_CHANNEL(Y, 1),
> + RM3100_CHANNEL(Z, 2),
> + IIO_CHAN_SOFT_TIMESTAMP(3),
> +};
> +
> +static const unsigned long rm3100_scan_masks[] = {GENMASK(2, 0), 0};
> +
> +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
> + "600 300 150 75 37 18 9 4.5 2.3 1.2 0.6 0.3 0.015 0.075"
> +);
> +
> +static struct attribute *rm3100_attributes[] = {
> + &iio_const_attr_sampling_frequency_available.dev_attr.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group rm3100_attribute_group = {
> + .attrs = rm3100_attributes,
> +};
> +
> +#define RM3100_SAMP_NUM 14

Move this to top or .h header file.

> +/*
> + * Frequency : rm3100_samp_rates[][0].rm3100_samp_rates[][1]Hz.
> + * Time between reading: rm3100_sam_rates[][2]ms.
> + * The first one is actually 1.7ms.
> + */
> +static const int rm3100_samp_rates[RM3100_SAMP_NUM][3] = {
> + {600, 0, 2}, {300, 0, 3}, {150, 0, 7}, {75, 0, 13}, {37, 0, 27},
> + {18, 0, 55}, {9, 0, 110}, {4, 500000, 220}, {2, 300000, 440},
> + {1, 200000, 800}, {0, 600000, 1600}, {0, 300000, 3300},
> + {0, 15000, 6700}, {0, 75000, 13000}
> +};
> +
> +static int rm3100_get_samp_freq(struct rm3100_data *data, int *val, int *val2)
> +{
> + int ret;
> + int tmp;
> +
> + mutex_lock(&data->lock);
> + ret = regmap_read(data->regmap, RM3100_REG_TMRC, &tmp);

use (unsigned int *) throughly as 3rd argument of
regmap_read() everywhere.

> + mutex_unlock(&data->lock);
> + if (ret < 0)
> + return ret;
> + *val = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][0];
> + *val2 = rm3100_samp_rates[tmp - RM3100_TMRC_OFFSET][1];
> +
> + return IIO_VAL_INT_PLUS_MICRO;
> +}
> +
> +static int rm3100_set_cycle_count(struct rm3100_data *data, int val)
> +{
> + int ret;
> + u8 i;
> +
> + for (i = 0; i < 3; i++) {
> + ret = regmap_write(data->regmap, RM3100_REG_CC_X + 2 * i, 100);

Would be better to use a descriptive macro for 100 instead ?

> + if (ret < 0)
> + return ret;
> + }
> + if (val == 50)
> + data->cycle_count_index = 0;
> + else if (val == 100)
> + data->cycle_count_index = 1;
> + else
> + data->cycle_count_index = 2;
> +
> + return 0;
> +}
> +
> +static int rm3100_set_samp_freq(struct rm3100_data *data, int val, int val2)
> +{
> + struct regmap *regmap = data->regmap;
> + int cycle_count;
> + int ret;
> + int i;
> +
> + mutex_lock(&data->lock);
> + /* All cycle count registers use the same value. */
> + ret = regmap_read(regmap, RM3100_REG_CC_X, &cycle_count);
> + if (ret < 0)
> + goto unlock_return;
> +
> + for (i = 0; i < RM3100_SAMP_NUM; i++) {
> + if (val == rm3100_samp_rates[i][0] &&
> + val2 == rm3100_samp_rates[i][1])
> + break;
> + }
> + if (i == RM3100_SAMP_NUM) {
> + ret = -EINVAL;
> + goto unlock_return;
> + }
> +
> + ret = regmap_write(regmap, RM3100_REG_TMRC, i + RM3100_TMRC_OFFSET);
> + if (ret < 0)
> + goto unlock_return;
> +
> + /* Checking if cycle count registers need changing. */
> + if (val == 600 && cycle_count == 200) {
> + ret = rm3100_set_cycle_count(data, 100);
> + if (ret < 0)
> + goto unlock_return;
> + } else if (val != 600 && cycle_count == 100) {
> + ret = rm3100_set_cycle_count(data, 200);
> + if (ret < 0)
> + goto unlock_return;
> + }
> +
> + /* Writing TMRC registers requires CMM reset. */
> + ret = regmap_write(regmap, RM3100_REG_CMM, 0);
> + if (ret < 0)
> + goto unlock_return;
> + ret = regmap_write(regmap, RM3100_REG_CMM,
> + RM3100_CMM_X | RM3100_CMM_Y | RM3100_CMM_Z | RM3100_CMM_START);
> + mutex_unlock(&data->lock);
> + if (ret < 0)
> + return ret;
> +
> + data->conversion_time = rm3100_samp_rates[i][2] + 3000;
> + return 0;
> +
> +unlock_return:
> + mutex_unlock(&data->lock);
> + return ret;
> +}
> +
> +/*
> + * Scale of this sensor depends on cycle count value, these three values
> + * are corresponding to cycle count value 50, 100, 200.
> + * scale = output / gain * 10e4.
10^4 ?

> +const static int rm3100_scale[] = {500, 263, 133};
> +
> +static int rm3100_read_raw(struct iio_dev *indio_dev,
> + const struct iio_chan_spec *chan,
> + int *val, int *val2, long mask)
> +{
> + struct rm3100_data *data = iio_priv(indio_dev);
> + int ret;
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + ret = iio_device_claim_direct_mode(indio_dev);
> + if (ret < 0) {
> + iio_device_release_direct_mode(indio_dev);
> + return ret;
> + }
> + ret = rm3100_read_mag(data, chan->scan_index, val);
> + iio_device_release_direct_mode(indio_dev);
> +
> + return ret;
> + case IIO_CHAN_INFO_SCALE:
> + *val = 0;
> + *val2 = rm3100_scale[data->cycle_count_index];
> +
> + return IIO_VAL_INT_PLUS_MICRO;
> + case IIO_CHAN_INFO_SAMP_FREQ:
> + return rm3100_get_samp_freq(data, val, val2);
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int rm3100_write_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int val, int val2, long mask)
> +{
> + struct rm3100_data *data = iio_priv(indio_dev);
> +
> + switch (mask) {
> + case IIO_CHAN_INFO_SAMP_FREQ:
> + return rm3100_set_samp_freq(data, val, val2);
> + default:
> + return -EINVAL;
> + }
> +
> +}
> +
> +static const struct iio_info rm3100_info = {
> + .attrs = &rm3100_attribute_group,
> + .read_raw = rm3100_read_raw,
> + .write_raw = rm3100_write_raw,
> +};
> +
> +static irqreturn_t rm3100_trigger_handler(int irq, void *p)
> +{
> + struct iio_poll_func *pf = p;
> + struct iio_dev *indio_dev = pf->indio_dev;
> + struct rm3100_data *data = iio_priv(indio_dev);
> + struct regmap *regmap = data->regmap;
> + u8 buffer[9];
> + int ret;
> + int i;
> +
> + mutex_lock(&data->lock);
> + ret = rm3100_wait_measurement(data);
> + if (ret < 0) {
> + mutex_unlock(&data->lock);
> + goto done;
> + }
> +
> + ret = regmap_bulk_read(regmap, RM3100_REG_MX2, buffer, sizeof(buffer));
> + mutex_unlock(&data->lock);
> + if (ret < 0)
> + goto done;
> +
> + /* Convert XXXYYYZZZxxx to XXXxYYYxZZZx. x for padding. */
> + for (i = 0; i < 3; i++)
> + memcpy(data->buffer + i * 4, buffer + i * 3, 3);
> +
> + iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
> + iio_get_time_ns(indio_dev));
> +
> +done:
> + iio_trigger_notify_done(indio_dev->trig);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static void rm3100_remove(void *dh)
> +{
> + struct rm3100_data *data = (struct rm3100_data *)dh;

No need for an explicit cast to dh.
Void pointer conversions are implicit.

> + int ret;
> +
> + ret = regmap_write(data->regmap, RM3100_REG_CMM, 0x00);
> + if (ret < 0)
> + dev_err(data->dev, "failed to stop device.\n");
> +}
> +
> +int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq)
> +{
> + struct iio_dev *indio_dev;
> + struct rm3100_data *data;
> + int tmp;
> + int ret;
> +
> + indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + data = iio_priv(indio_dev);
> + data->dev = dev;

Check this if it's really required and possible remove
the `struct device *dev` from the private chip data struct.

Use can use `regmap_get_device()` for `rm3100_remove()`

> + data->regmap = regmap;
> + data->buffer = devm_kzalloc(dev, RM3100_SCAN_BYTES, GFP_KERNEL);
> + if (!data->buffer)
> + return -ENOMEM;
> +
> + mutex_init(&data->lock);
> +
> + indio_dev->dev.parent = dev;
> + indio_dev->name = "rm3100";
> + indio_dev->info = &rm3100_info;
> + indio_dev->channels = rm3100_channels;
> + indio_dev->num_channels = ARRAY_SIZE(rm3100_channels);
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->available_scan_masks = rm3100_scan_masks;
> +
> + if (!irq)
> + data->use_interrupt = false;
> + else {
> + data->use_interrupt = true;
> + ret = devm_request_irq(dev,
> + irq,
> + rm3100_irq_handler,
> + IRQF_TRIGGER_RISING,
> + indio_dev->name,
> + data);
> + if (ret < 0) {
> + dev_err(dev, "request irq line failed.\n");
> + return ret;
> + }
> + init_completion(&data->measuring_done);
> + }
> +
> + ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
> + rm3100_trigger_handler, NULL);
> + if (ret < 0)
> + return ret;
> +
> + /* 3sec more wait time. */
> + ret = regmap_read(regmap, RM3100_REG_TMRC, &tmp);
> + if (ret < 0)
> + return ret;
> + data->conversion_time =
> + rm3100_samp_rates[tmp-RM3100_TMRC_OFFSET][2] + 3000;

This will fit in 80 char limit.

> + /* Cycle count values may not be what we want. */
> + ret = regmap_read(data->regmap, RM3100_REG_TMRC, &tmp);
> + if (ret < 0)
> + return ret;
> + if ((tmp - RM3100_TMRC_OFFSET) == 0)
> + rm3100_set_cycle_count(data, 100);
> + else
> + rm3100_set_cycle_count(data, 200);
> +
> + /* Starting all channels' conversion. */
> + ret = regmap_write(regmap, RM3100_REG_CMM,
> + RM3100_CMM_X | RM3100_CMM_Y | RM3100_CMM_Z | RM3100_CMM_START);
> + if (ret < 0)
> + return ret;
> +
> + ret = devm_iio_device_register(dev, indio_dev);
> + if (ret < 0)
> + return ret;
> +
> + return devm_add_action(dev, rm3100_remove, data);
> +}
> +EXPORT_SYMBOL_GPL(rm3100_common_probe);
> +
> +MODULE_AUTHOR("Song Qiang <songqiang1304521@xxxxxxxxx>");
> +MODULE_DESCRIPTION("PNI RM3100 3-axis magnetometer i2c driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/iio/magnetometer/rm3100-i2c.c b/drivers/iio/magnetometer/rm3100-i2c.c
> new file mode 100644
> index 000000000000..e8b84fac771b
> --- /dev/null
> +++ b/drivers/iio/magnetometer/rm3100-i2c.c
> @@ -0,0 +1,58 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Support for PNI RM3100 3-axis geomagnetic sensor a i2c bus.
> + *
> + * Copyright (C) 2018 Song Qiang <songqiang1304521@xxxxxxxxx>
> + *
> + * i2c slave address 0x20 + SA1 << 1 + SA0.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +
> +#include "rm3100.h"
> +
> +static const struct regmap_config rm3100_regmap_config = {
> + .reg_bits = 8,
> + .val_bits = 8,
> +
> + .rd_table = &rm3100_readable_table,
> + .wr_table = &rm3100_writable_table,
> + .volatile_table = &rm3100_volatile_table,
> +
> + .cache_type = REGCACHE_RBTREE,

I wonder when do we use other types of `.cache_type` ?

> +static int rm3100_probe(struct i2c_client *client)
> +{
> + struct regmap *regmap;
> +
> + if (!i2c_check_functionality(client->adapter,
> + I2C_FUNC_SMBUS_READ_I2C_BLOCK | I2C_FUNC_SMBUS_BYTE_DATA))
> + return -EOPNOTSUPP;
> +
> + regmap = devm_regmap_init_i2c(client, &rm3100_regmap_config);
> + if (IS_ERR(regmap))
> + return PTR_ERR(regmap);
> +
> + return rm3100_common_probe(&client->dev, regmap, client->irq);
> +}
> +
> +static const struct of_device_id rm3100_dt_match[] = {
> + { .compatible = "pni,rm3100", },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, rm3100_dt_match);
> +
> +static struct i2c_driver rm3100_driver = {
> + .driver = {
> + .name = "rm3100-i2c",
> + .of_match_table = rm3100_dt_match,
> + },
> + .probe_new = rm3100_probe,
> +};
> +module_i2c_driver(rm3100_driver);
> +
> +MODULE_AUTHOR("Song Qiang <songqiang1304521@xxxxxxxxx>");
> +MODULE_DESCRIPTION("PNI RM3100 3-axis magnetometer i2c driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/iio/magnetometer/rm3100-spi.c b/drivers/iio/magnetometer/rm3100-spi.c
> new file mode 100644
> index 000000000000..1a7a69fb9872
> --- /dev/null
> +++ b/drivers/iio/magnetometer/rm3100-spi.c
> @@ -0,0 +1,64 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Support for PNI RM3100 3-axis geomagnetic sensor a spi bus.
> + *
> + * Copyright (C) 2018 Song Qiang <songqiang1304521@xxxxxxxxx>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +
> +#include "rm3100.h"
> +
> +static const struct regmap_config rm3100_regmap_config = {
> + .reg_bits = 8,
> + .val_bits = 8,
> +
> + .rd_table = &rm3100_readable_table,
> + .wr_table = &rm3100_writable_table,
> + .volatile_table = &rm3100_volatile_table,
> +
> + .read_flag_mask = 0x80,
> +
> + .cache_type = REGCACHE_RBTREE,
> +};
> +
> +static int rm3100_probe(struct spi_device *spi)
> +{
> + struct regmap *regmap;
> + int ret;
> +
> + /* Actually this device supports both mode 0 and mode 3. */
> + spi->mode = SPI_MODE_0;
> + /* Data rates cannot exceed 1Mbits. */
> + spi->max_speed_hz = 1000000;
> + spi->bits_per_word = 8;
> + ret = spi_setup(spi);
> + if (ret)
> + return ret;
> +
> + regmap = devm_regmap_init_spi(spi, &rm3100_regmap_config);
> + if (IS_ERR(regmap))
> + return PTR_ERR(regmap);
> +
> + return rm3100_common_probe(&spi->dev, regmap, spi->irq);
> +}
> +
> +static const struct of_device_id rm3100_dt_match[] = {
> + { .compatible = "pni,rm3100", },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, rm3100_dt_match);
> +
> +static struct spi_driver rm3100_driver = {
> + .driver = {
> + .name = "rm3100-spi",
> + .of_match_table = rm3100_dt_match,
> + },
> + .probe = rm3100_probe,
> +};
> +module_spi_driver(rm3100_driver);
> +
> +MODULE_AUTHOR("Song Qiang <songqiang1304521@xxxxxxxxx>");
> +MODULE_DESCRIPTION("PNI RM3100 3-axis magnetometer spi driver");
> +MODULE_LICENSE("GPL v2");
> diff --git a/drivers/iio/magnetometer/rm3100.h b/drivers/iio/magnetometer/rm3100.h
> new file mode 100644
> index 000000000000..673647574add
> --- /dev/null
> +++ b/drivers/iio/magnetometer/rm3100.h
> @@ -0,0 +1,73 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Header file for PNI RM3100 driver

Remove this bogus line.

> + * Copyright (C) 2018 Song Qiang <songqiang1304521@xxxxxxxxx>
> + */
> +
> +#ifndef RM3100_CORE_H
> +#define RM3100_CORE_H
> +
> +#include <linux/regmap.h>
> +
> +#define RM3100_REG_REV_ID 0x36

Does this ID needs to be checked and validated during
intialisation with default state ID val ?

> +
> +/* Cycle Count Registers. */
> +#define RM3100_REG_CC_X 0x05
> +#define RM3100_REG_CC_Y 0x07
> +#define RM3100_REG_CC_Z 0x09
> +
> +/* Continues Measurement Mode register. */

Is it continuous ?

> +#define RM3100_REG_CMM 0x01
> +#define RM3100_CMM_START BIT(0)
> +#define RM3100_CMM_X BIT(4)
> +#define RM3100_CMM_Y BIT(5)
> +#define RM3100_CMM_Z BIT(6)
> +
> +/* TiMe Rate Configuration register. */

Time!

> +#define RM3100_REG_TMRC 0x0B
> +#define RM3100_TMRC_OFFSET 0x92
> +
> +/* Result Status register. */
> +#define RM3100_REG_STATUS 0x34
> +#define RM3100_STATUS_DRDY BIT(7)

If this status bit is a field of status register then
align this as:

#define RM3100_REG_STATUS 0x34
#define RM3100_STATUS_DRDY BIT(7)

> +/* Measurement result registers. */
> +#define RM3100_REG_MX2 0x24
> +#define RM3100_REG_MY2 0x27
> +#define RM3100_REG_MZ2 0x2a
> +
> +#define RM3100_W_REG_START RM3100_REG_CMM
> +#define RM3100_W_REG_END RM3100_REG_REV_ID
> +#define RM3100_R_REG_START RM3100_REG_CMM
> +#define RM3100_R_REG_END RM3100_REG_STATUS
> +#define RM3100_V_REG_START RM3100_REG_MX2
> +#define RM3100_V_REG_END RM3100_REG_STATUS
> +
> +#define RM3100_SCAN_BYTES 24
> +
> +struct rm3100_data {
> + struct device *dev;

Better remove this ?

--
Himanshu Jha
Undergraduate Student
Department of Electronics & Communication
Guru Tegh Bahadur Institute of Technology

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