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Subject: Re: [PATCH] iio: magnetometer: Add support for PNI RM3100 9-axis
 magnetometer
To:     Peter Meerwald-Stadler <pmeerw@pmeerw.net>,
        Song Qiang <songqiang1304521@gmail.com>
Cc:     jic23@kernel.org, lars@metafoo.de, linux-iio@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20180920131340.6699-1-songqiang1304521@gmail.com>
 <alpine.DEB.2.21.1809201522370.1482@vps.pmeerw.net>
From:   Phil Reid <preid@electromag.com.au>
Message-ID: <5a4d3868-902c-494e-76e4-4141ff5ec855@electromag.com.au>
Date:   Fri, 21 Sep 2018 13:07:17 +0800
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G'day Song,

One more comment below.
On 20/09/2018 9:46 PM, Peter Meerwald-Stadler wrote:
> On Thu, 20 Sep 2018, Song Qiang wrote:
> 
>> PNI RM3100 magnetometer is a high resolution, large signal immunity
>> magnetometer, composed of 3 single sensors and a processing chip.
>> PNI is currently not in the vendors list, so this is also adding it.
> 
> comments below
> 
>>
>> 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
>>     the 'interrupts' in DT is declared.
>>
>> Signed-off-by: Song Qiang <songqiang1304521@gmail.com>
>> ---
>>   .../bindings/iio/magnetometer/pni,rm3100.txt  |  57 +++
>>   .../devicetree/bindings/vendor-prefixes.txt   |   1 +
>>   MAINTAINERS                                   |  10 +
>>   drivers/iio/magnetometer/Kconfig              |  29 ++
>>   drivers/iio/magnetometer/Makefile             |   4 +
>>   drivers/iio/magnetometer/rm3100-core.c        | 399 ++++++++++++++++++
>>   drivers/iio/magnetometer/rm3100-i2c.c         |  66 +++
>>   drivers/iio/magnetometer/rm3100-spi.c         |  72 ++++
>>   drivers/iio/magnetometer/rm3100.h             |  90 ++++
>>   9 files changed, 728 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
>>   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/Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt b/Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
>> new file mode 100644
>> index 000000000000..d0d2063e943f
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/magnetometer/pni,rm3100.txt
>> @@ -0,0 +1,57 @@
>> +* PNI RM3100 9-axis magnetometer sensor
>> +
>> +I2C Bus:
>> +
>> +Required properties:
>> +
>> +- compatible : should be "pni,rm3100-i2c"
>> +- reg : the I2C address of the magnetometer
>> +
>> +Optional properties:
>> +
>> +- interrupts: data ready (DRDY) from the chip.
>> +  The interrupts can be triggered on rising edges.
>> +
>> +	Refer to interrupt-controller/interrupts.txt for generic
>> +	interrupt client node bindings.
>> +
>> +- pinctrl-*: pinctrl setup for DRDY line.
>> +
>> +Example:
>> +
>> +rm3100: rm3100@20 {
>> +	pinctrl-names = "default";
>> +	pinctrl-0 = <&rm3100_pins>;
>> +
>> +	compatible = "pni,rm3100-i2c";
>> +	reg = <0x20>;
>> +	interrupt-parent = <&gpio0>;
>> +	interrupts = <4 IRQ_TYPE_EDGE_RISING>;
>> +};
>> +
>> +SPI Bus:
>> +
>> +Required properties:
>> +
>> +- compatible : should be "pni,rm3100-spi"
>> +- reg : address of sensor, usually 0 or 1.
>> +
>> +Optional properties:
>> +
>> +- interrupts: data ready (DRDY) from the chip.
>> +  The interrupts can be triggered on rising edges.
>> +
>> +	Refer to interrupt-controller/interrupts.txt for generic
>> +	interrupt client node bindings.
>> +
>> +- pinctrl-*: pinctrl setup for DRDY line, depands on archtechture.
> 
> depends
> architecture
> 
>> +
>> +Example:
>> +
>> +rm3100: rm3100@0{
>> +	compatible = "pni,rm3100-spi";
>> +	reg = <0>;
>> +
>> +	interrupt-parent = <&gpio0>;
>> +	interrupts = <4 IRQ_TYPE_EDGE_RISING>;
>> +};
>> diff --git a/Documentation/devicetree/bindings/vendor-prefixes.txt b/Documentation/devicetree/bindings/vendor-prefixes.txt
>> index 41f0b97eb933..5bf3395fe9ae 100644
>> --- a/Documentation/devicetree/bindings/vendor-prefixes.txt
>> +++ b/Documentation/devicetree/bindings/vendor-prefixes.txt
>> @@ -288,6 +288,7 @@ pine64	Pine64
>>   pixcir  PIXCIR MICROELECTRONICS Co., Ltd
>>   plathome	Plat'Home Co., Ltd.
>>   plda	PLDA
>> +pni     PNI
>>   portwell	Portwell Inc.
>>   poslab	Poslab Technology Co., Ltd.
>>   powervr	PowerVR (deprecated, use img)
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 967ce8cdd1cc..30ee8cf98312 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -11393,6 +11393,16 @@ M:	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
>>   S:	Maintained
>>   F:	drivers/pnp/
>>   
>> +PNI RM3100 IIO DRIVER
>> +M:	Song Qiang <songqiang1304521@gmail.com>
>> +L:	linux-iio@vger.kernel.org
>> +S:	Maintained
>> +F:	drivers/iio/magnetometer/rm3100-core.c
>> +F:	drivers/iio/magnetometer/rm3100-i2c.c
>> +F:	drivers/iio/magnetometer/rm3100-spi.c
>> +F:	drivers/iio/magnetometer/rm3100.h
>> +F:	Documentation/devicetree/bindings/iio/magnetometer/rm3100.txt
>> +
>>   POSIX CLOCKS and TIMERS
>>   M:	Thomas Gleixner <tglx@linutronix.de>
>>   L:	linux-kernel@vger.kernel.org
>> 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.
>> +
>>   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..55d515e0fe67
>> --- /dev/null
>> +++ b/drivers/iio/magnetometer/rm3100-core.c
>> @@ -0,0 +1,399 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * PNI RM3100 9-axis geomagnetic sensor driver core.
>> + *
>> + * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
>> + *
>> + * User Manual available at
>> + * <https://www.pnicorp.com/download/rm3100-user-manual/>
>> + *
>> + * TODO: Scale channel, event generaton, pm.
> 
> at least read support for _SCALE is mandatory, IMHO
> 
>> + */
>> +
>> +#include <linux/delay.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/slab.h>
>> +
>> +#include <linux/iio/iio.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(RM_W_REG_START, RM_W_REG_END),
>> +};
>> +
>> +const struct regmap_access_table rm3100_readable_table = {
> 
> static
> 
>> +		.yes_ranges = rm3100_readable_ranges,
>> +		.n_yes_ranges = ARRAY_SIZE(rm3100_readable_ranges),
>> +};
>> +
>> +static const struct regmap_range rm3100_writable_ranges[] = {
>> +		regmap_reg_range(RM_R_REG_START, RM_R_REG_END),
>> +};
>> +
>> +const struct regmap_access_table rm3100_writable_table = {
> 
> static
> 
>> +		.yes_ranges = rm3100_writable_ranges,
>> +		.n_yes_ranges = ARRAY_SIZE(rm3100_writable_ranges),
>> +};
>> +
>> +static const struct regmap_range rm3100_volatile_ranges[] = {
>> +		regmap_reg_range(RM_V_REG_START, RM_V_REG_END),
>> +};
>> +
>> +const struct regmap_access_table rm3100_volatile_table = {
> 
> static
> 
>> +		.yes_ranges = rm3100_volatile_ranges,
>> +		.n_yes_ranges = ARRAY_SIZE(rm3100_volatile_ranges),
>> +};
>> +
>> +static irqreturn_t rm3100_measurement_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;
>> +	u16 tries = 20;
> 
> why not use int for tries?
> 
>> +	int ret;
>> +
>> +	/* A read cycle of 400kbits i2c bus is about 20us, plus the time
>> +	 * used for schduling, a read cycle of fast mode of this device
> 
> scheduling
> 
>> +	 * can reach 1.7ms, it may be possible for data arrives just
> 
> to arrive
> 
>> +	 * after we check the RM_REG_STATUS. In this case, irq_handler is
>> +	 * called before measuring_done is reinitialized, it will wait
>> +	 * forever for a data that has already been ready.
> 
> for data
> 
>> +	 * 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, RM_REG_STATUS, &val);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	if ((val & RM_STATUS_DRDY) != RM_STATUS_DRDY) {
>> +		if (data->use_interrupt) {
>> +			ret = wait_for_completion_timeout(&data->measuring_done,
>> +				msecs_to_jiffies(data->conversion_time));
>> +			if (!ret)
>> +				return -ETIMEDOUT;
>> +		} else {
>> +			do {
>> +				ret = regmap_read(regmap, RM_REG_STATUS, &val);
>> +				if (ret < 0)
>> +					return ret;
>> +
>> +				if (val & RM_STATUS_DRDY)
>> +					break;
>> +
>> +				usleep_range(1000, 5000);
>> +			} 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, RM_REG_MX2 + 3 * idx, buffer, 3);
> 
> sizeof(buf)
> 
>> +	mutex_unlock(&data->lock);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	*val = le32_to_cpu((buffer[0] << 16) + (buffer[1] << 8) + buffer[2]);
> 
> no need for le32_to_cpu()
> 
>> +	*val = sign_extend32(*val, 23);
>> +
>> +	return IIO_VAL_INT;
>> +}
>> +
>> +#define RM_CHANNEL(axis, idx)					\
> 
> use RM3100_ prefix please
> 
>> +	{								\
>> +		.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_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[] = {
>> +	RM_CHANNEL(X, 0),
>> +	RM_CHANNEL(Y, 1),
>> +	RM_CHANNEL(Z, 2),
>> +	IIO_CHAN_SOFT_TIMESTAMP(3),
>> +};
>> +
>> +static const unsigned long rm3100_scan_masks[] = {GENMASK(2, 0), 0};
>> +
>> +#define RM_SAMP_NUM	14
> 
> prefix
> 
>> +
>> +/* Frequency : rm3100_samp_rates[][0].rm3100_samp_rates[][1]Hz.
>> + * Time between reading: rm3100_sam_rates[][2]ms (The first on is actially 1.7).
> 
> one
> actually
> 1.7 what unit?
> 
> 
>> + */
>> +static const int rm3100_samp_rates[RM_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;
>> +
>> +	ret = regmap_read(data->regmap, RM_REG_TMRC, &tmp);
>> +	if (ret < 0)
>> +		return ret;
>> +	*val = rm3100_samp_rates[tmp-RM_TMRC_OFFSET][0];
> 
> space around - operator
> 
>> +	*val2 = rm3100_samp_rates[tmp-RM_TMRC_OFFSET][1];
>> +
>> +	return IIO_VAL_INT_PLUS_MICRO;
>> +}
>> +
>> +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;
>> +
>> +	/* All cycle count registers use the same value. */
>> +	ret = regmap_read(regmap, RM_REG_CCXL, &cycle_count);
> 
> check ret?
> 
>> +	if (cycle_count < 0)
>> +		return cycle_count;
>> +
>> +	for (i = 0; i < RM_SAMP_NUM; i++) {
>> +		if (val == rm3100_samp_rates[i][0] &&
>> +			val2 == rm3100_samp_rates[i][1])
>> +			break;
>> +	}
>> +
>> +	if (i != RM_SAMP_NUM) {
>> +		mutex_lock(&data->lock);
>> +		ret = regmap_write(regmap, RM_REG_TMRC, i + RM_TMRC_OFFSET);
>> +		if (ret < 0)
> 
> unlock?
> 
>> +			return ret;
>> +
>> +		/* Checking if cycle count registers need changing. */
>> +		if (val == 600 && cycle_count == 200) {
>> +			for (i = 0; i < 3; i++) {
>> +				regmap_write(regmap, RM_REG_CCXL + 2 * i, 100);
>> +				if (ret < 0)
> 
> unlock?
> 
>> +					return ret;
>> +			}
>> +		} else if (val != 600 && cycle_count == 100) {
>> +			for (i = 0; i < 3; i++) {
>> +				regmap_write(regmap, RM_REG_CCXL + 2 * i, 200);
>> +				if (ret < 0)
> 
> unlock?
> 
>> +					return ret;
>> +			}
>> +		}
>> +		/* Writing TMRC registers requires CMM reset. */
>> +		ret = regmap_write(regmap, RM_REG_CMM, 0);
>> +		if (ret < 0)
> 
> unlock?
> 
>> +			return ret;
>> +		ret = regmap_write(regmap, RM_REG_CMM, RM_CMM_PMX |
>> +			RM_CMM_PMY | RM_CMM_PMZ | RM_CMM_START);
>> +		if (ret < 0)
> 
> unlock?
> 
>> +			return ret;
>> +		mutex_unlock(&data->lock);
>> +
>> +		data->conversion_time = rm3100_samp_rates[i][2] + 3000;
>> +		return 0;
>> +	}
>> +	return -EINVAL;
>> +}
>> +
>> +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)
> 
> release_direct_mode() here?
> 
>> +			return ret;
>> +		ret = rm3100_read_mag(data, chan->scan_index, val);
>> +		iio_device_release_direct_mode(indio_dev);
>> +
>> +		return ret;
>> +	case IIO_CHAN_INFO_SAMP_FREQ:
>> +		return ret = rm3100_get_samp_freq(data, val, val2);
> 
> return ret = ???, just
> return rm3100_...
> 
>> +	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);
>> +	int ret;
>> +
>> +	switch (mask) {
>> +	case IIO_CHAN_INFO_SAMP_FREQ:
>> +		ret = rm3100_set_samp_freq(data, val, val2);
>> +		if (ret < 0)
>> +			return ret;
>> +		return 0;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +
>> +}
>> +
>> +static const struct iio_info rm3100_info = {
>> +	.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;
>> +	int ret;
>> +	int i;
>> +
>> +	buffer = devm_kzalloc(data->dev, indio_dev->scan_bytes, GFP_KERNEL);
> 
> try to allocate the maximum needed amount of memory beforehand, in
> _probe() perhaps
> 
>> +	if (!buffer)
>> +		goto done;
>> +
>> +	mutex_lock(&data->lock);
>> +	ret = rm3100_wait_measurement(data);
>> +	if (ret < 0) {
>> +		mutex_unlock(&data->lock);
>> +		goto done;
>> +	}
>> +
>> +	for (i = 0; i < 3; i++) {
>> +		ret = regmap_bulk_read(regmap, RM_REG_MX2 + 3 * i,
>> +				buffer + 4 * i, 3);
>> +		if (ret < 0)
>> +			return ret;
>> +	}

Wouldn't it be better to read the 3 axis with one transaction here.
And if required shuffle the data into the iio buffer.


>> +	mutex_unlock(&data->lock);
>> +
>> +	iio_push_to_buffers_with_timestamp(indio_dev, buffer,
>> +			iio_get_time_ns(indio_dev));
>> +done:
>> +	iio_trigger_notify_done(indio_dev->trig);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +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);
>> +	dev_set_drvdata(dev, indio_dev);
>> +	data->dev = dev;
>> +	data->regmap = regmap;
>> +
>> +	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_measurement_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 = iio_triggered_buffer_setup(indio_dev, NULL,
>> +					rm3100_trigger_handler, NULL);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	/* 3sec more wait time. */
>> +	ret = regmap_read(data->regmap, RM_REG_TMRC, &tmp);
> 
> check ret
> 
>> +	data->conversion_time = rm3100_samp_rates[tmp-RM_TMRC_OFFSET][2] + 3000;
>> +
>> +	/* Starting all channels' conversion. */
>> +	ret = regmap_write(regmap, RM_REG_CMM,
>> +		RM_CMM_PMX | RM_CMM_PMY | RM_CMM_PMZ | RM_CMM_START);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	return devm_iio_device_register(dev, indio_dev);
>> +}
>> +EXPORT_SYMBOL(rm3100_common_probe);
>> +
>> +int rm3100_common_remove(struct device *dev)
>> +{
>> +	struct iio_dev *indio_dev = dev_get_drvdata(dev);
>> +	struct rm3100_data *data = iio_priv(indio_dev);
>> +	struct regmap *regmap = data->regmap;
>> +
>> +	regmap_write(regmap, RM_REG_CMM, 0x00);
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL(rm3100_common_remove);
>> +
>> +MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
>> +MODULE_DESCRIPTION("PNI RM3100 9-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..b50dc5b1b30b
>> --- /dev/null
>> +++ b/drivers/iio/magnetometer/rm3100-i2c.c
>> @@ -0,0 +1,66 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * Support for PNI RM3100 9-axis geomagnetic sensor a i2c bus.
>> + *
>> + * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
>> + *
>> + * User Manual available at
>> + * <https://www.pnicorp.com/download/rm3100-user-manual/>
>> + *
>> + * i2c slave address 0x20 + SA1 << 1 + SA0.
>> + */
>> +
>> +#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,
>> +};
>> +
>> +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 int rm3100_remove(struct i2c_client *client)
>> +{
>> +	return rm3100_common_remove(&client->dev);
>> +}
>> +
>> +static const struct of_device_id rm3100_dt_match[] = {
>> +	{ .compatible = "pni,rm3100-i2c", },
>> +	{ }
>> +};
>> +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,
>> +	.remove = rm3100_remove,
>> +};
>> +module_i2c_driver(rm3100_driver);
>> +
>> +MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
>> +MODULE_DESCRIPTION("PNI RM3100 9-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..2c7dd9e3a1a2
>> --- /dev/null
>> +++ b/drivers/iio/magnetometer/rm3100-spi.c
>> @@ -0,0 +1,72 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * Support for PNI RM3100 9-axis geomagnetic sensor a spi bus.
>> + *
>> + * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
>> + *
>> + * User Manual available at
>> + * <https://www.pnicorp.com/download/rm3100-user-manual/>
>> + */
>> +
>> +#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 exceeds 1Mbits. */
> 
> exceed
> 
>> +	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 int rm3100_remove(struct spi_device *spi)
>> +{
>> +	return rm3100_common_remove(&spi->dev);
>> +}
>> +
>> +static const struct of_device_id rm3100_dt_match[] = {
>> +	{ .compatible = "pni,rm3100-spi", },
>> +	{ }
>> +};
>> +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,
>> +		.remove = rm3100_remove,
>> +};
>> +module_spi_driver(rm3100_driver);
>> +
>> +MODULE_AUTHOR("Song Qiang <songqiang1304521@gmail.com>");
>> +MODULE_DESCRIPTION("PNI RM3100 9-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..5e30bc0f5149
>> --- /dev/null
>> +++ b/drivers/iio/magnetometer/rm3100.h
>> @@ -0,0 +1,90 @@
>> +/* SPDX-License-Identifier: GPL-2.0+ */
>> +/*
>> + * Header file for PNI RM3100 driver
>> + *
>> + * Copyright (C) 2018 Song Qiang <songqiang1304521@gmail.com>
>> + */
>> +
>> +#ifndef RM3100_CORE_H
>> +#define RM3100_CORE_H
>> +
>> +#include <linux/module.h>
>> +#include <linux/regmap.h>
>> +
>> +#define RM_REG_REV_ID		0x36
>> +
>> +/* Cycle Count Registers MSBs and LSBs. */
>> +#define RM_REG_CCXM		0x04
>> +#define RM_REG_CCXL		0x05
>> +#define RM_REG_CCYM		0x06
>> +#define RM_REG_CCYL		0x07
>> +#define RM_REG_CCZM		0x08
>> +#define RM_REG_CCZL		0x09
>> +
>> +/* Single Measurement Mode register. */
>> +#define RM_REG_POLL		0x00
>> +#define RM_POLL_PMX		BIT(4)
>> +#define RM_POLL_PMY		BIT(5)
>> +#define RM_POLL_PMZ		BIT(6)
>> +
>> +/* Continues Measurement Mode register. */
>> +#define RM_REG_CMM		0x01
>> +#define RM_CMM_START		BIT(0)
>> +#define RM_CMM_DRDM		BIT(2)
>> +#define RM_CMM_PMX		BIT(4)
>> +#define RM_CMM_PMY		BIT(5)
>> +#define RM_CMM_PMZ		BIT(6)
>> +
>> +/* TiMe Rate Configuration register. */
>> +#define RM_REG_TMRC		0x0B
>> +#define RM_TMRC_OFFSET		0x92
>> +
>> +/* Result Status register. */
>> +#define RM_REG_STATUS		0x34
>> +#define RM_STATUS_DRDY		BIT(7)
>> +
>> +/* Measurement result registers. */
>> +#define RM_REG_MX2		0x24
>> +#define RM_REG_MX1		0x25
>> +#define RM_REG_MX0		0x26
>> +#define RM_REG_MY2		0x27
>> +#define RM_REG_MY1		0x28
>> +#define RM_REG_MY0		0x29
>> +#define RM_REG_MZ2		0x2a
>> +#define RM_REG_MZ1		0x2b
>> +#define RM_REG_MZ0		0x2c
>> +
>> +#define RM_REG_HSHAKE		0x35
>> +
>> +#define RM_W_REG_START		RM_REG_POLL
>> +#define RM_W_REG_END		RM_REG_REV_ID
>> +#define RM_R_REG_START		RM_REG_POLL
>> +#define RM_R_REG_END		RM_REG_HSHAKE
>> +#define RM_V_REG_START		RM_REG_MX2
>> +#define RM_V_REG_END		RM_REG_HSHAKE
>> +
>> +/* Built-In Self Test reigister. */
>> +#define RM_REG_BIST		0x33
>> +
>> +struct rm3100_data {
>> +	struct device *dev;
>> +	struct regmap *regmap;
>> +	struct completion measuring_done;
>> +	bool use_interrupt;
>> +
>> +	int conversion_time;
>> +
>> +	/* To protect consistency of every measurement and sampling
>> +	 * frequency change operations.
>> +	 */
>> +	struct mutex lock;
>> +};
>> +
>> +extern const struct regmap_access_table rm3100_readable_table;
>> +extern const struct regmap_access_table rm3100_writable_table;
>> +extern const struct regmap_access_table rm3100_volatile_table;
>> +
>> +int rm3100_common_probe(struct device *dev, struct regmap *regmap, int irq);
>> +int rm3100_common_remove(struct device *dev);
>> +
>> +#endif /* RM3100_CORE_H */
>>
> 


-- 
Regards
Phil Reid