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Date:   Fri, 21 Sep 2018 02:05:11 +0800
From:   Song Qiang <songqiang1304521@gmail.com>
To:     Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc:     jic23@kernel.org, lars@metafoo.de, knaack.h@gmx.de,
        robh+dt@kernel.org, mark.rutland@arm.com,
        devicetree@vger.kernel.org, linux-iio@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iio: magnetometer: Add support for PNI RM3100 9-axis
 magnetometer
Message-ID: <20180920180511.GA18559@Eros>
References: <20180920131340.6699-1-songqiang1304521@gmail.com>
 <alpine.DEB.2.21.1809201522370.1482@vps.pmeerw.net>
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On Thu, Sep 20, 2018 at 03:46:03PM +0200, 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
> 

Hi Peter,

Thanks for spending time with my patch!
Sorry for my English, I'll use a spell checker next time.

> > +
> > +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
> 

Okay, I'll add it in next version.

> > + */
> > +
> > +#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
> 

I was planning to let rm3100-i2c.c and rm3100-spi.c to share these 6
structures, because the only different configuration of regmap between
these two files lies in 'struct regmap_config'. To achieve this, I have
to expose these 3 structures to be referenced in rm3100-i2c.c and
rm3100-spi.c
Since *_common_probe() and *_common_remove() are exposed, I thought it
was fine to expose these structures to reduce redundant code, is this
prohibited?

> > +		.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?
> 

Okay.

> > +	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)
> 

Great!

> > +	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() 
> 

I think I didn't fully understand this, I'll look into it.

> > +	*val = sign_extend32(*val, 23);
> > +
> > +	return IIO_VAL_INT;
> > +}
> > +
> > +#define RM_CHANNEL(axis, idx)					\
> 
> use RM3100_ prefix please
> 

In the last driver I wrote, name of registers are so long that I have to
suppress them as possible as I can, it seems like this one doesn't need
to. :)

> > +	{								\
> > +		.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?
> 

It's in milliseconds. These time values are used for lookup so I do not
need to compute time between conversion from measurement frequency, and
they are used for wait time, I thought a little longer is better.
I think the comment above this structure isn't very clear, I'll find a
better way to explain it.

> 
> > + */
> > +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
> 

Okay.

> > +	*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?
> 

My fault.

> > +	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?
> 

These actions are for changing the sampling frequency. This device
cannot start conversion if CMM register is not reset after reading from
CCX/CCY/CCZ registers. So I unlock it later since conversion should have
already been stopped and other threads should not access the bus.

> > +			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?
> 

Oh..yes!

> > +			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_...
> 

Sorry for this...

> > +	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 
> 

Okay.

> > +	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;
> > +	}
> > +	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
> 

I'll put this in my future checklist.

> > +	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 */
> > 
> 
> -- 
> 
> Peter Meerwald-Stadler
> Mobile: +43 664 24 44 418

yours,
Song Qiang