Date:	Tue, 25 Nov 2014 01:45:05 +0100
From:	Hartmut Knaack <knaack.h@....de>
To:	Daniel Baluta <daniel.baluta@...el.com>, jic23@...nel.org,
	pmeerw@...erw.net, srinivas.pandruvada@...ux.intel.com
CC:	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] iio: imu: Add support for Kionix KMX61 sensor

Daniel Baluta schrieb am 18.11.2014 17:47:
> Minimal implementation for KMX61 6-axis accelerometer/magnetometer. It exports
> raw accel/magn readings together with scale and sampling frequency.
> 
> Datasheet will be available at:
> http://www.kionix.com/6-axis-accelerometer-magnetometer/kmx61
> 
Finally managed to have a close look, and found a few issues.
> Signed-off-by: Daniel Baluta <daniel.baluta@...el.com>
> ---
> Changes since v2:
> 	* mostly style fixes after comments received from Jonathan and Peter
> 		* http://marc.info/?l=linux-iio&m=141564019602400&w=2
> 	* implemented PM runtime and PM sleep resume/suspend hooks
> 	* introduced new parameter for kmx61_set_mode to help updating
> 	stby bits in kmx61_data.
> 	* use kmx6111021 instead of kmx61 for i2c_device_id.
> 
>  drivers/iio/imu/Kconfig  |   9 +
>  drivers/iio/imu/Makefile |   2 +
>  drivers/iio/imu/kmx61.c  | 766 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 777 insertions(+)
>  create mode 100644 drivers/iio/imu/kmx61.c
> 
> diff --git a/drivers/iio/imu/Kconfig b/drivers/iio/imu/Kconfig
> index 2b0e451..d675f43 100644
> --- a/drivers/iio/imu/Kconfig
> +++ b/drivers/iio/imu/Kconfig
> @@ -25,6 +25,15 @@ config ADIS16480
>  	  Say yes here to build support for Analog Devices ADIS16375, ADIS16480,
>  	  ADIS16485, ADIS16488 inertial sensors.
>  
> +config KMX61
> +	tristate "Kionix KMX61 6-axis accelerometer and magnetometer"
> +	depends on I2C
> +	help
> +	  Say Y here if you want to build a driver for Kionix KMX61 6-axis accelerometer
> +	  and magnetometer.
> +	  To compile this driver as module, choose M here: the module will be called
> +	  kmx61.
> +
This help text is more than 80 characters wide and may better be wrapped a bit differently.
>  source "drivers/iio/imu/inv_mpu6050/Kconfig"
>  
>  endmenu
> diff --git a/drivers/iio/imu/Makefile b/drivers/iio/imu/Makefile
> index 114d2c1..e1e6e3d 100644
> --- a/drivers/iio/imu/Makefile
> +++ b/drivers/iio/imu/Makefile
> @@ -14,3 +14,5 @@ adis_lib-$(CONFIG_IIO_ADIS_LIB_BUFFER) += adis_buffer.o
>  obj-$(CONFIG_IIO_ADIS_LIB) += adis_lib.o
>  
>  obj-y += inv_mpu6050/
> +
> +obj-$(CONFIG_KMX61) += kmx61.o
> diff --git a/drivers/iio/imu/kmx61.c b/drivers/iio/imu/kmx61.c
> new file mode 100644
> index 0000000..f68b3ef
> --- /dev/null
> +++ b/drivers/iio/imu/kmx61.c
> @@ -0,0 +1,766 @@
> +/*
> + * KMX61 - Kionix 6-axis Accelerometer/Magnetometer
> + *
> + * Copyright (c) 2014, Intel Corporation.
> + *
> + * This file is subject to the terms and conditions of version 2 of
> + * the GNU General Public License.  See the file COPYING in the main
> + * directory of this archive for more details.
> + *
> + * IIO driver for KMX61 (7-bit I2C slave address 0x0E or 0x0F).
> + *
> + * TODO: buffer, interrupt, thresholds, acpi, temperature sensor
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/i2c.h>
> +#include <linux/pm.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sysfs.h>
> +
> +#define KMX61_DRV_NAME "kmx61"
> +
> +#define KMX61_REG_WHO_AM_I	0x00
> +
> +/*
> + * three 16-bit accelerometer output registers for X/Y/Z axis
> + * we use only XOUT_L as a base register, all other addresses
> + * can be obtained by applying an offset and are provided here
> + * only for clarity.
> + */
> +#define KMX61_ACC_XOUT_L	0x0A
> +#define KMX61_ACC_XOUT_H	0x0B
> +#define KMX61_ACC_YOUT_L	0x0C
> +#define KMX61_ACC_YOUT_H	0x0D
> +#define KMX61_ACC_ZOUT_L	0x0E
> +#define KMX61_ACC_ZOUT_H	0x0F
> +
> +/*
> + * one 16-bit temperature output register
> + */
> +#define KMX61_TEMP_L		0x10
> +#define KMX61_TEMP_H		0x11
> +
> +/*
> + * three 16-bit magnetometer output registers for X/Y/Z axis
> + */
> +#define KMX61_MAG_XOUT_L	0x12
> +#define KMX61_MAG_XOUT_H	0x13
> +#define KMX61_MAG_YOUT_L	0x14
> +#define KMX61_MAG_YOUT_H	0x15
> +#define KMX61_MAG_ZOUT_L	0x16
> +#define KMX61_MAG_ZOUT_H	0x17
> +
> +#define KMX61_REG_ODCNTL	0x2C
> +#define KMX61_REG_STBY		0x29
> +#define KMX61_REG_CTRL1		0x2A
> +
> +#define KMX61_ACC_STBY_BIT	BIT(0)
> +#define KMX61_MAG_STBY_BIT	BIT(1)
> +#define KMX61_ACT_STBY_BIT	BIT(7)
> +
> +#define KMX61_ALL_STBY		(KMX61_ACC_STBY_BIT | KMX61_MAG_STBY_BIT)
> +
> +#define KMX61_REG_CTRL1_GSEL0_SHIFT	0
> +#define KMX61_REG_CTRL1_GSEL1_SHIFT	1
> +#define KMX61_REG_CTRL1_GSEL0_MASK	0x01
> +#define KMX61_REG_CTRL1_GSEL1_MASK	0x02
I don't see the benefit of separating GSEL0 and GSEL1.
> +
> +#define KMX61_REG_CTRL1_BIT_RES		BIT(4)
> +
> +#define KMX61_ACC_ODR_SHIFT	0
> +#define KMX61_MAG_ODR_SHIFT	4
> +#define KMX61_ACC_ODR_MASK	0x0F
> +#define KMX61_MAG_ODR_MASK	0xF0
> +
> +#define KMX61_SLEEP_DELAY_MS	2000
> +
> +#define KMX61_CHIP_ID		0x12
> +
> +struct kmx61_data {
> +	struct i2c_client *client;
> +
> +	/* serialize access to non-atomic ops, e.g set_mode */
> +	struct mutex lock;
> +	u8 range;
> +	u8 odr_bits;
> +
> +	/* standby state */
> +	u8 acc_stby;
> +	u8 mag_stby;
Why u8 instead of bool?
> +
> +	/* power state */
> +	bool acc_ps;
> +	bool mag_ps;
> +};
> +
> +enum kmx61_range {
> +	KMX61_RANGE_2G,
> +	KMX61_RANGE_4G,
> +	KMX61_RANGE_8G,
> +};
> +
> +enum kmx61_scan {
> +	KMX61_SCAN_ACC_X,
> +	KMX61_SCAN_ACC_Y,
> +	KMX61_SCAN_ACC_Z,
> +	KMX61_SCAN_TEMP,
> +	KMX61_SCAN_MAG_X,
> +	KMX61_SCAN_MAG_Y,
> +	KMX61_SCAN_MAG_Z,
> +};
> +
> +static const struct {
> +	u16 uscale;
> +	u8 gsel0;
> +	u8 gsel1;
> +} kmx61_scale_table[] = {
> +	{9582, 0, 0},
> +	{19163, 1, 0},
> +	{38326, 0, 1},
Why not consolidate gsel0 and gsel1 to gsel? Then this could become u16 kmx61_scale[] = {9582, 19163, 38326} with gsel as index.
> +};
> +
> +/* KMX61 devices */
> +#define KMX61_ACC	0x01
> +#define KMX61_MAG	0x02
> +
> +static const struct {
> +	int val;
> +	int val2;
> +	u8 odr_bits;
> +} kmx61_samp_freq_table[] = { {12, 500000, 0x00},
> +			{25, 0, 0x01},
> +			{50, 0, 0x02},
> +			{100, 0, 0x03},
> +			{200, 0, 0x04},
> +			{400, 0, 0x05},
> +			{800, 0, 0x06},
> +			{1600, 0, 0x07},
> +			{0, 781000, 0x08},
> +			{1, 563000, 0x09},
> +			{3, 125000, 0x0A},
> +			{6, 250000, 0x0B} };
> +
> +static IIO_CONST_ATTR(accel_scale_available, "0.009582 0.019163 0.038326");
> +static IIO_CONST_ATTR(magn_scale_available, "0.001465");
> +static IIO_CONST_ATTR_SAMP_FREQ_AVAIL(
> +	"0.781000 1.563000 3.125000 6.250000 12.500000 25 50 100 200 400 800");
> +
> +static struct attribute *kmx61_attributes[] = {
> +	&iio_const_attr_accel_scale_available.dev_attr.attr,
> +	&iio_const_attr_magn_scale_available.dev_attr.attr,
> +	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group kmx61_attribute_group = {
> +	.attrs = kmx61_attributes,
> +};
> +
> +#define KMX61_ACC_CHAN(_axis, _index) { \
> +	.type = IIO_ACCEL, \
> +	.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), \
> +	.address = KMX61_ACC, \
> +	.scan_index = _index, \
> +	.scan_type = { \
> +		.sign = 's', \
> +		.realbits = 12, \
> +		.storagebits = 16, \
> +		.shift = 4, \
> +		.endianness = IIO_LE, \
> +	}, \
> +}
> +
> +#define KMX61_MAG_CHAN(_axis, _index) { \
> +	.type = IIO_MAGN, \
> +	.modified = 1, \
> +	.channel2 = IIO_MOD_ ## _axis, \
> +	.address = KMX61_MAG, \
> +	.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 = _index, \
> +	.scan_type = { \
> +		.sign = 's', \
> +		.realbits = 14, \
> +		.storagebits = 16, \
> +		.shift = 2, \
> +		.endianness = IIO_LE, \
> +	}, \
> +}
> +
> +static const struct iio_chan_spec kmx61_channels[] = {
> +	KMX61_ACC_CHAN(X, KMX61_SCAN_ACC_X),
> +	KMX61_ACC_CHAN(Y, KMX61_SCAN_ACC_Y),
> +	KMX61_ACC_CHAN(Z, KMX61_SCAN_ACC_Z),
> +	KMX61_MAG_CHAN(X, KMX61_SCAN_MAG_X),
> +	KMX61_MAG_CHAN(Y, KMX61_SCAN_MAG_Y),
> +	KMX61_MAG_CHAN(Z, KMX61_SCAN_MAG_Z),
> +};
> +
> +static int kmx61_convert_freq_to_bit(int val, int val2)
> +{
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(kmx61_samp_freq_table); i++)
> +		if (val == kmx61_samp_freq_table[i].val &&
> +		    val2 == kmx61_samp_freq_table[i].val2)
> +			return kmx61_samp_freq_table[i].odr_bits;
> +	return -EINVAL;
> +}
> +/**
Like here, the first line of the following multiline comments have one asterisk too much.
> + * kmx61_set_mode() - set KMX61 device operating mode
> + * @data - kmx61 device private data pointer
> + * @mode - bitmask, indicating operating mode for @device
> + * @device - bitmask, indicating device for which @mode needs to be set
> + * @update - update stby bits stored in device's private  @data
> + *
> + * For each sensor (accelerometer/magnetometer) there are two operating modes
> + * STANDBY and OPERATION. Neither accel nor magn can be disabled independently
> + * if they are both enabled. Internal sensors state is saved in acc_stby and
> + * mag_stby members of driver's private @data.
> + */
> +static int kmx61_set_mode(struct kmx61_data *data, u8 mode, u8 device,
> +			  bool update)
> +{
> +	int ret;
> +	int acc_stby = -1, mag_stby = -1;
> +
> +	ret = i2c_smbus_read_byte_data(data->client, KMX61_REG_STBY);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "Error reading reg_stby\n");
> +		return ret;
> +	}
> +	if (device & KMX61_ACC) {
> +		if (mode & KMX61_ACC_STBY_BIT) {
> +			ret |= KMX61_ACC_STBY_BIT;
> +			acc_stby = 1;
> +		} else {
> +			ret &= ~KMX61_ACC_STBY_BIT;
> +			acc_stby = 0;
> +		}
> +	}
> +
> +	if (device & KMX61_MAG) {
> +		if (mode & KMX61_MAG_STBY_BIT) {
> +			ret |= KMX61_MAG_STBY_BIT;
> +			mag_stby = 1;
> +		} else {
> +			ret &= ~KMX61_MAG_STBY_BIT;
> +			mag_stby = 0;
> +		}
> +	}
> +
> +	ret = i2c_smbus_write_byte_data(data->client, KMX61_REG_STBY, ret);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "Error writing reg_stby\n");
> +		return ret;
> +	}
> +
> +	if (acc_stby != -1 && update)
> +		data->acc_stby = !!acc_stby;
> +	if (mag_stby != -1 && update)
> +		data->mag_stby = !!mag_stby;
Why is there a need for double negation?
> +
> +	return ret;
Since no error occured until this point, just return 0.
> +}
> +
> +static int kmx61_get_mode(struct kmx61_data *data, u8 *mode, u8 device)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_read_byte_data(data->client, KMX61_REG_STBY);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "Error reading reg_stby\n");
> +		return ret;
> +	}
> +	*mode = 0;
> +
> +	if (device & KMX61_ACC) {
> +		if (ret & KMX61_ACC_STBY_BIT)
> +			*mode |= KMX61_ACC_STBY_BIT;
> +		else
> +			*mode &= ~KMX61_ACC_STBY_BIT;
Simply:
		*mode |= ret & KMX61_ACC_STBY_BIT;
> +	}
> +
> +	if (device & KMX61_MAG) {
> +		if (ret & KMX61_MAG_STBY_BIT)
> +			*mode |= KMX61_MAG_STBY_BIT;
> +		else
> +			*mode &= ~KMX61_MAG_STBY_BIT;
Same here:
		*mode |= ret & KMX61_MAG_STBY_BIT;
> +	}
> +
> +	return 0;
> +}
> +
> +static int kmx61_set_odr(struct kmx61_data *data, int val, int val2, u8 device)
> +{
> +	int ret;
> +	u8 mode;
> +	int lodr_bits, odr_bits;
> +
> +	ret = kmx61_get_mode(data, &mode, KMX61_ACC | KMX61_MAG);
> +	if (ret < 0)
> +		return ret;
> +
> +	lodr_bits = kmx61_convert_freq_to_bit(val, val2);
> +	if (lodr_bits < 0)
> +		return lodr_bits;
> +
> +	/* To change ODR, accel and magn must be in STDBY */
> +	ret = kmx61_set_mode(data, KMX61_ALL_STBY, KMX61_ACC | KMX61_MAG,
> +			     true);
> +	if (ret < 0)
> +		return ret;
> +
> +	odr_bits = 0;
> +	if (device & KMX61_ACC)
> +		odr_bits |= lodr_bits;
> +	if (device & KMX61_MAG)
> +		odr_bits |= (lodr_bits << KMX61_MAG_ODR_SHIFT);
No need for parenthesis.
> +
> +	ret = i2c_smbus_write_byte_data(data->client, KMX61_REG_ODCNTL,
> +					odr_bits);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = kmx61_set_mode(data, mode, KMX61_ACC | KMX61_MAG, true);
> +	if (ret < 0)
> +		return ret;
> +
> +	data->odr_bits = lodr_bits;
> +
> +	return 0;
> +}
> +
> +static
> +int kmx61_get_odr(struct kmx61_data *data, int *val, int *val2, u8 device)
Usually wrap parameters? And don't put code on line with {.
> +{	int i;
> +	u8 lodr_bits;
> +
> +	if (device & KMX61_ACC)
> +		lodr_bits = (data->odr_bits >> KMX61_ACC_ODR_SHIFT) &
> +			     KMX61_ACC_ODR_MASK;
KMX61_ACC_ODR_SHIFT is just a placebo and not used in kmx61_set_odr. Choose one way and stay consistent.
> +	else if (device & KMX61_MAG)
> +		lodr_bits = (data->odr_bits >> KMX61_MAG_ODR_SHIFT) &
> +			     KMX61_MAG_ODR_MASK;
> +	else
> +		return -EINVAL;
> +
> +	for (i = 0; i < ARRAY_SIZE(kmx61_samp_freq_table); i++)
> +		if (lodr_bits == kmx61_samp_freq_table[i].odr_bits) {
> +			*val = kmx61_samp_freq_table[i].val;
> +			*val2 = kmx61_samp_freq_table[i].val2;
> +			return 0;
return IIO_VAL_INT_PLUS_MICRO allows you to faciliate _read_raw a bit to just return ret there.
> +		}
> +	return -EINVAL;
> +}
> +
> +static int kmx61_set_range(struct kmx61_data *data, int range)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_read_byte_data(data->client, KMX61_REG_CTRL1);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "Error reading reg_ctrl1\n");
> +		return ret;
> +	}
> +
> +	ret &= ~(KMX61_REG_CTRL1_GSEL0_MASK | KMX61_REG_CTRL1_GSEL1_MASK);
> +	ret |= kmx61_scale_table[range].gsel0 << KMX61_REG_CTRL1_GSEL0_SHIFT;
> +	ret |= kmx61_scale_table[range].gsel1 << KMX61_REG_CTRL1_GSEL1_SHIFT;
> +
> +	ret = i2c_smbus_write_byte_data(data->client, KMX61_REG_CTRL1, ret);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "Error writing reg_ctrl1\n");
> +		return ret;
> +	}
> +
> +	data->range = range;
> +
> +	return 0;
> +}
> +
> +static int kmx61_set_scale(struct kmx61_data *data, int uscale)
> +{
> +	int ret, i;
> +	u8  mode;
> +
> +	for (i = 0; i < ARRAY_SIZE(kmx61_scale_table); i++) {
> +		if (kmx61_scale_table[i].uscale == uscale) {
> +			ret = kmx61_get_mode(data, &mode,
> +					     KMX61_ACC | KMX61_MAG);
> +			if (ret < 0)
> +				return ret;
> +
> +			ret = kmx61_set_mode(data, KMX61_ALL_STBY,
> +					     KMX61_ACC | KMX61_MAG, true);
> +			if (ret < 0)
> +				return ret;
> +
> +			ret = kmx61_set_range(data, i);
> +			if (ret < 0)
> +				return ret;
> +
> +			return  kmx61_set_mode(data, mode,
> +					       KMX61_ACC | KMX61_MAG, true);
> +		}
> +	}
> +	return -EINVAL;
> +}
> +
> +static int kmx61_chip_init(struct kmx61_data *data)
> +{
> +	int ret;
> +
> +	ret = i2c_smbus_read_byte_data(data->client, KMX61_REG_WHO_AM_I);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "Error reading who_am_i\n");
> +		return ret;
> +	}
> +
> +	if (ret != KMX61_CHIP_ID) {
> +		dev_err(&data->client->dev,
> +			"Wrong chip id, got %x expected %x\n",
> +			 ret, KMX61_CHIP_ID);
> +		return -EINVAL;
> +	}
> +
> +	/* set accel 12bit, 4g range */
> +	ret = kmx61_set_range(data, KMX61_RANGE_4G);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* set acc/magn to OPERATION mode */
> +	ret = kmx61_set_mode(data, 0, KMX61_ACC | KMX61_MAG, true);
Just return kmx61_set_mode(data, 0, KMX61_ACC | KMX61_MAG, true);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +/**
> + * kmx61_set_power_state() - set power state for kmx61 @device
> + * @data - kmx61 device private pointer
> + * @on - power state to be set for @device
> + * @device - bitmask indicating device for which @on state needs to be set
> + *
> + * Notice that when ACC power state needs to be set to ON and MAG is in
> + * OPERATION then we know that kmx61_runtime_resume was already called
> + * so we must set ACC OPERATION mode here. The same happens when MAG power
> + * state needs to be set to ON and ACC is in OPERATION.
> + */
> +static int kmx61_set_power_state(struct kmx61_data *data, bool on, u8 device)
> +{
> +#ifdef CONFIG_PM_RUNTIME
> +	int ret;
> +
> +	if (device & KMX61_ACC) {
> +		if (on && !data->acc_ps && !data->mag_stby)
> +			kmx61_set_mode(data, 0, KMX61_ACC, true);
> +		data->acc_ps = on;
> +	}
> +	if (device & KMX61_MAG) {
> +		if (on && !data->mag_ps && !data->acc_stby)
> +			kmx61_set_mode(data, 0, KMX61_MAG, true);
> +		data->mag_ps = on;
> +	}
> +
> +	if (on) {
> +		ret = pm_runtime_get_sync(&data->client->dev);
> +	} else {
> +		pm_runtime_mark_last_busy(&data->client->dev);
> +		ret = pm_runtime_put_autosuspend(&data->client->dev);
> +	}
> +	if (ret < 0) {
> +		dev_err(&data->client->dev,
> +			"Failed: kmx61_set_power_state for %d, ret %d\n",
> +			on, ret);
> +		return ret;
> +	}
> +#endif
> +	return 0;
> +}
> +
> +static int kmx61_read_measurement(struct kmx61_data *data, int base, int offset)
u8 base, u8 offset?
> +{
> +	int ret;
> +	u8 reg = base + offset * 2;
> +
> +	ret = i2c_smbus_read_word_data(data->client, reg);
> +	if (ret < 0) {
> +		dev_err(&data->client->dev, "failed to read reg at %x\n", reg);
> +		return ret;
This return is unnecessary.
> +	}
> +
> +	return ret;
> +}
> +
> +static int kmx61_read_raw(struct iio_dev *indio_dev,
> +			      struct iio_chan_spec const *chan, int *val,
> +			      int *val2, long mask)
Indentation of the parameters is a bit too high.
> +{
> +	struct kmx61_data *data = iio_priv(indio_dev);
> +	int ret;
> +	u8 base_reg;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		switch (chan->type) {
> +		case IIO_ACCEL:
> +		case IIO_MAGN:
> +			base_reg = KMX61_ACC_XOUT_L;
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +		mutex_lock(&data->lock);
> +
> +		kmx61_set_power_state(data, true, chan->address);
> +		ret = kmx61_read_measurement(data, base_reg, chan->scan_index);
> +		if (ret < 0) {
> +			kmx61_set_power_state(data, false, chan->address);
> +			mutex_unlock(&data->lock);
> +			return ret;
> +		}
> +		*val = sign_extend32(ret >> chan->scan_type.shift,
> +				     chan->scan_type.realbits - 1);
> +		kmx61_set_power_state(data, false, chan->address);
> +
> +		mutex_unlock(&data->lock);
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->type) {
> +		case IIO_ACCEL:
> +			*val = 0;
> +			*val2 = kmx61_scale_table[data->range].uscale;
> +			return IIO_VAL_INT_PLUS_MICRO;
> +		case IIO_MAGN:
> +			/* 14 bits res, 1465 microGauss per magn count */
> +			*val = 0;
> +			*val2 = 1465;
> +			return IIO_VAL_INT_PLUS_MICRO;
> +		default:
> +			return -EINVAL;
> +		}
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		if (chan->type != IIO_ACCEL && chan->type != IIO_MAGN)
> +			return -EINVAL;
> +
> +		mutex_lock(&data->lock);
> +		ret = kmx61_get_odr(data, val, val2, chan->address);
> +		mutex_unlock(&data->lock);
Could be just return ret here, if kmx61_get_odr() returns IIO_VAL_INT_PLUS_MICRO on success and -EINVAL on error.
> +		if (ret)
> +			return -EINVAL;
> +		return IIO_VAL_INT_PLUS_MICRO;
> +	}
> +	return -EINVAL;
> +}
> +
> +static int kmx61_write_raw(struct iio_dev *indio_dev,
> +			       struct iio_chan_spec const *chan, int val,
> +			       int val2, long mask)
Indentation of parameters is too high.
> +{
> +	struct kmx61_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		if (chan->type != IIO_ACCEL && chan->type != IIO_MAGN)
> +			return -EINVAL;
> +
> +		mutex_lock(&data->lock);
> +		ret = kmx61_set_odr(data, val, val2, chan->address);
> +		mutex_unlock(&data->lock);
> +		return ret;
> +	case IIO_CHAN_INFO_SCALE:
> +		switch (chan->type) {
> +		case IIO_ACCEL:
> +			if (val != 0)
> +				return -EINVAL;
> +			mutex_lock(&data->lock);
> +			ret = kmx61_set_scale(data, val2);
> +			mutex_unlock(&data->lock);
> +			return ret;
> +		default:
> +			return -EINVAL;
> +		}
> +		return ret;
This won't be reached (if so, ret would not be initialized).
> +	default:
> +		return -EINVAL;
> +	}
> +	return ret;
Same here.
> +}
> +
> +static const struct iio_info kmx61_info = {
> +	.driver_module		= THIS_MODULE,
> +	.read_raw		= kmx61_read_raw,
> +	.write_raw		= kmx61_write_raw,
> +	.attrs			= &kmx61_attribute_group,
> +};
> +
> +static int kmx61_probe(struct i2c_client *client,
> +		       const struct i2c_device_id *id)
> +{
> +	struct kmx61_data *data;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +	const char *name = NULL;
> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	data = iio_priv(indio_dev);
> +	i2c_set_clientdata(client, indio_dev);
> +	data->client = client;
> +
> +	if (id)
> +		name = id->name;
> +
> +	indio_dev->dev.parent = &client->dev;
> +	indio_dev->channels = kmx61_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(kmx61_channels);
> +	indio_dev->name = name;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &kmx61_info;
> +
> +	mutex_init(&data->lock);
> +
> +	ret = kmx61_chip_init(data);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to register iio device\n");
> +		goto err_iio_device_register;
> +	}
> +
> +	ret = pm_runtime_set_active(&client->dev);
> +	if (ret < 0)
> +		goto err_pm_runtime_set_active;
> +
> +	pm_runtime_enable(&client->dev);
> +	pm_runtime_set_autosuspend_delay(&client->dev, KMX61_SLEEP_DELAY_MS);
> +	pm_runtime_use_autosuspend(&client->dev);
> +
> +	return 0;
> +
> +err_pm_runtime_set_active:
> +	iio_device_unregister(indio_dev);
> +err_iio_device_register:
> +	kmx61_set_mode(data, KMX61_ALL_STBY, KMX61_ACC | KMX61_MAG, true);
> +	return ret;
> +}
> +
> +static int kmx61_remove(struct i2c_client *client)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(client);
> +	struct kmx61_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	pm_runtime_disable(&client->dev);
> +	pm_runtime_set_suspended(&client->dev);
> +	pm_runtime_put_noidle(&client->dev);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	mutex_lock(&data->lock);
> +	ret = kmx61_set_mode(data, KMX61_ALL_STBY, KMX61_ACC | KMX61_MAG, true);
> +	mutex_unlock(&data->lock);
> +
> +	return ret;
> +}
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int kmx61_suspend(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
> +	struct kmx61_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&data->lock);
> +	ret = kmx61_set_mode(data, KMX61_ALL_STBY, KMX61_ACC | KMX61_MAG,
> +			     false);
> +	mutex_unlock(&data->lock);
> +
> +	return ret;
> +}
> +
> +static int kmx61_resume(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
> +	struct kmx61_data *data = iio_priv(indio_dev);
> +	u8 stby = 0;
> +
> +	if (data->acc_stby)
> +		stby |= KMX61_ACC_STBY_BIT;
> +	if (data->mag_stby)
> +		stby |= KMX61_MAG_STBY_BIT;
> +
> +	return kmx61_set_mode(data, stby, KMX61_ACC | KMX61_MAG, true);
> +}
> +#endif
> +
> +#ifdef CONFIG_PM_RUNTIME
> +static int kmx61_runtime_suspend(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
> +	struct kmx61_data *data = iio_priv(indio_dev);
> +	int ret;
> +
> +	mutex_lock(&data->lock);
> +	ret = kmx61_set_mode(data, KMX61_ALL_STBY, KMX61_ACC | KMX61_MAG, true);
> +	mutex_unlock(&data->lock);
> +
> +	return ret;
> +}
> +
> +static int kmx61_runtime_resume(struct device *dev)
> +{
> +	struct iio_dev *indio_dev = i2c_get_clientdata(to_i2c_client(dev));
> +	struct kmx61_data *data = iio_priv(indio_dev);
> +	u8 stby = 0;
> +
> +	if (!data->acc_ps)
> +		stby |= KMX61_ACC_STBY_BIT;
> +	if (!data->mag_ps)
> +		stby |= KMX61_MAG_STBY_BIT;
> +
> +	return kmx61_set_mode(data, stby, KMX61_ACC | KMX61_MAG, true);
> +}
> +#endif
> +
> +static const struct dev_pm_ops kmx61_pm_ops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(kmx61_suspend, kmx61_resume)
> +	SET_RUNTIME_PM_OPS(kmx61_runtime_suspend, kmx61_runtime_resume, NULL)
> +};
> +
> +static const struct i2c_device_id kmx61_id[] = {
> +	{"kmx611021", 0},
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(i2c, kmx61_id);
> +
> +static struct i2c_driver kmx61_driver = {
> +	.driver = {
> +		.name = KMX61_DRV_NAME,
> +		.pm = &kmx61_pm_ops,
> +	},
> +	.probe		= kmx61_probe,
> +	.remove		= kmx61_remove,
> +	.id_table	= kmx61_id,
> +};
> +
> +module_i2c_driver(kmx61_driver);
> +
> +MODULE_AUTHOR("Daniel Baluta <daniel.baluta@...el.com>");
> +MODULE_DESCRIPTION("KMX61 accelerometer/magnetometer driver");
> +MODULE_LICENSE("GPL v2");
> 

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