Re: [PATCH 1/2] iio: temperature: Add support for LTC2983

Jonathan Cameron
2019-09-15T11:28:04Z

On Mon, 9 Sep 2019 16:45:49 +0200
Nuno Sá <nuno.sa@analog.com> wrote:

> The LTC2983 is a Multi-Sensor High Accuracy Digital Temperature
> Measurement System. It measures a wide variety of temperature sensors and
> digitally outputs the result, in °C or °F, with 0.1°C accuracy and
> 0.001°C resolution. It can measure the temperature of all standard
> thermocouples (type B,E,J,K,N,S,R,T), standard 2-,3-,4-wire RTDs,
> thermistors and diodes.
>
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Some comments inline. Main concern is around the interface, rest is minor
stuff.

Jonathan

> ---
> .../testing/sysfs-bus-iio-temperature-ltc2983 | 43 +
> MAINTAINERS | 7 +
> drivers/iio/temperature/Kconfig | 10 +
> drivers/iio/temperature/Makefile | 1 +
> drivers/iio/temperature/ltc2983.c | 1327 +++++++++++++++++
> 5 files changed, 1388 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-temperature-ltc2983
> create mode 100644 drivers/iio/temperature/ltc2983.c
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio-temperature-ltc2983 b/Documentation/ABI/testing/sysfs-bus-iio-temperature-ltc2983
> new file mode 100644
> index 000000000000..3ad3440c0986
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-bus-iio-temperature-ltc2983
> @@ -0,0 +1,43 @@
> +What: /sys/bus/iio/devices/iio:deviceX/in_tempY_thermistor_raw
For each of these, I presume we know which type of device is attached at any time?
Using the channel naming to convey this (and I assume the fact that different
conversions need to be done in userspace?) is a bit messy. If we need
to convey the channel type, then a separate in_tempY_mode attribute may make more
sense. That would keep this ABI 'closer' to standard. Software that just logs
an unprocessed value could just work for example.

I'm not sure I've totally understood what is going on here though.

> +KernelVersion:
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Reads the raw (unscaled no bias removal etc) temperature from
> + channel Y. The value is returned by a Thermistor sensor measurement.
> + Units after application of scale are degrees Celsius or Fahrenheit
> + depending on the device configuration.
> +
> +What: /sys/bus/iio/devices/iio:deviceX/in_tempY_thermocouple_raw
> +KernelVersion:
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Reads the raw (unscaled no bias removal etc) temperature from
> + channel Y. The value is returned by a Thermocouple sensor measurement.
> + Units after application of scale are degrees Celsius or Fahrenheit
> + depending on the device configuration.
> +
> +What: /sys/bus/iio/devices/iio:deviceX/in_tempY_rtd_raw
> +KernelVersion:
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Reads the raw (unscaled no bias removal etc) temperature from
> + channel Y. The value is returned by a RTD sensor measurement.
> + Units after application of scale are degrees Celsius or Fahrenheit
> + depending on the device configuration.
> +
> +What: /sys/bus/iio/devices/iio:deviceX/in_tempY_diode_raw
> +KernelVersion:
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Reads the raw (unscaled no bias removal etc) temperature from
> + channel Y. The value is returned by a Diode sensor measurement.
> + Units after application of scale are degrees Celsius or Fahrenheit
> + depending on the device configuration.
> +
> +What: /sys/bus/iio/devices/iio:deviceX/in_voltageY_direct_adc_raw
> +KernelVersion:
> +Contact: linux-iio@vger.kernel.org
> +Description:
> + Reads the raw (unscaled no bias removal etc) voltage from
> + channel Y. The value is returned by a direct ADC measurement.
> + Units after application of scale are Volts.

What is the extended name adding?

in_voltageY_raw already tells you it's the raw voltage from channel y.

> diff --git a/MAINTAINERS b/MAINTAINERS
> index f0c03740b9fb..14a256e785ca 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9491,6 +9491,13 @@ S: Maintained
> F: Documentation/devicetree/bindings/iio/dac/ltc1660.txt
> F: drivers/iio/dac/ltc1660.c
>
> +LTC2983 IIO TEMPERATURE DRIVER
> +M: Nuno Sá <nuno.sa@analog.com>
> +W: http://ez.analog.com/community/linux-device-drivers
> +L: linux-iio@vger.kernel.org
> +S: Supported
> +F: drivers/iio/temperature/ltc2983.c
> +
> LTC4261 HARDWARE MONITOR DRIVER
> M: Guenter Roeck <linux@roeck-us.net>
> L: linux-hwmon@vger.kernel.org
> diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig
> index 737faa0901fe..04b5a67b593c 100644
> --- a/drivers/iio/temperature/Kconfig
> +++ b/drivers/iio/temperature/Kconfig
> @@ -4,6 +4,16 @@
> #
> menu "Temperature sensors"
>
> +config LTC2983
> + tristate "Analog Devices Multi-Sensor Digital Temperature Measurement System"
> + depends on SPI
> + help
> + Say yes here to build support for the LTC2983 Multi-Sensor
> + high accuracy digital temperature measurement system.
> +
> + To compile this driver as a module, choose M here: the module
> + will be called ltc2983.
> +
> config MAXIM_THERMOCOUPLE
> tristate "Maxim thermocouple sensors"
> depends on SPI
> diff --git a/drivers/iio/temperature/Makefile b/drivers/iio/temperature/Makefile
> index baca4776ca0d..d6b850b0cf63 100644
> --- a/drivers/iio/temperature/Makefile
> +++ b/drivers/iio/temperature/Makefile
> @@ -3,6 +3,7 @@
> # Makefile for industrial I/O temperature drivers
> #
>
> +obj-$(CONFIG_LTC2983) += ltc2983.o
> obj-$(CONFIG_HID_SENSOR_TEMP) += hid-sensor-temperature.o
> obj-$(CONFIG_MAXIM_THERMOCOUPLE) += maxim_thermocouple.o
> obj-$(CONFIG_MAX31856) += max31856.o
> diff --git a/drivers/iio/temperature/ltc2983.c b/drivers/iio/temperature/ltc2983.c
> new file mode 100644
> index 000000000000..2d97b5019e3b
> --- /dev/null
> +++ b/drivers/iio/temperature/ltc2983.c
> @@ -0,0 +1,1327 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Analog Devices LTC2983 Multi-Sensor Digital Temperature Measurement System
> + * driver
> + *
> + * Copyright 2019 Analog Devices Inc.
> + */
> +#include <linux/bitfield.h>
> +#include <linux/completion.h>
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <linux/iio/iio.h>
> +#include <linux/interrupt.h>
> +#include <linux/list.h>
> +#include <linux/module.h>
> +#include <linux/of_gpio.h>
> +#include <linux/regmap.h>
> +#include <linux/spi/spi.h>
> +
> +/* register map */
> +#define LTC2983_STATUS_REG 0x0000
> +#define LTC2983_TEMP_RES_START_REG 0x0010
> +#define LTC2983_TEMP_RES_END_REG 0x005F
> +#define LTC2983_GLOBAL_CONFIG_REG 0x00F0
> +#define LTC2983_MULT_CHANNEL_START_REG 0x00F4
> +#define LTC2983_MULT_CHANNEL_END_REG 0x00F7
> +#define LTC2983_MUX_CONFIG_REG 0x00FF
> +#define LTC2983_CHAN_ASSIGN_START_REG 0x0200
> +#define LTC2983_CHAN_ASSIGN_END_REG 0x024F
> +#define LTC2983_CUST_SENS_TBL_START_REG 0x0250
> +#define LTC2983_CUST_SENS_TBL_END_REG 0x03CF
> +
> +#define LTC2983_DIFFERENTIAL_CHAN_MIN 2
> +#define LTC2983_MAX_CHANNELS_NR 20
> +#define LTC2983_MIN_CHANNELS_NR 1
> +#define LTC2983_SLEEP 0x97
> +#define LTC2983_CUSTOM_STEINHART_SIZE 24
> +#define LTC2983_CUSTOM_SENSOR_ENTRY_SZ 6
> +#define LTC2983_CUSTOM_STEINHART_ENTRY_SZ 4
> +
> +#define LTC2983_CHAN_START_ADDR(chan) \
> + (((chan - 1) * 4) + LTC2983_CHAN_ASSIGN_START_REG)
> +#define LTC2983_CHAN_RES_ADDR(chan) \
> + (((chan - 1) * 4) + LTC2983_TEMP_RES_START_REG)
> +#define LTC2983_THERMOCOUPLE_DIFF_MASK BIT(3)
> +#define LTC2983_THERMISTOR_DIFF_MASK BIT(2)
> +#define LTC2983_DIODE_DIFF_MASK BIT(2)
> +#define LTC2983_RTD_4_WIRE_MASK BIT(3)
> +#define LTC2983_RTD_ROTATION_MASK BIT(1)
> +#define LTC2983_RTD_KELVIN_R_SENSE_MASK GENMASK(3, 2)
> +
> +#define LTC2983_COMMON_HARD_FAULT_MASK GENMASK(31, 30)
> +#define LTC2983_COMMON_SOFT_FAULT_MASK GENMASK(27, 25)
> +
> +#define LTC2983_STATUS_START_MASK BIT(7)
> +#define LTC2983_STATUS_START(x) FIELD_PREP(LTC2983_STATUS_START_MASK, x)
> +
> +#define LTC2983_STATUS_CHAN_SEL_MASK GENMASK(4, 0)
> +#define LTC2983_STATUS_CHAN_SEL(x) \
> + FIELD_PREP(LTC2983_STATUS_CHAN_SEL_MASK, x)
> +
> +#define LTC2983_TEMP_UNITS_MASK BIT(2)
> +#define LTC2983_TEMP_UNITS(x) FIELD_PREP(LTC2983_TEMP_UNITS_MASK, x)
> +
> +#define LTC2983_NOTCH_FREQ_MASK GENMASK(1, 0)
> +#define LTC2983_NOTCH_FREQ(x) FIELD_PREP(LTC2983_NOTCH_FREQ_MASK, x)
> +
> +#define LTC2983_RES_VALID_MASK BIT(24)
> +#define LTC2983_DATA_MASK GENMASK(23, 0)
> +#define LTC2983_DATA_SIGN_BIT 23
> +
> +#define LTC2983_CHAN_TYPE_MASK GENMASK(31, 27)
> +#define LTC2983_CHAN_TYPE(x) FIELD_PREP(LTC2983_CHAN_TYPE_MASK, x)
> +
> +/* cold junction for thermocouples and rsense for rtd's and thermistor's */
> +#define LTC2983_CHAN_ASSIGN_MASK GENMASK(26, 22)
> +#define LTC2983_CHAN_ASSIGN(x) FIELD_PREP(LTC2983_CHAN_ASSIGN_MASK, x)
> +
> +#define LTC2983_CUSTOM_LEN_MASK GENMASK(5, 0)
> +#define LTC2983_CUSTOM_LEN(x) FIELD_PREP(LTC2983_CUSTOM_LEN_MASK, x)
> +
> +#define LTC2983_CUSTOM_ADDR_MASK GENMASK(11, 6)
> +#define LTC2983_CUSTOM_ADDR(x) FIELD_PREP(LTC2983_CUSTOM_ADDR_MASK, x)
> +
> +#define LTC2983_THERMOCOUPLE_CFG_MASK GENMASK(21, 18)
> +#define LTC2983_THERMOCOUPLE_CFG(x) \
> + FIELD_PREP(LTC2983_THERMOCOUPLE_CFG_MASK, x)
> +#define LTC2983_THERMOCOUPLE_HARD_FAULT_MASK GENMASK(31, 29)
> +#define LTC2983_THERMOCOUPLE_SOFT_FAULT_MASK GENMASK(28, 25)
> +
> +#define LTC2983_RTD_CFG_MASK GENMASK(21, 18)
> +#define LTC2983_RTD_CFG(x) FIELD_PREP(LTC2983_RTD_CFG_MASK, x)
> +#define LTC2983_RTD_EXC_CURRENT_MASK GENMASK(17, 14)
> +#define LTC2983_RTD_EXC_CURRENT(x) \
> + FIELD_PREP(LTC2983_RTD_EXC_CURRENT_MASK, x)
> +#define LTC2983_RTD_CURVE_MASK GENMASK(13, 12)
> +#define LTC2983_RTD_CURVE(x) FIELD_PREP(LTC2983_RTD_CURVE_MASK, x)
> +
> +#define LTC2983_THERMISTOR_CFG_MASK GENMASK(21, 19)
> +#define LTC2983_THERMISTOR_CFG(x) \
> + FIELD_PREP(LTC2983_THERMISTOR_CFG_MASK, x)
> +#define LTC2983_THERMISTOR_EXC_CURRENT_MASK GENMASK(18, 15)
> +#define LTC2983_THERMISTOR_EXC_CURRENT(x) \
> + FIELD_PREP(LTC2983_THERMISTOR_EXC_CURRENT_MASK, x)
> +
> +#define LTC2983_DIODE_CFG_MASK GENMASK(26, 24)
> +#define LTC2983_DIODE_CFG(x) FIELD_PREP(LTC2983_DIODE_CFG_MASK, x)
> +#define LTC2983_DIODE_EXC_CURRENT_MASK GENMASK(23, 22)
> +#define LTC2983_DIODE_EXC_CURRENT(x) \
> + FIELD_PREP(LTC2983_DIODE_EXC_CURRENT_MASK, x)
> +#define LTC2983_DIODE_IDEAL_FACTOR_MASK GENMASK(21, 0)
> +#define LTC2983_DIODE_IDEAL_FACTOR(x) \
> + FIELD_PREP(LTC2983_DIODE_IDEAL_FACTOR_MASK, x)
> +
> +#define LTC2983_R_SENSE_VAL_MASK GENMASK(26, 0)
> +#define LTC2983_R_SENSE_VAL(x) FIELD_PREP(LTC2983_R_SENSE_VAL_MASK, x)
> +
> +#define LTC2983_ADC_SINGLE_ENDED_MASK BIT(26)
> +#define LTC2983_ADC_SINGLE_ENDED(x) \
> + FIELD_PREP(LTC2983_ADC_SINGLE_ENDED_MASK, x)
> +
> +enum {
> + LTC2983_SENSOR_THERMOCOUPLE = 1,
> + LTC2983_SENSOR_THERMOCOUPLE_CUSTOM = 9,
> + LTC2983_SENSOR_RTD = 10,
> + LTC2983_SENSOR_RTD_CUSTOM = 18,
> + LTC2983_SENSOR_THERMISTOR = 19,
> + LTC2983_SENSOR_THERMISTOR_STEINHART = 26,
> + LTC2983_SENSOR_THERMISTOR_CUSTOM = 27,
> + LTC2983_SENSOR_DIODE = 28,
> + LTC2983_SENSOR_SENSE_RESISTOR = 29,
> + LTC2983_SENSOR_DIRECT_ADC = 30,
> +};
> +
> +#define to_thermocouple(_sensor) \
> + container_of(_sensor, struct ltc2983_thermocouple, sensor)
> +
> +#define to_rtd(_sensor) \
> + container_of(_sensor, struct ltc2983_rtd, sensor)
> +
> +#define to_thermistor(_sensor) \
> + container_of(_sensor, struct ltc2983_thermistor, sensor)
> +
> +#define to_diode(_sensor) \
> + container_of(_sensor, struct ltc2983_diode, sensor)
> +
> +#define to_rsense(_sensor) \
> + container_of(_sensor, struct ltc2983_rsense, sensor)
> +
> +#define to_adc(_sensor) \
> + container_of(_sensor, struct ltc2983_adc, sensor)
> +
> +struct ltc2983_data {
> + struct regmap *regmap;
> + struct spi_device *spi;
> + struct mutex lock;
> + struct completion completion;
> + struct iio_chan_spec *iio_chan;
> + struct ltc2983_sensor **sensors;
> + u32 mux_delay_config;
> + u32 filter_notch_freq;
> + u16 custom_table_size;
> + u8 num_channels;
> + u8 iio_channels;
> + bool temp_farenheit;
> + bool reset;
> +};
> +
> +struct ltc2983_sensor {
> + int (*fault_handler)(const struct ltc2983_data *st, const u32 result);
> + int (*assign_chan)(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor);
> + const char *name;
> + /* specifies the sensor channel */
> + u32 chan;
> + /* sensor type */
> + u32 type;
> +};
> +
> +struct ltc2983_custom_sensor {
> + /* raw table sensor data */
> + u8 *table;
> + size_t size;
> + /* address offset */
> + s8 offset;
> + bool is_steinhart;
> +};
> +
> +struct ltc2983_thermocouple {
> + struct ltc2983_sensor sensor;
> + struct ltc2983_custom_sensor *custom;
> + u32 sensor_config;
> + u32 cold_junction_chan;
> +};
> +
> +struct ltc2983_rtd {
> + struct ltc2983_sensor sensor;
> + struct ltc2983_custom_sensor *custom;
> + u32 sensor_config;
> + u32 r_sense_chan;
> + u32 excitation_current;
> + u32 rtd_curve;
> +};
> +
> +struct ltc2983_thermistor {
> + struct ltc2983_sensor sensor;
> + struct ltc2983_custom_sensor *custom;
> + u32 sensor_config;
> + u32 r_sense_chan;
> + u32 excitation_current;
> +};
> +
> +struct ltc2983_diode {
> + struct ltc2983_sensor sensor;
> + u32 sensor_config;
> + u32 excitation_current;
> + u32 ideal_factor_value;
> +};
> +
> +struct ltc2983_rsense {
> + struct ltc2983_sensor sensor;
> + u32 r_sense_val;
> +};
> +
> +struct ltc2983_adc {
> + struct ltc2983_sensor sensor;
> + bool single_ended;
> +};
> +
> +/*
> + * Convert to Q format numbers. These number's are integers where
> + * the number of integer and fractional bits are specified. The resolution
> + * is given by 1/@resolution and tell us the number of fractional bits. For
> + * instance a resolution of 2^-10 means we have 10 fractional bits.
> + */
> +static u32 __convert_to_raw(const u64 val, const u32 resolution)
> +{
> + u64 __res = val * resolution;
> +
> + /* all values are multiplied by 1000000 to remove the fraction */
> + do_div(__res, 1000000);
> +
> + return __res;
> +}
> +
> +static u32 __convert_to_raw_sign(const u64 val, const u32 resolution)
> +{
> + s64 __res = -(s32)val;
> +
> + __res = __convert_to_raw(__res, resolution);
> +
> + return (u32)-__res;
> +}
> +
> +static int __ltc2983_fault_handler(const struct ltc2983_data *st,
> + const u32 result, const u32 hard_mask,
> + const u32 soft_mask)
> +{
> + const struct device *dev = &st->spi->dev;
> +
> + if (result & hard_mask) {
> + dev_err(dev, "Invalid conversion: Sensor HARD fault\n");
> + return -EIO;
> + } else if (result & soft_mask) {
> + /* just print a warning */
> + dev_warn(dev, "Suspicious conversion: Sensor SOFT fault\n");
> + }
> +
> + return 0;
> +}
> +
> +static int __ltc2983_chan_assign_common(const struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor,
> + u32 chan_val)
> +{
> + u32 reg = LTC2983_CHAN_START_ADDR(sensor->chan);
> + __be32 __chan_val;
> +
> + chan_val |= LTC2983_CHAN_TYPE(sensor->type);
> + dev_dbg(&st->spi->dev, "Assign %s, reg:0x%04X, val:0x%08X\n",
> + sensor->name,
> + reg, chan_val);
> + __chan_val = cpu_to_be32(chan_val);
> + return regmap_bulk_write(st->regmap, reg, &__chan_val,
> + sizeof(__chan_val));
> +}
> +
> +static int __ltc2983_chan_custom_sensor_assign(struct ltc2983_data *st,
> + struct ltc2983_custom_sensor *custom,
> + u32 *chan_val)
> +{
> + u32 reg;
> + u8 mult = custom->is_steinhart ? LTC2983_CUSTOM_STEINHART_ENTRY_SZ :
> + LTC2983_CUSTOM_SENSOR_ENTRY_SZ;
> + const struct device *dev = &st->spi->dev;
> + /*
> + * custom->size holds the raw size of the table. However, when
> + * configuring the sensor channel, we must write the number of
> + * entries of the table minus 1. For steinhart sensors 0 is written
> + * since the size is constant!
> + */
> + const u8 len = custom->is_steinhart ? 0 :
> + (custom->size / LTC2983_CUSTOM_SENSOR_ENTRY_SZ) - 1;
> + /*
> + * Check if the offset was assigned already. It should be for steinhart
> + * sensors. When coming from sleep, it should be assigned for all.
> + */
> + if (custom->offset < 0) {
> + /*
> + * This needs to be done again here because, from the moment
> + * when this test was done (successfully) for this custom
> + * sensor, a steinhart sensor might have been added changing
> + * custom_table_size...
> + */
> + if (st->custom_table_size + custom->size >
> + (LTC2983_CUST_SENS_TBL_END_REG -
> + LTC2983_CUST_SENS_TBL_START_REG) + 1) {
> + dev_err(dev,
> + "Not space left(%d) for new custom sensor(%zu)",
> + st->custom_table_size,
> + custom->size);
> + return -EINVAL;
> + }
> +
> + custom->offset = st->custom_table_size /
> + LTC2983_CUSTOM_SENSOR_ENTRY_SZ;
> + st->custom_table_size += custom->size;
> + }
> +
> + reg = (custom->offset * mult) + LTC2983_CUST_SENS_TBL_START_REG;
> +
> + *chan_val |= LTC2983_CUSTOM_LEN(len);
> + *chan_val |= LTC2983_CUSTOM_ADDR(custom->offset);
> + dev_dbg(dev, "Assign custom sensor, reg:0x%04X, off:%d, sz:%zu",
> + reg, custom->offset,
> + custom->size);
> + /* write custom sensor table */
> + return regmap_bulk_write(st->regmap, reg, custom->table, custom->size);
> +}
> +
> +static struct ltc2983_custom_sensor *__ltc2983_custom_sensor_new(
> + struct ltc2983_data *st,
> + const struct device_node *np,
> + const bool is_steinhart,
> + const u32 resolution,
> + const bool has_signed)
> +{
> + struct ltc2983_custom_sensor *new_custom;
> + u8 index, n_entries, tbl = 0;
> + struct device *dev = &st->spi->dev;
> + /*
> + * For custom steinhart, the full u32 is taken. For all the others
> + * the MSB is discarded.
> + */
> + const u8 n_size = (is_steinhart == true) ? 4 : 3;
> +
> + n_entries = of_property_count_elems_of_size(np, "adi,custom-sensor",
> + sizeof(u64));
> + /* n_entries must be an even number */
> + if (!n_entries || (n_entries % 2) != 0) {
> + dev_err(dev, "Number of entries either 0 or not even\n");
> + return ERR_PTR(-EINVAL);
> + }
> +
> + new_custom = devm_kzalloc(dev, sizeof(*new_custom), GFP_KERNEL);
> + if (!new_custom)
> + return ERR_PTR(-ENOMEM);
> +
> + new_custom->size = n_entries * n_size;
> + /* check Steinhart size */
> + if (is_steinhart && new_custom->size != LTC2983_CUSTOM_STEINHART_SIZE) {
> + dev_err(dev, "Steinhart sensors size(%zu) must be 24",
> + new_custom->size);
> + return ERR_PTR(-EINVAL);
> + }
> + /* Check space on the table. */
> + if (st->custom_table_size + new_custom->size >
> + (LTC2983_CUST_SENS_TBL_END_REG -
> + LTC2983_CUST_SENS_TBL_START_REG) + 1) {
> + dev_err(dev, "No space left(%d) for new custom sensor(%zu)",
> + st->custom_table_size, new_custom->size);
> + return ERR_PTR(-EINVAL);
> + }
> +
> + /* allocate the table */
> + new_custom->table = devm_kzalloc(dev, new_custom->size, GFP_KERNEL);
> + if (!new_custom->table)
> + return ERR_PTR(-ENOMEM);
> +
> + for (index = 0; index < n_entries; index++) {
> + u64 temp = 0, j;
> +
> + of_property_read_u64_index(np, "adi,custom-sensor", index,
> + &temp);
> + /*
> + * Steinhart sensors are configured with raw values in the
> + * devicetree. For the other sensors we must convert the
> + * value to raw. The odd index's correspond to temperarures
> + * and always have 1/1024 of resolution. Temperatures also
> + * come in kelvin, so signed values is not possible
> + */
> + if (!is_steinhart) {
> + if ((index % 2) != 0)
> + temp = __convert_to_raw(temp, 1024);
> + else if (has_signed && (s64)temp < 0)
> + temp = __convert_to_raw_sign(temp, resolution);
> + else
> + temp = __convert_to_raw(temp, resolution);
> + }
> +
> + for (j = 0; j < n_size; j++)
> + new_custom->table[tbl++] =
> + temp >> (8 * (n_size - j - 1));
> + }
> +
> + new_custom->is_steinhart = is_steinhart;
> + /*
> + * This is done to first add all the steinhart sensors to the table,
> + * in order to maximize the table usage. If we mix adding steinhart
> + * with the other sensors, we might have to do some roundup to make
> + * sure that sensor_addr - 0x250(start address) is a multiple of 4
> + * (for steinhart), and a multiple of 6 for all the other sensors.
> + * Since we have const 24 bytes for steinhart sensors and 24 is
> + * also a multiple of 6, we guarantee that the first non-steinhart
> + * sensor will sit in a correct address without the need of filling
> + * addresses.
> + */
> + if (is_steinhart) {
> + new_custom->offset = st->custom_table_size /
> + LTC2983_CUSTOM_STEINHART_ENTRY_SZ;
> + st->custom_table_size += new_custom->size;
> + } else {
> + /* mark as unset. This is checked later on the assign phase */
> + new_custom->offset = -1;
> + }
> +
> + return new_custom;
> +}
> +
> +static int ltc2983_thermocouple_fault_handler(const struct ltc2983_data *st,
> + const u32 result)
> +{
> + return __ltc2983_fault_handler(st, result,
> + LTC2983_THERMOCOUPLE_HARD_FAULT_MASK,
> + LTC2983_THERMOCOUPLE_SOFT_FAULT_MASK);
> +}
> +
> +static int ltc2983_common_fault_handler(const struct ltc2983_data *st,
> + const u32 result)
> +{
> + return __ltc2983_fault_handler(st, result,
> + LTC2983_COMMON_HARD_FAULT_MASK,
> + LTC2983_COMMON_SOFT_FAULT_MASK);
> +}
> +
> +static int ltc2983_thermocouple_assign_chan(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_thermocouple *thermo = to_thermocouple(sensor);
> + u32 chan_val;
> +
> + chan_val = LTC2983_CHAN_ASSIGN(thermo->cold_junction_chan);
> + chan_val |= LTC2983_THERMOCOUPLE_CFG(thermo->sensor_config);
> +
> + if (thermo->custom) {
> + int ret;
> +
> + ret = __ltc2983_chan_custom_sensor_assign(st, thermo->custom,
> + &chan_val);
> + if (ret)
> + return ret;
> + }
> + return __ltc2983_chan_assign_common(st, sensor, chan_val);
> +}
> +
> +static int ltc2983_rtd_assign_chan(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_rtd *rtd = to_rtd(sensor);
> + u32 chan_val;
> +
> + chan_val = LTC2983_CHAN_ASSIGN(rtd->r_sense_chan);
> + chan_val |= LTC2983_RTD_CFG(rtd->sensor_config);
> + chan_val |= LTC2983_RTD_EXC_CURRENT(rtd->excitation_current);
> + chan_val |= LTC2983_RTD_CURVE(rtd->rtd_curve);
> +
> + if (rtd->custom) {
> + int ret;
> +
> + ret = __ltc2983_chan_custom_sensor_assign(st, rtd->custom,
> + &chan_val);
> + if (ret)
> + return ret;
> + }
> + return __ltc2983_chan_assign_common(st, sensor, chan_val);
> +}
> +
> +static int ltc2983_thermistor_assign_chan(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_thermistor *thermistor = to_thermistor(sensor);
> + u32 chan_val;
> +
> + chan_val = LTC2983_CHAN_ASSIGN(thermistor->r_sense_chan);
> + chan_val |= LTC2983_THERMISTOR_CFG(thermistor->sensor_config);
> + chan_val |=
> + LTC2983_THERMISTOR_EXC_CURRENT(thermistor->excitation_current);
> +
> + if (thermistor->custom) {
> + int ret;
> +
> + ret = __ltc2983_chan_custom_sensor_assign(st,
> + thermistor->custom,
> + &chan_val);
> + if (ret)
> + return ret;
> + }
> + return __ltc2983_chan_assign_common(st, sensor, chan_val);
> +}
> +
> +static int ltc2983_diode_assign_chan(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_diode *diode = to_diode(sensor);
> + u32 chan_val;
> +
> + chan_val = LTC2983_DIODE_CFG(diode->sensor_config);
> + chan_val |= LTC2983_DIODE_EXC_CURRENT(diode->excitation_current);
> + chan_val |= LTC2983_DIODE_IDEAL_FACTOR(diode->ideal_factor_value);
> +
> + return __ltc2983_chan_assign_common(st, sensor, chan_val);
> +}
> +
> +static int ltc2983_r_sense_assign_chan(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_rsense *rsense = to_rsense(sensor);
> + u32 chan_val;
> +
> + chan_val = LTC2983_R_SENSE_VAL(rsense->r_sense_val);
> +
> + return __ltc2983_chan_assign_common(st, sensor, chan_val);
> +}
> +
> +static int ltc2983_adc_assign_chan(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_adc *adc = to_adc(sensor);
> + u32 chan_val;
> +
> + chan_val = LTC2983_ADC_SINGLE_ENDED(adc->single_ended);
> +
> + return __ltc2983_chan_assign_common(st, sensor, chan_val);
> +}
> +
> +static struct ltc2983_sensor *ltc2983_thermocouple_new(
> + const struct device_node *child,
> + struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_thermocouple *thermo;
> + struct device_node *phandle;
> +
> + thermo = devm_kzalloc(&st->spi->dev, sizeof(*thermo), GFP_KERNEL);
> + if (!thermo)
> + return ERR_PTR(-ENOMEM);
> +
> + of_property_read_u32(child, "adi,sensor-config",
> + &thermo->sensor_config);
> + /* validate channel index */
> + if (!(thermo->sensor_config & LTC2983_THERMOCOUPLE_DIFF_MASK) &&
> + sensor->chan < LTC2983_DIFFERENTIAL_CHAN_MIN) {
> + dev_err(&st->spi->dev,
> + "Invalid chann:%d for differential thermocouple",
> + sensor->chan);
> + return ERR_PTR(-EINVAL);
> + }
> +
> + phandle = of_parse_phandle(child, "adi,cold-junction-handle", 0);
> + if (phandle) {
> + int ret;
> +
> + ret = of_property_read_u32(phandle, "reg",
> + &thermo->cold_junction_chan);
> + if (ret) {
> + /*
> + * This would be catched later but we can just return
> + * the error right away.
> + */
> + dev_err(&st->spi->dev, "Property reg must be given\n");
> + of_node_put(phandle);
> + return ERR_PTR(-EINVAL);
> + }
> + }
> +
> + /* check custom sensor */
> + if (sensor->type == LTC2983_SENSOR_THERMOCOUPLE_CUSTOM) {
> + thermo->custom = __ltc2983_custom_sensor_new(st, child, false,
> + 16384, true);
> + if (IS_ERR(thermo->custom)) {
> + of_node_put(phandle);
> + return ERR_CAST(thermo->custom);
> + }
> + }
> +
> + /* set common parameters */
> + thermo->sensor.name = "thermocouple";
> + thermo->sensor.fault_handler = ltc2983_thermocouple_fault_handler;
> + thermo->sensor.assign_chan = ltc2983_thermocouple_assign_chan;
> +
> + of_node_put(phandle);
> + return &thermo->sensor;
> +}
> +
> +static struct ltc2983_sensor *ltc2983_rtd_new(const struct device_node *child,
> + struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_rtd *rtd;
> + int ret = 0;
> + struct device *dev = &st->spi->dev;
> + struct device_node *phandle;
> +
> + rtd = devm_kzalloc(dev, sizeof(*rtd), GFP_KERNEL);
> + if (!rtd)
> + return ERR_PTR(-ENOMEM);
> +
> + phandle = of_parse_phandle(child, "adi,rsense-handle", 0);
> + if (!phandle) {
> + dev_err(dev, "Property adi,rsense-handle missing or invalid");
> + return ERR_PTR(-EINVAL);
> + }
> +
> + ret = of_property_read_u32(phandle, "reg",
> + &rtd->r_sense_chan);

Doesn't look like that lines needs wrapping. Check for similar elsewhere.

> + if (ret) {
> + dev_err(dev, "Property reg must be given\n");
> + goto fail;
> + }
> +
> + of_property_read_u32(child, "adi,sensor-config", &rtd->sensor_config);
> + /*
> + * rtd channel indexes are a bit more complicated to validate.
> + * For 4wire RTD with rotation, the channel selection cannot be
> + * >=19 since the chann + 1 is used in this configuration.
> + * For 4wire RTDs with kelvin rsense, the rsense channel cannot be
> + * <=1 since chanel - 1 and channel - 2 are used.
> + */
> + if (rtd->sensor_config & LTC2983_RTD_4_WIRE_MASK) {
> + /* 4-wire */
> + u8 min = LTC2983_DIFFERENTIAL_CHAN_MIN,
> + max = LTC2983_MAX_CHANNELS_NR;
> +
> + if (rtd->sensor_config & LTC2983_RTD_ROTATION_MASK)
> + max = LTC2983_MAX_CHANNELS_NR - 1;
> +
> + if (((rtd->sensor_config & LTC2983_RTD_KELVIN_R_SENSE_MASK)
> + == LTC2983_RTD_KELVIN_R_SENSE_MASK) &&
> + (rtd->r_sense_chan <= min)) {
> + /* kelvin rsense*/
> + dev_err(dev,
> + "Invalid rsense chann:%d to use in kelvin rsense",
> + rtd->r_sense_chan);
> +
> + ret = -EINVAL;
> + goto fail;
> + }
> +
> + if (sensor->chan < min || sensor->chan > max) {
> + dev_err(dev, "Invalid chann:%d for the rtd config",
> + sensor->chan);
> +
> + ret = -EINVAL;
> + goto fail;
> + }
> + } else {
> + /* same as differential case */
> + if (sensor->chan < LTC2983_DIFFERENTIAL_CHAN_MIN) {
> + dev_err(&st->spi->dev,
> + "Invalid chann:%d for RTD", sensor->chan);
> +
> + ret = -EINVAL;
> + goto fail;
> + }
> + }
> +
> + /* check custom sensor */
> + if (sensor->type == LTC2983_SENSOR_RTD_CUSTOM) {
> + rtd->custom = __ltc2983_custom_sensor_new(st, child, false,
> + 2048, false);
> + if (IS_ERR(rtd->custom)) {
> + of_node_put(phandle);
> + return ERR_CAST(rtd->custom);
> + }
> + }
> +
> + /* set common parameters */
> + rtd->sensor.name = "rtd";
> + rtd->sensor.fault_handler = ltc2983_common_fault_handler;
> + rtd->sensor.assign_chan = ltc2983_rtd_assign_chan;
> +
> + ret = of_property_read_u32(child, "adi,excitation-current",
> + &rtd->excitation_current);
> + if (ret)
> + /* default to 1uA */
> + rtd->excitation_current = 1;
> +
> + of_property_read_u32(child, "adi,rtd-curve", &rtd->rtd_curve);
> +
> + of_node_put(phandle);
> + return &rtd->sensor;
> +fail:
> + of_node_put(phandle);
> + return ERR_PTR(ret);
> +}
> +
> +static struct ltc2983_sensor *ltc2983_thermistor_new(
> + const struct device_node *child,
> + struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_thermistor *thermistor;
> + struct device *dev = &st->spi->dev;
> + struct device_node *phandle;
> + int ret = 0;
> +
> + thermistor = devm_kzalloc(dev, sizeof(*thermistor), GFP_KERNEL);
> + if (!thermistor)
> + return ERR_PTR(-ENOMEM);
> +
> + phandle = of_parse_phandle(child, "adi,rsense-handle", 0);
> + if (!phandle) {
> + dev_err(dev, "Property adi,rsense-handle missing or invalid");
> + return ERR_PTR(-EINVAL);
> + }
> +
> + ret = of_property_read_u32(phandle, "reg",
> + &thermistor->r_sense_chan);
> + if (ret) {
> + dev_err(dev, "rsense channel must be configured...\n");
> + goto fail;
> + }
> +
> + of_property_read_u32(child, "adi,sensor-config",
> + &thermistor->sensor_config);
> + /* validate channel index */
> + if (!(thermistor->sensor_config & LTC2983_THERMISTOR_DIFF_MASK) &&
> + sensor->chan < LTC2983_DIFFERENTIAL_CHAN_MIN) {
> + dev_err(&st->spi->dev,
> + "Invalid chann:%d for differential thermistor",
> + sensor->chan);
> + ret = -EINVAL;
> + goto fail;
> + }
> +
> + /* check custom sensor */
> + if (sensor->type >= LTC2983_SENSOR_THERMISTOR_STEINHART) {
> + thermistor->custom = __ltc2983_custom_sensor_new(st, child,
> + sensor->type == LTC2983_SENSOR_THERMISTOR_STEINHART ?
> + true : false, 64,
> + false);
> + if (IS_ERR(thermistor->custom)) {
> + of_node_put(phandle);
> + return ERR_CAST(thermistor->custom);
> + }
> + }
> + /* set common parameters */
> + thermistor->sensor.name = "thermistor";
> + thermistor->sensor.fault_handler = ltc2983_common_fault_handler;
> + thermistor->sensor.assign_chan = ltc2983_thermistor_assign_chan;
> +
> + ret = of_property_read_u32(child, "adi,excitation-current",
> + &thermistor->excitation_current);
> + if (ret)
> + /* default to auto-range */
> + thermistor->excitation_current = 0x0c;
> +
> + of_node_put(phandle);
> + return &thermistor->sensor;
> +fail:
> + of_node_put(phandle);
> + return ERR_PTR(ret);
> +}
> +
> +static struct ltc2983_sensor *ltc2983_diode_new(
> + const struct device_node *child,
> + const struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_diode *diode;
> + u32 temp = 0;
> +
> + diode = devm_kzalloc(&st->spi->dev, sizeof(*diode), GFP_KERNEL);
> + if (!diode)
> + return ERR_PTR(-ENOMEM);
> +
> + of_property_read_u32(child, "adi,sensor-config", &diode->sensor_config);
> + /* validate channel index */
> + if (!(diode->sensor_config & LTC2983_DIODE_DIFF_MASK) &&
> + sensor->chan < LTC2983_DIFFERENTIAL_CHAN_MIN) {
> + dev_err(&st->spi->dev,
> + "Invalid chann:%d for differential thermistor",
> + sensor->chan);
> + return ERR_PTR(-EINVAL);
> + }
> + /* set common parameters */
> + diode->sensor.name = "diode";
> + diode->sensor.fault_handler = ltc2983_common_fault_handler;
> + diode->sensor.assign_chan = ltc2983_diode_assign_chan;
> +
> + of_property_read_u32(child, "adi,excitation-current",
> + &diode->excitation_current);
> +
> + of_property_read_u32(child, "adi,ideal-factor-value", &temp);
> +
> + /* 2^20 resolution */
> + diode->ideal_factor_value = __convert_to_raw(temp, 1048576);
> +
> + return &diode->sensor;
> +}
> +
> +static struct ltc2983_sensor *ltc2983_r_sense_new(struct device_node *child,
> + struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_rsense *rsense;
> + int ret;
> + u64 temp;
> +
> + rsense = devm_kzalloc(&st->spi->dev, sizeof(*rsense), GFP_KERNEL);
> + if (!rsense)
> + return ERR_PTR(-ENOMEM);
> +
> + /* validate channel index */
> + if (sensor->chan < LTC2983_DIFFERENTIAL_CHAN_MIN) {
> + dev_err(&st->spi->dev, "Invalid chann:%d for r_sense",
> + sensor->chan);
> + return ERR_PTR(-EINVAL);
> + }
> + /* get raw value */
> + ret = of_property_read_u64(child, "adi,rsense-val-micro-ohms", &temp);
> + if (ret) {
> + dev_err(&st->spi->dev, "Property adi,rsense-val-micro-ohms missing\n");
> + return ERR_PTR(-EINVAL);
> + }
> +
> + /* 2^10 resolution */
> + rsense->r_sense_val = __convert_to_raw(temp, 1024);
> +
> + /* set common parameters */
> + rsense->sensor.name = "r_sense";
> + rsense->sensor.assign_chan = ltc2983_r_sense_assign_chan;
> +
> + return &rsense->sensor;
> +}
> +
> +static struct ltc2983_sensor *ltc2983_adc_new(struct device_node *child,
> + struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor)
> +{
> + struct ltc2983_adc *adc;
> +
> + adc = devm_kzalloc(&st->spi->dev, sizeof(*adc), GFP_KERNEL);
> + if (!adc)
> + return ERR_PTR(-ENOMEM);
> +
> + if (of_property_read_bool(child, "adi,single-ended"))
> + adc->single_ended = true;
> +
> + if (!adc->single_ended &&
> + sensor->chan < LTC2983_DIFFERENTIAL_CHAN_MIN) {
> + dev_err(&st->spi->dev, "Invalid chan:%d for differential adc\n",
> + sensor->chan);
> + return ERR_PTR(-EINVAL);
> + }
> + /* set common parameters */
> + adc->sensor.name = "direct_adc";
> + adc->sensor.assign_chan = ltc2983_adc_assign_chan;
> + adc->sensor.fault_handler = ltc2983_common_fault_handler;
> +
> + return &adc->sensor;
> +}
> +
> +static int ltc2983_chan_read(struct ltc2983_data *st,
> + const struct ltc2983_sensor *sensor, int *val)
> +{
> + u32 start_conversion = 0;
> + int ret;
> + unsigned long time;
> + __be32 temp;
> +
> + /*
> + * Do not allow channel readings if device is in sleep state.
> + * A read/write on the spi bus would bring the device prematurely
> + * out of sleep.
> + */
> + if (st->reset)
> + return -EPERM;
> +
> + start_conversion = LTC2983_STATUS_START(true);
> + start_conversion |= LTC2983_STATUS_CHAN_SEL(sensor->chan);
> + dev_dbg(&st->spi->dev, "Start conversion on chan:%d, status:%02X\n",
> + sensor->chan, start_conversion);
> + /* start conversion */
> + ret = regmap_write(st->regmap, LTC2983_STATUS_REG, start_conversion);
> + if (ret)
> + return ret;
> +
> + reinit_completion(&st->completion);
> + /*
> + * wait for conversion to complete.
> + * 300 ms should be more than enough to complete the conversion.
> + * Depending on the sensor configuration, there are 2/3 conversions
> + * cycles of 82ms.
> + */
> + time = wait_for_completion_timeout(&st->completion,
> + msecs_to_jiffies(300));
> + if (!time) {
> + dev_warn(&st->spi->dev, "Conversion timed out\n");
> + return -ETIMEDOUT;
> + }
> +
> + /* read the converted data */
> + ret = regmap_bulk_read(st->regmap, LTC2983_CHAN_RES_ADDR(sensor->chan),
> + &temp, sizeof(temp));
> + if (ret)
> + return ret;
> +
> + *val = __be32_to_cpu(temp);
> + dev_dbg(&st->spi->dev, "Converted data: 0x%08X (addr:0x%04X)\n", *val,
> + LTC2983_CHAN_RES_ADDR(sensor->chan));

Probably drop all the dev_dbg stuff unless it is providing information that
isn't otherwise available (from reading channel etc, kprobe / ftrace).

> +
> + if (!(LTC2983_RES_VALID_MASK & *val)) {
> + dev_err(&st->spi->dev, "Invalid conversion detected\n");
> + return -EIO;
> + }
> +
> + ret = sensor->fault_handler(st, *val);
> + if (ret)
> + return ret;
> +
> + *val = sign_extend32((*val) & LTC2983_DATA_MASK, LTC2983_DATA_SIGN_BIT);
> + return 0;
> +}
> +
> +static int ltc2983_read_raw(struct iio_dev *indio_dev,
> + struct iio_chan_spec const *chan,
> + int *val, int *val2, long mask)
> +{
> + struct ltc2983_data *st = iio_priv(indio_dev);
> + int ret;
> +
> + /* sanity check */
> + if (chan->address >= st->num_channels) {
> + dev_err(&st->spi->dev, "Invalid chan address:%ld",
> + chan->address);
> + return -EINVAL;
> + }
> + switch (mask) {
> + case IIO_CHAN_INFO_RAW:
> + mutex_lock(&st->lock);
> + ret = ltc2983_chan_read(st, st->sensors[chan->address], val);
> + mutex_unlock(&st->lock);
> + return ret ?: IIO_VAL_INT;
> + case IIO_CHAN_INFO_SCALE:
> + switch (chan->type) {
> + case IIO_TEMP:
> + *val = 1;
> + /* 2^10 */
> + *val2 = 1024;
> + return IIO_VAL_FRACTIONAL;
> + case IIO_VOLTAGE:
> + *val = 1;
> + /* 2^21 */
> + *val2 = 2097152;
> + return IIO_VAL_FRACTIONAL;
> + default:
> + return -EINVAL;
> + }
> + }
> +
> + return -EINVAL;
> +}
> +
> +static int ltc2983_reg_access(struct iio_dev *indio_dev,
> + unsigned int reg,
> + unsigned int writeval,
> + unsigned int *readval)
> +{
> + struct ltc2983_data *st = iio_priv(indio_dev);
> +
> + /* check comment in ltc2983_chan_read() */
> + if (st->reset)
> + return -EPERM;
> +
> + if (readval)
> + return regmap_read(st->regmap, reg, readval);
> + else
> + return regmap_write(st->regmap, reg, writeval);
> +}
> +
> +static irqreturn_t ltc2983_irq_handler(int irq, void *data)
> +{
> + struct ltc2983_data *st = data;
> +
> + complete(&st->completion);
> + return IRQ_HANDLED;
> +}
> +
> +#define LTC2983_CHAN(__type, index, __address, ext_name) ({ \
> + struct iio_chan_spec __chan = { \
> + .type = __type, \
> + .indexed = 1, \
> + .channel = index, \
> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
> + .address = __address, \
> + .extend_name = ext_name, \
> + }; \
> + __chan; \
> +})
> +
> +static int ltc2983_parse_dt(struct ltc2983_data *st)
> +{
> + struct device_node *child;
> + struct device *dev = &st->spi->dev;
> + int ret = 0, chan = 0, channel_avail_mask = 0;
> +
> + if (!of_property_read_bool(dev->of_node, "adi,temperature-celcius"))
> + st->temp_farenheit = true;
> +
> + of_property_read_u32(dev->of_node, "adi,mux-delay-config",
> + &st->mux_delay_config);
> +
> + of_property_read_u32(dev->of_node, "adi,filter-notch-freq",
> + &st->filter_notch_freq);
> +
> + st->num_channels = of_get_available_child_count(dev->of_node);
> + st->sensors = devm_kcalloc(dev, st->num_channels, sizeof(*st->sensors),
> + GFP_KERNEL);
> + if (!st->sensors)
> + return -ENOMEM;
> +
> + st->iio_channels = st->num_channels;
> + for_each_available_child_of_node(dev->of_node, child) {
> + struct ltc2983_sensor sensor;
> +
> + ret = of_property_read_u32(child, "reg", &sensor.chan);
> + if (ret) {
> + dev_err(dev, "reg property must given for child nodes\n");
> + return ret;
> + }
> +
> + /* check if we have a valid channel */
> + if (sensor.chan < LTC2983_MIN_CHANNELS_NR ||
> + sensor.chan > LTC2983_MAX_CHANNELS_NR) {
> + dev_err(dev,
> + "chan:%d must be from 1 to 20\n", sensor.chan);
> + return -EINVAL;
> + } else if (channel_avail_mask & BIT(sensor.chan)) {
> + dev_err(dev, "chan:%d already in use\n", sensor.chan);
> + return -EINVAL;
> + }
> +
> + ret = of_property_read_u32(child, "adi,sensor-type",
> + &sensor.type);
> + if (ret) {
> + dev_err(dev,
> + "adi,sensor-type property must given for child nodes\n");
> + return ret;
> + }
> +
> + dev_dbg(dev, "Create new sensor, type %u, chann %u",
> + sensor.type,
> + sensor.chan);
> +
> + if (sensor.type >= LTC2983_SENSOR_THERMOCOUPLE &&
> + sensor.type <= LTC2983_SENSOR_THERMOCOUPLE_CUSTOM) {
> + st->sensors[chan] = ltc2983_thermocouple_new(child, st,
> + &sensor);
> + } else if (sensor.type >= LTC2983_SENSOR_RTD &&
> + sensor.type <= LTC2983_SENSOR_RTD_CUSTOM) {
> + st->sensors[chan] = ltc2983_rtd_new(child, st, &sensor);
> + } else if (sensor.type >= LTC2983_SENSOR_THERMISTOR &&
> + sensor.type <= LTC2983_SENSOR_THERMISTOR_CUSTOM) {
> + st->sensors[chan] = ltc2983_thermistor_new(child, st,
> + &sensor);
> + } else if (sensor.type == LTC2983_SENSOR_DIODE) {
> + st->sensors[chan] = ltc2983_diode_new(child, st,
> + &sensor);
> + } else if (sensor.type == LTC2983_SENSOR_SENSE_RESISTOR) {
> + st->sensors[chan] = ltc2983_r_sense_new(child, st,
> + &sensor);
> + /* don't add rsense to iio */
> + st->iio_channels--;
> + } else if (sensor.type == LTC2983_SENSOR_DIRECT_ADC) {
> + st->sensors[chan] = ltc2983_adc_new(child, st, &sensor);
> + } else {
> + dev_err(dev, "Unknown sensor type %d\n", sensor.type);
> + return -EINVAL;
> + }
> +
> + if (IS_ERR(st->sensors[chan])) {
> + dev_err(dev, "Failed to create sensor %ld",
> + PTR_ERR(st->sensors[chan]));
> + return PTR_ERR(st->sensors[chan]);
> + }
> + /* set generic sensor parameters */
> + st->sensors[chan]->chan = sensor.chan;
> + st->sensors[chan]->type = sensor.type;
> +
> + channel_avail_mask |= BIT(sensor.chan);
> + chan++;
> + }
> + /* allocate iio_chan array */

This last block isn't really about parsing the DT, perhaps drop it out of
here?

> + st->iio_chan = devm_kzalloc(dev,
> + st->iio_channels * sizeof(*st->iio_chan),
> + GFP_KERNEL);
> + if (!st->iio_chan)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +static int ltc2983_setup(struct ltc2983_data *st, bool assign_iio)
> +{
> + u32 iio_chan_t = 0, iio_chan_v = 0, chan, iio_idx = 0;
> + u32 global_cfg = 0;
> + int ret;
> + unsigned long time;
> +
> + /* make sure the device is up */
> + time = wait_for_completion_timeout(&st->completion,
> + msecs_to_jiffies(250));
> + if (!time) {
> + dev_err(&st->spi->dev, "Device startup timed out\n");
> + return -ETIMEDOUT;
> + }

Blank line here, slightly helps readability be clearly separating the
error handling path from normal flow.

> + /* set generic global cfg and mux delay */

Not sure this comment adds anything not obvious from the code. Comments
like this are always at risk of 'rotting' over time, so better to not
put them if they don't bring significant value.

> + global_cfg = LTC2983_NOTCH_FREQ(st->filter_notch_freq);
> + global_cfg |= LTC2983_TEMP_UNITS(st->temp_farenheit);
> + regmap_write(st->regmap, LTC2983_GLOBAL_CONFIG_REG, global_cfg);
> + regmap_write(st->regmap, LTC2983_MUX_CONFIG_REG, st->mux_delay_config);
> + /* setup channels */

This comment also not stating anything non obvious.

> + for (chan = 0; chan < st->num_channels; chan++) {
> + u32 chan_type = 0, *iio_chan;
> +
> + ret = st->sensors[chan]->assign_chan(st, st->sensors[chan]);
> + if (ret)
> + return ret;
> + /*
> + * The assign_iio flag is necessary for when the device is
> + * coming out of sleep. In that case, we just need to
> + * re-configure the device channels.
> + * We also don't assign iio channels for rsense.
> + */
> + if (st->sensors[chan]->type == LTC2983_SENSOR_SENSE_RESISTOR ||
> + !assign_iio)
> + continue;
> +
> + /* assign iio channel */
> + if (st->sensors[chan]->type != LTC2983_SENSOR_DIRECT_ADC) {
> + chan_type = IIO_TEMP;
> + iio_chan = &iio_chan_t;
> + } else {
> + chan_type = IIO_VOLTAGE;
> + iio_chan = &iio_chan_v;
> + }
> +
> + /*
> + * add chan as the iio .address so that, we can directly
> + * reference the sensor given the iio_chan_spec
> + */
> + st->iio_chan[iio_idx++] = LTC2983_CHAN(chan_type, (*iio_chan)++,
> + chan,
> + st->sensors[chan]->name);
> + }
> +
> + return 0;
> +}
> +
> +static const struct regmap_range ltc2983_reg_ranges[] = {
> + regmap_reg_range(LTC2983_STATUS_REG, LTC2983_STATUS_REG),
> + regmap_reg_range(LTC2983_TEMP_RES_START_REG, LTC2983_TEMP_RES_END_REG),
> + regmap_reg_range(LTC2983_GLOBAL_CONFIG_REG, LTC2983_GLOBAL_CONFIG_REG),
> + regmap_reg_range(LTC2983_MULT_CHANNEL_START_REG,
> + LTC2983_MULT_CHANNEL_END_REG),
> + regmap_reg_range(LTC2983_MUX_CONFIG_REG, LTC2983_MUX_CONFIG_REG),
> + regmap_reg_range(LTC2983_CHAN_ASSIGN_START_REG,
> + LTC2983_CHAN_ASSIGN_END_REG),
> + regmap_reg_range(LTC2983_CUST_SENS_TBL_START_REG,
> + LTC2983_CUST_SENS_TBL_END_REG),
> +};
> +
> +static const struct regmap_access_table ltc2983_reg_table = {
> + .yes_ranges = ltc2983_reg_ranges,
> + .n_yes_ranges = ARRAY_SIZE(ltc2983_reg_ranges),
> +};

Blank line here.

> +/*
> + * The reg_bits are actually 12 but the device needs the first *complete*
> + * byte for the command (R/W).
> + */
> +static const struct regmap_config ltc2983_regmap_config = {
> + .reg_bits = 24,
> + .val_bits = 8,
> + .wr_table = &ltc2983_reg_table,
> + .rd_table = &ltc2983_reg_table,
> + .read_flag_mask = GENMASK(1, 0),
> + .write_flag_mask = BIT(1),
> +};
> +
> +static const struct iio_info ltc2983_iio_info = {
> + .read_raw = ltc2983_read_raw,
> + .debugfs_reg_access = ltc2983_reg_access,
> +};
> +
> +static int ltc2983_probe(struct spi_device *spi)
> +{
> + struct ltc2983_data *st;
> + struct iio_dev *indio_dev;
> + const char *name = spi_get_device_id(spi)->name;
> + int ret;
> +
> + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> + if (!indio_dev)
> + return -ENOMEM;
> +
> + st = iio_priv(indio_dev);
> +
> + st->regmap = devm_regmap_init_spi(spi, &ltc2983_regmap_config);
> + if (IS_ERR(st->regmap)) {
> + dev_err(&spi->dev, "Failed to initialize regmap\n");
> + return PTR_ERR(st->regmap);
> + }
> +
> + mutex_init(&st->lock);
> + init_completion(&st->completion);
> + st->spi = spi;
> + spi_set_drvdata(spi, st);
> +
> + ret = ltc2983_parse_dt(st);
> + if (ret)
> + return ret;
> + /*
> + * let's request the irq now so it is used to sync the device
> + * startup in ltc2983_setup()
> + */
> + ret = devm_request_threaded_irq(&spi->dev, spi->irq, NULL,
> + ltc2983_irq_handler, IRQF_ONESHOT |
> + IRQF_TRIGGER_RISING, name, st);
> + if (ret) {
> + dev_err(&spi->dev, "failed to request an irq, %d", ret);
> + return ret;
> + }
> +
> + ret = ltc2983_setup(st, true);
> + if (ret)
> + return ret;
> +
> + indio_dev->dev.parent = &spi->dev;
> + indio_dev->name = name;
> + indio_dev->num_channels = st->iio_channels;
> + indio_dev->channels = st->iio_chan;
> + indio_dev->modes = INDIO_DIRECT_MODE;
> + indio_dev->info = &ltc2983_iio_info;
> +
> + return devm_iio_device_register(&spi->dev, indio_dev);
> +}
> +
> +static int __maybe_unused ltc2983_resume(struct device *dev)
> +{
> + struct ltc2983_data *st = spi_get_drvdata(to_spi_device(dev));
> + int ret;
> +
> + mutex_lock(&st->lock);
> + /* dummy read to bring the device out of sleep */
> + regmap_read(st->regmap, LTC2983_STATUS_REG, &ret);
> + /* we need to re-assign the channels */
> + ret = ltc2983_setup(st, false);
> + st->reset = false;
> + mutex_unlock(&st->lock);
> +
> + return ret;
> +}
> +
> +static int __maybe_unused ltc2983_suspend(struct device *dev)
> +{
> + struct ltc2983_data *st = spi_get_drvdata(to_spi_device(dev));
> + int ret;
> +
> + mutex_lock(&st->lock);
> + ret = regmap_write(st->regmap, LTC2983_STATUS_REG, LTC2983_SLEEP);
> + st->reset = true;

Naming seems a bit odd. The register field is called sleep, but we call
it reset internally?

> + mutex_unlock(&st->lock);
> +
> + return ret;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(ltc2983_pm_ops, ltc2983_suspend, ltc2983_resume);
> +
> +static const struct spi_device_id ltc2983_id_table[] = {
> + { "ltc2983" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(spi, ltc2983_id_table);
> +
> +static const struct of_device_id ltc2983_of_match[] = {
> + { .compatible = "adi,ltc2983" },
> + {},
> +};
> +MODULE_DEVICE_TABLE(of, ltc2983_id_table);
> +
> +static struct spi_driver ltc2983_driver = {
> + .driver = {
> + .name = "ltc2983",
> + .of_match_table = ltc2983_of_match,
> + .pm = &ltc2983_pm_ops,
> + },
> + .probe = ltc2983_probe,
> + .id_table = ltc2983_id_table,
> +};
> +
> +module_spi_driver(ltc2983_driver);
> +
> +MODULE_AUTHOR("Nuno Sa <nuno.sa@analog.com>");
> +MODULE_DESCRIPTION("Analog Devices LTC2983 SPI Temperature sensors");
> +MODULE_LICENSE("GPL");