Re: [PATCH v5 2/2] iio: adc: add support for Nuvoton NCT7201

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Wed, Apr 09, 2025 at 09:23:51AM +0800, Eason Yang wrote:
> Add Nuvoton NCT7201/NCT7202 system voltage monitor 12-bit ADC driver
> 
> NCT7201/NCT7202 supports up to 12 analog voltage monitor inputs and up to
> 4 SMBus addresses by ADDR pin. Meanwhile, ALERT# hardware event pins for
> independent alarm signals, and all the threshold values could be set for
> system protection without any timing delay. It also supports reset input
> RSTIN# to recover system from a fault condition.
> 
> Currently, only single-edge mode conversion and threshold events are
> supported.

> +#include <linux/array_size.h>
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/regmap.h>
> +#include <linux/types.h>
> +#include <linux/unaligned.h>

...

> +#define NCT7201_VIN_MAX				12

Is this in volts? Can you add a unit suffix?

...

> +#define NCT7201_IN_SCALING				4995

Interesting number, just want to confirm it's indeed 4995 and not 4095.

...

> +static int nct7201_read_event_value(struct iio_dev *indio_dev,
> +				    const struct iio_chan_spec *chan,
> +				    enum iio_event_type type,
> +				    enum iio_event_direction dir,
> +				    enum iio_event_info info,
> +				    int *val, int *val2)
> +{
> +	struct nct7201_chip_info *chip = iio_priv(indio_dev);
> +	unsigned int value;
> +	int err;
> +
> +	if (chan->type != IIO_VOLTAGE)
> +		return -EOPNOTSUPP;
> +
> +	if (info != IIO_EV_INFO_VALUE)
> +		return -EINVAL;

> +	if (dir == IIO_EV_DIR_FALLING) {
> +		err = regmap_read(chip->regmap16, NCT7201_REG_VIN_LOW_LIMIT(chan->address),
> +				  &value);
> +		if (err < 0)
> +			return err;
> +	} else {
> +		err = regmap_read(chip->regmap16, NCT7201_REG_VIN_HIGH_LIMIT(chan->address),
> +				  &value);
> +		if (err < 0)
> +			return err;
> +	}

	if (dir == IIO_EV_DIR_FALLING) {
		err = regmap_read(chip->regmap16, NCT7201_REG_VIN_LOW_LIMIT(chan->address),
				  &value);
	} else {
		err = regmap_read(chip->regmap16, NCT7201_REG_VIN_HIGH_LIMIT(chan->address),
				  &value);
	}
	if (err)
		return err;

Here and elsewhere why ' < 0' is used? Do you expect positive return values
from those?

> +	*val = FIELD_GET(NCT7201_REG_VIN_MASK, value);
> +
> +	return IIO_VAL_INT;
> +}

...

> +static int nct7201_write_event_value(struct iio_dev *indio_dev,
> +				     const struct iio_chan_spec *chan,
> +				     enum iio_event_type type,
> +				     enum iio_event_direction dir,
> +				     enum iio_event_info info,
> +				     int val, int val2)
> +{
> +	struct nct7201_chip_info *chip = iio_priv(indio_dev);

> +	int  err = 0;

Useless assignment.

> +	if (chan->type != IIO_VOLTAGE)
> +		return -EOPNOTSUPP;
> +
> +	if (info != IIO_EV_INFO_VALUE)
> +		return -EOPNOTSUPP;
> +
> +	if (dir == IIO_EV_DIR_FALLING) {
> +		err = regmap_write(chip->regmap16, NCT7201_REG_VIN_LOW_LIMIT(chan->address),
> +				   FIELD_PREP(NCT7201_REG_VIN_MASK, val));
> +		if (err < 0)
> +			return err;
> +	} else {
> +		err = regmap_write(chip->regmap16, NCT7201_REG_VIN_HIGH_LIMIT(chan->address),
> +				   FIELD_PREP(NCT7201_REG_VIN_MASK, val));
> +		if (err < 0)
> +			return err;
> +	}
> +
> +	return 0;

	if (dir == IIO_EV_DIR_FALLING) {
		err = regmap_write(chip->regmap16, NCT7201_REG_VIN_LOW_LIMIT(chan->address),
				   FIELD_PREP(NCT7201_REG_VIN_MASK, val));
	} else {
		err = regmap_write(chip->regmap16, NCT7201_REG_VIN_HIGH_LIMIT(chan->address),
				   FIELD_PREP(NCT7201_REG_VIN_MASK, val));
	}
	return err;


> +}

...

> +static int nct7201_write_event_config(struct iio_dev *indio_dev,
> +				      const struct iio_chan_spec *chan,
> +				      enum iio_event_type type,
> +				      enum iio_event_direction dir,
> +				      bool state)
> +{
> +	struct nct7201_chip_info *chip = iio_priv(indio_dev);
> +	unsigned int mask;
> +	int err;
> +
> +	if (chan->type != IIO_VOLTAGE)
> +		return -EOPNOTSUPP;
> +
> +	mask = BIT(chan->address);
> +
> +	if (state)
> +		chip->vin_mask |= mask;
> +	else
> +		chip->vin_mask &= ~mask;

> +	if (chip->num_vin_channels <= 8) {
> +		err = regmap_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1,
> +				   chip->vin_mask);
> +		if (err < 0)
> +			return err;
> +	} else {
> +		err = regmap_bulk_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1,
> +					&chip->vin_mask, sizeof(chip->vin_mask));
> +		if (err < 0)
> +			return err;
> +	}
> +
> +	return 0;

Same as above.

> +}

...

> +static int nct7201_init_chip(struct nct7201_chip_info *chip)
> +{
> +	u8 data[2] = {0};

'0' is not needed. Shouldn't this be __le16 or __be16 instead?

> +	unsigned int value;
> +	int err;
> +
> +	err = regmap_write(chip->regmap, NCT7201_REG_CONFIGURATION,
> +			   NCT7201_BIT_CONFIGURATION_RESET);
> +	if (err < 0)
> +		return dev_err_probe(&chip->client->dev, -EIO,

	struct device *dev = &chip->client->dev;

at the top of the function will help a lot in tiding up the below code.

Shadowed error code, why?

> +				     "Failed to write NCT7201_REG_CONFIGURATION\n");
> +
> +	/*
> +	 * After about 25 msecs, the device should be ready and then the Power
> +	 * Up bit will be set to 1. If not, wait for it.
> +	 */
> +	mdelay(25);

No sleep? Why? Can't you use fsleep()?

> +	err = regmap_read(chip->regmap, NCT7201_REG_BUSY_STATUS, &value);
> +	if (err < 0)
> +		return err;
> +	if (!(value & NCT7201_BIT_PWR_UP))
> +		return dev_err_probe(&chip->client->dev, -EIO,

Shadowed error code, why?

> +				     "Failed to power up after reset\n");
> +
> +	/* Enable Channel */
> +	if (chip->num_vin_channels <= 8) {
> +		data[0] = NCT7201_REG_CHANNEL_ENABLE_1_MASK;
> +		err = regmap_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1, data[0]);
> +		if (err < 0)
> +			return dev_err_probe(&chip->client->dev, -EIO,

Why error code is shadowed?

> +					     "Failed to write NCT7201_REG_CHANNEL_ENABLE_1\n");
> +	} else {
> +		data[0] = NCT7201_REG_CHANNEL_ENABLE_1_MASK;
> +		data[1] = NCT7201_REG_CHANNEL_ENABLE_2_MASK;
> +		err = regmap_bulk_write(chip->regmap, NCT7201_REG_CHANNEL_ENABLE_1,
> +					data, ARRAY_SIZE(data));
> +		if (err < 0)
> +			return dev_err_probe(&chip->client->dev, -EIO,

Ditto.

> +					     "Failed to write NCT7201_REG_CHANNEL_ENABLE_1 and NCT7201_REG_CHANNEL_ENABLE_2\n");
> +	}

Just make it 16-bit type, define one value and use just simple English
in the error message: "Failed to write channel enable mask\n");

Same to all your error messages.

> +	chip->vin_mask = get_unaligned_le16(data);
> +
> +	/* Start monitoring if needed */
> +	err = regmap_read(chip->regmap, NCT7201_REG_CONFIGURATION, &value);
> +	if (err < 0)
> +		return dev_err_probe(&chip->client->dev, -EIO,
> +				     "Failed to read NCT7201_REG_CONFIGURATION\n");

> +	regmap_set_bits(chip->regmap, NCT7201_REG_CONFIGURATION, NCT7201_BIT_CONFIGURATION_START);

> +	return 0;

No error check? Why?

> +}

...

> +static int nct7201_probe(struct i2c_client *client)
> +{
> +	const struct nct7201_adc_model_data *model_data;

	struct device *dev = &client->dev;

> +	struct nct7201_chip_info *chip;
> +	struct iio_dev *indio_dev;
> +	int ret;
> +
> +	model_data = i2c_get_match_data(client);
> +	if (!model_data)
> +		return -EINVAL;

ENODEV is more suitable here.

> +
> +	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*chip));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +	chip = iio_priv(indio_dev);
> +
> +	chip->regmap = devm_regmap_init_i2c(client, &nct7201_regmap8_config);
> +	if (IS_ERR(chip->regmap))
> +		return dev_err_probe(&client->dev, PTR_ERR(chip->regmap),
> +				     "Failed to init regmap\n");
> +
> +	chip->regmap16 = devm_regmap_init_i2c(client, &nct7201_regmap16_config);
> +	if (IS_ERR(chip->regmap16))
> +		return dev_err_probe(&client->dev, PTR_ERR(chip->regmap16),
> +				     "Failed to init regmap16\n");
> +
> +	chip->num_vin_channels = model_data->num_vin_channels;

> +	chip->client = client;

How exactly is _client_ used elsewhere? Shouldn't it be just a struct device
pointer?

> +	ret = nct7201_init_chip(chip);
> +	if (ret < 0)

Do you expect positive returned values? What is their meaning?
Why do you skip them?

> +		return ret;
> +
> +	indio_dev->name = model_data->model_name;
> +	indio_dev->channels = model_data->channels;
> +	indio_dev->num_channels = model_data->num_channels;
> +	if (client->irq)
> +		indio_dev->info = &nct7201_info;
> +	else
> +		indio_dev->info = &nct7201_info_no_irq;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	return devm_iio_device_register(&client->dev, indio_dev);
> +}

-- 
With Best Regards,
Andy Shevchenko