Re: [PATCH v6 05/17] iio: adc: Add AD7768 and AD7768-4 core support

[Janani Sunil <jananisunil.dev@gmail.com>]

On 9/6/26 05:50, Jonathan Cameron wrote:
>> Add core support for the AD7768 and AD7768-4 simultaneous sampling ADCs.
>> Configure supplies, clock and reset, use a custom regmap bus for the SPI
>> protocol, and parse the enabled channels and input buffer settings from
>> devicetree.
>>
>> Connect the converter to an IIO backend for buffered capture with CRC,
>> provide a fixed safe wideband sampling configuration and add runtime
>> power management.
>>
>> Signed-off-by: Janani Sunil <janani.sunil@analog.com>
> ...
>
>> +
>> +static int ad7768_get_enable_vref(struct device *dev, unsigned int index)
>> +{
>> +	const char * const *supply = ad7768_vref_supply_names[index];
>> +	int refp_uV;
>> +	int refn_uV;
>> +
>> +	refp_uV = devm_regulator_get_enable_read_voltage(dev, supply[0]);
>> +	if (refp_uV < 0)
>> +		return dev_err_probe(dev, refp_uV,
>> +				     "Failed to get %s supply voltage\n", supply[0]);
>> +
>> +	refn_uV = devm_regulator_get_enable_read_voltage(dev, supply[1]);
>> +	if (refn_uV == -ENODEV)
>> +		refn_uV = 0;
>> +	else if (refn_uV < 0)
>> +		return dev_err_probe(dev, refn_uV,
>> +				     "Failed to get %s supply voltage\n", supply[1]);
>> +
>> +	if (refp_uV <= refn_uV)
>> +		return dev_err_probe(dev, -EINVAL,
>> +				     "Invalid reference %u voltage\n", index + 1);
>> +
>> +	return refp_uV - refn_uV;
> Do we never care about the offset inherent in where the negative sits?

The absolute REFx- voltage does not introduce an offset into the ADC transfer function. The datasheet defines VREF as REFx+ - REFx- and the LSB size as (2 * VREF)/2^24. Zero code remains at AINx+ - AINx- = 0.

Regards,
Jan