Re: [PATCH v3] iio: adc: Add support for TI ADC108S102 and ADC128S102

[Jan Kiszka]

On 2017-05-05 11:54, Andy Shevchenko wrote:
> On Fri, 2017-05-05 at 08:31 +0200, Jan Kiszka wrote:
>> This is an upstream port of an IIO driver for the TI ADC108S102 and
>> ADC128S102. The former can be found on the Intel Galileo Gen2 and the
>> Siemens SIMATIC IOT2000. For those boards, ACPI-based enumeration is
>> included.
>>
>> Due to the lack of regulators under ACPI, we need a special device
>> property to define the voltage provide to the VA pin of the ADC
>> ("va-millivolt"). For DT usage, the regulator "vref-supply" is
>> requested. Note that DT usage has not been tested.
> 
> +1 to what Mika commented on this and just some additional information.
> 
> Other than that looks pretty good.
> 
>> Changes in v3:
>>  - Reworked reference voltage handling, splitting up the different
>> ACPI
>>    case from DT usage. This also means that the "va-millivolt"
>>    (formerly and incorrectly called "ext-vin-microvolt") becomes
>>    ACPI-only
> 
> Just to be clean, there is *no* such thing as *XYZ-only* device
> properties. The idea behind them is to provide resource provider
> agnostic API to read properties.

Well, as along as ACPI does its own thing /wrt regulators, we have that
problem. But let's wait until someone designs an ACPI board with that
chip and a different reference voltage.

> 
>> +			if (st->reg)
>> +				*val = regulator_get_voltage(st->reg) 
>> / 1000;
>> +			else
>> +				*val = st->va_millivolt;
>> +
> 
> Another way is to not just hard code the value, but create a fixed
> voltage regulator out of it. In this case you will have one way to get
> its value.

That's a good idea.

> 
>> +		st->reg = devm_regulator_get(&spi->dev, "vref");
> 
> It should be _optional like I mentioned in one of previous review.
> 
>> +	if (!IS_ERR(st->reg))
> 
> This is redundant

It's not for the existing code because regulator_disable doesn't test
this for us. It will be, though, when I switch back to making it
mandatory for everyone.

Jan

> 
>> +		regulator_disable(st->reg);
> 
>> +	if (!IS_ERR(st->reg))
> 
> Ditto.
> 
>> +		regulator_disable(st->reg);
> 
> 

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