linux-kernel - Re: [PATCH v6 9/9] iio: adc: ad7173: Add support for AD411x devices

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Message-ID: <1c6d409b-ba9e-4a19-a6cb-e06209a24154@gmail.com>
Date: Fri, 7 Jun 2024 12:41:42 +0300
From: "Ceclan, Dumitru" <mitrutzceclan@...il.com>
To: Nuno Sá <noname.nuno@...il.com>,
 dumitru.ceclan@...log.com
Cc: Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, David Lechner <dlechner@...libre.com>,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 9/9] iio: adc: ad7173: Add support for AD411x devices

On 07/06/2024 12:20, Nuno Sá wrote:
> On Thu, 2024-06-06 at 19:07 +0300, Dumitru Ceclan via B4 Relay wrote:
>> From: Dumitru Ceclan <dumitru.ceclan@...log.com>
>>
>> Add support for AD4111/AD4112/AD4114/AD4115/AD4116.
>>
>> The AD411X family encompasses a series of low power, low noise, 24-bit,
>> sigma-delta analog-to-digital converters that offer a versatile range of
>> specifications.
>>
>> This family of ADCs integrates an analog front end suitable for processing
>> both fully differential and single-ended, bipolar voltage inputs
>> addressing a wide array of industrial and instrumentation requirements.
>>
>> - All ADCs have inputs with a precision voltage divider with a division
>>   ratio of 10.
>> - AD4116 has 5 low level inputs without a voltage divider.
>> - AD4111 and AD4112 support current inputs (0 mA to 20 mA) using a 50ohm
>>   shunt resistor.
>>
>> Signed-off-by: Dumitru Ceclan <dumitru.ceclan@...log.com>
>> ---
>>  drivers/iio/adc/ad7173.c | 317 ++++++++++++++++++++++++++++++++++++++++++----
>> -
>>  1 file changed, 285 insertions(+), 32 deletions(-)
>>
>> diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
>> index 58da5717fd36..cfcd12447e24 100644
>> --- a/drivers/iio/adc/ad7173.c
>> +++ b/drivers/iio/adc/ad7173.c
>>
> ...
> 
>>  static const struct ad7173_device_info ad7172_2_device_info = {
>>  	.name = "ad7172-2",
>>  	.id = AD7172_2_ID,
>> -	.num_inputs = 5,
>> +	.num_voltage_in = 5,
>>  	.num_channels = 4,
>>  	.num_configs = 4,
>>  	.num_gpios = 2,
>> +	.higher_gpio_bits = false,
> 
> No need to explicitly set to 'false'. Ditto for the other places...
> 
> ...
> 
>>
>>  static int ad7173_validate_voltage_ain_inputs(struct ad7173_state *st,
>>  					      unsigned int ain0, unsigned int
>> ain1)
>>  {
>> @@ -946,15 +1145,30 @@ static int ad7173_validate_voltage_ain_inputs(struct
>> ad7173_state *st,
>>  	    st->info->has_pow_supply_monitoring)
>>  		return 0;
>>  
>> -	special_input0 = AD7173_IS_REF_INPUT(ain0);
>> -	special_input1 = AD7173_IS_REF_INPUT(ain1);
>> +	special_input0 = AD7173_IS_REF_INPUT(ain0) ||
>> +			 (ain0 == AD4111_VINCOM_INPUT && st->info-
>>> has_vincom_input);
>> +	special_input1 = AD7173_IS_REF_INPUT(ain1) ||
>> +			 (ain1 == AD4111_VINCOM_INPUT && st->info-
>>> has_vincom_input);
>> +
> 
> Wondering... can ain1 (or ain0) be AD4111_VINCOM_INPUT and !st->info-
>> has_vincom_input? Would that actually be acceptable? It would assume it's not
> so we should check that right? Or am I missing something?
> 
> - Nuno Sá
> 

It will fail when we check for the number of voltage inputs:
(ain0 >= st->info->num_voltage_in && !special_input0) 
as special_input will not be true if has_vincom_input is false

Indeed this check is a bit hidden, should it be more explicit?