linux-kernel - Re: [PATCH v5 3/5] iio: adc: ad7192: Add aincom supply

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Date: Sun, 14 Apr 2024 16:58:20 +0300
From: Alisa-Dariana Roman <alisadariana@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: michael.hennerich@...log.com, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 alexandru.tachici@...log.com, lars@...afoo.de, jic23@...nel.org,
 robh@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 lgirdwood@...il.com, broonie@...nel.org, andy@...nel.org,
 nuno.sa@...log.com, marcelo.schmitt@...log.com, bigunclemax@...il.com,
 okan.sahin@...log.com, fr0st61te@...il.com, alisa.roman@...log.com,
 marcus.folkesson@...il.com, schnelle@...ux.ibm.com, liambeguin@...il.com
Subject: Re: [PATCH v5 3/5] iio: adc: ad7192: Add aincom supply

On 13.04.2024 22:10, David Lechner wrote:
> On Sat, Apr 13, 2024 at 10:12 AM Alisa-Dariana Roman
> <alisadariana@...il.com> wrote:
>>
>> AINCOM should actually be a supply. If present and it has a non-zero
>> voltage, the pseudo-differential channels are configured as single-ended
>> with an offset. Otherwise, they are configured as differential channels
>> between AINx and AINCOM pins.
>>
>> Signed-off-by: Alisa-Dariana Roman <alisa.roman@...log.com>
>> ---
>>   drivers/iio/adc/ad7192.c | 53 +++++++++++++++++++++++++++++++++++++---
>>   1 file changed, 49 insertions(+), 4 deletions(-)

..

>> @@ -745,6 +746,9 @@ static int ad7192_read_raw(struct iio_dev *indio_dev,
>>                  /* Kelvin to Celsius */
> 
> Not related to this patch, but I'm not a fan of the way the
> temperature case writes over *val (maybe clean that up using a switch
> statement instead in another patch while we are working on this?).
> Adding the else if to this makes it even harder to follow.
> 
>>                  if (chan->type == IIO_TEMP)
>>                          *val -= 273 * ad7192_get_temp_scale(unipolar);
>> +               else if (st->aincom_mv && chan->channel2 == -1)
> 
> I think the logic should be !chan->differential instead of
> chan->channel2 = -1 (more explanation on this below).
> 
>> +                       *val += DIV_ROUND_CLOSEST_ULL((u64)st->aincom_mv * 1000000000,
>> +                                                     st->scale_avail[gain][1]);
>>                  return IIO_VAL_INT;

Hi David,

I am very grateful for your suggestions!

	case IIO_CHAN_INFO_OFFSET:
		if (!unipolar)
			*val = -(1 << (chan->scan_type.realbits - 1));
		else
			*val = 0;
		switch(chan->type) {
		case IIO_VOLTAGE:
			if (st->aincom_mv && !chan->differential)
				*val += DIV_ROUND_CLOSEST_ULL((u64)st->aincom_mv * 1000000000,
							      st->scale_avail[gain][1]);
			return IIO_VAL_INT;
		/* Kelvin to Celsius */
		case IIO_TEMP:
			*val -= 273 * ad7192_get_temp_scale(unipolar);
			return IIO_VAL_INT;
		default:
			return -EINVAL;
		}

I added a switch because it looks neater indeed. But I would keep the if 
else for the unipolar in order not to have duplicate code. Is this alright?