linux-kernel - Re: [PATCH v4 3/6] iio: adc: ad7173: refactor ain and vref selection

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Date: Mon, 3 Jun 2024 16:08:24 +0300
From: "Ceclan, Dumitru" <mitrutzceclan@...il.com>
To: Nuno Sá <noname.nuno@...il.com>,
 Jonathan Cameron <jic23@...nel.org>,
 Dumitru Ceclan via B4 Relay <devnull+dumitru.ceclan.analog.com@...nel.org>
Cc: dumitru.ceclan@...log.com, Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 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 v4 3/6] iio: adc: ad7173: refactor ain and vref selection

On 03/06/2024 16:00, Nuno Sá wrote:
> On Sat, 2024-06-01 at 19:49 +0100, Jonathan Cameron wrote:
>> On Fri, 31 May 2024 22:42:29 +0300
>> Dumitru Ceclan via B4 Relay <devnull+dumitru.ceclan.analog.com@...nel.org> wrote:
>>
>>> From: Dumitru Ceclan <dumitru.ceclan@...log.com>
>>>
>>> Move validation of analog inputs and reference voltage selection to
>>> separate functions to reduce the size of the channel config parsing
>>> function and improve readability.
>>> Add defines for the number of analog inputs in a channel.
>>>
>>> Reviewed-by: David Lechner <dlechner@...libre.com>
>>> Signed-off-by: Dumitru Ceclan <dumitru.ceclan@...log.com>
>>> ---
>>>  drivers/iio/adc/ad7173.c | 71 ++++++++++++++++++++++++++++++++++--------------
>>>  1 file changed, 50 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
>>> index 6e249628bc64..a20831d99aa5 100644
>>> --- a/drivers/iio/adc/ad7173.c
>>> +++ b/drivers/iio/adc/ad7173.c
>>> @@ -60,6 +60,7 @@
>>>  #define AD7173_CH_SETUP_AINPOS_MASK	GENMASK(9, 5)
>>>  #define AD7173_CH_SETUP_AINNEG_MASK	GENMASK(4, 0)
>>>  
>>> +#define AD7173_NO_AINS_PER_CHANNEL	2
>>>  #define AD7173_CH_ADDRESS(pos, neg) \
>>>  	(FIELD_PREP(AD7173_CH_SETUP_AINPOS_MASK, pos) | \
>>>  	 FIELD_PREP(AD7173_CH_SETUP_AINNEG_MASK, neg))
>>> @@ -623,6 +624,7 @@ static int ad7173_setup(struct iio_dev *indio_dev)
>>>  static unsigned int ad7173_get_ref_voltage_milli(struct ad7173_state *st,
>>>  						 u8 reference_select)
>>>  {
>>> +	struct device *dev = &st->sd.spi->dev;
>>>  	int vref;
>>>  
>>>  	switch (reference_select) {
>>> @@ -646,9 +648,11 @@ static unsigned int ad7173_get_ref_voltage_milli(struct
>>> ad7173_state *st,
>>>  		return -EINVAL;
>>>  	}
>>>  
>>> -	if (vref < 0)
>>> +	if (vref < 0) {
>>> +		dev_err(dev, "Cannot use reference %u. Error:%d\n",
>>> +			reference_select, vref);
>>>  		return vref;
>>> -
>>> +	}
>>>  	return vref / (MICRO / MILLI);
>>>  }
>>>  
>>> @@ -905,13 +909,50 @@ static int ad7173_register_clk_provider(struct iio_dev
>>> *indio_dev)
>>>  					   &st->int_clk_hw);
>>>  }
>>>  
>>> +static int ad7173_validate_voltage_ain_inputs(struct ad7173_state *st,
>>> +					      const unsigned int
>>> ain[AD7173_NO_AINS_PER_CHANNEL])
>> I was late to the game in replying to previous thread.
>>
>> This is neater without the loop and with 2 parameters.  Anyhow see reply to v3.
>>
> 
> Yeps, even more given that we're passing/copying the complete array which always
> fells awkward to me :)
> 
> - Nuno Sá
> 
> 

I rewrote the function, but it feels a bit awkward, perhaps I could get a bit of
advice before sending V5:

static int ad7173_validate_voltage_ain_inputs(struct ad7173_state *st,
					      unsigned int ain0, unsigned int ain1)
{
	struct device *dev = &st->sd.spi->dev;
	bool special_input0, special_input1;

	special_input0 = ain0 == AD7173_AIN_REF_POS || ain0 == AD7173_AIN_REF_NEG ||
			 ((ain0 == AD7173_AIN_COM_IN_POS || ain0 == AD7173_AIN_COM_IN_NEG) &&
			 (st->info->has_common_input)) || ain0 == AD4111_VINCOM_INPUT;
	special_input1 = (ain1 == AD7173_AIN_REF_POS || ain1 == AD7173_AIN_REF_NEG) ||
			 ((ain1 == AD7173_AIN_COM_IN_POS || ain1 == AD7173_AIN_COM_IN_NEG) &&
			 (st->info->has_common_input)) || ain1 == AD4111_VINCOM_INPUT;

	if (st->info->has_vincom_input) {
		if (ain0 == AD4111_VINCOM_INPUT &&
		    ain1 < st->info->num_voltage_in && /* Normal input */
		    ain1 >= st->info->num_voltage_in_div) /* Input without divider */
			return dev_err_probe(dev, -EINVAL,
				"VINCOM must be paired with inputs having divider.\n");

		if (ain1 == AD4111_VINCOM_INPUT &&
		    ain0 < st->info->num_voltage_in && /* Normal input */
		    ain0 >= st->info->num_voltage_in_div) /* Input without divider */
			return dev_err_probe(dev, -EINVAL,
				"VINCOM must be paired with inputs having divider.\n");
	}

	if ((ain0 >= st->info->num_voltage_in && !special_input0) ||
	    (ain1 >= st->info->num_voltage_in && !special_input1))
		return dev_err_probe(dev, -EINVAL,
				     "Input pin number out of range for pair (%d %d).\n",
				     ain0, ain1);

	if (!special_input0 && !special_input1 &&
	    ((ain0 >= st->info->num_voltage_in_div) !=
	     (ain1 >= st->info->num_voltage_in_div)))
		return dev_err_probe(dev, -EINVAL,
			"Both inputs must either have a voltage divider or not have: (%d %d).\n",
			ain0, ain1);

	return 0;
}

It feels a bit too verbose, but I could not come up with a better way to
incorporate all those cases.