Received-SPF: pass (google.com: domain of linux-kernel+bounces-175891-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.80.249 as permitted sender) client-ip=147.75.80.249;
Message-ID: <d5b8b193-0694-4e65-9b0a-64fa689ed344@baylibre.com>
Date: Fri, 10 May 2024 09:21:37 -0500
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v7 5/6] dt-bindings: iio: adc: ad7192: Add AD7194 support
To: Alisa-Dariana Roman <alisadariana@gmail.com>,
 Conor Dooley <conor@kernel.org>
Cc: michael.hennerich@analog.com, linux-iio@vger.kernel.org,
 devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
 alexandru.tachici@analog.com, lars@metafoo.de, jic23@kernel.org,
 robh@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
 lgirdwood@gmail.com, broonie@kernel.org, andy@kernel.org,
 nuno.sa@analog.com, marcelo.schmitt@analog.com, bigunclemax@gmail.com,
 okan.sahin@analog.com, fr0st61te@gmail.com, alisa.roman@analog.com,
 marcus.folkesson@gmail.com, schnelle@linux.ibm.com, liambeguin@gmail.com
References: <20240430162946.589423-1-alisa.roman@analog.com>
 <20240430162946.589423-6-alisa.roman@analog.com>
 <20240430-winnings-wrongness-32328ccfe3b5@spud>
 <73365049-670b-4068-a159-fbdd0539f5a9@gmail.com>
Content-Language: en-US
From: David Lechner <dlechner@baylibre.com>
In-Reply-To: <73365049-670b-4068-a159-fbdd0539f5a9@gmail.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

On 5/10/24 5:05 AM, Alisa-Dariana Roman wrote:
> On 30.04.2024 20:21, Conor Dooley wrote:
>> On Tue, Apr 30, 2024 at 07:29:45PM +0300, Alisa-Dariana Roman wrote:
>>> +      diff-channels:
>>> +        description:
>>> +          Both inputs can be connected to pins AIN1 to AIN16 by choosing the
>>> +          appropriate value from 1 to 16.
>>> +        items:
>>> +          minimum: 1
>>> +          maximum: 16
>>> +
>>> +      single-channel:
>>> +        description:
>>> +          Positive input can be connected to pins AIN1 to AIN16 by choosing the
>>> +          appropriate value from 1 to 16. Negative input is connected to AINCOM.
>>> +        items:
>>> +          minimum: 1
>>> +          maximum: 16
>>
>> Up to 16 differential channels and 16 single-ended channels, but only 16
>> pins? Would the number of differential channels not max out at 8?
> 
> Hello, Conor! I really appreciate the feedback!
> 
> The way I thought about it, the only thing constraining the number of channels is the reg number (minimum: 0, maximum: 271). 272 channels cover all possible combinations (16*16 differential and 16 single ended) and I thought there is no need for anything stricter. I added items: minimum:1 maximum:16 to make sure the numbers are from 1 to 16, corresponding to AIN1-AIN16.
> 
> Please let me know what should be improved!
> 
> Kind regards,
> Alisa-Dariana Roman.
> 

Having looked at the datasheet for this and other similar chips, I agree
that this reasoning makes sense. Some of the similar chips that have fixed
channel assignments still have, e.g. a channel where + and - are both
AIN2 (I assume for diagnostics). So I think it makes sense to allow for
doing something similar here even if the most common use cases will
probably have at most 16 channels defined in the .dts.