linux-kernel - Re: [PATCH v3 2/2] iio: add MCP4728 I2C DAC driver

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Message-ID: <15ee98bd-b92b-8a34-e3f9-a1537edf2da9@gmail.com>
Date:   Sun, 23 Jul 2023 14:15:10 +0200
From:   Andrea Collamati <andrea.collamati@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] iio: add MCP4728 I2C DAC driver


On 7/23/23 13:41, Jonathan Cameron wrote:
>>>> +
>>>> +	if (mode == MCP4728_VREF_EXTERNAL_VDD &&
>>>> +	    data->channel_data[chan->channel].g_mode == MCP4728_GAIN_X2) {
>>>> +		dev_warn(&data->client->dev,
>>>> +			 "CH%d: Gain x2 not effective when vref is vdd, force to x1",
>>>> +			 chan->channel);  
>>> Even better if you don't present the option at all and wrap it up in the
>>> standard ABI of _scale
>>>  
>> I think that the solution could be:
>>
>> - Removing custom ABI (vref/gain)
>>
>> - Initialize them at device tree level using two 4-elements arrays.
> If doing with device tree, they should reflect something that is a characteristic
> of how the chips is wired up.  So you would need to explain why that is the case here.
>
> However, I'm still not understanding why _SCALE is not appropriate here.  We have
> a small set of options with well defined scales.

SCALE is appropriate. I didn't know that scale_available was a standard ABI.

I will follow  the implementation done n https://github.com/torvalds/linux/blob/c2782531397f5cb19ca3f8f9c17727f1cdf5bee8/drivers/iio/dac/ad5592r-base.c#L487