linux-kernel - Re: [PATCH v4 03/10] iio: adc: add helpers for parsing ADC nodes

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Message-ID: <f8f7154b-460a-4ca5-b31b-746bd23a3d61@gmail.com>
Date: Sun, 2 Mar 2025 15:00:21 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
 Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
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Subject: Re: [PATCH v4 03/10] iio: adc: add helpers for parsing ADC nodes

On 02/03/2025 05:35, Jonathan Cameron wrote:
> On Mon, 24 Feb 2025 20:33:16 +0200
> Matti Vaittinen <mazziesaccount@...il.com> wrote:
> 
>> There are ADC ICs which may have some of the AIN pins usable for other
>> functions. These ICs may have some of the AIN pins wired so that they
>> should not be used for ADC.
>>
>> (Preferred?) way for marking pins which can be used as ADC inputs is to
>> add corresponding channels@N nodes in the device tree as described in
>> the ADC binding yaml.
> I think it's worth exploring if we can tweak this slightly to make
> that something a driver specifies.  Either skip the unspecified or
> fill them with default values depending on a parameter.
> 
> Would make this code cover the existing cases better.
> Might be a little fiddly as we'd want to maintain ordering so
> the code would need to index slightly differently. I've not tried it
> so maybe not worth it for now.

Thanks for the review!

I don't remember seeing users which would have benefited from this (but 
maybe I just quickly discarded them as unsuitable for this API and 
forgot them). Anyways, I think it might be cleaner (from the caller's 
perspective) to have own function for supporting such cases.

>> +
>> +int iio_adc_device_num_channels(struct device *dev)
>> +{
>> +	return device_get_child_node_count_named(dev, "channel");
>> +}
>> +EXPORT_SYMBOL_GPL(iio_adc_device_num_channels);
> 
> Maybe one to promote to a static inline in the header and avoid need for
> the export given it is very simple.

Makes sense, thanks.

...

>> +
>> +		if (max_chan_id != -1)
>> +			if (ch > max_chan_id)
>> +				return -ERANGE;
> 
> Might as well combine.
> 		if (max_chan_id != -1 && ch > max_chan_id)
> 			return -ERANGE;

Ack.

Yours,
	-- Matti