Re: [PATCH 2/5] iio: adc: Add ti-ads1262 driver

[Kurt Borja]

On Sun Jun 21, 2026 at 9:33 AM -05, Jonathan Cameron wrote:
> On Mon, 15 Jun 2026 06:30:28 +0200
> Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
>
>> On 14/06/2026 22:56, Kurt Borja wrote:
>> > On Sat Jun 13, 2026 at 1:59 PM -05, Krzysztof Kozlowski wrote:
>> > 
>> > [...]
>> >   
>> >> Functions used by probe() should be before probe(), not somewhere in the
>> >> middle of the code. IOW, entire probe is together.  
>> > 
>> > I they all are, it's just that regmap stuff takes a huge chunk. I'll
>> > check how to reorganize.
>> > 
>> > [...]
>> >   
>> >>> +static const struct of_device_id ads1262_of_match[] = {
>> >>> +	{ .compatible = "ti,ads1262" },
>> >>> +	{ .compatible = "ti,ads1263" },  
>> >>
>> >> So devices are fully compatible? Then it should be expressed in the
>> >> binding and drop one entry here.  
>> > 
>> > Not fully compatible as Jonathan said. One is a subset of the other.  
>> 
>> This is THE meaning of compatible!
>
> This one I'm in agreement with. It is a strict subset, so should be
> using a fallback.  If the fallback is used, you just get support of the
> stuff in the simpler chip (or if you can override it with a chip ID
> you might still 'upgrade' to the more complex driver support).
> If you do end up with properties that only apply to 'new' parts of
> the more complex chip then they should be verified as part of the
> binding (assuming you can do that without the verifier complaining
> - I haven't checked!)

In v1 I had the "adc" subnode which was specific to ADS1263. Then I
agreed to drop the subnode but I'm having second thoughts...

If we dropped it, then we would still have some specific stuff.
#io-channel-cells would be "const: 2" in ADS1263 chips. Also ADS1263's
channels would have an extra ti,vref-adc2 prop, for ADC2 voltage
reference selection. I should maybe also add a vref-adc2-supply.

Maybe it's better to keep the subnode or, again, go for something like:

    spi {
        multi-adc@0 {
            adc@0 {
                ...
                vref-suppy = <&adc1-vref>;

                channel@0 {
                    ...
                    reference-source = <ADS1262_VREF_AIN0_AIN1>;
                };
            };
            adc@1 {
                ...
                vref-suppy = <&adc2-vref>;

                channel@0 {
                    ...
                    reference-source = <ADS1262_VREF_AIN2_AIN3>;
                };
            };
        };
    };

In this case we would have to kinda duplicate channel description, but I
don't think it's that bad.

Jonathan, Krzysztof, David, thoughts?

IMO the ADC2 specific voltage reference stuff is a strong argument for a
subnode or the above solution.

>
> The SLF3F discussion is about (to me) less obvious case of not a strict
> subset, but rather being detectable parts with different channel related
> properties.  In that case the ID match is necessary for anything to work.
> Anyhow, that discussion is in a different thread and not really relevant
> here.
>
> Jonathan
>
>> 
>> 
>> Best regards,
>> Krzysztof

-- 
Thanks,
 ~ Kurt