Re: [PATCH v4 2/8] dt-bindings: adc: axi-adc: deprecate 'adi,adc-dev'

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 22 Dec 2023 10:07:34 +0100
Nuno Sá <noname.nuno@gmail.com> wrote:

> On Thu, 2023-12-21 at 17:25 +0000, Jonathan Cameron wrote:
> > On Wed, 20 Dec 2023 16:34:05 +0100
> > Nuno Sa <nuno.sa@analog.com> wrote:
> >   
> > > 'adi,adc-dev' is now deprecated and must not be used anymore. Hence,
> > > also remove it from being required.  
> > 
> > With my 'specifications language' brain engaged (also know as pedantic)
> > I think this is a 'should' not a 'must' case. You aren't breaking
> > backwards compatibility just advising moving to the newer / better interface.
> >   
> 
> Well, you surely know better than me as a native speaker :)
> 
> >   
> > > 
> > > The reason why it's being deprecated is because the axi-adc CORE is now
> > > an IIO service provider hardware (IIO backends) for consumers to make use
> > > of. Before, the logic with 'adi,adc-dev' was the opposite (it was kind
> > > of consumer referencing other nodes/devices) and that proved to be wrong
> > > and to not scale.
> > > 
> > > Now, IIO consumers of this hardware are expected to reference it using the
> > > io-backends property.
> > > 
> > > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > > ---
> > >  Documentation/devicetree/bindings/iio/adc/adi,axi-adc.yaml | 4 +---
> > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,axi-adc.yaml
> > > b/Documentation/devicetree/bindings/iio/adc/adi,axi-adc.yaml
> > > index 9996dd93f84b..835b40063343 100644
> > > --- a/Documentation/devicetree/bindings/iio/adc/adi,axi-adc.yaml
> > > +++ b/Documentation/devicetree/bindings/iio/adc/adi,axi-adc.yaml
> > > @@ -39,12 +39,12 @@ properties:
> > >      $ref: /schemas/types.yaml#/definitions/phandle
> > >      description:
> > >        A reference to a the actual ADC to which this FPGA ADC interfaces to.
> > > +    deprecated: true
> > >  
> > >  required:
> > >    - compatible
> > >    - dmas
> > >    - reg
> > > -  - adi,adc-dev  
> > 
> > Dropping it from required is fine, but do we have a new condition where one or the
> > other
> > should be required?  If so good to add the dt-binding magic to enforce that. Look
> > for a oneOf combined with required. There are a few IIO examples of this either or
> > type required. You may want to then enforce that both are not provided though I
> > guess we perhaps don't care - the driver will just prioritise one approach over the
> > other.
> >   
> 
> Hmm, the thing is that io-backends is applied in the frontend device (so other
> binding) and in here we should only have the adi,adc-dev which is now deprecated so
> I'm not sure how that would look like?

Ah. I'd somehow failed to register the property is now in the other device. 
Not much we can do then :(

> 
> I think new users of the deprecated property are very unlikely unless they choose to
> ignore the deprecated warning. As for old users (if they add the new one and don't
> remove this one, the new one will have priority). But I'm still confident there are
> no users of this out there :(

Sometimes it's easier to cater for non existent users than get into too much
debate on whether they exist :)

Jonathan

> 
> 
> - Nuno Sá
> 
>