Re: [PATCH 1/2] dt-bindings: iio: ti,tmp117: add binding for the TMP119

[Jonathan Cameron]

On Fri, 05 Jun 2026 14:24:45 +0200
Romain Gantois <romain.gantois@xxxxxxxxxxx> wrote:

> Hi Jonathan,
> 
> On Friday, 5 June 2026 13:53:32 CEST Jonathan Cameron wrote:
> > On Fri, 05 Jun 2026 11:01:35 +0200
> > 
> > Romain Gantois <romain.gantois@xxxxxxxxxxx> wrote:  
> > > The TMP119 has the same register layout as the TMP117, and a better local
> > > sensor accuracy.  
> > 
> > Sounds like (and the driver changes pretty much confirm) that this could
> > use a fallback compatible to the tmp117.
> >   
> 
> What do you mean by "fallback compatible" in this case? Do you mean we should 
> do something like this in the bindings:
> 
> ```
> enum:
>        - ti,tmp116
>        - ti,tmp119
> const:
>        - ti,tmp117
> ```
Something like (I can never remember the syntax so this is modified from
another binding doc and untested)

    oneOf:
      - enum:
          - ti,tmp116
          - ti,tmp117
      - items:
          - enum:  #enum here because once we have one we tend to get more ;)
              - ti,tmp119
          - const: ti,tmp117

> 
> But wouldn't this invalidate existing device trees which only have:
> 
> `compatible = "ti,tmp116";`
> 
> > The second patch then just resolves the print that would happen on older
> > kernels using that fallback due to ID mismatch.  That's fine but nice
> > if older kernels can work with this part.  
> 
> Sorry I don't quite understand: since this is a feature patch, I don't expect 
> it would get backported onto older kernels. Therefore why would the second 
> patch resolve the print happening on older kernels?
> 
The point of a fallback compatible is that we don't have to backport anything.
New device tree comes along that lists

compatible = "ti,tmp119", "ti,tmp117"

will just work. Older kernel will think it has a tmp117 which is fine as they
are register interface compatible.  It will print a message to say that it
found an unknown ID but then assume it is what the firmware told it, here the
tmp117 fallback.  With your second patch in place, that harmless message will
disappear for new kernels.

Jonathan


> Thanks,
>