Re: [PATCH 1/5] dt-bindings: iio: dac: ti,dac5571: Add DAC081C081 support

Laurent Pinchart
2024-03-25T20:57:11Z

Hi Jonathan,

On Mon, Mar 25, 2024 at 08:48:57PM +0000, Jonathan Cameron wrote:
> On Mon, 25 Mar 2024 22:32:41 +0200 Laurent Pinchart wrote:
>
> > The DAC081C081 is a TI DAC whose software interface is compatible with
> > the DAC5571. It is the 8-bit version of the DAC121C081, already
> > supported by the DAC5571 bindings. Extends the bindings to support this
> > chip.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>
> Hi Laurent,
>
> Given it's a part number where no one is going to guess it is compatible
> with the DAC5571 and that we don't have a history of fallback compatibles
> I'm fine with this change, but just wanted to ask is a fallback compatible
> useful to you to run with older kernels?
>
> I should have noticed when Peter added the dac121c081. If we add a fallback
> should do that one as well.

I've indeed noticed that there should have been a fallback for
dac121c081, but didn't stop to ponder why that wasn't the case, and just
went along with the flow :-) I agree a fallback could be useful, which
would then allow dropping patch 2/5 from this series (*). I can do so if
you prefer.

* This is not entirely true. While the DAC1081C081 is largely compatible
with the DAC5573, they have different values for one of the power-down
resistors (2.5kΩ instead of 1kΩ if I recall correctly). To be completely
accurate, the driver should report that. We could still use the fallback
compatible, reporting the wrong power-down resistor value.

> > ---
> > Documentation/devicetree/bindings/iio/dac/ti,dac5571.yaml | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/Documentation/devicetree/bindings/iio/dac/ti,dac5571.yaml b/Documentation/devicetree/bindings/iio/dac/ti,dac5571.yaml
> > index 79da0323c327..e59db861e2eb 100644
> > --- a/Documentation/devicetree/bindings/iio/dac/ti,dac5571.yaml
> > +++ b/Documentation/devicetree/bindings/iio/dac/ti,dac5571.yaml
> > @@ -21,6 +21,7 @@ properties:
> > - ti,dac5573
> > - ti,dac6573
> > - ti,dac7573
> > + - ti,dac081c081
> > - ti,dac121c081
> >
> > reg:

--
Regards,

Laurent Pinchart