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

Laurent Pinchart
2024-03-26T16:51:14Z

On Tue, Mar 26, 2024 at 03:29:27PM +0000, Jonathan Cameron wrote:
> On Mon, 25 Mar 2024 22:56:41 +0200 Laurent Pinchart wrote:
> > 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.
>
> Hmm - Would anyone really care about that value being wrong?

I don't have enough expertise with IIO to be sure, but my guess is that
nobody would.

> I think perhaps that's just about significant enough that maybe a fallback
> compatible doesn't make sense here.

Then let's keep it simple and just merge this patch as-is ? :-)

> > > > ---
> > > > 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