Re: [PATCH 1/2] dt-bindings: iio: stm32-adc: add option to set resolution

[Fabrice Gasnier]

On 02/25/2017 04:11 PM, Jonathan Cameron wrote:
> On 24/02/17 16:04, Fabrice Gasnier wrote:
> > On 02/19/2017 01:09 PM, Jonathan Cameron wrote:
> > > On 15/02/17 16:55, Fabrice Gasnier wrote:
> > > > Add documentation for 'st,adc-res' dt optional property.
> > > >
> > > > Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
> > > I'm happy with this, but would like to leave time for a device tree review.
> > >
> > > Ultimately we may well want to make this a generic property and call it something
> > > like adc-resolution but perhaps we need to wait until we have a few more devices
> > > supporting setting it via device tree to figure out what the best interface is.
> > > It would exactly be a problem to support this as a deprecated binding at that
> > > point.
> >
> > Hi Jonathan,
> >
> > I agree with you on this... It may be better to have generic property
> > for this, especially if you see that it will come in the near future.
> > May I suggest this prop to be less restrictive, e.g. like
> > resolution-bits as is may also be worth for other device types, e.g.
> > DAC as an example ?>
> Sure, why not - no loss of meaning here.  We may never use it for anything
> else but that doesn't matter.

Hi Jonathan,

Following Rob's comment, how you see such a common property can be
integrated. Currently I don't see much devices are doing this.
Do you have ideas or preferences on this ?

- Do you think replacing 'st,adc-res' by 'resolution-bits' in current 
patchset is enough for now ?
- Or do I need to add dt parsing routine in IIO core, e.g. as simple
as of_iio_get_resolution(), or something like this ? Or parsing routine
that may fill in a common properties structure (but only resolution
will be there from the start)...

Please let me know.

Thanks,
Fabrice

> > > Give me a poke if we hear nothing from Rob or Mark for say another week.
> >
> > No news yet, but it can wait a little longer.
> Rob / Mark, can you take a look at this if you have time?
>
> Thanks,
>
> Jonathan
> > Please advise,
> > Regards,
> > Fabrice
> >
> > > Thanks,
> > >
> > > Jonathan
> > >
> > > > ---
> > > >  Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt | 4 ++++
> > > >  1 file changed, 4 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> > > > index 5dfc88e..45f7ff2 100644
> > > > --- a/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> > > > +++ b/Documentation/devicetree/bindings/iio/adc/st,stm32-adc.txt
> > > > @@ -57,6 +57,9 @@ Optional properties:
> > > >  - dmas: Phandle to dma channel for this ADC instance.
> > > >    See ../../dma/dma.txt for details.
> > > >  - dma-names: Must be "rx" when dmas property is being used.
> > > > +- st,adc-res: Resolution (bits) to use for conversions. Must match device
> > > > +  available resolutions (e.g. can be 6, 8, 10 or 12 on stm32f4). Default
> > > > +  is maximum resolution if unset.
> > > >
> > > >  Example:
> > > >      adc: adc@40012000 {
> > > > @@ -84,6 +87,7 @@ Example:
> > > >              st,adc-channels = <8>;
> > > >              dmas = <&dma2 0 0 0x400 0x0>;
> > > >              dma-names = "rx";
> > > > +            st,adc-res = <8>;
> > > >          };
> > > >          ...
> > > >          other adc child nodes follow...
> > --
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