Re: [PATCH v2 1/3] dt-bindings: iio: dac: Add AD5529R

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 8 May 2026 13:48:43 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Fri, 8 May 2026 13:55:47 +0200
> Janani Sunil <janani.sunil@analog.com> wrote:
> 
> > Devicetree bindings for AD5529R 16 channel 12/16 bit high voltage,
> > buffered voltage output digital-to-analog converter (DAC) with an
> > integrated precision reference.
> > 
> > Signed-off-by: Janani Sunil <janani.sunil@analog.com>
> > ---
> >  .../devicetree/bindings/iio/dac/adi,ad5529r.yaml   | 96 ++++++++++++++++++++++
> >  MAINTAINERS                                        |  7 ++
> >  2 files changed, 103 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/dac/adi,ad5529r.yaml b/Documentation/devicetree/bindings/iio/dac/adi,ad5529r.yaml
> > new file mode 100644
> > index 000000000000..f531b4865b01
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/dac/adi,ad5529r.yaml
> > @@ -0,0 +1,96 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/dac/adi,ad5529r.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Analog Devices AD5529R 16-Channel 12/16-bit High Voltage DAC  
> 
> How is one device bother 12 and 16-bit? That sometimes happens for
> ADCs where it is really reflecting oversampling or for device with hardware
> FIFOs where storage space is saved by using lower bit rate. I'm not sure either
> applies here.

Having read the driver I now understand. This is supporting two parts and
doing device ID based detection.  In an unusual step for Analog they have
the same base part number with a post fix.  Whilst this approach works today
it fundamentally breaks fallback dt-compatibles being used in future (the
driver fails for any non match of WHOAMI value as it needs them to look
up device specific data)  As such I think you need to have separate
compatibles for the 12 and 16 bit versions.