linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: dac: adding support for Microchip MCP47FEB02

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Message-ID: <20250927180056.38b1822f@jic23-huawei>
Date: Sat, 27 Sep 2025 18:00:56 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Ariana Lazar <ariana.lazar@...rochip.com>, Nuno Sá
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: iio: dac: adding support for Microchip
 MCP47FEB02

> > +  vref-supply:
> > +    description: |
> > +      Vref pin is used as a voltage reference when this supply is specified.
> > +      Into the datasheet it could be found as a Vref0.
> > +      If it does not exists the internal reference will be used.  
> 
> It looks like there is also the possibility to use V_DD as the reference
> voltage. Not sure the best way to handle that though.

Indeed that's awkward.  I suppose a custom property as choice of VDD or internal
reference is unusual and it might be critical to how what is downstream of the DAC
so we can't even do it via userspace _scale control.

I'm lazy so haven't checked the values. If the internal reference is near VDD
it is probably safe enough to just make this a userspace problem if anyone
ever needs it.