linux-kernel - Re: [PATCH 1/4] dt-bindings: Add Raspberry Pi's RP1 ADC

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Message-ID: <89dd04b9-e261-4bdd-83ab-499e46fc9c01@roeck-us.net>
Date: Thu, 25 Sep 2025 13:37:35 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Conor Dooley <conor@...nel.org>
Cc: Stanimir Varbanov <svarbanov@...e.de>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-rpi-kernel@...ts.infradead.org,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
	Rob Herring <robh@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
	Stefan Wahren <wahrenst@....net>,
	Saenz Julienne <nsaenz@...nel.org>,
	Andrea della Porta <andrea.porta@...e.com>,
	Phil Elwell <phil@...pberrypi.com>,
	Jonathan Bell <jonathan@...pberrypi.com>,
	Dave Stevenson <dave.stevenson@...pberrypi.com>
Subject: Re: [PATCH 1/4] dt-bindings: Add Raspberry Pi's RP1 ADC

On Thu, Sep 25, 2025 at 08:40:54PM +0100, Conor Dooley wrote:
> On Thu, Sep 25, 2025 at 03:04:13AM +0300, Stanimir Varbanov wrote:
> > Document dt-bindings for Raspberry Pi's RP1 ADC.
> > 
> > Signed-off-by: Stanimir Varbanov <svarbanov@...e.de>
> > ---
> >  .../bindings/hwmon/raspberrypi,rp1-adc.yaml   | 46 +++++++++++++++++++
> >  1 file changed, 46 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/hwmon/raspberrypi,rp1-adc.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/hwmon/raspberrypi,rp1-adc.yaml b/Documentation/devicetree/bindings/hwmon/raspberrypi,rp1-adc.yaml
> > new file mode 100644
> > index 000000000000..5266b253fd2b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/hwmon/raspberrypi,rp1-adc.yaml
> > @@ -0,0 +1,46 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/hwmon/raspberrypi,rp1-adc.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Rasberry Pi RP1 ADC device
> > +
> > +maintainers:
> > +  - Stanimir Varbanov <svarbanov@...e.de>
> > +
> > +description: |
> > +  The RP1 ADC is a five input successive-approximation ADC with 12-bit
> > +  resolution (ENOB 9.5-bit) at 500kSPS. It has four external inputs
> > +  and one internal temperature sensor.
> > +
> > +properties:
> > +  compatible:
> > +    const: raspberrypi,rp1-adc
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    maxItems: 1
> > +
> > +  vref-supply:
> > +    description:
> > +      Reference voltage regulator 3.3V.
> 
> Looks like you're missing the io-channels-cells property that allows
> this device to be a provider of adc channels to other devices.
> 
Only makes sense if the driver is implemented as iio driver.
Which would be fine with me, assuming this is a generic ADC.
The iio -> hwmon bridge can then be used to instantiate a
hwmon device if needed.

Guenter