Re: [PATCH v1 1/2] bindings: iio: adc: Add StarFive JHB100 SARADC

[Jonathan Cameron]

On Tue, 19 May 2026 10:59:59 +0100
Conor Dooley <conor@xxxxxxxxxx> wrote:

> On Tue, May 19, 2026 at 09:26:03AM +0000, Xingyu Wu wrote:
> > On 2026/5/19 00:24, Conor Dooley wrote:  
> > > 
> > > On Mon, May 18, 2026 at 04:18:51PM +0800, Xingyu Wu wrote:  
> > > > Add the new documentation of SAR-ADC for the StarFive JHB100 SoC.
> > > >
> > > > Signed-off-by: Xingyu Wu <xingyu.wu@xxxxxxxxxxxxxxxx>
> > > > ---
> > > >  .../iio/adc/starfive,jhb100-saradc.yaml       | 62 +++++++++++++++++++
> > > >  1 file changed, 62 insertions(+)
> > > >  create mode 100644
> > > > Documentation/devicetree/bindings/iio/adc/starfive,jhb100-saradc.yaml
> > > >
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/iio/adc/starfive,jhb100-saradc.yam
> > > > l
> > > > b/Documentation/devicetree/bindings/iio/adc/starfive,jhb100-saradc.yam
> > > > l
> > > > new file mode 100644
> > > > index 000000000000..ba8e19b72ad7
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/iio/adc/starfive,jhb100-saradc
> > > > +++ .yaml
> > > > @@ -0,0 +1,62 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) %YAML 1.2
> > > > +---
> > > > +$id:
> > > > +http://devicetree.org/schemas/iio/adc/starfive,jhb100-saradc.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Successive Approximation Register (SAR) A/D converter for the
> > > > +StarFive JHB100 SoC
> > > > +
> > > > +maintainers:
> > > > +  - Xingyu Wu <xingyu.wu@xxxxxxxxxxxxxxxx>
> > > > +
> > > > +properties:
> > > > +  compatible:
> > > > +    const: starfive,jhb100-saradc
> > > > +
> > > > +  reg:
> > > > +    maxItem: 1
> > > > +
> > > > +  interrupts:
> > > > +    maxItems: 1
> > > > +
> > > > +  clocks:
> > > > +    maxItems: 1
> > > > +
> > > > +  resets:
> > > > +    maxItems: 2
> > > > +
> > > > +  "#io-channel-cells":
> > > > +    const: 1
> > > > +
> > > > +  upper-bound-mv:
> > > > +    description: The upper bound voltage value of the monitor.
> > > > +    $ref: /schemas/types.yaml#/definitions/uint16
> > > > +
> > > > +  lower-bound-mv:
> > > > +    description: The lower bound voltage value of the monitor.
> > > > +    $ref: /schemas/types.yaml#/definitions/uint16
> > > > +
> > > > +  scan-freq:
> > > > +    description: Number of the scan cycle interval.
> > > > +    $ref: /schemas/types.yaml#/definitions/uint16  
> > > 
> > > Can you explain why any of these three properties are something that should be in
> > > the devicetree rather than software controlled?  
> > 
> > My intention is to be able to obtain the initial values from the devicetree during probe and preset them.
> > Do I need to drop them and just set them through sysfs?  
> 
> Unless the hardware configuration determines the values (which I can't
> really see being the case for scan-freq at least) then yes, you need to
> drop and set them via sysfs.
> 
> > > How are the bounds calculated?  
> > 
> > The measurement range of this ADC hardware is from 0 to 1800 mV. This set value cannot exceed it. This explanation will be added later.  
> 
> I'm asking how this is calculated so that I can tell if you the property
> is permitted or not. 

Far as I can tell this stuff is boot script / udev rule stuff - doesn't
belong in DT.

Jonathan

> 
> Cheers,
> Conor.