linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: ad74413r: add binding for digital input threshold

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Message-ID: <20230702173648.00006a1d@Huawei.com>
Date:   Sun, 2 Jul 2023 17:36:48 +0800
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Rob Herring <robh@...nel.org>, Conor Dooley <conor@...nel.org>,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        "Michael Hennerich" <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        <devicetree@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH 1/2] dt-bindings: iio: ad74413r: add binding for digital
 input threshold

On Mon, 26 Jun 2023 10:29:22 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 26/06/2023 10:15, Rasmus Villemoes wrote:
> > On 23/06/2023 23.57, Rob Herring wrote:  
> >> On Fri, Jun 23, 2023 at 05:44:50PM +0100, Conor Dooley wrote:  
> >>> On Fri, Jun 23, 2023 at 01:33:25PM +0200, Rasmus Villemoes wrote:  
> >>>> diff --git a/Documentation/devicetree/bindings/iio/addac/adi,ad74413r.yaml b/Documentation/devicetree/bindings/iio/addac/adi,ad74413r.yaml
> >>>> index 590ea7936ad7..1f90ce3c7932 100644
> >>>> --- a/Documentation/devicetree/bindings/iio/addac/adi,ad74413r.yaml
> >>>> +++ b/Documentation/devicetree/bindings/iio/addac/adi,ad74413r.yaml
> >>>> @@ -51,6 +51,14 @@ properties:
> >>>>        Shunt (sense) resistor value in micro-Ohms.
> >>>>      default: 100000000
> >>>>  
> >>>> +  digital-input-threshold-microvolt:  
> >>>
> >>> Should this not have an adi vendor prefix, similar to
> >>> "adi,digital-input-threshold-mode-fixed"?  
> >>
> >> Yes.  
> > 
> > OK. But I'm not really sure what the rules are for when such a prefix
> > must be added, so some guidance would be appreciated. There's
> > 
> > - DO use a vendor prefix on device specific property names. Consider if
> >   properties could be common among devices of the same class.
> > 
> > And my thinking was that a threshold for when a digital input should
> > count as high/low would be a rather generic thing, so not particularly
> > device specific.  
> 
> Then find some more users of it.

The hi8435 could make use of this, but it currently doesn't get these thresholds
from DT (despite there being a reasonable argument that these should be characteristics
of the board wiring etc) but rather from userspace controls.

Might well be something in gpio drivers?  Linus / Bartosz, any of the input gpio
devices really threshold detectors?  If so is there any precedence for a DT
binding to set the threshold?

> 
> > 
> > Also, this very binding has a shunt-resistor-micro-ohms, and the
> > individual channels have a drive-strength-microamp (granted, that latter
> > one is a recent one of mine and may have slipped through review?). I can
> > certainly understand that when a property specifies a raw value to put
> > into some register (or field), that's very specific to that chip (or
> > small family of chips) - the adi,ch-func properties fall into that category.  
> 
> Best regards,
> Krzysztof
>