linux-kernel - Re: [PATCH v5 1/2] dt-bindings: adc: provide max34408/9 device tree binding document

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Date:   Fri, 13 Oct 2023 19:12:18 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Ivan Mikhaylov <fr0st61te@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v5 1/2] dt-bindings: adc: provide max34408/9 device tree
 binding document

On Fri, 13 Oct 2023 11:53:33 +0200
Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> wrote:

> On 13/10/2023 11:09, Jonathan Cameron wrote:
> >>>>>>>> +  shtdn-enable-gpios:        
> >>>>>>>
> >>>>>>> I guess the review crossed with you sending v5.  There is some
> >>>>>>> feedback on v4 you need
> >>>>>>> to address here.        
> >>>>>>
> >>>>>> Jonathan, I thought I did, I've changed ena to powerdown-gpios from
> >>>>>> Krzysztof's comments but about this one pin I'm still not sure, it
> >>>>>> looks like *-enable-gpios (like in *-enable-gpios pins in
> >>>>>> iio/frequency/adi,adf4377.yaml) pin or is it not? Or maybe any
> >>>>>> other
> >>>>>> suggestions about naming of this one?
> >>>>>>
> >>>>>> Thanks.      
> >>>>>
> >>>>> shutdown-gpios and make the sense (active high / low) such that
> >>>>> setting
> >>>>> it results in teh device being shut down.
> >>>>> Or treat it as an enable and enable-gpios
> >>>>>
> >>>>> Something that indicates both shutdown and enable is confusing ;)
> >>>>>
> >>>>> Jonathan      
> >>>>
> >>>>
> >>>> Jonathan, then I make these changes:
> >>>>
> >>>> powerdown-gpios: -> output-enable:    
> >>> Needs to retain the gpios bit as we want the standard gpio stuff to pick
> >>> them up. I'm not that keen on output-enable-gpios though.  The activity
> >>> here is very much 'shutdown because of error or not enabled' I think.
> >>> So perhaps we flip the sense and document that it needs to be active low?
> >>>     
> >>>> shtdn-enable-gpios: -> enable-gpios:
> >>>>
> >>>> Is it ok?    
> >>>
> >>> Conor, Rob, Krzysztof - you probably have a better insight into this than
> >>> I do.
> >>>     
> >>
> >> "enable-gpios" are for turning on a specific feature, not powering
> >> on/off entire device. For example to enable regulator output.
> >>
> >> "powerdown-gpios" are for turning device on/off.
> >>
> >> I don't know what do you have in your device.  
> > Ok. Sounds like that what is enable-gpios above should be shutdown-gpios.  
> 
> shutdown-gpios sounds exactly the same as powerdown-gpios and it is
> already used in exactly same context.
Oops. Yup. powerdown-gpios seems appropriate.
> 
> > The other case is a device output indicating whether the device is
> > shutdown.  That can happen because it was told to do so (via the other gpio),
> > or because it is in an error state. What's a good naming convention for that?  
> 
> There is no convention and I did not see such case so far.
> powerdown-status-gpios? powerdown-state-gpios?
Either seems reasonable.

Thanks,

J
> 
> 
> 
> Best regards,
> Krzysztof
>