linux-kernel - Re: [PATCH v5 1/2] dt-bindings: iio: vadc: Update example to include unit address for node 'usb-id-nopull'

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Message-ID: <20181018194010.GV22824@google.com>
Date:   Thu, 18 Oct 2018 12:40:10 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH v5 1/2] dt-bindings: iio: vadc: Update example to include
 unit address for node 'usb-id-nopull'

On Fri, Oct 12, 2018 at 10:15:23AM -0700, Matthias Kaehlcke wrote:
> On Fri, Oct 05, 2018 at 03:47:43PM -0500, Rob Herring wrote:
> > On Wed, Oct 03, 2018 at 05:14:31PM -0700, Matthias Kaehlcke wrote:
> > > The node has a reg property, therefore its name should include a unit
> > > address.
> > > 
> > > Also change the name from 'usb_id_nopull' to 'usb-id-nopull' to follow
> > > DT conventions.
> > 
> > This is ADC channels? If so, then DT convention would really be 
> > "adc@...". 
> 
> Is it really? A grep for 'adc@' in arch/${ARCH}/boot/dts yields
> mostly ADC controller not channel nodes.
> 
> I'm totally fine with changing the name to 'adc@...' if that's the
> preference/convention, just want to reconfirm since the actual use is
> a bit ambiguous.

Could we please reach a conclusion on this?

Summarizing the options on the table so far are:

1. usb-id-nopull@...C_LR_MUX10_USB_ID
2. usb-id-nopull@57
3. adc@...C_LR_MUX10_USB_ID
4. adc@57

My personal preference goes to something <node name>@<define>
since the unit address doesn't just resolve to an ADC channel number
but also includes configuation information. A literal like '57'
conveys less information than the define, it's easier to introduce
errors and these errors are harder to spot.

If 'adc@...' really was the convention (or should be) I'd be clearly
in favor of following it. As mentioned above, in practice the use of
the 'adc@...' node name seems to be more prevalent for ADC controllers
than channels, so I'm more inclined towards 'usb-id-nopull@...' or
similar.

All that said, these are just my preferences for the reasons outlined
above, if DT maintainers really want it to be 'adc@57' or some
variation of that, I'm fine with that too. Please let me know and we
can move forward with this trivial series.

Thanks

Matthias