linux-kernel - Re: [PATCH v3 0/2] iio: add unit converter

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Message-ID: <fe90dc62-ef2b-d999-6841-2d9d5943654c@ti.com>
Date:   Wed, 11 Apr 2018 10:34:40 -0500
From:   "Andrew F. Davis" <afd@...com>
To:     Peter Rosin <peda@...ntia.se>, <linux-kernel@...r.kernel.org>
CC:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Fabio Estevam <festevam@...il.com>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3 0/2] iio: add unit converter

On 04/11/2018 09:15 AM, Peter Rosin wrote:
> Hi!
> 
> I'm now following up with one more binding for the unit-converter.
> This time with a real IC, namely LT6106 from Analog Devices.

This makes more sense to me, I wasn't thinking about more complex ICs
like this when I made my "resistor being part of the sensing device"
argument.

I can see how having a new node will probably be needed. It just seems
strange to ask a resistor for its current, although it is the "device"
that "knows" how much current if flowing though it..

A case I'm more familiar with, fuel gauges, we have a gauge device that
has a handle to the battery it is gauging [0], we still ask the
"fuel-gauge" node to get out the state of charge, not the "battery"
node, the battery is not a "device" from our perspective.

Thinking more about that, I like your way better, so I recant my earlier
objections.

Andrew

[0] Documentation/devicetree/bindings/power/supply/bq27xxx.txt

> It's
> a current sense amplifier. I was a but unsure if I should have
> the Rin and Rout resistors in the binding or if I instead should
> have used the "gain". In the end I went with the resistors since
> while the normal case is an integer gain, that may not always be
> the case. And when it's not, that could get tricky. But I'm open
> for arguments on that.
> 
> Cheers,
> Peter
> 
> Peter Rosin (2):
>   dt-bindings: iio: afe: add binding for adi,lt6106
>   iio: afe: unit-converter: add support for adi,lt6106
> 
>  .../devicetree/bindings/iio/afe/adi,lt6106.txt     | 50 ++++++++++++++++++++
>  MAINTAINERS                                        |  1 +
>  drivers/iio/afe/Kconfig                            |  3 +-
>  drivers/iio/afe/iio-unit-converter.c               | 54 ++++++++++++++++++++++
>  4 files changed, 107 insertions(+), 1 deletion(-)
>  create mode 100644 Documentation/devicetree/bindings/iio/afe/adi,lt6106.txt
>