linux-kernel - Re: [PATCH v2 0/2] iio: add unit converter

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Date:   Tue, 3 Apr 2018 12:41:49 -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>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Michael Hennerich <michael.hennerich@...log.com>,
        Phil Reid <preid@...ctromag.com.au>,
        <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 0/2] iio: add unit converter

On 04/03/2018 10:36 AM, Peter Rosin wrote:
> Hi!
> 
> This driver implements support for voltage dividers and current
> sense circuits. It's pretty generic and should be easily adaptable
> to other linear scaling purposes...
> 

I really like this idea, defining channel scaling / channel type
conversion in DT will be very useful. So much so that I would recommend
this not be a use specific driver but instead moved into the IIO core.

This would allow defining these channel conversions in the device node
itself, so as to not need a separate node just for the converter (the
conversion is not a device and probably should not have it's own node
anyway). It would also help with enabling this support for buffered
readers/writers and not just devices only supporting _raw reads/writes.

Andrew

> The driver is still named "unit converter", because it was not
> clear to me that there was a real problem with the driver being
> named that. I got the impression that the naming discussion in
> v1 was mainly about the category, and that it kind of looked odd
> and non-specific with unit-converter in the DT bindings, but
> what do I know?
> 
> Cheers,
> Peter
> 
> Changes since v1:    https://lkml.org/lkml/2018/3/19/801
> - Put the driver in the new afe category (Analog Front Ends) and do not
>   move the iio-mux driver.
> - Do not refer to the source channel as "parent", use "source" instead.
> - Have the DT compatible drive the target unit, instead of relying on a
>   "type" DT-property for that.
> - In the DT bindings, use an unnamed source channel.
> - Do not set up writes to _RAW (sorry Phil) as I don't need it and have
>   not tested it. It's easy to add back if needed.
> - Fail if the source channel does not support _RAW or _SCALE.
> - Fix various spelling issues.
> - Fix various code style issues.
> 
> Peter Rosin (2):
>   dt-bindings: iio: afe: add current-sense-cuicuit and voltage-divider
>   iio: afe: unit-converter: new driver
> 
>  .../bindings/iio/afe/current-sense-circuit.txt     |  45 ++++
>  .../bindings/iio/afe/voltage-divider.txt           |  45 ++++
>  MAINTAINERS                                        |   8 +
>  drivers/iio/Kconfig                                |   1 +
>  drivers/iio/Makefile                               |   1 +
>  drivers/iio/afe/Kconfig                            |  18 ++
>  drivers/iio/afe/Makefile                           |   6 +
>  drivers/iio/afe/iio-unit-converter.c               | 257 +++++++++++++++++++++
>  8 files changed, 381 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt
>  create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt
>  create mode 100644 drivers/iio/afe/Kconfig
>  create mode 100644 drivers/iio/afe/Makefile
>  create mode 100644 drivers/iio/afe/iio-unit-converter.c
>