Messages in this thread |  | | Subject | Re: [RFC PATCH v1 0/2] hwmon: (iio_hwmon) optionally force iio channel type | From | Guenter Roeck <> | Date | Sun, 16 May 2021 08:54:06 -0700 |
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On 5/16/21 8:02 AM, Liam Beguin wrote: > Hi Jonathan, > > On Sun May 16, 2021 at 5:06 AM EDT, Jonathan Cameron wrote: >> On Sun, 16 May 2021 00:43:13 -0400 >> Liam Beguin <liambeguin@gmail.com> wrote: >> >>> Add a devicetree binding to optionally force a different IIO channel >>> type. >>> >>> This is useful in cases where ADC channels are connected to a circuit >>> that represent another unit such as a temperature or a current. >>> >>> `channel-types` was chosen instead of `io-channel-types` as this is not >>> part of the iio consumer bindings. >>> >>> In the current form, this patch does what it's intended to do: >>> change the unit displayed by `sensors`, but feels like the wrong way to >>> address the problem. >>> >>> Would it be possible to force the type of different IIO channels for >>> this kind of use case with a devicetree binding from the IIO subsystem? >>> >>> It would be convenient to do it within the IIO subsystem to have the >>> right unit there too. >>> >>> Thanks for your time, >>> Liam >> >> Hi Liam, >> >> +CC Peter for AFE part. >> >> It's an interesting approach, but I would suggest we think about this >> a different way. >> >> Whenever a channel is being used to measure something 'different' from >> what it actually measures (e.g. a voltage ADC measuring a current) that >> reflects their being some analog component involved. >> If you look at drivers/iio/afe/iio-rescale.c you can see the approach >> we currently use to handle this. > > Many thanks for pointing out the AFE code. That look like what I was > hoping to accomplish, but in a much better way. > >> >> Effectively what you add to devicetree is a consumer of the ADC channel >> which in turn provides services to other devices. For this current case >> it would be either a current-sense-amplifier or a current-sense-shunt >> depending on what the analog front end looks like. We have to describe >> the characteristics of that front end which isn't something that can >> be done via a simple channel type. >> > > Understood. My original intention was to use sensors.conf to do the > conversions and take into accounts those parameters. > >> That afe consumer device can then provide services to another consumer >> (e.g. iio-hwmon) which work for your usecase. >> >> The main limitation of this approach currently is you end up with >> one device per channel. That could be improved upon if you have a >> usecase >> where it matters. >> >> I don't think we currently have an equivalent for temperature sensing >> but it would be easy enough to do something similar. > > Wonderful, thanks again for pointing out the AFE! >
Please don't reinvent the ntc_thermistor driver.
Thanks, Guenter
> Liam > >> >> Jonathan >> >> >>> >>> Liam Beguin (2): >>> hwmon: (iio_hwmon) optionally force iio channel type >>> dt-bindings: hwmon: add iio-hwmon bindings >>> >>> .../devicetree/bindings/hwmon/iio-hwmon.yaml | 41 +++++++++++++++++++ >>> drivers/hwmon/iio_hwmon.c | 2 + >>> 2 files changed, 43 insertions(+) >>> create mode 100644 Documentation/devicetree/bindings/hwmon/iio-hwmon.yaml >>> >>> >>> base-commit: 9f4ad9e425a1d3b6a34617b8ea226d56a119a717 >
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