linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: adc: Add binding for current-from-voltage

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Message-ID: <CY4PR04MB06639E2715E2E965F12360DBA38E0@CY4PR04MB0663.namprd04.prod.outlook.com>
Date:   Thu, 28 May 2020 13:16:41 -0700
From:   Jonathan Bakker <xc-racer2@...e.ca>
To:     Rob Herring <robh@...nel.org>
Cc:     jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linus.walleij@...aro.org
Subject: Re: [PATCH 1/2] dt-bindings: iio: adc: Add binding for
 current-from-voltage

Hi Rob,

On 2020-05-28 1:13 p.m., Rob Herring wrote:
> On Fri, May 15, 2020 at 07:26:18PM -0700, Jonathan Bakker wrote:
>> Some devices may require a current adc, but only have a voltage
>> ADC onboard.  In order to read the current, they have a resistor
>> connected to the ADC.  Add bindings for this possibility.
>>
>> Signed-off-by: Jonathan Bakker <xc-racer2@...e.ca>
>> ---
>>  .../iio/adc/linux,current-from-voltage.yaml   | 47 +++++++++++++++++++
>>  1 file changed, 47 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/iio/adc/linux,current-from-voltage.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/iio/adc/linux,current-from-voltage.yaml b/Documentation/devicetree/bindings/iio/adc/linux,current-from-voltage.yaml
>> new file mode 100644
>> index 000000000000..385d317607c3
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/iio/adc/linux,current-from-voltage.yaml
>> @@ -0,0 +1,47 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/iio/adc/linux,current-from-voltage.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Current ADC from voltage ADC and resistor
>> +
>> +maintainers:
>> +  - Jonathan Bakker <xc-racer2@...e.ca>
>> +
>> +properties:
>> +  compatible:
>> +    const: linux,current-from-voltage
> 
> How is an ADC with a resistor attached a Linux thing? So you don't need 
> 'linux', but then 'current-from-voltage' isn't the best naming. I don't 
> have a suggestion ATM.
> 

The good/bad news is that I was re-implementing an existing driver under a new name :)

The compatible is current-sense-shunt for this exact same purpose.

Thanks,
Jonathan

>> +
>> +  io-channel-names:
>> +    const: adc
>> +
>> +  io-channels:
>> +    maxItems: 1
>> +    description: Voltage ADC channel
>> +
>> +  linux,resistor-ohms:
>> +    description: Strength of resistor connected to voltage ADC
> 
> Wouldn't you need this to be micro-ohms? Otherwise, there'd be too much 
> voltage drop?
> 
> Rob
>