2020-05-16 02:28:57

by Jonathan Bakker

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

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 <[email protected]>
---
.../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 <[email protected]>
+
+properties:
+ compatible:
+ const: linux,current-from-voltage
+
+ io-channel-names:
+ const: adc
+
+ io-channels:
+ maxItems: 1
+ description: Voltage ADC channel
+
+ linux,resistor-ohms:
+ description: Strength of resistor connected to voltage ADC
+
+ "#io-channel-cells":
+ const: 0
+
+required:
+ - compatible
+ - io-channel-names
+ - io-channels
+ - linux,resistor-ohms
+ - "#io-channel-cells"
+
+examples:
+ - |
+ current-from-voltage {
+ compatible = "linux,current-from-voltage";
+ io-channel-names = "adc";
+ io-channels = <&adc 9>;
+ linux,resistor-ohms = <47>;
+ #io-channel-cells = <0>;
+ io-channel-ranges;
+ };
+
+...
--
2.20.1

2020-05-28 20:15:21

by Rob Herring

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

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 <[email protected]>
> ---
> .../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 <[email protected]>
> +
> +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.

> +
> + 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

2020-05-28 20:20:05

by Jonathan Bakker

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 <[email protected]>
>> ---
>> .../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 <[email protected]>
>> +
>> +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
>