linux-kernel - Re: [PATCH 2/3] dt-bindings: regulator: Add regulator-output binding

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Date:   Thu, 29 Sep 2022 14:27:19 -0700
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Rob Herring <robh@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Naresh Solanki <naresh.solanki@...ements.com>,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        openbmc@...ts.ozlabs.org
Subject: Re: [PATCH 2/3] dt-bindings: regulator: Add regulator-output binding

On Thu, Sep 29, 2022 at 02:07:14PM PDT, Rob Herring wrote:
>On Sun, Sep 25, 2022 at 03:03:18PM -0700, Zev Weiss wrote:
>> This describes a power output supplied by a regulator, such as a
>> power outlet on a power distribution unit (PDU).
>>
>> Signed-off-by: Zev Weiss <zev@...ilderbeest.net>
>> ---
>>  .../bindings/regulator/regulator-output.yaml  | 47 +++++++++++++++++++
>>  1 file changed, 47 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/regulator/regulator-output.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/regulator/regulator-output.yaml b/Documentation/devicetree/bindings/regulator/regulator-output.yaml
>> new file mode 100644
>> index 000000000000..40953ec48e9e
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/regulator/regulator-output.yaml
>> @@ -0,0 +1,47 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +
>> +$id: http://devicetree.org/schemas/regulator/regulator-output.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Regulator output connector
>> +
>> +maintainers:
>> +  - Zev Weiss <zev@...ilderbeest.net>
>> +
>> +description: |
>> +  This describes a power output connector supplied by a regulator,
>> +  such as a power outlet on a power distribution unit (PDU).  The
>> +  connector may be standalone or merely one channel or set of pins
>> +  within a ganged physical connector carrying multiple independent
>> +  power outputs.
>> +
>> +properties:
>> +  compatible:
>> +    const: regulator-output
>> +
>> +  vout-supply:
>> +    description:
>> +      Phandle of the regulator supplying the output.
>> +
>> +  regulator-leave-on:
>> +    description: |
>> +      If the regulator is enabled when software relinquishes control
>> +      of it (such as when shutting down) it should be left enabled
>> +      instead of being turned off.
>> +    type: boolean
>
>I'm not too sure about this one as there could be various times when
>control is relinquished. It is userspace closing its access?
>driver unbind? module unload? Does a bootloader pay attention to this?
>
>Rob

Thanks for the feedback, Rob -- I'll admit I was a bit unsure how to 
approach that, and this may well not be the right answer.  What I'm 
really aiming for is an appropriate way to express that regulator on/off 
state should only ever be changed by explicit (external, e.g. userspace) 
request, never as any sort of default/automatic action.  The two obvious 
things to guard against there seem to be automatic enablement during 
initialization and automatic disablement on de-init (shutdown, unbind, 
etc.).  The former I think can be avoided by simply not setting 
regulator-boot-on, so I added this as a corresponding property to avoid 
the latter.

I'm definitely open to suggestions for a better approach though.


Thanks,
Zev