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

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Message-ID: <Y1rRCq9Kdd2zPPkw@hatter.bewilderbeest.net>
Date:   Thu, 27 Oct 2022 11:42:18 -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 02:27:20PM PDT, Zev Weiss wrote:
>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.
>

Ping...

Would something like this be preferable as a more direct description of 
that?

   regulator-manually-controlled:
     description: |
       The regulator should never be enabled or disabled automatically,
       only when explicitly requested by an external actor (e.g.  
       userspace).
     type: boolean

That would leave the question of which property takes priority if both 
regulator-manually-controlled and regulator-boot-on are set -- should 
the binding document the answer to that?  (I personally don't have a 
strong opinion on which it should be.)

Thanks,
Zev