linux-kernel - Re: [PATCH] dt-bindings: mfd: Explain lack of child dependency in simple-mfd

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Date: Sun, 23 Jun 2024 09:21:23 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Lee Jones <lee@...nel.org>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: mfd: Explain lack of child dependency in
 simple-mfd

On 21/06/2024 13:10, Lee Jones wrote:
> On Thu, 20 Jun 2024, Krzysztof Kozlowski wrote:
> 
>> On 20/06/2024 19:17, Lee Jones wrote:
>>> On Sun, 16 Jun 2024, Krzysztof Kozlowski wrote:
>>>
>>>> Common mistake of usage of 'simple-mfd' compatible is a dependency of
>>>> children on resources acquired and managed by the parent, e.g. clocks.
>>>> Extend the simple-mfd documentation to cover this case.
>>>>
>>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>>> ---
>>>>  Documentation/devicetree/bindings/mfd/mfd.txt | 13 +++++++------
>>>>  1 file changed, 7 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/mfd/mfd.txt b/Documentation/devicetree/bindings/mfd/mfd.txt
>>>> index 336c0495c8a3..98b4340b65f3 100644
>>>> --- a/Documentation/devicetree/bindings/mfd/mfd.txt
>>>> +++ b/Documentation/devicetree/bindings/mfd/mfd.txt
>>>> @@ -18,12 +18,13 @@ A typical MFD can be:
>>>>  Optional properties:
>>>>  
>>>>  - compatible : "simple-mfd" - this signifies that the operating system should
>>>> -  consider all subnodes of the MFD device as separate devices akin to how
>>>> -  "simple-bus" indicates when to see subnodes as children for a simple
>>>> -  memory-mapped bus. For more complex devices, when the nexus driver has to
>>>> -  probe registers to figure out what child devices exist etc, this should not
>>>> -  be used. In the latter case the child devices will be determined by the
>>>> -  operating system.
>>>> +  consider all subnodes of the MFD device as separate and independent devices
>>>> +  akin to how "simple-bus" indicates when to see subnodes as children for a
>>>> +  simple memory-mapped bus. "Independent devices" means that children do not
>>>
>>> I'm not against the change, but I think it can be phased better.
>>>
>>> Quoting the new part and going on to explain what you mean by it doesn't
>>> flow very well.  Are you able to massage it so it reads a little more
>>> nicely please?
>>
>> Does this feels better?
>>
>> compatible : "simple-mfd" - this signifies that the operating system
>> should consider all subnodes of the MFD device as separate and
>> independent devices, so not needing any resources to be provided by the
>> parent device. Similarly to how "simple-bus" indicates when to see
>> subnodes as children for a simple memory-mapped bus.
>>
>> For more complex devices, when the nexus driver has to probe registers
>> to figure out what child devices exist etc, this should not be used. In
>> the latter case the child devices will be determined by the operating
>> system.
> 
> Flows a lot better, yes.

Sure.

> 
> Submit it and please include the original author this time.

Everything is scripted, so you ask me for additional, manual steps just
to find the author and then Cc-them. I'll do it but it would be much
easier if the interested party added themself as reviewer or maintainer
of the binding.

> 

Best regards,
Krzysztof