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

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Message-ID: <97b84ce1-3ed2-48a8-bed4-9a671b61cd6d@linaro.org>
Date: Thu, 20 Jun 2024 21:42:43 +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 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.


Best regards,
Krzysztof