linux-kernel - Re: [RFC PATCH v2 02/31] Documentation: Add binding for kalray,kv3-1-core-intc

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Message-ID: <348c3416-be44-b912-98ef-7f394bd408c0@linaro.org>
Date:   Fri, 27 Jan 2023 09:32:52 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Jules Maselbas <jmaselbas@...ray.eu>
Cc:     Yann Sionneau <ysionneau@...ray.eu>, Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Waiman Long <longman@...hat.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Piggin <npiggin@...il.com>,
        Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...hat.com>,
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        Albert Ou <aou@...s.berkeley.edu>,
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        Vincent Chardon <vincent.chardon@...ys-design.com>,
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        Ashley Lesdalons <alesdalons@...ray.eu>,
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        Marius Gligor <mgligor@...ray.eu>,
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Subject: Re: [RFC PATCH v2 02/31] Documentation: Add binding for
 kalray,kv3-1-core-intc

On 26/01/2023 17:10, Jules Maselbas wrote:

>>> +  reg:
>>> +    maxItems: 0
>>
>> ??? No way... What's this?
> This (per CPU) interrupt controller is not memory mapped at all, it is
> controlled and configured through system registers.
> 
> I do not have found existing .yaml bindings for such devices, only the
> file snps,archs-intc.txt has something similar.
> 
> I do not know what is the best way to represent such devices in the
> device-tree.  Any suggestions are welcome.

You cannot have an array property with 0 items. How would it look like
in DTS? There are many, many bindings which are expressing it. Just drop
the reg.

> 
>>
>>> +  "kalray,intc-nr-irqs":
>>
>> Drop quotes.
>>
>>> +    description: Number of irqs handled by the controller.
>>
>> Why this is variable per board? Why do you need it ?
> This property is not even used in our device-tree, this will be removed
> from the documentation and from the driver as well.
> 
>>> +
>>> +required:
>>> +  - compatible
>>> +  - "#interrupt-cells"
>>> +  - interrupt-controller
>>
>> missing additionalProperties: false
>>
>> This binding looks poor, like you started from something odd. Please
>> don't. Take the newest reviewed binding or better example-schema and use
>> it to build yours. This would solve several trivial mistakes and style
>> issues.
> I am starting over from the example-schema.
> 
>>> +
>>> +examples:
>>> +  - |
>>> +    intc: interrupt-controller {
>>
>> What's the IO address space?
> As said above, this is not a memory mapped device, but is accessed
> through system registers.

Sure, but then you cannot define a reg which was confusing...

Best regards,
Krzysztof