linux-kernel - Re: [PATCH v3 1/2] dt-bindings: mailbox: Add support for bcm74110

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Message-ID: <8b8ff49e-c72e-4cb4-a412-a6b9f15d2ec6@kernel.org>
Date: Fri, 25 Apr 2025 08:28:07 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Justin Chen <justin.chen@...adcom.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: florian.fainelli@...adcom.com, conor+dt@...nel.org, krzk+dt@...nel.org,
 robh@...nel.org, jassisinghbrar@...il.com,
 bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v3 1/2] dt-bindings: mailbox: Add support for bcm74110

On 10/04/2025 20:44, Justin Chen wrote:
> 
> 
> On 4/7/25 11:05 PM, Krzysztof Kozlowski wrote:
>> On 07/04/2025 22:57, Justin Chen wrote:
>>
>>
>>> from v2 of my patch was copied from said generated DTS.
>>>
>>> Apologies as I navigate through the different yaml keywords here. The HW
>>> isn't changing, I am just struggling with representing the HW using the
>>> different keywords. And the different implications of using said keywords.
>>>
>>> Here is what I have for v4.
>>>        items:
>>>          - description: RX doorbell and watermark interrupts
>>>          - description: TX doorbell and watermark interrupts
>>> +    description:
>>> +      RX interrupts are required to notify the host of pending messages. TX
>>> +      interrupts are optional. The TX doorbell interrupt is not used by the
>>> +      host, but watermark interrupts may be used to notify a host
>>> waiting on
>>> +      a full out queue.
>> What does it mean optional? Board decides on SoC connections? Given SoC
>> is fixed isn't it?
>>
> 
> Maybe I misunderstand optional here. We have optional from the SoC 
> perspective and optional from a driver perspective. I was thinking if we 
> have a HW feature that the software may choose to use, it is considered 
> optional. If that is not the correct understanding, I can make 

Both meanings are considered. Optional for driver means hardware has it
but also has default values and driver implementations can work without
it on these defaults, e.g. some property configuring registers like
min/max regulator voltages.
Optional for hardware means it can really be "not connected" on some
hardwares/boards, e.g. some pins are grounded. The "interrupts" do not
really fit into the first category, so they could be optional only if
your hardware really allows this interrupt to be missing (or such
hardware exists).

> adjustments. I will remove minItems, which from understanding, means 
> both IRQs are required.

Best regards,
Krzysztof