linux-kernel - Re: [PATCH] dt-bindings: firmware: arm,scmi: Restrict protocol child node properties

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Message-ID: <Y9JLUIioxFPn4BS0@e120937-lin>
Date:   Thu, 26 Jan 2023 09:43:44 +0000
From:   Cristian Marussi <cristian.marussi@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: firmware: arm,scmi: Restrict protocol child
 node properties

On Wed, Jan 25, 2023 at 02:11:13PM +0000, Sudeep Holla wrote:
> On Wed, Jan 25, 2023 at 01:43:48PM +0000, Cristian Marussi wrote:
> > so now that the catch-all protocol@ patternProperty is gone in favour
> > of the 'protocol-node' definition and $refs, does that mean that any
> > current and future SCMI officially published protocol <N> has to be
> > added to the above explicit protocol list, even though it does not
> > have any special additional required property beside reg ?
> > (like protocol@18 above...)
> >
> 
> If there are no consumers, should we just not add and deal with it
> entirely within the kernel. I know we rely today on presence of node
> before we initialise, but hey we have exception for system power protocol
> for other reasons, why not add this one too.
> 
> In short we shouldn't have to add a node if there are no consumers. It
> was one of the topic of discussion initially when SCMI binding was added
> and they exist only for the consumers otherwise we don't need it as
> everything is discoverable from the interface.

It is fine for me the no-consumers/no-node argument (which anyway would
require a few changes in the core init logic anyway to work this way...),
BUT is it not that ANY protocol (even future-ones) does have, potentially,
consumers indeed, since each protocol-node can potentially have a dedicated
channel and related DT channel-descriptor ? (when multiple channels are
allowed by the transport)

I mean, as an example, you dont strictly need protos 0x18/0x12 nodes for
anything (if we patch the core init as said) UNLESS you want to dedicate
a channel to those protocols; so I'm just checking here if these kind of
scenarios will still be allowed with this binding change, or if I am
missing something.

Thanks,
Cristian