linux-kernel - Re: [RFC 3/7] firmware: arm_scmi: Add QCOM vendor protocol

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Message-ID: <ZeCTp5jP51gnkc3u@bogus>
Date: Thu, 29 Feb 2024 14:24:39 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Sibi Sankar <quic_sibis@...cinc.com>
Cc: <cristian.marussi@....com>, <andersson@...nel.org>,
	Sudeep Holla <sudeep.holla@....com>, <konrad.dybcio@...aro.org>,
	<jassisinghbrar@...il.com>, <robh+dt@...nel.org>,
	<krzysztof.kozlowski+dt@...aro.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<quic_rgottimu@...cinc.com>, <quic_kshivnan@...cinc.com>,
	<conor+dt@...nel.org>, Amir Vajid <avajid@...cinc.com>
Subject: Re: [RFC 3/7] firmware: arm_scmi: Add QCOM vendor protocol

On Wed, Jan 17, 2024 at 11:04:54PM +0530, Sibi Sankar wrote:
> From: Shivnandan Kumar <quic_kshivnan@...cinc.com>
> 
> SCMI QCOM vendor protocol provides interface to communicate with SCMI
> controller and enable vendor specific features like bus scaling capable
> of running on it.
> 

I would expect a proper description of the protocol specification
either as part of the header file qcom_scmi_vendor.h or somewhere
in the Documentation. It helps to understand the design instead of
assuming and/or getting confused with the assumption while reviewing.
I will point out at couple of individual place why I am asking for this.

You can follow some pattern to describe the command using SCMI spec as
reference. That will act as a contract for the software instead of changing
the implementation every time someone thinks it should work in certain
way. I have seen that quite a lot with the Qcom firmware lately with zero
transparency provided for these firmware by Qcom. In short I don't trust
just code to understand these vendor protocols. I need them to be documented
and version where needed so that we can refer back and make maintenance
smooth and easy.

-- 
Regards,
Sudeep