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

From: Sudeep Holla <sudeep.holla@arm.com>
To: Sibi Sankar <quic_sibis@quicinc.com>
Cc: <cristian.marussi@arm.com>, <andersson@kernel.org>,
	Sudeep Holla <sudeep.holla@arm.com>, <konrad.dybcio@linaro.org>,
	<jassisinghbrar@gmail.com>, <robh+dt@kernel.org>,
	<krzysztof.kozlowski+dt@linaro.org>,
	<linux-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
	<devicetree@vger.kernel.org>, <quic_rgottimu@quicinc.com>,
	<quic_kshivnan@quicinc.com>, <conor+dt@kernel.org>,
	Amir Vajid <avajid@quicinc.com>
Subject: Re: [RFC 3/7] firmware: arm_scmi: Add QCOM vendor protocol
Date: Thu, 29 Feb 2024 14:24:39 +0000	[thread overview]
Message-ID: <ZeCTp5jP51gnkc3u@bogus> (raw)
In-Reply-To: <20240117173458.2312669-4-quic_sibis@quicinc.com>

On Wed, Jan 17, 2024 at 11:04:54PM +0530, Sibi Sankar wrote:
> From: Shivnandan Kumar <quic_kshivnan@quicinc.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