linux-kernel - Re: [PATCH v2 03/28] interconnect: qcom: rpmh: make nodes a NULL

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Message-ID: <a2b837f8-eb34-4283-8d7c-17031a7a682b@oss.qualcomm.com>
Date: Sat, 19 Jul 2025 00:17:47 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Georgi Djakov <djakov@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 03/28] interconnect: qcom: rpmh: make nodes a
 NULL_terminated array

On 7/18/25 7:26 PM, Dmitry Baryshkov wrote:
> On Fri, Jul 18, 2025 at 04:38:02PM +0300, Georgi Djakov wrote:
>> Hi Dmitry,
>>
>> On 7/4/25 7:35 PM, Dmitry Baryshkov wrote:
>>> Having the .num_nodes as a separate struct field can provoke errors as
>>> it is easy to omit it or to put an incorrect value into that field. Turn
>>> .nodes into a NULL-terminated array, removing a need for a separate
>>> .num_nodes field.
>>
>> I am not entirely convinced that an error in the termination is more
>> unlikely than an error in the num_nodes. Aren't we trading one kind of
>> error for another? Also if we omit the num_nodes i expect that just the
>> QoS of a specific path will fail, but if we miss the NULL - worse things
>> might happen.
> 
> Exactly, that's the point. It is easy to miss num_nodes, while omitting
> NULL will crash the driver. So the error will be noted during
> development.

I really don't wanna step on your development, but again, I don't think
this is a good solution.. maybe WARN_ON(!desc->num_nodes) would be better?
Some static checks?

Konrad