linux-kernel - Re: [PATCH 1/4] perf vendor events: Syntax corrections in Neoverse N1 json

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Message-ID: <83767166-e379-a352-d920-ad8b6e923800@huawei.com>
Date:   Wed, 6 Oct 2021 17:26:02 +0100
From:   John Garry <john.garry@...wei.com>
To:     James Clark <james.clark@....com>,
        Andrew Kilroy <andrew.kilroy@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        "acme@...nel.org" <acme@...nel.org>
CC:     Will Deacon <will@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        "Namhyung Kim" <namhyung@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH 1/4] perf vendor events: Syntax corrections in Neoverse N1
 json

On 06/10/2021 09:43, James Clark wrote:

+ Andi

> 
> 
> On 05/10/2021 11:10, John Garry wrote:
>> On 04/10/2021 17:00, Andrew Kilroy wrote:
>>> There are some syntactical mistakes in the json files for the Cortex A76
>>> N1 (Neoverse N1).  This was obstructing parsing from an external tool.
>>
>> If the trailing comma is not allowed by standard, then maybe we should fix our parsing tool to not allow it also. However maybe there is a good reason why we allow it..
> 
> It would be nice to do, because I have also made similar fixes before. We looked at the STRICT option
> in the parser (https://github.com/zserge/jsmn), but even then it seems to allow trailing commas.
> 
> Trailing commas are not allowed in the json standard, but there is a split between parsers
> where some allow it and others don't. Specifically the Python parser doesn't allow it, and Python
> can easily be involved in some workflow that parses these files.
> 
> The only way forwards I can think of is either getting a change accepted upstream to the parser
> and then updating it in perf, switching to a different parser, or doing some hack to add an extra
> step in perf to look for commas. None of which sound ideal.
> 

Looking at the license in jsmn.c, we seem to be ok to modify it (to 
error on non-standard trailing ',') - that parser has already apparently 
been modified in mainline.

If we do that then I hope that there are not to many violations in out 
JSONs, including downstream.

Thanks,
John