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

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Message-ID: <b24041af-1c92-3855-9659-133e73a0c241@linux.intel.com>
Date:   Thu, 7 Oct 2021 17:03:25 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     John Garry <john.garry@...wei.com>,
        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>
Subject: Re: [PATCH 1/4] perf vendor events: Syntax corrections in Neoverse N1
 json


On 10/6/2021 9:26 AM, John Garry wrote:
> 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.


Sure we can modify the file. I already did some minor changes when I 
submitted it originally.

-Andi