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

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Date:   Thu, 7 Oct 2021 19:59:42 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     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>, 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 Thu, Oct 7, 2021 at 5:03 PM Andi Kleen <ak@...ux.intel.com> wrote:
>
>
> 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

jsmn is a somewhat frustrating way to work on json code and working on
a forked version of jsmn was frustrating in [1]. Could we assume
python on build systems and rewrite jevents in python?

Thanks,
Ian

[1] https://lore.kernel.org/lkml/20201110100346.2527031-1-irogers@google.com/