linux-kernel - Re: [PATCH v2 0/4] kbuild: Per arch/platform dtc warning levels

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Date:   Thu, 23 Nov 2023 21:00:58 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     Rob Herring <robh@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Conor Dooley <conor@...nel.org>, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v2 0/4] kbuild: Per arch/platform dtc warning levels

On Thu, Nov 23, 2023 at 6:44 PM Conor Dooley <conor.dooley@...rochip.com> wrote:
>
> Yo,
>
> On Thu, Nov 23, 2023 at 04:38:37PM +0900, Masahiro Yamada wrote:
> > On Thu, Nov 23, 2023 at 7:12 AM Rob Herring <robh@...nel.org> wrote:
> > >
> > > This series adds support to set the dtc extra warning level on a per
> > > arch or per platform (directory really) basis.
> > >
> > > The first version of this was just a simple per directory override for
> > > Samsung platforms, but Conor asked to be able to do this for all of
> > > riscv.
> > >
> > > For merging, either I can take the whole thing or the riscv and samsung
> > > patches can go via their normal trees. The added variable will have no
> > > effect until merged with patch 2.
> > >
> > > v1:
> > >  - https://lore.kernel.org/all/20231116211739.3228239-1-robh@kernel.org/
> > >
> > > Signed-off-by: Rob Herring <robh@...nel.org>
> > > ---
> >
> >
> > There were some attempts in the past to enable W=1 in particular subsystems,
> > so here is a similar comment.
> >
> > Adding a new warning flag to W=1 is always safe without doing any compile test.
> >
> > With this series, it would not be true any more because a new warning in W=1
> > would potentially break riscv/samsung platforms.
>
> We carry a copy of the dtc in scripts/dtc, so I would expect that before
> an upgrade is done that would introduce new warnings we can fix them in
> the relevant platforms.


It might be easy to fix up only riscv and samsung platforms.

If more and more platforms add KBUILD_EXTRA_WARN=1 in their Makefiles,
it will become harder to sort them out before adding a new warning flag.


The sync of scripts/dtc will be delayed until then, or
you will end up with demoting them (i.e. delete KBUILD_EXTRA_WARN=1).



> Perhaps I am misunderstanding something there,
> but I'm sure Rob can clear it up if I made a mistake.
>
> > Linus requires a clean build (i.e. zero warning) when W= option is not given.
>
> For RISC-V at least, there are currently no W=1 warnings while building
> the dtbs (because I put effort into fixing them all) and I would like to
> keep it that way, so that requirement is not a concern.
>
> Cheers,
> Conor.
>


-- 
Best Regards
Masahiro Yamada