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

From: Masahiro Yamada <masahiroy@kernel.org>
To: Conor Dooley <conor.dooley@microchip.com>
Cc: Rob Herring <robh@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Nicolas Schier <nicolas@fjasle.eu>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
	Alim Akhtar <alim.akhtar@samsung.com>,
	Conor Dooley <conor@kernel.org>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org,
	devicetree@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org
Subject: Re: [PATCH v2 0/4] kbuild: Per arch/platform dtc warning levels
Date: Thu, 23 Nov 2023 21:00:58 +0900	[thread overview]
Message-ID: <CAK7LNAQ6e9=RtCJYSof8NwOD2npoKNRN-Fo8GBLvYS0sz5DsqQ@mail.gmail.com> (raw)
In-Reply-To: <20231123-deviator-camisole-645715ad02e9@wendy>

On Thu, Nov 23, 2023 at 6:44 PM Conor Dooley <conor.dooley@microchip.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@kernel.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@kernel.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