Re: Linux 6.3-rc3

From: Nick Desaulniers <ndesaulniers@google.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	Masahiro Yamada <masahiroy@kernel.org>
Cc: sedat.dilek@gmail.com, Kalle Valo <kvalo@kernel.org>,
	Nathan Chancellor <nathan@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
	dri-devel@lists.freedesktop.org,
	linux-toolchains@vger.kernel.org, llvm@lists.linux.dev,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>
Subject: Re: Linux 6.3-rc3
Date: Wed, 22 Mar 2023 11:17:35 -0700	[thread overview]
Message-ID: <CAKwvOdm1VpSSxN9zPVdEuDcyq2z2quQ1-qAQ5H+Q4y2xp1Focg@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=whdrvCkSWh=BRrwZwNo3=yLBXXM88NGx8VEpP1VTgmkyQ@mail.gmail.com>

+ Masahiro and linux-kbuild for the proposal

On Wed, Mar 22, 2023 at 9:56 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Wed, Mar 22, 2023 at 9:40 AM Sedat Dilek <sedat.dilek@gmail.com> wrote:
> >
> > You have to pass `make LLVM=1` in any case... to `oldconfig` or when
> > adding any MAKEFLAGS like -j${number-of-available-cpus}.
>
> I actually think we should look (again) at just making the compiler
> choice (and the prefix) be a Kconfig option.
>
> That would simplify *so* many use cases.
>
> It used to be that gcc was "THE compiler" and anything else was just
> an odd toy special case, but that's clearly not true any more.

<3

>
> So it would be lovely to make the kernel choice a Kconfig choice - so
> you'd set it only at config time, and then after that a kernel build
> wouldn't need special flags any more, and you'd never need to play
> games with GNUmakefile or anything like that.
>
> Yes, you'd still use environment variables (or make arguments) for
> that initial Kconfig, but that's no different from the other
> environment variables we already have, like KCONFIG_SEED that kconfig
> uses internally, but also things like "$(ARCH)" that we already use
> *inside* the Kconfig files themselves.
>
> I really dislike how you have to set ARCH and CROSS_COMPILE etc
> externally, and can't just have them *in* the config file.

Not needing CROSS_COMPILE for LLVM=1 has been great. ;)

(Still need it for ARCH=s390 until LLD gets s390 support though)

>
> So when you do cross-compiles, right now you have to do something like
>
>     make ARCH=i386 allmodconfig
>
> to build the .config file, but then you have to *repeat* that
> ARCH=i386 when you actually build things:
>
>     make ARCH=i386
>
> because the ARCH choice ends up being in the .config file, but the
> makefiles themselves always take it from the environment.
>
> There are good historical reasons for our behavior (and probably a
> number of extant practical reasons too), but it's a bit annoying, and
> it would be lovely if we could start moving away from this model.
>
>             Linus
>

-- 
Thanks,
~Nick Desaulniers