Re: [PATCH 03/19] LoongArch: Add build infrastructure

From: Arnd Bergmann <arnd@kernel.org>
To: Huacai Chen <chenhuacai@gmail.com>
Cc: Huacai Chen <chenhuacai@loongson.cn>,
	Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Airlie <airlied@linux.ie>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Xuefeng Li <lixuefeng@loongson.cn>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH 03/19] LoongArch: Add build infrastructure
Date: Mon, 19 Jul 2021 09:43:21 +0200	[thread overview]
Message-ID: <CAK8P3a1kX_wHz_BpdD=pB-Fd2Cy3_xDvTsRKVvKR+_9GP0NSmA@mail.gmail.com> (raw)
In-Reply-To: <CAAhV-H796UQNaRkiaJhYRHsO-36KE_5d6sT=sJaKXCKfHtP-Mg@mail.gmail.com>

On Mon, Jul 19, 2021 at 3:26 AM Huacai Chen <chenhuacai@gmail.com> wrote:
> On Tue, Jul 6, 2021 at 6:12 PM Arnd Bergmann <arnd@kernel.org> wrote:
> >  Tue, Jul 6, 2021 at 6:18 AM Huacai Chen <chenhuacai@loongson.cn> wrote:
> > > --- /dev/null
> > > +++ b/arch/loongarch/Kbuild
> > > @@ -0,0 +1,21 @@
> > > +# Fail on warnings - also for files referenced in subdirs
> > > +# -Werror can be disabled for specific files using:
> > > +# CFLAGS_<file.o> := -Wno-error
> > > +ifeq ($(W),)
> > > +subdir-ccflags-y := -Werror
> > > +endif
> >
> > This tends to break building with 'make W=12' or similar, I would recommend not
> > adding -Werror. It is a good idea though to have your CI systems build
> > with -Werror
> > enabled on the command line though.
> If we use W=???, corresponding flags will be used; if we don't use
> W=???, -Werrer flag is used here. So it seems not break the building.

The thing is that we get three new compiler releases every year, one gcc
and two llvm. Usually every release introduces new warnings, so even if
you quickly address those in mainline kernels, anyone using an older kernel
will find themselves unable to build it with a newer compiler.

> > > +       select ARCH_MIGHT_HAVE_PC_PARPORT
> > > +       select ARCH_MIGHT_HAVE_PC_SERIO
> > > +       select GENERIC_ISA_DMA
> > > +       select ISA
> >
> > Do you actually have ISA-style add-on cards? If not, then
> > remove the ISA options. If you do, which drivers are they?
> Yes, there is an LPC controller in LS7A, and superio is connected on
> it for laptops.

CONFIG_ISA only refers to actual 16-bit add-on cards, not LPC
style on-board devices. Sometimes the options are used inconsistently,
but unless you need an original Soundblaster or NE2000 card, this
should not be needed. Note that some older x86-64 and arm64 have
LPC as well, but do not support CONFIG_ISA.

For GENERIC_ISA_DMA, I suppose that could be used for the parallel
port driver, but even if you have one of those, it might be easier to leave
it out and just no longer support Zip drives or dot matrix printers attached
to them.

ARCH_MIGHT_HAVE_PC_SERIO is probably needed if this is how
you attach your keyboard and trackball, but it should work without the
others.

       Arnd