Re: [PATCH v3 01/38] Kconfig: introduce HAS_IOPORT option and select it as necessary

From: Niklas Schnelle <schnelle@linux.ibm.com>
To: Arnd Bergmann <arnd@arndb.de>,
	Richard Henderson <richard.henderson@linaro.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	Matt Turner <mattst88@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Michal Simek <monstr@monstr.eu>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	"James E . J . Bottomley" <James.Bottomley@HansenPartnership.com>,
	Helge Deller <deller@gmx.de>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Nicholas Piggin <npiggin@gmail.com>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
	John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
	"David S . Miller" <davem@davemloft.net>,
	Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Alan Stern" <stern@rowland.harvard.edu>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	linux-kernel@vger.kernel.org,
	Linux-Arch <linux-arch@vger.kernel.org>,
	linux-pci@vger.kernel.org, "Arnd Bergmann" <arnd@kernel.org>,
	linux-alpha@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org,
	linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org,
	sparclinux@vger.kernel.org, linux-um@lists.infradead.org
Subject: Re: [PATCH v3 01/38] Kconfig: introduce HAS_IOPORT option and select it as necessary
Date: Tue, 14 Mar 2023 17:11:40 +0100	[thread overview]
Message-ID: <c524798dd2039e5b2b0f0f964b927ced65070377.camel@linux.ibm.com> (raw)
In-Reply-To: <f8bdc245-38b0-4973-bd01-34f594a0ede4@app.fastmail.com>

On Tue, 2023-03-14 at 14:29 +0100, Arnd Bergmann wrote:
> On Tue, Mar 14, 2023, at 13:11, Niklas Schnelle wrote:
> > We introduce a new HAS_IOPORT Kconfig option to indicate support for I/O
> > Port access. In a future patch HAS_IOPORT=n will disable compilation of
> > the I/O accessor functions inb()/outb() and friends on architectures
> > which can not meaningfully support legacy I/O spaces such as s390. Also
> > add dependencies on HAS_IOPORT for the ISA and HAVE_EISA config options
> > as these busses always go along with HAS_IOPORT.
> > 
> > The "depends on" relations on HAS_IOPORT in drivers as well as ifdefs
> > for HAS_IOPORT specific sections will be added in subsequent patches on
> > a per subsystem basis.
> 
> I think it would be helpful to enumerate which architectures
> do not get HAS_IOPORT added, as they will be affected more.
> 
> > Co-developed-by: Arnd Bergmann <arnd@kernel.org>
> > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> 
> If there are no objections, I could send this first patch for the
> asm-generic tree as a preparation for 6.3, so we are able to merge
> the other patches through subsystem maintainer tree for 6.4.
> 
> arch/loongarch/ will now also need to select HAS_IOPORT
> uncontitionally, this architecture was added after you
> sent v2.

Ah right. Added "select HAS_IOPORT" for LoongArch.

> 
> > diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
> > index a98940e64243..5eeacc72e4da 100644
> > --- a/arch/parisc/Kconfig
> > +++ b/arch/parisc/Kconfig
> > @@ -47,6 +47,7 @@ config PARISC
> >  	select MODULES_USE_ELF_RELA
> >  	select CLONE_BACKWARDS
> >  	select TTY # Needed for pdc_cons.c
> > +	select HAS_IOPORT if PCI
> 
> It's also needed for EISA and I think you should select it
> from CONFIG_GSC in drivers/parisc/Kconfig for this purpose.
> 
> This could also be 'select HAS_IOPORT if PCI || EISA', but
> that would require removing the 'depends on HAS_IOPORT'
> under drivers/eisa/.

I did use "select HAS_IOPORT if PCI || ISA || ATARI_ROM_ISA" in m68k so
I think ideally we would handle both in the same way. I don't have a
strong preference but I think the "select HAS_IOPORT if ..." puts it
all in a single place which is nice. Also I think this would make it
more similar architectures with unconditional HAS_IOPORT that thus
don't need "depends on HAS_IOPORT" in their "config ISA" either. As
also pointed by your comment below for x86. So will try to go this
route.

> 
> >  	select HAVE_DEBUG_STACKOVERFLOW
> >  	select HAVE_ARCH_AUDITSYSCALL
> >  	select HAVE_ARCH_HASH
> > @@ -131,6 +132,7 @@ config STACKTRACE_SUPPORT
> > 
> >  config ISA_DMA_API
> >  	bool
> > +	depends on HAS_IOPORT
> > 
> 
> This line is not really needed since there is no way to
> enable ISA_DMA_API.

Removed

> 
> > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > index a6c4407d3ec8..f7de646c074a 100644
> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -188,6 +188,7 @@ config PPC
> >  	select GENERIC_SMP_IDLE_THREAD
> >  	select GENERIC_TIME_VSYSCALL
> >  	select GENERIC_VDSO_TIME_NS
> > +	select HAS_IOPORT			if PCI
> >  	select HAVE_ARCH_AUDITSYSCALL
> >  	select HAVE_ARCH_HUGE_VMALLOC		if HAVE_ARCH_HUGE_VMAP
> >  	select HAVE_ARCH_HUGE_VMAP		if PPC_RADIX_MMU || PPC_8xx
> > @@ -1070,7 +1071,6 @@ menu "Bus options"
> > 
> >  config ISA
> >  	bool "Support for ISA-bus hardware"
> > -	depends on PPC_CHRP
> >  	select PPC_I8259
> >  	help
> >  	  Find out whether you have ISA slots on your motherboard.  ISA is the
> 
> This line looks wrong, I think we should keep that dependency.
> Did you get a circular dependency if you leave it in?

I don't recall why this was removed. I guess it happened when I was
experimenting with adding "depends on HAS_IOPORT" for the ISA config
options but that ultimately lead to circular dependencies, must have
messed up when removing this here.

> 
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index a825bf031f49..634dd42532f3 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -162,6 +162,7 @@ config X86
> >  	select GUP_GET_PXX_LOW_HIGH		if X86_PAE
> >  	select HARDIRQS_SW_RESEND
> >  	select HARDLOCKUP_CHECK_TIMESTAMP	if X86_64
> > +	select HAS_IOPORT
> >  	select HAVE_ACPI_APEI			if ACPI
> >  	select HAVE_ACPI_APEI_NMI		if ACPI
> >  	select HAVE_ALIGNED_STRUCT_PAGE		if SLUB
> > @@ -2893,6 +2894,7 @@ if X86_32
> > 
> >  config ISA
> >  	bool "ISA support"
> > +	depends on HAS_IOPORT
> >  	help
> 
> HAS_IOPORT is selected unconditionally already, so this doesn't
> really do anything.

Removed.

> 
> > diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb
> > index 3b9a44008433..c68e4d9dcecb 100644
> > --- a/lib/Kconfig.kgdb
> > +++ b/lib/Kconfig.kgdb
> > @@ -121,7 +121,8 @@ config KDB_DEFAULT_ENABLE
> > 
> >  config KDB_KEYBOARD
> >  	bool "KGDB_KDB: keyboard as input device"
> > -	depends on VT && KGDB_KDB && !PARISC
> > +	depends on HAS_IOPORT
> > +	depends on VT && KGDB_KDB
> >  	default n
> 
> This loses the !PARISC dependency, which I don't think is
> intentional. The added HAS_IOPORT dependency makes sense
> here, but I think this should be in a different patch
> and not in the preparation.
> 
>     Arnd

Agree will put into its own patch and re-add the !PARISC