Re: [RFC 02/32] Kconfig: introduce HAS_IOPORT option and select it as necessary

[Michael Schmitz]

Hi Geert, Niklas,



Am 28.12.2021 um 23:08 schrieb Geert Uytterhoeven:
> Hi Niklas,
>
> On Mon, Dec 27, 2021 at 5:44 PM Niklas Schnelle <schnelle@xxxxxxxxxxxxx> wrote:
> > We introduce a new HAS_IOPORT Kconfig option to gate 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. On these platforms
> > inb()/outb() etc are currently just stubs in asm-generic/io.h which when
> > called will cause a NULL pointer access which some compilers actually
> > detect and warn about.
> >
> > The dependencies 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. Then a final patch will ifdef the I/O access
> > functions on HAS_IOPORT thus turning any use not gated by HAS_IOPORT
> > into a compile-time warning.
> >
> > Link: https://lore.kernel.org/lkml/CAHk-=wg80je=K7madF4e7WrRNp37e3qh6y10Svhdc7O8SZ_-8g@xxxxxxxxxxxxxx/
> > Co-developed-by: Arnd Bergmann <arnd@xxxxxxxxxx>
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxxxx>
> > Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
>
> Thanks for your patch!
>
> > --- a/arch/m68k/Kconfig
> > +++ b/arch/m68k/Kconfig
> > @@ -16,6 +16,7 @@ config M68K
> >         select GENERIC_CPU_DEVICES
> >         select GENERIC_IOMAP
> >         select GENERIC_IRQ_SHOW
> > +       select HAS_IOPORT
> >         select HAVE_AOUT if MMU
> >         select HAVE_ASM_MODVERSIONS
> >         select HAVE_DEBUG_BUGVERBOSE
>
> This looks way too broad to me: most m68k platform do not have I/O
> port access support.
>
> My gut feeling says:
>
>     select HAS_IOPORT if PCI || ISA
>
> but that might miss some intricate details...

In particular, this misses the Atari ROM port ISA adapter case -

	select HAS_IOPORT if PCI || ISA || ATARI_ROM_ISA

might do instead.

Cheers,

	Michael


> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds