Messages in this thread | | | Subject | Re: [RFC 02/32] Kconfig: introduce HAS_IOPORT option and select it as necessary | From | Michael Schmitz <> | Date | Wed, 29 Dec 2021 17:15:23 +1300 |
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Hi Arnd,
Am 29.12.2021 um 16:41 schrieb Arnd Bergmann: > On Tue, Dec 28, 2021 at 8:20 PM Michael Schmitz <schmitzmic@gmail.com> wrote: >> Am 28.12.2021 um 23:08 schrieb Geert Uytterhoeven: >>> On Mon, Dec 27, 2021 at 5:44 PM Niklas Schnelle <schnelle@linux.ibm.com> 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@mail.gmail.com/ >>>> Co-developed-by: Arnd Bergmann <arnd@kernel.org> >>>> Signed-off-by: Arnd Bergmann <arnd@kernel.org> >>>> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> >>> >>> 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. > > Right, makes sense. I had suggested to go the easy way and assume that > each architecture would select HAS_IOPORT if any configuration supports > it, but it looks like for m68k there is a clearly defined set of platforms that > do. > > Note that for the platforms that don't set any of the three symbols, the > fallback makes inb() an alias for readb() with a different argument type, > so there may be m68k specific drivers that rely on this, but those would > already be broken if ATARI_ROM_ISA is set.
I'd hope not - we spent some effort to make sure setting ATARI_ROM_ISA does not affect other m68k platforms when e.g. building multiplatform kernels.
Replacing inb() by readb() without any address translation won't do much good for m68k though - addresses in the traditional ISA I/O port range would hit the (unmapped) zero page.
Cheers,
Michael
> > Arnd >
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