Hi Arnd,
Am 29.12.2021 um 16:41 schrieb Arnd Bergmann:
On Tue, Dec 28, 2021 at 8:20 PM Michael Schmitz <schmitzmic@xxxxxxxxx> wrote:
Am 28.12.2021 um 23:08 schrieb Geert Uytterhoeven:
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.
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
