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_BUGVERBOSEThis 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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