Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary
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- To: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
- Subject: Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary
- From: "Maciej W. Rozycki" <macro@xxxxxxxxxxx>
- Date: Fri, 6 May 2022 16:03:14 +0100 (BST)
- Cc: David Laight <David.Laight@xxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxxxx>, Rich Felker <dalias@xxxxxxxx>, "open list:IA64 (Itanium) PLATFORM" <linux-ia64@xxxxxxxxxxxxxxx>, "open list:SUPERH" <linux-sh@xxxxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "open list:MIPS" <linux-mips@xxxxxxxxxxxxxxx>, "James E.J. Bottomley" <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>, "open list:SPARC + UltraSPARC (sparc/sparc64)" <sparclinux@xxxxxxxxxxxxxxx>, "open list:RISC-V ARCHITECTURE" <linux-riscv@xxxxxxxxxxxxxxxxxxx>, Will Deacon <will@xxxxxxxxxx>, linux-arch <linux-arch@xxxxxxxxxxxxxxx>, Yoshinori Sato <ysato@xxxxxxxxxxxxx>, Helge Deller <deller@xxxxxx>, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@xxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, linux-pci <linux-pci@xxxxxxxxxxxxxxx>, Bjorn Helgaas <helgaas@xxxxxxxxxx>, Matt Turner <mattst88@xxxxxxxxx>, Albert Ou <aou@xxxxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Niklas Schnelle <schnelle@xxxxxxxxxxxxx>, "open list:M68K ARCHITECTURE" <linux-m68k@xxxxxxxxxxxxxxx>, Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, "moderated list:ARM PORT" <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>, Richard Henderson <rth@xxxxxxxxxxxxxxx>, Michal Simek <monstr@xxxxxxxxx>, Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>, "open list:PARISC ARCHITECTURE" <linux-parisc@xxxxxxxxxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, "open list:ALPHA PORT" <linux-alpha@xxxxxxxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" <linuxppc-dev@xxxxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>
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Hi Geert,
> > Sane access would require a single CPU instruction to read or write from
> > the configuration space. To access the conventional PCI configuration
> > space in a direct linear manner you need 256 * 21 * 8 * 256 = 10.5MiB of
> > address space. Such amount of address space seems affordable even with
> > 32-bit systems.
>
> Won't have fit in the legacy 1 MiB space ("640 KiB...").
Haha, but anyway you're supposed to use BIOS calls under DOS and the like
so it doesn't really matter. You can't poke at the APIC in the legacy
space either.
Maciej
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