Re: [RFC v2 01/39] Kconfig: introduce HAS_IOPORT option and select it as necessary
From: "Maciej W. Rozycki" <macro@orcam.me.uk>
Date: 2022-05-06 15:03:32
Also in:
linux-alpha, linux-arch, linux-arm-kernel, linux-m68k, linux-mips, linux-pci, linux-riscv, linux-sh, lkml, sparclinux
Hi Geert,
quoted
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