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 14:40:09 +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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On Fri, 6 May 2022, Geert Uytterhoeven wrote:
> A loooong time ago, it was suggested to add register accessor
> functions to struct device, so e.g. readl(dev, offset) would call
> into these accessors, which would implement the bus-specific behavior.
> No more worries about readl(), __raw_readl(), ioread32b(), or whatever
> quirk is needed, at the (small on nowadays' machines) expense of
> some indirection...
I guess you'd need an additional parameter for the endianness policy
required (to match either bit or byte lanes, according to ultimate data
interpretation) where crossing between buses of a different endianness
each. Otherwise you'd end up with the mess elsewhere.
Maciej
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