Re: [kvm-unit-tests PATCH v2 01/10] asm-generic: add portio accessors to io.h

["Radim Krčmář" <rkrcmar@redhat.com>]

2016-01-15 17:51+0100, Andrew Jones:
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
> diff --git a/lib/asm-generic/io.h b/lib/asm-generic/io.h
> @@ -152,6 +152,58 @@ static inline u64 __bswap64(u64 x)
> +#ifndef PCI_IOBASE
> +#define PCI_IOBASE ((void *)0)
> +#endif
> +
> +#ifndef inb
> +#define inb inb

(I consider this repeated pattern to be very ugly, even by C standards.)

> +static inline u8 inb(unsigned long addr)
> +{
> +	return readb(PCI_IOBASE + addr);
> +}

My first reaction was "throw this abomination out!", but Drew explained
that in*/out* is here because we'll also generalize the x86 PCI code
(which uses PIO and MMIO) and that Linux has the same code.

arm, arm64, and unicore32 define PCI_IOBASE in Linux.  I didn't figure
out why they want to use a PIO based abstraction for MMIO, so the
interface is fine with me as long as
 - functions are hidden behind a single #ifndef, like ARCH_HAS_PORT_IO.
   (Ideally defined as part of global configuration, because it's harder
    to fail that way.)
 - "unsigned long addr" is changed to "u16 port";
   x86 ought to have that and we should use different names if we need
   different types, because behavior couldn't be the same then.