Messages in this thread |  | | Date | Wed, 6 Feb 2013 20:51:26 +0100 | Subject | Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be) | From | Geert Uytterhoeven <> |
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On Wed, Feb 6, 2013 at 6:40 PM, Michal Simek <monstr@monstr.eu> wrote: > One question regarding to asm-generic/io.h about iowrite16be implementation > > #define iowrite16be(v, addr) iowrite16(be16_to_cpu(v), (addr)) > #define iowrite16(v, addr) writew((v), (addr)) > #define writew(b,addr) __raw_writew(__cpu_to_le16(b),addr) > > static inline void __raw_writew(u16 b, volatile void __iomem *addr) > { > *(volatile u16 __force *) addr = b; > } > > How is this suppose to work on Big Endian? > be16_to_cpu(v) is (v) > and > __cpu_to_le16(b) is swab16(v)
Yes.
> On little > be16_to_cpu(v) is swab16(v)
Yes.
> and > __cpu_to_le16(swab(b)) is swab16(v)
???
Don't you mean "__cpu_to_le16(b) is (b)"?
> What I would expect is > #define iowrite16be(v, addr) __raw_writew(__cpu_to_be16(v), addr)
Indeed, it should be "__cpu_to_be16(v)" instead of "be16_to_cpu(v)".
Same for iowrite32be().
> on Big endian: > __cpu_to_be16(v) is (v) > on Little endian: > __cpu_to_be16(v) is swab(v) > > What am I missing here?
But as both conversions are identical (just swapping 2 bytes), It Just Works.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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