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SubjectRe: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be)
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On Thu, Feb 7, 2013 at 8:23 AM, Michal Simek <monstr@monstr.eu> wrote:
>>> #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.
>
> But on native BE system ( I expect that v is in big endian)
> iowrite16be(v, addr) should be just *(volatile u16 __force *) addr =
> v; not *(volatile u16 __force *) addr = swab16(v);

>>> 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)".
>
> What do you mean by that?

Bummer, I missed that current iowrite16be() uses (the little endian)
iowrite16(),
not _raw_writew(), and thought the only difference between the original
and your version was the endianness conversion macro.

Yes,

#define iowrite16be(v, addr) __raw_writew(__cpu_to_be16(v), addr)

should be correct.

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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