On Thu, Apr 10, 2008 at 05:06:34PM -0700, Harvey Harrison wrote:
> +#define __get_unaligned_cpu(ptr) ({ \
> + const void *__gu_p = (ptr); \
> + typeof(*(ptr)) __val; \
> + switch (sizeof(*(ptr))) { \
> + case 1: \
> + __val = *(const u8 *)__gu_p; \
> + break; \
> + case 2: \
> + __val = __get_unaligned_cpu16(__gu_p); \
> + break; \
> + case 4: \
> + __val = __get_unaligned_cpu32(__gu_p); \
> + break; \
> + case 8: \
> + __val = __get_unaligned_cpu64(__gu_p); \
> + break; \
> + default: \
> + BUILD_BUG_ON(1); \
> + break; \
> + }; \
> + __val; })
This won't work - on ARM we used to use this style, but it fails in
some corner case, so we ended up switching to using GCC's
__builtin_choose_expr() instead.
Such a corner case:
static unsigned long foo(const unsigned long *ptr)
{
return __get_unaligned_cpu(ptr);
}
This results in '__val' being declared as const, and therefore the
compiler errors out in the switch statement since the code tries to
assign to a const '__val'.
See 17b602b1c1a38f3f0a4461bb1f571346e751b36b.
So, for the present set of patches, NAK for changing ARM.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
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