Re: [RFC][PATCH] compat_uint64_t type

[Patrick McHardy <kaber@trash.net>]

Dmitry Mishin wrote:
> This patch introduces compat_uint64_t type, which is required for proper 
> handling different alignment of structures, containing u64 objects, on 
> compatible with ia32 64bit platforms and others.
> 

> diff --git a/include/asm-ia64/compat.h b/include/asm-ia64/compat.h
> index 40d01d8..3e6417b 100644
> --- a/include/asm-ia64/compat.h
> +++ b/include/asm-ia64/compat.h
> @@ -34,6 +34,8 @@ typedef s32		compat_long_t;
>  typedef u32		compat_uint_t;
>  typedef u32		compat_ulong_t;
>  
> +typedef u64 __attribute__((aligned(4)))	compat_uint64_t;
> +
>  struct compat_timespec {
>  	compat_time_t	tv_sec;
>  	s32		tv_nsec;

I'm not sure if we should really introduce this new type, it is
misleading for at least x86. IIRC the situation there is:

- gcc < 4.0 always aligns u64 types to 4byte
- gcc >= 4.0 aligns basic u64 types to 8byte, u64's embedded in
  structures to 4 byte

So there is no one compat_uint64_t type, but it depends on the
situation.