linux-kernel - Re: [PATCH 1/4] LOG2: Implement a general integer log2 facility in the kernel [try #4]

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Date:	Mon, 9 Oct 2006 05:51:14 -0400
From:	Kyle Moffett <mrmacman_g4@....com>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
Cc:	David Howells <dhowells@...hat.com>,
	Matthew Wilcox <matthew@....cx>, torvalds@...l.org,
	akpm@...l.org, sfr@...b.auug.org.au, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH 1/4] LOG2: Implement a general integer log2 facility in the kernel [try #4]

On Oct 09, 2006, at 04:36:12, Jan Engelhardt wrote:i
>>>> Were you planning on porting Linux to a machine with non-8-bit- 
>>>> bytes any
>>>> time soon?  Because there's a lot more to fix than this.
>>>
>>> I am considering the case [assuming 8-bit-byte machines] where
>>> sizeof(u32) is not 4. Though I suppose GCC will probably make a  
>>> 32-bit
>>> type up if the hardware does not know one.
>>
>> If the machine has 8-bit bytes, how can sizeof(u32) be anything  
>> other than 4?
>
> 	typedef unsigned int u32;
>
> Though this should not be seen in the linux kernel.

Well, uhh, actually...

All presently-supported architectures do exactly that.  Well, some do:

   typedef unsigned int __u32;
   #ifdef __KERNEL__
   typedef __u32 u32;
   #endif

It might be possible to clean up the types.h files a bit with  
something like the following in linux/types.h (nearly identical code  
is found in all of the asm-*/types.h files):

   typedef unsigned char  __u8;
   typedef   signed char  __s8;
   typedef unsigned short __u16;
   typedef   signed short __s16;
   typedef unsigned int   __u32;
   typedef   signed int   __s32;
   #if defined(CONFIG_ARCH_HAS_64BIT_WORD)
   typedef unsigned long  __u64;
   typedef   signed long  __s64;
   #elif defined(__GNUC__)
   __extension__ typedef unsigned long long __u64;
   __extension__ typedef   signed long long __s64;
   #endif

   #ifdef __KERNEL__
   typedef __u8  u8;
   typedef __s8  s8;
   typedef __u16 u16;
   typedef __s16 s16;
   typedef __u32 u32;
   typedef __s32 s32;
   typedef __u64 u64;
   typedef __s64 s64;
   #endif

With that you could delete ~30 lines from each of the various asm-*/ 
types.h files in exchange for 3 lines in each of the various arch/*/ 
Kconfig files.

I'll try to whip up a quick patch later today if I get the time.

Cheers,
Kyle Moffett

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