Re: [PATCH 1/2] Make cramfs little endian only

["Jörn Engel" <joern@logfs.org>]

On Thu, 6 December 2007 17:27:26 +0100, Andi Drebes wrote:
> [...]
> > 	static inline u32 cramfs_offset(struct cramfs_inode *inode)
> > 	{
> > 		return le32_to_cpu(node->namelen_offset) >> CRAMFS_NAMELEN_WIDTH;
> > 	}
> This requires changing the on-disk-structure (even the current "little endian only" one).
> The problem is caused by the way GCC (and perhaps other compilers aswell) arranges
> the 6 bits bits for the namelength and the 26 bits for the offset within the 32 bits.
> I spent quite some time on figuring out how this is actually done. For little endian
> machines, the data arranged in the following way:
> 
> |o02.o01.n06.n05.n04.n03.n02.n01|o10.o09.o08.o07.o06.o05.o04.o03|
> |o18.o17.o16.o15.o14.o13.o12.o11|o26.o25.o24.o23.o22.o21.o20.o19| 

How about shifting and masking _before_ converting to host endianness?

	static inline u32 cramfs_offset(struct cramfs_inode *inode)
	{
		return le32_to_cpu(node->namelen_offset >> CRAMFS_NAMELEN_WIDTH);
	}

Jörn

-- 
With a PC, I always felt limited by the software available. On Unix,
I am limited only by my knowledge.
-- Peter J. Schoenster
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