Re: [PATCH] Big-endian reading/writing cramfs (vs 2.4.10)

[Andreas Dilger]

On Sep 28, 2001  15:54 -0700, Brad Bozarth wrote:
> > On Sep 28, 2001  14:58 -0700, Brad wrote:
> > > +#define CRAM_SWAB_16(x)	( ( (0x0000FF00 & (x)) >> 8   ) | \
> > > +			  ( (0x000000FF & (x)) << 8 ) )
> >
> > Why not just use the well-defined le16_to_cpu() and le32_to_cpu() macros?
> 
> I did, originally... And it worked in inode.c, but I couldn't get mkcramfs
> to compile using those macros.  It's outside of __KERNEL__ so I tried
> using __cpu_to_le32.  The following error occurred:

I didn't realize that the header was also used in user-space.  I would
still use the le32_to_cpu() style macros in the code, but only define
macros of your own if the kernel ones were not defined, using either
#ifndef __KERNEL__ or #ifndef le32_to_cpu, or both.

This way, you get the benefit of the fast asm-based instructions in
the kernel, and you only use the slow ones in user-space (mkcramfs)
where you don't really care.

Cheers, Andreas
--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert