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

Andreas Dilger
2001-09-28T23:18:10Z

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