Re: [PATCH 1/12] generic *_bit()

Geert Uytterhoeven
2006-02-03T10:24:30Z

On Wed, 1 Feb 2006, Russell King wrote:
> On Wed, Feb 01, 2006 at 10:07:28AM -0800, Chen, Kenneth W wrote:
> > Christoph Hellwig wrote on Wednesday, February 01, 2006 10:03 AM
> > > > Akinobu Mita wrote on Wednesday, January 25, 2006 7:29 PM
> > > > > This patch introduces the C-language equivalents of the functions below:
> > > > >
> > > > > - atomic operation:
> > > > > void set_bit(int nr, volatile unsigned long *addr);
> > > > > void clear_bit(int nr, volatile unsigned long *addr);
> > > > > void change_bit(int nr, volatile unsigned long *addr);
> > > > > int test_and_set_bit(int nr, volatile unsigned long *addr);
> > > > > int test_and_clear_bit(int nr, volatile unsigned long *addr);
> > > > > int test_and_change_bit(int nr, volatile unsigned long *addr);
> > > >
> > > > I wonder why you did not make these functions take volatile
> > > > unsigned int * address argument?
> > >
> > > Because they are defined to operate on arrays of unsigned long
> >
> > I think these should be defined to operate on arrays of unsigned int.
> > Bit is a bit, no matter how many byte you load (8/16/32/64), you can
> > only operate on just one bit.
>
> Invalid assumption, from the point of view of endianness across different
> architectures. Consider where bit 0 is for a LE and BE unsigned long *
> vs a LE and BE unsigned char *.

Intel doesn't care about big endian (cfr. your lkml back issues of January
2006).

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds