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

Russell King
2006-02-01T19:19:57Z

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 *.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core