On Wed, Feb 25, 2004 at 11:56:35AM -0500, McGranaghan, Sean wrote:

> 	#define rCTRLREG(b)	(*(b + REG_OFFSET))
> 
> 	vaddr_t b;
> 
> 	b = (vaddr_t) bus_space_vaddr(sc->sc_iot, sc->ioh);
> 	rCTRLREG(b) |= BITMSK;
> 
> Seems preferable to:
> 
> 	u_int32_t value;
> 
> 	value = bus_space_read_4(sc->sc_iot, sc->ioh, REG_OFFSET);
> 	value |= BITMSK;
>       bus_space_write_4(sc->sc_iot, sc->ioh, offset, REG_OFFSET);
> 
> Are these equivalent? Do I need to specify a barrier after my

The bus_space* macros handle such things as endianness,
write buffers, cache flushing, etc.  You should use those
routines whenever possible.

bus_space_vaddr() is only appropriate for things like
accessing on-board framebuffers where you are doing
lots of fancy block move operations where performance
is critical and know you need to handle endiannes and 
cache issues explicitly.

Eduardo