On Fri, Jan 12, 2007 at 02:03:37PM +0100, Jachym Holecek wrote:
> # Manuel Bouyer 2007-01-12:
> > On Fri, Jan 12, 2007 at 12:42:15PM +0200, Yorick Hardy wrote:
> > > >Yes. Maybe it should be better to add this as a parameter to
> > > >bus_dmamap_create(), and compute the proper _dm_bounce_thresh at this
> > > >time. But this is a big change in the bus_dma API, and require
> > > >changing a lot of files, unless we keep bus_dmamap_create() as is and
> > > >intruduce a new function with this extra parameter.
> > > >
> > > >  
> > > Is there an advantage to passing by parameter rather than by flag (as in 
> > > my patch) ?
> > 
> > This is a gross hack, a flag is meant as a boolean, not an arbitrary
> > value. And this doesn't handle bus_dmamem
> > 
> > > Obviously my patch limits the address to a power of 2, will this be a 
> > > problem?
> > 
> > And it can't sepcify a minimum address.
> 
> Do we add "bus_addr_t minaddr, bus_addr_t limit" arguments to the affected
> functions, or perhaps "bus_addr_t addrbits" (where only lowest and highest
> bit set are considered)?

I think it really has to be minaddr, maxaddr (i.e. 2 different arguments).
We could create a bus_dmamem_alloc_range() and bus_dmamap_create_range()
if we don't want to change all  bus_dmamem_alloc/bus_dmamap_create calls.
Another interface could be bus_dmamem_alloc_range() and bus_dmamap_set_range()
(to be called after bus_dmamap_create()).

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--