On Sun, Jun 26, 2005 at 12:41:11PM +0200, Martin Husemann wrote:
> On Sat, Jun 25, 2005 at 03:31:57PM -0700, Jason Thorpe wrote:
> > We could add this sort of capability, I guess... but it would require  
> > all of the back-ends to implement all of the bounce buffering  
> > capability... and for what?  For a single broken device?
> 
> If we could lazy-implement them, I guess we'd be done with i386 and maybe
> amd64 for quite some time.
> 
> Like, say, have a few __BUSDMA_HAS.... macros in ctypes.h and make drivers
> that need those features #error with a good message if they are compiled on
> an arch that doesn't have it.

	That's overly restrictive.  If the machine you're running on has
less memory than the cutoff point for that device then it should still
work even without bounce buffers.  A better option might be to have
the driver check at attach time if any busdma memory it got allocated
is within the right range.

eric