svn commit: r208850 - projects/ppc64/sys/powerpc/include

[M. Warner Losh]

In message: <184A275D-B98A-4DBF-9F4D-22F27B9319DD at mac.com>
            Marcel Moolenaar <xcllnt at mac.com> writes:
: 
: On Jun 5, 2010, at 1:41 PM, Nathan Whitehorn wrote:
: 
: > Author: nwhitehorn
: > Date: Sat Jun  5 20:41:22 2010
: > New Revision: 208850
: > URL: http://svn.freebsd.org/changeset/base/208850
: > 
: > Log:
: >  BUS_SPACE_UNRESTRICTED is a flag, not an address, so it should be an int,
: >  not a long.
: 
: This probably isn't right. How would you distinguish between a 32-bit
: maximum of and unlimited if both can have the value 0xFFFFFFFF.
: Making BUS_SPACE_UNRESTRICTED a long prevents zero-extension to 64-bit
: and thus prevents this ambiguity.

But this define is used for busdma's number of segments.  It isn't
used for an address at all...

from the busdma man page for bus_dma_tag_create:
             nsegments    Number of discontinuities (scatter/gather segments)
                          allowed in a DMA mapped region.  If there is no
                          restriction, BUS_SPACE_UNRESTRICTED may be speci-
                          fied.

so an argument consistent with the definition of nsegments is what is
needed.  The man page doesn't specify a type for nsegments, but
sys/bus_dma.h defines it as:

int bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
		       bus_size_t boundary, bus_addr_t lowaddr,
		       bus_addr_t highaddr, bus_dma_filter_t *filtfunc,
		       void *filtfuncarg, bus_size_t maxsize, int nsegments,
		       bus_size_t maxsegsz, int flags, bus_dma_lock_t *lockfunc,
		       void *lockfuncarg, bus_dma_tag_t *dmat);

so it is more proper to have it be an int than a long.

I got tripped up on this stupid name too when I was adding it for
MIPS.  Any why it is in a MD file instead of an MI file is beyond me.
I think it should be defined in sys/bus_dma.h, but maybe I'm just nuts...

Warner