K 10
svn:author
V 6
marcel
K 8
svn:date
V 27
2012-06-30T18:56:08.587781Z
K 7
svn:log
V 1029
Create zones for busdma_tag, busdma_md and busdma_md_seg structures.
In particular, this is driven by not wanting to create a single blob
comprising the busdma_md and all its busdma_md_seg structures:
1.  the number of segments is an upper bound that is very rarely
    reached. Pre-allocating them means we're wasting a lot of memory.
2.  The allocation size for these structures combined can vary per
    tag, which isn't always good.
3.  During load operations we may need to keep track of more than the
    maximum number of segments. In particular this can happen before
    we've gone through I/O MMU mappings and/or bounce buffers.

Now we can create segment structures when needed for busdma allocs
and we can reserve some amount of segment structures and keep them
in a pool when an unused busdma_md structure is allocated for use
by the load functions later.

For now, put the segment structures in a TAILQ and put the index in
the structure. This probably changes over time when the whole logic
of loading solidifies.

END