Hello Gurus,
    I have some questions on DMA mapping.Pls. try to answer them at your
best.
The info I have is ( from man page of bus_dma) :
    BUS_DMASYNC_PREREAD
        Perform any pre-read DMA cache and/or bounce operations.
    BUS_DMASYNC_POSTREAD
        Perform any post-read DMA cache and/or bounce operations.
    BUS_DMASYNC_PREWRITE
        Perform any pre-write DMA cache and/or bounce operations.
    BUS_DMASYNC_POSTWRITE
        Perform any post-write DMA cache and/or bounce operations.
Now can some one explain me
1) Whart is DMA cacheing?
2) What are these bounce operations?
3) When it is used and it's advantages.

,Vikram