cvs commit: src/share/man/man9 bus_dma.9

[Justin T. Gibbs]

> mux         2003/06/13 13:07:49 PDT
> 
>   FreeBSD src repository
> 
>   Modified files:
>     share/man/man9       bus_dma.9 
>   Log:
>   - Document the fact that you can specify several DMA operations to
>     bus_dmamap_sync() by OR'ing them together.
>   - Don't document what BUS_DMASYNC_PREREAD|BUS_DMASYNC_PREWRITE and
>     BUS_DMASYNC_POSTREAD|BUS_DMASYNC_POSTWRITE is supposed to do when
>     passed to bus_dmamap_sync().  There are other possible combinations
>     and the reader just needs to know what the individual flags do and
>     that he can combine different DMA operations.

I purposely documented the only combinations that make sense.  This
would also allow us to change back to using an enum in the future
since the combinations are limited just by changing the names of the
operations.  It simply does not make sense to combine pre and post sync
ops since doing so implies that you will lose data if your buffers are
being bounced.  In other words, any update from the CPU that you expect
your device to see must occur after you have POST'ed any PRE'ed operation
so that the buffer contents updated by the CPU are synced.

--
Justin