On 10/26/05 01:27 John Baldwin said the following:
On Tuesday 25 October 2005 09:15 am, Dinesh Nair wrote:
(must i malloc space for them before passing them into those functions, or
will the call to bus_dmamem_alloc do it for me ?)
bus_dmamem_alloc() will do it for you.
thanx.
Probably not as the sync()'s don't really do anything with memory allocated
via bus_dmamem_alloc(). The operations are named from the CPU's perspective,
however, the man page at
http://www.freebsd.org/cgi/man.cgi?query=bus_dmamap_sync&apropos=0&sektion=0&manpath=FreeBSD+5.4-stable&format=html
says,
"Although no explicit loading is required to access the memory referenced
by the returned map, the synchronization requirements as described in the
bus_dmamap_sync() section still apply."
also, is bus_dmamap_load() required, since the same man page section above
says it isnt ?
have things changed between freebsd 4.x (which i'm using) and freebsd 5.x ?
thus when you send data to your device, that is a WRITE operation (even
though your device is doing a DMA to read data), and when you get data back
from your device, that is a READ operation (even though your device is doing
a DMA to write the data into the buffer).
thanx, the verbiage on the man page is slightly confusing with it's use of
CPU, giving the opposite impression.
--
Regards, /\_/\ "All dogs go to heaven."
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