On Feb 9, 2009, at 6:23 AM, John Baldwin wrote:
On Monday 09 February 2009 12:37:53 am Marcel Moolenaar wrote:
On Feb 8, 2009, at 5:00 PM, Scott Long wrote:
Busdma allows you to request bouncing for realignment.
How exactly?
The 'align' parameter to bus_dma_tag_create(). If your hardware
needs buffers
to be aligned on a 4-byte boundary and you bus_dmamap_load() a buffer
where 'addr % 4 != 0', then the buffer is bounced. Since by default
the new
buffer starts on a page boundary, it satifies the 'addr % 4'.
But according to the man page, bounce buffering may not
be implemented or not be applicable to a platform. It
seems to me that you cannot depend on this side-effect
in a generic driver. Are you guys talking only in terms
of i386 or is this generally applicable?
--
Marcel Moolenaar
xcl...@mac.com
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