svn commit: r188350 - in head/sys: amd64/amd64 arm/arm
dev/usb2/core i386/i386 ia64/ia64 sys
John Baldwin
jhb at freebsd.org
Mon Feb 9 06:39:40 PST 2009
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'.
--
John Baldwin
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