svn commit: r188350 - in head/sys: amd64/amd64 arm/arm dev/usb2/core i386/i386 ia64/ia64 sys

[Marcel Moolenaar]

On Feb 8, 2009, at 4:05 PM, M. Warner Losh wrote:

> In message: <9E40268E-A2E2-4CAA-AAFE-EB2491175CEE at mac.com>
>            Marcel Moolenaar <xcllnt at mac.com> writes:
> :
> : On Feb 8, 2009, at 2:54 PM, Warner Losh wrote:
> :
> : > Author: imp
> : > Date: Sun Feb  8 22:54:58 2009
> : > New Revision: 188350
> : > URL: http://svn.freebsd.org/changeset/base/188350
> : >
> : > Log:
> : >  When bouncing pages, allow a new option to preserve the intra- 
> page
> : >  offset.  This is needed for the ehci hardware buffer rings that
> : > assume
> : >  this behavior.
> :
> : I thought we ended up with always doing that?
> :
> : Bounce buffers may or may not be used, so if the page offset
> : must be zero for bounce buffers, they must be zero for the
> : original DMA request. I see no value in re-aligning the DMA
> : request to a page boundary when bounce buffers are used, but
> : it is required in some cases to not realign. Hence, why not
> : always (and unconditionally) preserve the alignment?
>
> I'm not entirely sure either.  However, at this stage of the game I'd
> rather be a little conservative in what we change and do a more
> careful and thorough analysis.

Fair enough.

-- 
Marcel Moolenaar
xcllnt at mac.com