Date: Sun, 08 Feb 2009 17:05:15 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: xcllnt@mac.com Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: svn commit: r188350 - in head/sys: amd64/amd64 arm/arm dev/usb2/core i386/i386 ia64/ia64 sys Message-ID: <20090208.170515.1031215309.imp@bsdimp.com> In-Reply-To: <9E40268E-A2E2-4CAA-AAFE-EB2491175CEE@mac.com> References: <200902082254.n18MsxVt037307@svn.freebsd.org> <9E40268E-A2E2-4CAA-AAFE-EB2491175CEE@mac.com>
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In message: <9E40268E-A2E2-4CAA-AAFE-EB2491175CEE@mac.com>
Marcel Moolenaar <xcllnt@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. One area we do need to fix is the
inability to flush a subset of the range.
Warner
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