Date: Tue, 10 Jan 2012 14:23:42 -0800 (PST) From: Matthew Jacob <mj@feral.com> To: Andriy Gapon <avg@freebsd.org> Cc: FreeBSD current <freebsd-current@freebsd.org>, mj@feral.com Subject: Re: bus dma: a flag/quirk for page zero Message-ID: <alpine.BSF.2.00.1201101422380.92131@ns1.feral.com> In-Reply-To: <4F0CAD03.1090605@FreeBSD.org> References: <4F0C9D14.60705@FreeBSD.org> <alpine.BSF.2.00.1201101252530.86261@ns1.feral.com> <4F0CAD03.1090605@FreeBSD.org>
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>> At the very least, require bounce buffers. > > Not sure if I got this suggestion in this terse form. > Could you please explain? Physical address zero can be DMA'd, but via bounce buffers. bcopy from address zero up through a pagesize to a bounce buffer, do the dma from there (read case), write case the opposite order
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