Date: Wed, 11 Jan 2012 00:28:08 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: mj@feral.com Cc: FreeBSD current <freebsd-current@FreeBSD.org> Subject: Re: bus dma: a flag/quirk for page zero Message-ID: <4F0CBB78.502@FreeBSD.org> In-Reply-To: <alpine.BSF.2.00.1201101422380.92131@ns1.feral.com> References: <4F0C9D14.60705@FreeBSD.org> <alpine.BSF.2.00.1201101252530.86261@ns1.feral.com> <4F0CAD03.1090605@FreeBSD.org> <alpine.BSF.2.00.1201101422380.92131@ns1.feral.com>
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on 11/01/2012 00:23 Matthew Jacob said the following: >>> 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 Ah, right. I think that that's what the patch tries to do (among other things) if the flag is set. -- Andriy Gapon
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