From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:45789)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <dgibson@ozlabs.org>) id 1TRY9i-0001Qn-QY
	for qemu-devel@nongnu.org; Thu, 25 Oct 2012 20:52:12 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <dgibson@ozlabs.org>) id 1TRY9f-0005Gf-VS
	for qemu-devel@nongnu.org; Thu, 25 Oct 2012 20:52:10 -0400
Received: from ozlabs.org ([203.10.76.45]:60292)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <dgibson@ozlabs.org>) id 1TRY9f-0005Fy-KW
	for qemu-devel@nongnu.org; Thu, 25 Oct 2012 20:52:07 -0400
Date: Fri, 26 Oct 2012 11:48:32 +1100
From: David Gibson <david@gibson.dropbear.id.au>
Message-ID: <20121026004832.GG7222@truffula.fritz.box>
References: <1351013211-1907-1-git-send-email-peter.maydell@linaro.org>
	<CAEgOgz7xTwcdP_MAGaU6jpqs0ms9E6MyF_e4P4ivNdV_QPJGrA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAEgOgz7xTwcdP_MAGaU6jpqs0ms9E6MyF_e4P4ivNdV_QPJGrA@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH] dma: Define dma_context_memory and use in
 sysbus-ohci
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Avi Kivity <avi@redhat.com>, patches@linaro.org, Gerd Hoffmann <kraxel@redhat.com>, qemu-devel@nongnu.org

On Thu, Oct 25, 2012 at 08:33:13PM +1000, Peter Crosthwaite wrote:
> On Oct 24, 2012 3:27 AM, "Peter Maydell" <peter.maydell@linaro.org> wrote:
> >
> > Define a new global dma_context_memory which is a DMAContext corresponding
> > to the global address_space_memory AddressSpace. This can be used by
> > sysbus peripherals like sysbus-ohci which need to do DMA.
> >
> > In particular, use it in the sysbus-ohci device, which fixes a
> > segfault when attempting to use that device.
> >
> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>

Hrm.  So, as I originally conceived DMAContext, a NULL context pointer
means "no translation" which is to say that DMA addresses are the same
as memory space addresses.  Which would mean a context explicitly for
this purpose should not be necessary.

Has this assumption changed with the newer memory region integrated
dma context stuff?

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson