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Date: Fri, 4 Dec 2015 13:49:28 -0500
From: Kevin O'Connor <kevin@koconnor.net>
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Subject: Re: [Qemu-devel] [PATCH 1/3] hw/sd/pxa2xx_mmci: convert to
 SysBusDevice object
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Patch Tracking <patches@linaro.org>, Markus Armbruster <armbru@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>

On Fri, Dec 04, 2015 at 12:55:07PM +0000, Peter Maydell wrote:
> On 4 December 2015 at 12:50, Markus Armbruster <armbru@redhat.com> wrote:
> > To finally answer your question: the proper owner of the property
> > connecting the backend is the frontend half of the split device.  So, if
> > we have separate device models for controller and the block devices
> > connected to it, the block backend property belongs to the latter, not
> > the former.  If we have separate device models for SD controller and
> > card, the block backend property belongs to the card, not the
> > controller.
> 
> I thought this might be your answer, but this is problematic because
> we now have a device in the tree (the sdhci pci card) which has the
> property on the controller, and so that's now user-facing command
> line ABI which we can't change...

If by ABI, you mean the command line format:

 -device sdhci-pci,drive=drive0 -drive id=drive0,if=sd,file=myimage

then I don't see why that should change.  As Paolo points out, there
is only one card per controller.  That's how real hardware does it as
well.

Cheers,
-Kevin