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Date: Mon, 24 Aug 2009 17:07:25 +0200
From: Gerd Hoffmann <kraxel@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 2/3] Clean up upcast from PCIDevice
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To: Markus Armbruster <armbru@redhat.com>
Cc: qemu-devel@nongnu.org

   Hi,

> play.  However, the *next* commit (conversion to qdev) is wrong if qdev
> requires the PCIDevice at offset zero (not obvious to me, document it?).

qdev_create() allocates DeviceInfo->size bytes for you and assumes 
DeviceState starts at offset zero of your FooDeviceState.  I think that 
is the only place though.

Could probably be relaxed by adding a offset field to DeviceInfo, but I 
don't think that buys us much, so unless there is some real need I'd 
just go with the "DeviceState must be first" convention.

It also could be that there is some old code which does casts instead of 
using DO_UPCAST, especially for PCI because PCIDevice predates qdev. 
That I'd consider a bug though.

cheers,
   Gerd