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Date: Fri, 16 Dec 2011 13:24:49 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 00/20] qom: dynamic properties and
	composition tree
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To: Kevin Wolf <kwolf@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Anthony Liguori <aliguori@us.ibm.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>, Markus Armbruster <armbru@redhat.com>

On 12/16/2011 11:36 AM, Kevin Wolf wrote:
> >  I think actually this is not the biggest problem.  child properties are
> >  dynamic, and it's not a problem IMO if they are created like that.
>
> That they are added in an init function is an indicator that they aren't
> really dynamic.

That's true.  However, another indicator is that anything that does not 
have a struct field is also not really static. :)

So right now, child properties are all "dynamic" in this sense.  This 
could change when Anthony converts buses to QOM.  The bus right now is 
embedded into the HBA's struct, is not a pointer.  This likely would 
change when buses are QOM-ized, but then the bus would indeed be a 100% 
static child.

> I think having a child property that can be NULL could be
> reasonable.

I think Anthony convinced me this is not the case (unlike links).  Even 
if buses and similar objects are changed to pointers because the 
implementation needs that, those pointers should never be NULL (or if 
they can, the child property should not exist when they are NULL).

Paolo