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Date: Fri, 02 Dec 2011 08:54:51 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH 06/18] qom: add child properties
	(composition)
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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, Markus Armbruster <armbru@redhat.com>, Luiz Capitulino <lcapitulino@redhat.com>

On 12/02/2011 05:54 AM, Kevin Wolf wrote:
> Am 30.11.2011 22:03, schrieb Anthony Liguori:
>> Child properties express a relationship of composition.
>>
>> Signed-off-by: Anthony Liguori<aliguori@us.ibm.com>
>
> Do we have a flag or something that makes sure that a child is never
> removed without its parent? The code assumes that child stays valid as
> long as the parent lives.

Good question.  This is an interesting issue with qdev.

The child property is not writable so you cannot detach a child.  That's because 
the child's life cycle is supposed to be tied to the parents.

qdev doesn't have the right bits to handle this right now.  I think that's 
fixable by just adding a new flag to DeviceState.

>
>> @@ -499,4 +499,24 @@ gchar *qdev_get_canonical_path(DeviceState *dev);
>>    */
>>   DeviceState *qdev_resolve_path(const char *path, bool *ambiguous);
>>
>> +/**
>> + * @qdev_property_add_child - Add a child property to a device
>> + *
>> + * Child properties form the composition tree.  All devices need to be a child
>> + * of another device.  Devices can only be a child of one device.
>> + *
>> + * There is no way for a child to determine what it's parent is.  It is not
>
> s/it's/its/

Ack.

Regards,

Anthony Liguori

> Kevin
>