Re: [Qemu-devel] [RFC 1/9] hostdev: introduce the infrastructure for host device model

[Paolo Bonzini <pbonzini@redhat.com>]

Il 27/03/2012 16:18, Zhi Yong Wu ha scritto:
> On Tue, Mar 27, 2012 at 9:58 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> Il 27/03/2012 13:59, Zhi Yong Wu ha scritto:
>>> On Tue, Mar 27, 2012 at 6:15 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>>> Il 27/03/2012 11:06, Zhi Yong Wu ha scritto:
>>>>>>>>> +#define DEFINE_HOSTDEV_PROP_PEER(_n, _s, _f)             \
>>>>>>>>> +    DEFINE_HOSTDEV_PROP(_n, _s, _f, hostdev_prop_netdev, NetClientState*)
>>>>>>>
>>>>>>> This should be simply a link<NetDev> property.
>>>>> IMHO, i don't fully understand what link<NetDev> mean. What is the
>>>>> difference between it and Child<NetDev>. Can you elaborate this?
>>>>
>>>> link<NetDev> is a pointer to another object.  child<NetDev> means that
>>> Where are link<NetDev> used?
>>
>> The peer property needs to be one.
> sorry, i don't get what it means.

Links are pointers.  As you convert host devices to QOM, pointer
properties such as drive or chardev need to become links.  Peer is
another pointer property that needs to become a link.

>>> what is relationship between the two objects?
>>
>> A has a pointer to B.
>
> I knew this, but can you say one example in QEMU device model? I
> checked QEMU code, and found that those link functions in object.c are
> not currently used. right?

Yes, that's correct.  Everything that uses PROP_PTR needs to become a
link.  We cannot do that yet because devices do not yet have a canonical
path.

>>> Moreover, -device has exposed network card info.
>>
>> ... this is extremely confused.  Each NIC device has a NIC-type
>> NetClientState.  If NetClientState is converted to QOM, all of its
> The original idea about -netdev QOM is to convert NetClientState to
> QOM, but now this idea seems to be changed.

I cannot parse this at all.  You have not converted all of
NetClientState to QOM, have you?

>>> We hope that -netdev options info can be configurated or changed
>>> purely via QOM, not command line.
>>
>> Yes, but does it buy anything or it is just a nice exercise?
> 
> buy anything? sorry, i don't understand this.

What's the advantage?  Converting chardev would give hotplug.  What can
we do with a QOMified netdev that we cannot do now?

Paolo