qdev: drop extra references at creation time
qdev_free and qbus_free have to do unparent+unref, because nobody else drops the initial reference (the one included by object_initialize) before them. For device_init_func and do_device_add, this is trivially correct, since the DeviceState goes out of scope. For qdev_create, qdev_try_create and qbus_init, it is a bit more tricky. What we are doing here is just assuming that the caller knows what it's doing, and won't call qdev_free/qbus_free while the device is still there. This is a pretty reasonable assumption and (behind the scenes) is also what GObject/GTK does. GTK actually has a "floating reference" that goes away as soon as the caller does gtk_container_add or something like that, but in the end qbus_init and qdev_try_create are already adding the new object to its qdev parent! So in the end the two solutions are the same. Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com> Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>
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