Quoting Paolo Bonzini (2015-09-14 09:24:23)
>
>
> On 14/09/2015 16:06, Alexey Kardashevskiy wrote:
> >>>>>
> >>>>> === * There is no way for a child to determine what its parent
> >>>>> is. It is not * a bidirectional relationship. This is by
> >>>>> design. ===
> >>>>>
> >>>>> This part always confused me as there is "Object *parent" in
> >>>>> the "struct Object". So there is way to determine but it must
> >>>>> not be used? Is it debug only?
> >>>>>
> >>>>> Anyway, all members of the Object class are under /*< private
> >>>>>> */ so they should not be accesses in sPAPR code, I believe.
> >>> Ah, good point, I missed that. I guess we have to keep the owner
> >>> field, redundant though it seems. Blech.
> >>
> >> I think the comment is wrong or at least inaccurate; it only applies
> >> to the external QOM interface.
> >
> > Is this case external?
>
> I meant external as in qom-get, qom-set, qom-list. There isn't a ".."
> property.
>
> > Originally I was looking for a object_get_parent() but it is not there
> > so I decided that the comment is correct or I just fail to understand it :)
>
> Yes, we can add such an API.
>
> Let's look also at what ->owner is used for.
>
> > object_property_add_alias(root_container, link_name,
> > drc->owner, child_name, &err);
>
> This can be rewritten as
>
> object_property_add_const_link(root_container, link_name,
> drc, &err);
>
> > QTAILQ_FOREACH(prop, &root_container->properties, node) {
> > Object *obj;
> > sPAPRDRConnector *drc;
> > sPAPRDRConnectorClass *drck;
> > uint32_t drc_index, drc_power_domain;
> >
> > if (!strstart(prop->type, "link<", NULL)) {
> > continue;
> > }
> >
> > obj = object_property_get_link(root_container, prop->name, NULL);
> > drc = SPAPR_DR_CONNECTOR(obj);
> > drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
> >
> > if (owner && (drc->owner != owner)) {
>
> Could the PCI host bridge instead store the DR connectors when it
> creates them with spapr_dr_connector_new? Then you can just call
> spapr_drc_populate_dt directly with the right objects, and avoid another
> O(n^2) loop.
It could be done I think, but in some cases the DRC lists can include a mix
of DRC types/indexes from multiple parents, so we'd need to add some logic
to modify/append to existing paths in FDT.
We end up needing a global registry of some sort anyway, since RTAS
calls from the guest address the DRCs purely by the DRC index, so I
think if we can make use of that same registry to simply the above case
there's no reason not to.
>
> Paolo
>
