Re: Realize methods realizing "sideways" in the composition tree

[Peter Maydell]

On Fri, 15 Jan 2021 at 15:45, Markus Armbruster <armbru@redhat.com> wrote:
>
> The .realize() method realizes the child at (1).  It should use
> qdev_realize() like we do everywhere else, since commit ce189ab230
> "qdev: Convert bus-less devices to qdev_realize() with Coccinelle".
>
> It sets a link property from the child back to the parent at (2).  Why
> do we need a link?  Each QOM Object contains a pointer to its parent,
> doesn't it?

It does, but what should parent object pointers be used for?
My assumption is that you'd only use those where you really
wanted to traverse the QOM tree. Generally I would use a link
property when I wanted one object to have a pointer to the
other regardless of what the QOM-tree relationship happens to
be. Today all the users of XHCIState happen to create it in a
way that means they're parents of it, but that doesn't seem
like it should be an inherent requirement that we bake into
its API.

thanks
-- PMM