On Thu, Feb 6, 2025 at 8:29 AM Zhao Liu <zhao1....@intel.com> wrote: > The ref count of Owned<> is decreased on exit, so we need to use > sysbus_realize() instead of sysbus_realize_and_unref() to ensure ref > count is correct at C side. > > Initially, I hesitated here for an entire morning because this didn't > seem to conform to the usual usage of sysbus_realize_and_unref() (or, > further, qdev_realize_and_unref()). > > But now I realize that qdev_realize() is used for embedded objects, > while qdev_realize_and_unref() is used for non-embedded cases. Therefore, > moving forward, perhaps qdev_realize_and_unref() should not exist on the > Rust side.
Correct, all unref() operations are handled implicitly by the Drop implementation of Owned<> > Owned<> will automatically drop and thus automatically unref, while > Child<> will not unref. No, Child<> will also unref. The point of Child<> is to prolong the life of the child object, so that it dies after instance_finalize instead() of dying during object_property_del_all(). In C that has to be done manually (as is the case in the clock creation functions), in Rust it will be enforced by the type system. > In the future, maybe we need some wrappers on qdev_realize()/sysbus_realize(). Yep, I'll add a conversion of pl011_create to safe Rust to clarify the rules around usage of Owned<>. Paolo
