We already have two ways of creating a QOM object with a parent set from birth: object_initialize_child() for objects embedded in the parent struct, and object_new_with_props() for heap-allocated objects that also want a list of string properties applied. What we do not have is the plain heap-allocated dual of object_initialize_child(): create the object, add it as a child<> of a given parent under a given name, and hand the reference to the parent.
Board and composite-device code that heap-allocates children today therefore either open-codes object_new()+object_property_add_child() +object_unref(), or skips the parenting step entirely and lets device_set_realized() dump the object into /machine/unattached. Add object_new_child(parent, id, typename) as that missing primitive. The reference created by object_new() is transferred to the parent's child<> property, so on return the sole reference is held by @parent and the caller does not need to unref. Later patches build the qdev and per-bus creation helpers on top of this. @id must be a valid QOM child<> property name: non-empty and without the "/" QOM path separator. It may contain the "[*]" auto-index suffix; the qdev id_wellformed() grammar does not apply here. The compiler enforces non-NULL arguments via __attribute__((nonnull)) instead of runtime asserts, as suggested by Richard and Peter. Link: https://lore.kernel.org/qemu-devel/[email protected]/ Suggested-by: Markus Armbruster <[email protected]> Reviewed-by: Richard Henderson <[email protected]> AI-used-for: code (refactoring) Signed-off-by: Alexander Graf <[email protected]> --- include/qom/object.h | 32 ++++++++++++++++++++++++++++++++ qom/object.c | 12 ++++++++++++ 2 files changed, 44 insertions(+) diff --git a/include/qom/object.h b/include/qom/object.h index 11f55613fc..299673d040 100644 --- a/include/qom/object.h +++ b/include/qom/object.h @@ -632,6 +632,38 @@ Object *object_new_with_class(ObjectClass *klass); */ Object *object_new(const char *typename); +/** + * object_new_child: + * @parent: the QOM composition-tree parent + * @id: the child<> property name; the object's canonical QOM path + * becomes @parent's path plus "/" plus @id + * @typename: the name of the type of the object to instantiate + * + * Create a heap-allocated object and immediately add it to the QOM + * composition tree as a child of @parent. + * + * This is the heap-allocated dual of object_initialize_child(): use + * this when the child is a pointer member of the parent, and use + * object_initialize_child() when the child is embedded in the parent + * struct. See also object_new_with_props() for the variant that + * additionally sets a list of properties. + * + * The reference returned by object_new() is transferred to the child<> + * property of @parent, so the object has a reference count of 1 held + * by @parent, and the caller does not need to unref. + * + * The @id assert is a sanity check on the caller's string literal; + * the authoritative uniqueness check is object_property_add_child(), + * which will error_abort() on a duplicate @id under @parent. Use + * the "[*]" auto-index suffix when multiple children of the same + * kind may be created. + * + * Returns: the newly allocated, instantiated and parented object. + */ +Object *object_new_child(Object *parent, const char *id, + const char *typename) + __attribute__((nonnull(1, 2, 3), returns_nonnull)); + /** * object_new_with_props: * @typename: The name of the type of the object to instantiate. diff --git a/qom/object.c b/qom/object.c index f79b2cf361..64b0faf1f5 100644 --- a/qom/object.c +++ b/qom/object.c @@ -718,6 +718,18 @@ Object *object_new(const char *typename) return object_new_with_type(ti); } +Object *object_new_child(Object *parent, const char *id, + const char *typename) +{ + Object *obj; + + g_assert(id[0] && !strchr(id, '/')); + + obj = object_new(typename); + object_property_add_child(parent, id, obj); + object_unref(obj); + return obj; +} Object *object_new_with_props(const char *typename, Object *parent, -- 2.47.1
