Re: [PATCH v5 02/10] object: qom module support

[Christophe de Dinechin <dinechin@redhat.com>]

On 2020-06-24 at 15:10 CEST, Gerd Hoffmann wrote...
> Little helper function to load modules on demand.  In most cases adding
> module loading support for devices and other objects is just
> s/object_class_by_name/module_object_class_by_name/ in the right spot.
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  include/qom/object.h | 12 ++++++++++++
>  qom/object.c         | 14 ++++++++++++++
>  2 files changed, 26 insertions(+)
>
> diff --git a/include/qom/object.h b/include/qom/object.h
> index 94a61ccc3fe8..51f188137f1f 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -994,6 +994,18 @@ bool object_class_is_abstract(ObjectClass *klass);
>   */
>  ObjectClass *object_class_by_name(const char *typename);
>
> +/**
> + * module_object_class_by_name:
> + * @typename: The QOM typename to obtain the class for.
> + *
> + * For objects which might be provided by a module.  Behaves like
> + * object_class_by_name, but additionally tries to load the module
> + * needed in case the class is not available.
> + *
> + * Returns: The class for @typename or %NULL if not found.
> + */
> +ObjectClass *module_object_class_by_name(const char *typename);
> +
>  void object_class_foreach(void (*fn)(ObjectClass *klass, void *opaque),
>                            const char *implements_type, bool include_abstract,
>                            void *opaque);
> diff --git a/qom/object.c b/qom/object.c
> index 6ece96bc2bfc..34daaf1280f5 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -985,6 +985,20 @@ ObjectClass *object_class_by_name(const char *typename)
>      return type->class;
>  }
>
> +ObjectClass *module_object_class_by_name(const char *typename)
> +{
> +    ObjectClass *oc;
> +
> +    oc = object_class_by_name(typename);
> +#ifdef CONFIG_MODULES
> +    if (!oc) {
> +        module_load_qom_one(typename);
> +        oc = object_class_by_name(typename);
> +    }
> +#endif

I'm wondering if there is any reason to only trigger the module load when
you don't find the object class. You could simply call module_load_qom_one
under #ifdef CONFIG_MODULES.

Performance wise, I don't think this makes much of a difference, and it
simplifies the logical flow IMO.

> +    return oc;
> +}
> +
>  ObjectClass *object_class_get_parent(ObjectClass *class)
>  {
>      TypeImpl *type = type_get_parent(class->type);


--
Cheers,
Christophe de Dinechin (IRC c3d)