Re: [Qemu-devel] [PATCH RFC V2 7/9] qom: add object_property_is_set

[Paolo Bonzini]

Il 02/03/2014 14:07, Marcel Apfelbaum ha scritto:
> Sometimes is not enough to get property's value,
> but it is needed to know if the value was actually set.
>
> This is especially useful when querying bool properties
> and having different defaults on different scenarios.
>
> Signed-off-by: Marcel Apfelbaum <address@hidden>

I suggested some replacements for this in the review to patch 8/9.

The problem is that tristate properties implemented with 
object_property_is_set cannot be "round-trip"-ped out and back in of QEMU.

Paolo

> ---
>  include/qom/object.h | 11 +++++++++++
>  qom/object.c         | 12 ++++++++++++
>  2 files changed, 23 insertions(+)
>
> diff --git a/include/qom/object.h b/include/qom/object.h
> index 9c7c361..4a4f026 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -319,6 +319,7 @@ typedef struct ObjectProperty
>  {
>      gchar *name;
>      gchar *type;
> +    bool is_set;
>      ObjectPropertyAccessor *get;
>      ObjectPropertyAccessor *set;
>      ObjectPropertyRelease *release;
> @@ -931,6 +932,16 @@ void object_property_set(Object *obj, struct Visitor *v, 
> const char *name,
>                           Error **errp);
>
>  /**
> + * object_property_is_set:
> + * @obj: the object
> + * @name: the name of the property
> + * @errp: returns an error if this function fails
> + *
> + * Returns: true if object's property is set, false otherwise.
> + */
> +bool object_property_is_set(Object *obj, const char *name,
> +                            Error **errp);
> +/**
>   * object_property_parse:
>   * @obj: the object
>   * @string: the string that will be used to parse the property value.
> diff --git a/qom/object.c b/qom/object.c
> index 660859c..5b9d8af 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -817,9 +817,21 @@ void object_property_set(Object *obj, Visitor *v, const 
> char *name,
>          error_set(errp, QERR_PERMISSION_DENIED);
>      } else {
>          prop->set(obj, v, prop->opaque, name, errp);
> +        prop->is_set = true;
>      }
>  }
>
> +bool object_property_is_set(Object *obj, const char *name,
> +                            Error **errp)
> +{
> +    ObjectProperty *prop = object_property_find(obj, name, errp);
> +    if (prop == NULL) {
> +        return false;
> +    }
> +
> +    return prop->is_set;
> +}
> +
>  void object_property_set_str(Object *obj, const char *value,
>                               const char *name, Error **errp)
>  {