[qemu,v3,2/2] qmp: Add qom-list-properties to list QOM object properties

There is already 'device-list-properties' which does most of the job,
however it does not handle everything returned by qom-list-types such
as machines as they inherit directly from TYPE_OBJECT and not TYPE_DEVICE.
It does not handle abstract classes either.

This adds a new qom-list-properties command which prints properties
of a specific class and its instance. It is pretty much a simplified copy
of the device-list-properties handler.

Since it creates an object instance, device properties should appear
in the output as they are copied to QOM properties at the instance_init
hook.

This adds a object_class_property_iter_init() helper to allow class
properties enumeration uses it in the new QMP command to allow properties
listing for abstract classes.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
---
Changes:
v3:
* Used ObjectPropertyInfo instead of QOMPropertyInfo

v2:
* added abstract classes support, now things like "pci-device" or
"spapr-machine" show properties, previously these would produce
an "abstract class" error

# Conflicts:
#	qapi-schema.json
---
 qapi-schema.json     | 15 +++++++++++++++
 include/qom/object.h | 16 ++++++++++++++++
 qmp.c                | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 qom/object.c         |  7 +++++++
 4 files changed, 87 insertions(+)

On Fri, Mar 02, 2018 at 12:09:39AM +1100, Alexey Kardashevskiy wrote:
> There is already 'device-list-properties' which does most of the job,
> however it does not handle everything returned by qom-list-types such
> as machines as they inherit directly from TYPE_OBJECT and not TYPE_DEVICE.
> It does not handle abstract classes either.
> 
> This adds a new qom-list-properties command which prints properties
> of a specific class and its instance. It is pretty much a simplified copy
> of the device-list-properties handler.
> 
> Since it creates an object instance, device properties should appear
> in the output as they are copied to QOM properties at the instance_init
> hook.
> 
> This adds a object_class_property_iter_init() helper to allow class
> properties enumeration uses it in the new QMP command to allow properties
> listing for abstract classes.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v3:
> * Used ObjectPropertyInfo instead of QOMPropertyInfo
> 
> v2:
> * added abstract classes support, now things like "pci-device" or
> "spapr-machine" show properties, previously these would produce
> an "abstract class" error
> 
> # Conflicts:
> #	qapi-schema.json
> ---
>  qapi-schema.json     | 15 +++++++++++++++
>  include/qom/object.h | 16 ++++++++++++++++
>  qmp.c                | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
>  qom/object.c         |  7 +++++++
>  4 files changed, 87 insertions(+)
> 
> diff --git a/qapi-schema.json b/qapi-schema.json
> index 87327e5..32e836f 100644
> --- a/qapi-schema.json
> +++ b/qapi-schema.json
> @@ -1442,6 +1442,21 @@
>    'returns': [ 'ObjectPropertyInfo' ] }
>  
>  ##
> +# @qom-list-properties:
> +#
> +# List properties associated with a QOM object.
> +#
> +# @typename: the type name of an object
> +#
> +# Returns: a list of ObjectPropertyInfo describing object properties
> +#
> +# Since: 2.12
> +##
> +{ 'command': 'qom-list-properties',
> +  'data': { 'typename': 'str'},
> +  'returns': [ 'ObjectPropertyInfo' ] }
> +
> +##
>  # @xen-set-global-dirty-log:
>  #
>  # Enable or disable the global dirty log mode.
> diff --git a/include/qom/object.h b/include/qom/object.h
> index dc73d59..ef07d78 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -1017,6 +1017,22 @@ void object_property_iter_init(ObjectPropertyIterator *iter,
>                                 Object *obj);
>  
>  /**
> + * object_class_property_iter_init:
> + * @klass: the class
> + *
> + * Initializes an iterator for traversing all properties
> + * registered against an object class and all parent classes.
> + *
> + * It is forbidden to modify the property list while iterating,
> + * whether removing or adding properties.
> + *
> + * This can be used on abstract classes as it does not create a temporary
> + * instance.
> + */
> +void object_class_property_iter_init(ObjectPropertyIterator *iter,
> +                                     ObjectClass *klass);
> +
> +/**
>   * object_property_iter_next:
>   * @iter: the iterator instance
>   *
> diff --git a/qmp.c b/qmp.c
> index 8a74038..1f15f68 100644
> --- a/qmp.c
> +++ b/qmp.c
> @@ -576,6 +576,55 @@ ObjectPropertyInfoList *qmp_device_list_properties(const char *typename,
>      return prop_list;
>  }
>  
> +ObjectPropertyInfoList *qmp_qom_list_properties(const char *typename,
> +                                             Error **errp)
> +{
> +    ObjectClass *klass;
> +    Object *obj = NULL;
> +    ObjectProperty *prop;
> +    ObjectPropertyIterator iter;
> +    ObjectPropertyInfoList *prop_list = NULL;
> +
> +    klass = object_class_by_name(typename);
> +    if (klass == NULL) {
> +        error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
> +                  "Class '%s' not found", typename);
> +        return NULL;
> +    }
> +
> +    klass = object_class_dynamic_cast(klass, TYPE_OBJECT);
> +    if (klass == NULL) {
> +        error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "typename", TYPE_OBJECT);
> +        return NULL;
> +    }
> +
> +    if (object_class_is_abstract(klass)) {
> +        object_class_property_iter_init(&iter, klass);

I remain a bit concerned about the subtle difference in behaviour
between abstract and non-abstract classes.

> +    } else {
> +        obj = object_new(typename);
> +        object_property_iter_init(&iter, obj);
> +    }
> +    while ((prop = object_property_iter_next(&iter))) {
> +        ObjectPropertyInfo *info;
> +        ObjectPropertyInfoList *entry;
> +
> +        info = g_malloc0(sizeof(*info));
> +        info->name = g_strdup(prop->name);
> +        info->type = g_strdup(prop->type);
> +        info->has_description = !!prop->description;
> +        info->description = g_strdup(prop->description);
> +
> +        entry = g_malloc0(sizeof(*entry));
> +        entry->value = info;
> +        entry->next = prop_list;
> +        prop_list = entry;
> +    }
> +
> +    object_unref(obj);
> +
> +    return prop_list;
> +}
> +
>  CpuDefinitionInfoList *qmp_query_cpu_definitions(Error **errp)
>  {
>      return arch_query_cpu_definitions(errp);
> diff --git a/qom/object.c b/qom/object.c
> index 5dcee46..e7978bd 100644
> --- a/qom/object.c
> +++ b/qom/object.c
> @@ -1037,6 +1037,13 @@ ObjectProperty *object_property_iter_next(ObjectPropertyIterator *iter)
>      return val;
>  }
>  
> +void object_class_property_iter_init(ObjectPropertyIterator *iter,
> +                                     ObjectClass *klass)
> +{
> +    g_hash_table_iter_init(&iter->iter, klass->properties);
> +    iter->nextclass = klass;
> +}
> +
>  ObjectProperty *object_class_property_find(ObjectClass *klass, const char *name,
>                                             Error **errp)
>  {