Re: [Qemu-devel] [PATCH qemu v2] qmp: Add qom-list-properties to list QOM object properties

[Alexey Kardashevskiy]

On 01/03/18 14:59, David Gibson wrote:
> On Mon, Feb 26, 2018 at 07:22:59PM +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 <address@hidden>
>> ---
>> Changes:
>> v2:
>> * added abstract classes support, now things like "pci-device" or
>> "spapr-machine" show properties, previously these would produce
>> an "abstract class" error
>> ---
>>  qapi-schema.json     | 29 +++++++++++++++++++++++++++++
>>  include/qom/object.h | 16 ++++++++++++++++
>>  qmp.c                | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
>>  qom/object.c         |  7 +++++++
>>  4 files changed, 101 insertions(+)
>>
>> diff --git a/qapi-schema.json b/qapi-schema.json
>> index 0262b9f..fa5f189 100644
>> --- a/qapi-schema.json
>> +++ b/qapi-schema.json
>> @@ -1455,6 +1455,35 @@
>>    'returns': [ 'DevicePropertyInfo' ] }
>>  
>>  ##
>> +# @QOMPropertyInfo:
>> +#
>> +# Information about object properties.
>> +#
>> +# @name: the name of the property
>> +# @type: the typename of the property
>> +# @description: if specified, the description of the property.
>> +#
>> +# Since: 2.12
>> +##
>> +{ 'struct': 'QOMPropertyInfo',
>> +  'data': { 'name': 'str', 'type': 'str', '*description': 'str' } }
> 
> So, this has identical contents to DevicePropertyInfo, and is very
> similar to ObjectPropertyInfo.  Is there any way we could consolidate
> those types?

Sure, I can get rid of DevicePropertyInfo in favour of QOMPropertyInfo, I
am just not sure if this typename is visible anywhere in the QMP protocol.
I'll post v3 in minutes.


> 
>> +##
>> +# @qom-list-properties:
>> +#
>> +# List properties associated with a QOM object.
>> +#
>> +# @typename: the type name of an object
>> +#
>> +# Returns: a list of QOMPropertyInfo describing object properties
>> +#
>> +# Since: 2.12
>> +##
>> +{ 'command': 'qom-list-properties',
>> +  'data': { 'typename': 'str'},
>> +  'returns': [ 'QOMPropertyInfo' ] }
>> +
>> +##
>>  # @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 793f6f3..151d3d7 100644
>> --- a/qmp.c
>> +++ b/qmp.c
>> @@ -576,6 +576,55 @@ DevicePropertyInfoList 
>> *qmp_device_list_properties(const char *typename,
>>      return prop_list;
>>  }
>>  
>> +QOMPropertyInfoList *qmp_qom_list_properties(const char *typename,
>> +                                             Error **errp)
>> +{
>> +    ObjectClass *klass;
>> +    Object *obj = NULL;
>> +    ObjectProperty *prop;
>> +    ObjectPropertyIterator iter;
>> +    QOMPropertyInfoList *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 like the idea of adding abstract classes in principle, but I'm a
> little concerned about the effect of this in practice, because it only
> lists class properties.
>> Although nearly all properties in qemu *should* be class properties,
> they're nearly all defined as instance properties in practice.  AFAICT
> this is just because most people didn't get the memo on class
> properties and how to use them.
> 
> Just listing class properties in general might be ok - it would
> encourage people to move things to class properties if they should
> be.  However listing class properties in some cases and all properties
> in other sounds like a recipe for confusion.

This lists all properties one can get for a specific type. For an abstract
class, an instance cannot be created, hence only class properties are
listed. Quite straight forward imho.




>> +    } else {
>> +        obj = object_new(typename);
>> +        object_property_iter_init(&iter, obj);
>> +    }
>> +    while ((prop = object_property_iter_next(&iter))) {
>> +        QOMPropertyInfo *info;
>> +        QOMPropertyInfoList *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)
>>  {
> 


-- 
Alexey

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