QEMU Object Model¶

The documentation of QEMU’s Object Model header described in qom/object.h .

typedef void(ObjectPropertyAccessor)¶

Parameters

ObjectPropertyAccessor: undescribed

Description

The QEMU Object Model provides a framework for registering user creatable types and instantiating objects from those types. QOM provides the following features:

System for dynamically registering types

Support for single-inheritance of types

Multiple inheritance of stateless interfaces

<example>: <title>Creating a minimal type</title> <programlisting>

#include “qdev.h”

#define TYPE_MY_DEVICE “my-device”

// No new virtual functions: we can reuse the typedef for the // superclass. typedef DeviceClass MyDeviceClass; typedef struct MyDevice {

DeviceState parent;

int reg0, reg1, reg2;

} MyDevice;

static const TypeInfo my_device_info = {: .name = TYPE_MY_DEVICE, .parent = TYPE_DEVICE, .instance_size = sizeof(MyDevice),

};

static void my_device_register_types(void) {

type_register_static(my_device_info);

}

type_init(my_device_register_types): </programlisting>

</example>

In the above example, we create a simple type that is described by #TypeInfo. #TypeInfo describes information about the type including what it inherits from, the instance and class size, and constructor/destructor hooks.

Alternatively several static types could be registered using helper macro DEFINE_TYPES()

<example>

static const TypeInfo device_types_info[] = {

{: .name = TYPE_MY_DEVICE_A, .parent = TYPE_DEVICE, .instance_size = sizeof(MyDeviceA),

}, {

.name = TYPE_MY_DEVICE_B, .parent = TYPE_DEVICE, .instance_size = sizeof(MyDeviceB),

},

};

DEFINE_TYPES(device_types_info): </programlisting>

</example>

Every type has an #ObjectClass associated with it. #ObjectClass derivatives are instantiated dynamically but there is only ever one instance for any given type. The #ObjectClass typically holds a table of function pointers for the virtual methods implemented by this type.

Using object_new(), a new #Object derivative will be instantiated. You can cast an #Object to a subclass (or base-class) type using object_dynamic_cast(). You typically want to define macro wrappers around OBJECT_CHECK() and OBJECT_CLASS_CHECK() to make it easier to convert to a specific type:

<example>

<title>Typecasting macros</title> <programlisting>

#define MY_DEVICE_GET_CLASS(obj) * OBJECT_GET_CLASS(MyDeviceClass, obj, TYPE_MY_DEVICE) #define MY_DEVICE_CLASS(klass) * OBJECT_CLASS_CHECK(MyDeviceClass, klass, TYPE_MY_DEVICE) #define MY_DEVICE(obj) * OBJECT_CHECK(MyDevice, obj, TYPE_MY_DEVICE)

</programlisting>

</example>

# Class Initialization #

Before an object is initialized, the class for the object must be initialized. There is only one class object for all instance objects that is created lazily.

Classes are initialized by first initializing any parent classes (if necessary). After the parent class object has initialized, it will be copied into the current class object and any additional storage in the class object is zero filled.

The effect of this is that classes automatically inherit any virtual function pointers that the parent class has already initialized. All other fields will be zero filled.

Once all of the parent classes have been initialized, #TypeInfo::class_init is called to let the class being instantiated provide default initialize for its virtual functions. Here is how the above example might be modified to introduce an overridden virtual function:

<example>: <title>Overriding a virtual function</title> <programlisting>

#include “qdev.h”

void my_device_class_init(ObjectClass *klass, void *class_data) {

DeviceClass *dc = DEVICE_CLASS(klass); dc->reset = my_device_reset;

}

static const TypeInfo my_device_info = {: .name = TYPE_MY_DEVICE, .parent = TYPE_DEVICE, .instance_size = sizeof(MyDevice), .class_init = my_device_class_init,
};: </programlisting>

</example>

Introducing new virtual methods requires a class to define its own struct and to add a .class_size member to the #TypeInfo. Each method will also have a wrapper function to call it easily:

<example>: <title>Defining an abstract class</title> <programlisting>

#include “qdev.h”

typedef struct MyDeviceClass {

DeviceClass parent;

void (*frobnicate) (MyDevice *obj);

} MyDeviceClass;

static const TypeInfo my_device_info = {: .name = TYPE_MY_DEVICE, .parent = TYPE_DEVICE, .instance_size = sizeof(MyDevice), .abstract = true, // or set a default in my_device_class_init .class_size = sizeof(MyDeviceClass),

};

void my_device_frobnicate(MyDevice *obj) {

MyDeviceClass *klass = MY_DEVICE_GET_CLASS(obj);

klass->frobnicate(obj);

}: </programlisting>

</example>

# Interfaces #

Interfaces allow a limited form of multiple inheritance. Instances are similar to normal types except for the fact that are only defined by their classes and never carry any state. You can dynamically cast an object to one of its #Interface types and vice versa.

# Methods #

A <emphasis>method</emphasis> is a function within the namespace scope of a class. It usually operates on the object instance by passing it as a strongly-typed first argument. If it does not operate on an object instance, it is dubbed <emphasis>class method</emphasis>.

Methods cannot be overloaded. That is, the #ObjectClass and method name uniquely identity the function to be called; the signature does not vary except for trailing varargs.

Methods are always <emphasis>virtual</emphasis>. Overriding a method in #TypeInfo.class_init of a subclass leads to any user of the class obtained via OBJECT_GET_CLASS() accessing the overridden function. The original function is not automatically invoked. It is the responsibility of the overriding class to determine whether and when to invoke the method being overridden.

To invoke the method being overridden, the preferred solution is to store the original value in the overriding class before overriding the method. This corresponds to |[ {super,base}.method(...) ]| in Java and C# respectively; this frees the overriding class from hardcoding its parent class, which someone might choose to change at some point.

<example>: <title>Overriding a virtual method</title> <programlisting>

typedef struct MyState MyState;

typedef void (*MyDoSomething)(MyState *obj);

typedef struct MyClass {

ObjectClass parent_class;

MyDoSomething do_something;

} MyClass;

static void my_do_something(MyState *obj) {

// do something

}

static void my_class_init(ObjectClass *oc, void *data) {

MyClass *mc = MY_CLASS(oc);

mc->do_something = my_do_something;

}

static const TypeInfo my_type_info = {: .name = TYPE_MY, .parent = TYPE_OBJECT, .instance_size = sizeof(MyState), .class_size = sizeof(MyClass), .class_init = my_class_init,

};

typedef struct DerivedClass {

MyClass parent_class;

MyDoSomething parent_do_something;

} DerivedClass;

static void derived_do_something(MyState *obj) {

DerivedClass *dc = DERIVED_GET_CLASS(obj);

// do something here dc->parent_do_something(obj); // do something else here

}

static void derived_class_init(ObjectClass *oc, void *data) {

MyClass *mc = MY_CLASS(oc); DerivedClass *dc = DERIVED_CLASS(oc);

dc->parent_do_something = mc->do_something; mc->do_something = derived_do_something;

}

static const TypeInfo derived_type_info = {: .name = TYPE_DERIVED, .parent = TYPE_MY, .class_size = sizeof(DerivedClass), .class_init = derived_class_init,
};: </programlisting>

</example>

Alternatively, object_class_by_name() can be used to obtain the class and its non-overridden methods for a specific type. This would correspond to |[ MyClass::method(...) ]| in C++.

The first example of such a QOM method was #CPUClass.reset, another example is #DeviceClass.realize.

typedef void(ObjectPropertyRelease)

Parameters

ObjectPropertyRelease: undescribed

Description

Called when a property is removed from a object.

typedef void(ObjectUnparent)

Parameters

ObjectUnparent: undescribed

Description

Called when an object is being removed from the QOM composition tree. The function should remove any backlinks from children objects to obj.

typedef void(ObjectFree)

Parameters

ObjectFree: undescribed

Description

Called when an object’s last reference is removed.

OBJECT(obj)¶

Parameters

obj: A derivative of #Object

Description

Converts an object to a #Object. Since all objects are #Objects, this function will always succeed.

OBJECT_CLASS(class)¶

Parameters

class: A derivative of #ObjectClass.

Description

Converts a class to an #ObjectClass. Since all objects are #Objects, this function will always succeed.

OBJECT_CHECK(type, obj, name)¶

Parameters

type: The C type to use for the return value.
obj: A derivative of type to cast.
name: The QOM typename of type

Description

A type safe version of object_dynamic_cast_assert. Typically each class will define a macro based on this type to perform type safe dynamic_casts to this object type.

If an invalid object is passed to this function, a run time assert will be generated.

OBJECT_CLASS_CHECK(class_type, class, name)¶

Parameters

class_type: The C type to use for the return value.
class: A derivative class of class_type to cast.
name: the QOM typename of class_type.

Description

A type safe version of object_class_dynamic_cast_assert. This macro is typically wrapped by each type to perform type safe casts of a class to a specific class type.

OBJECT_GET_CLASS(class, obj, name)¶

Parameters

class: The C type to use for the return value.
obj: The object to obtain the class for.
name: The QOM typename of obj.

Description

This function will return a specific class for a given object. Its generally used by each type to provide a type safe macro to get a specific class type from an object.

INTERFACE_CLASS(klass)¶

Parameters

klass: class to cast from

Return

An #InterfaceClass or raise an error if cast is invalid

INTERFACE_CHECK(interface, obj, name)¶

Parameters

interface: the type to return
obj: the object to convert to an interface
name: the interface type name

Return

obj casted to interface if cast is valid, otherwise raise error.

Object * object_new(const char * typename)¶

Parameters

const char * typename: The name of the type of the object to instantiate.

Description

This function will initialize a new object using heap allocated memory. The returned object has a reference count of 1, and will be freed when the last reference is dropped.

Return

The newly allocated and instantiated object.

Object * object_new_with_props(const char * typename, Object * parent, const char * id, Error ** errp, ...)¶

Parameters

const char * typename: The name of the type of the object to instantiate.
Object * parent: the parent object
const char * id: The unique ID of the object
Error ** errp: pointer to error object
...: list of property names and values

Description

This function will initialize a new object using heap allocated memory. The returned object has a reference count of 1, and will be freed when the last reference is dropped.

The id parameter will be used when registering the object as a child of parent in the composition tree.

The variadic parameters are a list of pairs of (propname, propvalue) strings. The propname of NULL indicates the end of the property list. If the object implements the user creatable interface, the object will be marked complete once all the properties have been processed.

<example>

<title>Creating an object with properties</title> <programlisting> Error *err = NULL; Object *obj;

obj = object_new_with_props(TYPE_MEMORY_BACKEND_FILE,

object_get_objects_root(), “hostmem0”, err, “share”, “yes”, “mem-path”, “/dev/shm/somefile”, “prealloc”, “yes”, “size”, “1048576”, NULL);

if (!obj) {

g_printerr(“Cannot create memory backend: sn”,: error_get_pretty(err));

} </programlisting>

</example>

The returned object will have one stable reference maintained for as long as it is present in the object hierarchy.

Return

The newly allocated, instantiated & initialized object.

Object * object_new_with_propv(const char * typename, Object * parent, const char * id, Error ** errp, va_list vargs)¶

Parameters

const char * typename: The name of the type of the object to instantiate.
Object * parent: the parent object
const char * id: The unique ID of the object
Error ** errp: pointer to error object
va_list vargs: list of property names and values

Description

See object_new_with_props() for documentation.

int object_set_props(Object * obj, Error ** errp, ...)¶

Parameters

Object * obj: the object instance to set properties on
Error ** errp: pointer to error object
...: list of property names and values

Description

This function will set a list of properties on an existing object instance.

The variadic parameters are a list of pairs of (propname, propvalue) strings. The propname of NULL indicates the end of the property list.

<example>

<title>Update an object’s properties</title> <programlisting> Error *err = NULL; Object *obj = ...get / create object...;

obj = object_set_props(obj,

err, “share”, “yes”, “mem-path”, “/dev/shm/somefile”, “prealloc”, “yes”, “size”, “1048576”, NULL);

if (!obj) {

g_printerr(“Cannot set properties: sn”,: error_get_pretty(err));

} </programlisting>

</example>

The returned object will have one stable reference maintained for as long as it is present in the object hierarchy.

Return

-1 on error, 0 on success

int object_set_propv(Object * obj, Error ** errp, va_list vargs)¶

Parameters

Object * obj: the object instance to set properties on
Error ** errp: pointer to error object
va_list vargs: list of property names and values

Description

See object_set_props() for documentation.

Return

-1 on error, 0 on success

void object_initialize(void * obj, size_t size, const char * typename)¶

Parameters

void * obj: A pointer to the memory to be used for the object.
size_t size: The maximum size available at obj for the object.
const char * typename: The name of the type of the object to instantiate.

Description

This function will initialize an object. The memory for the object should have already been allocated. The returned object has a reference count of 1, and will be finalized when the last reference is dropped.

void object_initialize_child(Object * parentobj, const char * propname, void * childobj, size_t size, const char * type, Error ** errp, ...)¶

Parameters

Object * parentobj: The parent object to add a property to
const char * propname: The name of the property
void * childobj: A pointer to the memory to be used for the object.
size_t size: The maximum size available at childobj for the object.
const char * type: The name of the type of the object to instantiate.
Error ** errp: If an error occurs, a pointer to an area to store the error
...: list of property names and values

Description

This function will initialize an object. The memory for the object should have already been allocated. The object will then be added as child property to a parent with object_property_add_child() function. The returned object has a reference count of 1 (for the “child<...>” property from the parent), so the object will be finalized automatically when the parent gets removed.

The variadic parameters are a list of pairs of (propname, propvalue) strings. The propname of NULL indicates the end of the property list. If the object implements the user creatable interface, the object will be marked complete once all the properties have been processed.

void object_initialize_childv(Object * parentobj, const char * propname, void * childobj, size_t size, const char * type, Error ** errp, va_list vargs)¶

Parameters

Object * parentobj: The parent object to add a property to
const char * propname: The name of the property
void * childobj: A pointer to the memory to be used for the object.
size_t size: The maximum size available at childobj for the object.
const char * type: The name of the type of the object to instantiate.
Error ** errp: If an error occurs, a pointer to an area to store the error
va_list vargs: list of property names and values

Description

See object_initialize_child() for documentation.

Object * object_dynamic_cast(Object * obj, const char * typename)¶

Parameters

Object * obj: The object to cast.
const char * typename: The typename to cast to.

Description

This function will determine if obj is-a typename. obj can refer to an object or an interface associated with an object.

Return

This function returns obj on success or #NULL on failure.

Object * object_dynamic_cast_assert(Object * obj, const char * typename, const char * file, int line, const char * func)¶

Parameters

Object * obj: undescribed
const char * typename: undescribed
const char * file: undescribed
int line: undescribed
const char * func: undescribed

Description

See object_dynamic_cast() for a description of the parameters of this function. The only difference in behavior is that this function asserts instead of returning #NULL on failure if QOM cast debugging is enabled. This function is not meant to be called directly, but only through the wrapper macro OBJECT_CHECK.

ObjectClass * object_get_class(Object * obj)¶

Parameters

Object * obj: A derivative of #Object

Return

The #ObjectClass of the type associated with obj.

const char * object_get_typename(const Object * obj)¶

Parameters

const Object * obj: A derivative of #Object.

Return

The QOM typename of obj.

Type type_register_static(const TypeInfo * info)¶

Parameters

const TypeInfo * info: The #TypeInfo of the new type.

Description

info and all of the strings it points to should exist for the life time that the type is registered.

Return

the new #Type.

Type type_register(const TypeInfo * info)¶

Parameters

const TypeInfo * info: The #TypeInfo of the new type

Description

Unlike type_register_static(), this call does not require info or its string members to continue to exist after the call returns.

Return

the new #Type.

void type_register_static_array(const TypeInfo * infos, int nr_infos)¶

Parameters

const TypeInfo * infos: The array of the new type #TypeInfo structures.
int nr_infos: number of entries in infos

Description

infos and all of the strings it points to should exist for the life time that the type is registered.

DEFINE_TYPES(type_array)¶

Parameters

type_array: The array containing #TypeInfo structures to register

Description

type_array should be static constant that exists for the life time that the type is registered.

ObjectClass * object_class_dynamic_cast_assert(ObjectClass * klass, const char * typename, const char * file, int line, const char * func)¶

Parameters

ObjectClass * klass: The #ObjectClass to attempt to cast.
const char * typename: The QOM typename of the class to cast to.
const char * file: undescribed
int line: undescribed
const char * func: undescribed

Description

See object_class_dynamic_cast() for a description of the parameters of this function. The only difference in behavior is that this function asserts instead of returning #NULL on failure if QOM cast debugging is enabled. This function is not meant to be called directly, but only through the wrapper macros OBJECT_CLASS_CHECK and INTERFACE_CHECK.

ObjectClass * object_class_dynamic_cast(ObjectClass * klass, const char * typename)¶

Parameters

ObjectClass * klass: The #ObjectClass to attempt to cast.
const char * typename: The QOM typename of the class to cast to.

Return

If typename is a class, this function returns klass if typename is a subtype of klass, else returns #NULL.

If typename is an interface, this function returns the interface definition for klass if klass implements it unambiguously; #NULL is returned if klass does not implement the interface or if multiple classes or interfaces on the hierarchy leading to klass implement it. (FIXME: perhaps this can be detected at type definition time?)

ObjectClass * object_class_get_parent(ObjectClass * klass)¶

Parameters

ObjectClass * klass: The class to obtain the parent for.

Return

The parent for klass or NULL if none.

const char * object_class_get_name(ObjectClass * klass)¶

Parameters

ObjectClass * klass: The class to obtain the QOM typename for.

Return

The QOM typename for klass.

bool object_class_is_abstract(ObjectClass * klass)¶

Parameters

ObjectClass * klass: The class to obtain the abstractness for.

Return

true if klass is abstract, false otherwise.

ObjectClass * object_class_by_name(const char * typename)¶

Parameters

const char * typename: The QOM typename to obtain the class for.

Return

The class for typename or NULL if not found.

GSList * object_class_get_list(const char * implements_type, bool include_abstract)¶

Parameters

const char * implements_type: The type to filter for, including its derivatives.
bool include_abstract: Whether to include abstract classes.

Return

A singly-linked list of the classes in reverse hashtable order.

GSList * object_class_get_list_sorted(const char * implements_type, bool include_abstract)¶

Parameters

const char * implements_type: The type to filter for, including its derivatives.
bool include_abstract: Whether to include abstract classes.

Return

A singly-linked list of the classes in alphabetical case-insensitive order.

void object_ref(Object * obj)¶

Parameters

Object * obj: the object

Description

Increase the reference count of a object. A object cannot be freed as long as its reference count is greater than zero.

void object_unref(Object * obj)¶

Parameters

Object * obj: the object

Description

Decrease the reference count of a object. A object cannot be freed as long as its reference count is greater than zero.

ObjectProperty * object_property_add(Object * obj, const char * name, const char * type, ObjectPropertyAccessor * get, ObjectPropertyAccessor * set, ObjectPropertyRelease * release, void * opaque, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property. This can contain any character except for a forward slash. In general, you should use hyphens ‘-‘ instead of underscores ‘_’ when naming properties.
const char * type: the type name of the property. This namespace is pretty loosely defined. Sub namespaces are constructed by using a prefix and then to angle brackets. For instance, the type ‘virtio-net-pci’ in the ‘link’ namespace would be ‘link<virtio-net-pci>’.
ObjectPropertyAccessor * get: The getter to be called to read a property. If this is NULL, then the property cannot be read.
ObjectPropertyAccessor * set: the setter to be called to write a property. If this is NULL, then the property cannot be written.
ObjectPropertyRelease * release: called when the property is removed from the object. This is meant to allow a property to free its opaque upon object destruction. This may be NULL.
void * opaque: an opaque pointer to pass to the callbacks for the property
Error ** errp: returns an error if this function fails

Return

The #ObjectProperty; this can be used to set the resolve callback for child and link properties.

ObjectProperty * object_property_find(Object * obj, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Look up a property for an object and return its #ObjectProperty if found.

void object_property_iter_init(ObjectPropertyIterator * iter, Object * obj)¶

Parameters

ObjectPropertyIterator * iter: undescribed
Object * obj: the object

Description

Initializes an iterator for traversing all properties registered against an object instance, its class and all parent classes.

It is forbidden to modify the property list while iterating, whether removing or adding properties.

Typical usage pattern would be

<example>

<title>Using object property iterators</title> <programlisting> ObjectProperty *prop; ObjectPropertyIterator iter;

object_property_iter_init(iter, obj); while ((prop = object_property_iter_next(iter))) {

... do something with prop ...

} </programlisting>

</example>

void object_class_property_iter_init(ObjectPropertyIterator * iter, ObjectClass * klass)¶

Parameters

ObjectPropertyIterator * iter: undescribed
ObjectClass * klass: the class

Description

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.

ObjectProperty * object_property_iter_next(ObjectPropertyIterator * iter)¶

Parameters

ObjectPropertyIterator * iter: the iterator instance

Description

Return the next available property. If no further properties are available, a NULL value will be returned and the iter pointer should not be used again after this point without re-initializing it.

Return

the next property, or NULL when all properties have been traversed.

void object_property_get(Object * obj, Visitor * v, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
Visitor * v: the visitor that will receive the property value. This should be an Output visitor and the data will be written with name as the name.
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Reads a property from a object.

void object_property_set_str(Object * obj, const char * value, const char * name, Error ** errp)¶

Parameters

Object * obj: undescribed
const char * value: the value to be written to the property
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Writes a string value to a property.

char * object_property_get_str(Object * obj, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Return

the value of the property, converted to a C string, or NULL if an error occurs (including when the property value is not a string). The caller should free the string.

void object_property_set_link(Object * obj, Object * value, const char * name, Error ** errp)¶

Parameters

Object * obj: undescribed
Object * value: the value to be written to the property
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Writes an object’s canonical path to a property.

If the link property was created with <code>OBJ_PROP_LINK_STRONG</code> bit, the old target object is unreferenced, and a reference is added to the new target object.

Object * object_property_get_link(Object * obj, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Return

the value of the property, resolved from a path to an Object, or NULL if an error occurs (including when the property value is not a string or not a valid object path).

void object_property_set_bool(Object * obj, bool value, const char * name, Error ** errp)¶

Parameters

Object * obj: undescribed
bool value: the value to be written to the property
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Writes a bool value to a property.

bool object_property_get_bool(Object * obj, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Return

the value of the property, converted to a boolean, or NULL if an error occurs (including when the property value is not a bool).

void object_property_set_int(Object * obj, int64_t value, const char * name, Error ** errp)¶

Parameters

Object * obj: undescribed
int64_t value: the value to be written to the property
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Writes an integer value to a property.

int64_t object_property_get_int(Object * obj, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Return

the value of the property, converted to an integer, or negative if an error occurs (including when the property value is not an integer).

void object_property_set_uint(Object * obj, uint64_t value, const char * name, Error ** errp)¶

Parameters

Object * obj: undescribed
uint64_t value: the value to be written to the property
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Writes an unsigned integer value to a property.

uint64_t object_property_get_uint(Object * obj, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Return

the value of the property, converted to an unsigned integer, or 0 an error occurs (including when the property value is not an integer).

int object_property_get_enum(Object * obj, const char * name, const char * typename, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
const char * typename: the name of the enum data type
Error ** errp: returns an error if this function fails

Return

the value of the property, converted to an integer, or undefined if an error occurs (including when the property value is not an enum).

void object_property_get_uint16List(Object * obj, const char * name, uint16List ** list, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
uint16List ** list: the returned int list
Error ** errp: returns an error if this function fails

Return

the value of the property, converted to integers, or undefined if an error occurs (including when the property value is not an list of integers).

void object_property_set(Object * obj, Visitor * v, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
Visitor * v: the visitor that will be used to write the property value. This should be an Input visitor and the data will be first read with name as the name and then written as the property value.
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Writes a property to a object.

void object_property_parse(Object * obj, const char * string, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * string: the string that will be used to parse the property value.
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Description

Parses a string and writes the result into a property of an object.

char * object_property_print(Object * obj, const char * name, bool human, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
bool human: if true, print for human consumption
Error ** errp: returns an error if this function fails

Description

Returns a string representation of the value of the property. The caller shall free the string.

const char * object_property_get_type(Object * obj, const char * name, Error ** errp)¶

Parameters

Object * obj: the object
const char * name: the name of the property
Error ** errp: returns an error if this function fails

Return

The type name of the property.

Object * object_get_root(void)¶

Parameters

void: no arguments

Return

the root object of the composition tree

Object * object_get_objects_root(void)¶

Parameters

void: no arguments

Description

Get the container object that holds user created object instances. This is the object at path “/objects”

Return

the user object container

Object * object_get_internal_root(void)¶

Parameters

void: no arguments

Description

Get the container object that holds internally used object instances. Any object which is put into this container must not be user visible, and it will not be exposed in the QOM tree.

Return

the internal object container

gchar * object_get_canonical_path_component(Object * obj)¶

Parameters

Object * obj: undescribed

Return

The final component in the object’s canonical path. The canonical path is the path within the composition tree starting from the root. NULL if the object doesn’t have a parent (and thus a canonical path).

gchar * object_get_canonical_path(Object * obj)¶

Parameters

Object * obj: undescribed

Return

The canonical path for a object. This is the path within the composition tree starting from the root.

Object * object_resolve_path(const char * path, bool * ambiguous)¶

Parameters

const char * path: the path to resolve
bool * ambiguous: returns true if the path resolution failed because of an ambiguous match

Description

There are two types of supported paths–absolute paths and partial paths.

Absolute paths are derived from the root object and can follow child<> or link<> properties. Since they can follow link<> properties, they can be arbitrarily long. Absolute paths look like absolute filenames and are prefixed with a leading slash.

Partial paths look like relative filenames. They do not begin with a prefix. The matching rules for partial paths are subtle but designed to make specifying objects easy. At each level of the composition tree, the partial path is matched as an absolute path. The first match is not returned. At least two matches are searched for. A successful result is only returned if only one match is found. If more than one match is found, a flag is returned to indicate that the match was ambiguous.

Return

The matched object or NULL on path lookup failure.

Object * object_resolve_path_type(const char * path, const char * typename, bool * ambiguous)¶

Parameters

const char * path: the path to resolve
const char * typename: the type to look for.
bool * ambiguous: returns true if the path resolution failed because of an ambiguous match

Description

This is similar to object_resolve_path. However, when looking for a partial path only matches that implement the given type are considered. This restricts the search and avoids spuriously flagging matches as ambiguous.

For both partial and absolute paths, the return value goes through a dynamic cast to typename. This is important if either the link, or the typename itself are of interface types.

Return

The matched object or NULL on path lookup failure.

Object * object_resolve_path_component(Object * parent, const gchar * part)¶

Parameters

Object * parent: the object in which to resolve the path
const gchar * part: the component to resolve.

Description

This is similar to object_resolve_path with an absolute path, but it only resolves one element (part) and takes the others from parent.

Return

The resolved object or NULL on path lookup failure.

void object_property_add_child(Object * obj, const char * name, Object * child, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
Object * child: the child object
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Child properties form the composition tree. All objects need to be a child of another object. Objects can only be a child of one object.

There is no way for a child to determine what its parent is. It is not a bidirectional relationship. This is by design.

The value of a child property as a C string will be the child object’s canonical path. It can be retrieved using object_property_get_str(). The child object itself can be retrieved using object_property_get_link().

void object_property_allow_set_link(Error **, Error **, Error **, Error **)¶

Parameters

``Error ** ``: undescribed
``Error ** ``: undescribed
``Error ** ``: undescribed
``Error ** ``: undescribed

Description

The default implementation of the object_property_add_link() check() callback function. It allows the link property to be set and never returns an error.

void object_property_add_link(Object * obj, const char * name, const char * type, Object ** child, void (*check) (const Object *obj, const char *name, Object *val, Error **errp, ObjectPropertyLinkFlags flags, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
const char * type: the qobj type of the link
Object ** child: a pointer to where the link object reference is stored
void (*)(const Object *obj, const char *name, Object *val, Error **errp) check: callback to veto setting or NULL if the property is read-only
ObjectPropertyLinkFlags flags: additional options for the link
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Links establish relationships between objects. Links are unidirectional although two links can be combined to form a bidirectional relationship between objects.

Links form the graph in the object model.

The <code>**check()**</code> callback is invoked when object_property_set_link() is called and can raise an error to prevent the link being set. If <code>**check**</code> is NULL, the property is read-only and cannot be set.

Ownership of the pointer that child points to is transferred to the link property. The reference count for <code>***child**</code> is managed by the property from after the function returns till the property is deleted with object_property_del(). If the <code>**flags**</code> <code>OBJ_PROP_LINK_STRONG</code> bit is set, the reference count is decremented when the property is deleted or modified.

void object_property_add_str(Object * obj, const char * name, char *(*get) (Object *, Error **, void (*set) (Object *, const char *, Error **, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
char *(*)(Object *, Error **) get: the getter or NULL if the property is write-only. This function must return a string to be freed by g_free().
void (*)(Object *, const char *, Error **) set: the setter or NULL if the property is read-only
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add a string property using getters/setters. This function will add a property of type ‘string’.

void object_property_add_bool(Object * obj, const char * name, bool (*get) (Object *, Error **, void (*set) (Object *, bool, Error **, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
bool (*)(Object *, Error **) get: the getter or NULL if the property is write-only.
void (*)(Object *, bool, Error **) set: the setter or NULL if the property is read-only
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add a bool property using getters/setters. This function will add a property of type ‘bool’.

void object_property_add_enum(Object * obj, const char * name, const char * typename, const QEnumLookup * lookup, int (*get) (Object *, Error **, void (*set) (Object *, int, Error **, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
const char * typename: the name of the enum data type
const QEnumLookup * lookup: undescribed
int (*)(Object *, Error **) get: the getter or NULL if the property is write-only.
void (*)(Object *, int, Error **) set: the setter or NULL if the property is read-only
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add an enum property using getters/setters. This function will add a property of type ‘typename‘.

void object_property_add_tm(Object * obj, const char * name, void (*get) (Object *, struct tm *, Error **, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
void (*)(Object *, struct tm *, Error **) get: the getter or NULL if the property is write-only.
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add a read-only struct tm valued property using a getter function. This function will add a property of type ‘struct tm’.

void object_property_add_uint8_ptr(Object * obj, const char * name, const uint8_t * v, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
const uint8_t * v: pointer to value
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add an integer property in memory. This function will add a property of type ‘uint8’.

void object_property_add_uint16_ptr(Object * obj, const char * name, const uint16_t * v, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
const uint16_t * v: pointer to value
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add an integer property in memory. This function will add a property of type ‘uint16’.

void object_property_add_uint32_ptr(Object * obj, const char * name, const uint32_t * v, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
const uint32_t * v: pointer to value
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add an integer property in memory. This function will add a property of type ‘uint32’.

void object_property_add_uint64_ptr(Object * obj, const char * name, const uint64_t * v, Error ** Errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
const uint64_t * v: pointer to value
Error ** Errp: undescribed

Description

Add an integer property in memory. This function will add a property of type ‘uint64’.

void object_property_add_alias(Object * obj, const char * name, Object * target_obj, const char * target_name, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
Object * target_obj: the object to forward property access to
const char * target_name: the name of the property on the forwarded object
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add an alias for a property on an object. This function will add a property of the same type as the forwarded property.

The caller must ensure that <code>**target_obj**</code> stays alive as long as this property exists. In the case of a child object or an alias on the same object this will be the case. For aliases to other objects the caller is responsible for taking a reference.

void object_property_add_const_link(Object * obj, const char * name, Object * target, Error ** errp)¶

Parameters

Object * obj: the object to add a property to
const char * name: the name of the property
Object * target: the object to be referred by the link
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Add an unmodifiable link for a property on an object. This function will add a property of type link<TYPE> where TYPE is the type of target.

The caller must ensure that target stays alive as long as this property exists. In the case target is a child of obj, this will be the case. Otherwise, the caller is responsible for taking a reference.

void object_property_set_description(Object * obj, const char * name, const char * description, Error ** errp)¶

Parameters

Object * obj: the object owning the property
const char * name: the name of the property
const char * description: the description of the property on the object
Error ** errp: if an error occurs, a pointer to an area to store the error

Description

Set an object property’s description.

int object_child_foreach(Object * obj, int (*fn) (Object *child, void *opaque, void * opaque)¶

Parameters

Object * obj: the object whose children will be navigated
int (*)(Object *child, void *opaque) fn: the iterator function to be called
void * opaque: an opaque value that will be passed to the iterator

Description

Call fn passing each child of obj and opaque to it, until fn returns non-zero.

It is forbidden to add or remove children from obj from the fn callback.

Return

The last value returned by fn, or 0 if there is no child.

int object_child_foreach_recursive(Object * obj, int (*fn) (Object *child, void *opaque, void * opaque)¶

Parameters

Object * obj: the object whose children will be navigated
int (*)(Object *child, void *opaque) fn: the iterator function to be called
void * opaque: an opaque value that will be passed to the iterator

Description

Call fn passing each child of obj and opaque to it, until fn returns non-zero. Calls recursively, all child nodes of obj will also be passed all the way down to the leaf nodes of the tree. Depth first ordering.

It is forbidden to add or remove children from obj (or its child nodes) from the fn callback.

Return

The last value returned by fn, or 0 if there is no child.

Object * container_get(Object * root, const char * path)¶

Parameters

Object * root: root of the #path, e.g., object_get_root()
const char * path: path to the container

Description

Return a container object whose path is path. Create more containers along the path if necessary.

Return

the container object.

size_t object_type_get_instance_size(const char * typename)¶

Parameters

const char * typename: Name of the Type whose instance_size is required

Description

Returns the instance_size of the given typename.