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authorPeter Maydell <peter.maydell@linaro.org>2020-10-01 12:23:19 +0100
committerPeter Maydell <peter.maydell@linaro.org>2020-10-01 12:23:19 +0100
commit37a712a0f969ca2df7f01182409a6c4825cebfb5 (patch)
tree6eeb0b7f0bde4c8a0f8e1115b990530c5c62e9fe /docs/devel
parentcbba3dc6ea3fc9aa66e9f9eb41051536e3ad7cd0 (diff)
parent37aeb7a28ddbf52dd25dd53ae1b8391bc2287858 (diff)
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Merge remote-tracking branch 'remotes/bonzini-gitlab/tags/for-upstream' into staging
* SCSI fix (Dmitry, Li Feng, Li Qiang) * memory API fixes (Eduardo) * removal of deprecated '-numa node', 'cpu-add', '-smp' (Igor) * ACPI fix for VMBus (Jon) * relocatable install (myself) * always remove docker containers (myself) * serial cleanups (Philippe) * vmware cpuid leaf for tsc and apic frequency (Sunil) * KVM_FEATURE_ASYNC_PF_INT support (Vitaly) * i386 XSAVE bugfix (Xiaoyao) * QOM developer documentation in docs/devel (Eduardo) * new checkpatch tests (Dov) * x86_64 syscall fix (Douglas) * interrupt-based APF fix (Vitaly) * always create kvmclock (Vitaly) * fix bios-tables-test (Eduardo) * KVM PV features cleanup (myself) * CAN FD (Pavel) meson: * fixes (Marc-André, Max, Stefan, Alexander, myself) * moved libmpathpersist, cocoa, malloc tests (myself) * support for 0.56 introspected test dependencies (myself) # gpg: Signature made Wed 30 Sep 2020 18:11:45 BST # gpg: using RSA key F13338574B662389866C7682BFFBD25F78C7AE83 # gpg: issuer "pbonzini@redhat.com" # gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full] # gpg: aka "Paolo Bonzini <pbonzini@redhat.com>" [full] # Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4 E2F7 7E15 100C CD36 69B1 # Subkey fingerprint: F133 3857 4B66 2389 866C 7682 BFFB D25F 78C7 AE83 * remotes/bonzini-gitlab/tags/for-upstream: (86 commits) hw/net/can: Correct Kconfig dependencies hw/net/can: Documentation for CTU CAN FD IP open hardware core emulation. hw/net/can: CTU CAN FD IP open hardware core emulation. hw/net/can/ctucafd: Add CTU CAN FD core register definitions. net/can: Add can_dlc2len and can_len2dlc for CAN FD. hw/net/can: sja1000 ignore CAN FD frames net/can: Initial host SocketCan support for CAN FD. target/i386: kvm: do not use kvm_check_extension to find paravirtual capabilities bios-tables-test: Remove kernel-irqchip=off option target/i386: always create kvmclock device target/i386: Fix VM migration when interrupt based APF is enabled helper_syscall x86_64: clear exception_is_int checkpatch: Detect '%#' or '%0#' in printf-style format strings typedefs: Restrict PCMachineState to 'hw/i386/pc.h' hw/xen: Split x86-specific declaration from generic hardware ones stubs: Split accelerator / hardware related stubs sysemu/xen: Add missing 'exec/cpu-common.h' header for ram_addr_t type hw/i386/xen: Rename X86/PC specific function as xen_hvm_init_pc() docs: Move object.h overview doc comment to qom.rst docs: Create docs/devel/qom.rst ... Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'docs/devel')
-rw-r--r--docs/devel/build-system.rst5
-rw-r--r--docs/devel/index.rst1
-rw-r--r--docs/devel/qom.rst378
3 files changed, 384 insertions, 0 deletions
diff --git a/docs/devel/build-system.rst b/docs/devel/build-system.rst
index 08e85c6..2ee368f 100644
--- a/docs/devel/build-system.rst
+++ b/docs/devel/build-system.rst
@@ -193,6 +193,11 @@ compilation as possible. The Meson "sourceset" functionality is used
to list the files and their dependency on various configuration
symbols.
+All executables are built by default, except for some `contrib/`
+binaries that are known to fail to build on some platforms (for example
+32-bit or big-endian platforms). Tests are also built by default,
+though that might change in the future.
+
Various subsystems that are common to both tools and emulators have
their own sourceset, for example `block_ss` for the block device subsystem,
`chardev_ss` for the character device subsystem, etc. These sourcesets
diff --git a/docs/devel/index.rst b/docs/devel/index.rst
index 04773ce..c34b43e 100644
--- a/docs/devel/index.rst
+++ b/docs/devel/index.rst
@@ -31,3 +31,4 @@ Contents:
reset
s390-dasd-ipl
clocks
+ qom
diff --git a/docs/devel/qom.rst b/docs/devel/qom.rst
new file mode 100644
index 0000000..0b943b2
--- /dev/null
+++ b/docs/devel/qom.rst
@@ -0,0 +1,378 @@
+===========================
+The QEMU Object Model (QOM)
+===========================
+
+.. highlight:: c
+
+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
+
+.. code-block:: c
+ :caption: Creating a minimal type
+
+ #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)
+
+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()
+
+.. code-block:: c
+
+ 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)
+
+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:
+
+.. code-block:: c
+ :caption: Typecasting macros
+
+ #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)
+
+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:
+
+.. code-block:: c
+ :caption: Overriding a virtual function
+
+ #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,
+ };
+
+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:
+
+.. code-block:: c
+ :caption: Defining an abstract class
+
+ #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);
+ }
+
+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. As a consequence, a pointer to
+an interface instance should always be of incomplete type in order to be
+sure it cannot be dereferenced. That is, you should define the
+'typedef struct SomethingIf SomethingIf' so that you can pass around
+``SomethingIf *si`` arguments, but not define a ``struct SomethingIf { ... }``.
+The only things you can validly do with a ``SomethingIf *`` are to pass it as
+an argument to a method on its corresponding SomethingIfClass, or to
+dynamically cast it to an object that implements the interface.
+
+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.
+
+.. code-block:: c
+ :caption: Overriding a virtual method
+
+ 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,
+ };
+
+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.
+
+Standard type declaration and definition macros
+===============================================
+
+A lot of the code outlined above follows a standard pattern and naming
+convention. To reduce the amount of boilerplate code that needs to be
+written for a new type there are two sets of macros to generate the
+common parts in a standard format.
+
+A type is declared using the OBJECT_DECLARE macro family. In types
+which do not require any virtual functions in the class, the
+OBJECT_DECLARE_SIMPLE_TYPE macro is suitable, and is commonly placed
+in the header file:
+
+.. code-block:: c
+ :caption: Declaring a simple type
+
+ OBJECT_DECLARE_SIMPLE_TYPE(MyDevice, my_device, MY_DEVICE, DEVICE)
+
+This is equivalent to the following:
+
+.. code-block:: c
+ :caption: Expansion from declaring a simple type
+
+ typedef struct MyDevice MyDevice;
+ typedef struct MyDeviceClass MyDeviceClass;
+
+ G_DEFINE_AUTOPTR_CLEANUP_FUNC(MyDeviceClass, object_unref)
+
+ #define MY_DEVICE_GET_CLASS(void *obj) \
+ OBJECT_GET_CLASS(MyDeviceClass, obj, TYPE_MY_DEVICE)
+ #define MY_DEVICE_CLASS(void *klass) \
+ OBJECT_CLASS_CHECK(MyDeviceClass, klass, TYPE_MY_DEVICE)
+ #define MY_DEVICE(void *obj)
+ OBJECT_CHECK(MyDevice, obj, TYPE_MY_DEVICE)
+
+ struct MyDeviceClass {
+ DeviceClass parent_class;
+ };
+
+The 'struct MyDevice' needs to be declared separately.
+If the type requires virtual functions to be declared in the class
+struct, then the alternative OBJECT_DECLARE_TYPE() macro can be
+used. This does the same as OBJECT_DECLARE_SIMPLE_TYPE(), but without
+the 'struct MyDeviceClass' definition.
+
+To implement the type, the OBJECT_DEFINE macro family is available.
+In the simple case the OBJECT_DEFINE_TYPE macro is suitable:
+
+.. code-block:: c
+ :caption: Defining a simple type
+
+ OBJECT_DEFINE_TYPE(MyDevice, my_device, MY_DEVICE, DEVICE)
+
+This is equivalent to the following:
+
+.. code-block:: c
+ :caption: Expansion from defining a simple type
+
+ static void my_device_finalize(Object *obj);
+ static void my_device_class_init(ObjectClass *oc, void *data);
+ static void my_device_init(Object *obj);
+
+ static const TypeInfo my_device_info = {
+ .parent = TYPE_DEVICE,
+ .name = TYPE_MY_DEVICE,
+ .instance_size = sizeof(MyDevice),
+ .instance_init = my_device_init,
+ .instance_finalize = my_device_finalize,
+ .class_size = sizeof(MyDeviceClass),
+ .class_init = my_device_class_init,
+ };
+
+ static void
+ my_device_register_types(void)
+ {
+ type_register_static(&my_device_info);
+ }
+ type_init(my_device_register_types);
+
+This is sufficient to get the type registered with the type
+system, and the three standard methods now need to be implemented
+along with any other logic required for the type.
+
+If the type needs to implement one or more interfaces, then the
+OBJECT_DEFINE_TYPE_WITH_INTERFACES() macro can be used instead.
+This accepts an array of interface type names.
+
+.. code-block:: c
+ :caption: Defining a simple type implementing interfaces
+
+ OBJECT_DEFINE_TYPE_WITH_INTERFACES(MyDevice, my_device,
+ MY_DEVICE, DEVICE,
+ { TYPE_USER_CREATABLE }, { NULL })
+
+If the type is not intended to be instantiated, then then
+the OBJECT_DEFINE_ABSTRACT_TYPE() macro can be used instead:
+
+.. code-block:: c
+ :caption: Defining a simple abstract type
+
+ OBJECT_DEFINE_ABSTRACT_TYPE(MyDevice, my_device, MY_DEVICE, DEVICE)
+
+
+
+API Reference
+-------------
+
+.. kernel-doc:: include/qom/object.h