We have two separate type trees, object types rooted at TYPE_OBJECT, and
interface types at TYPE_INTERFACE.
Object types are fore defining ultimately concrete types, i.e. any
concrete type is a descendant of TYPE_OBJECT. Interior nodes of the
TYPE_OBJECT tree are commonly abstract, with a few exceptions. Leaves
need to be concrete to be of any use.
Interface types are for defining interfaces object types provide (by
listing them in a type's .interfaces). TYPE_INTERFACE and all its
descendants are abstract.
Issue #1: INTERFACE_CLASS()
#define OBJECT_CLASS(class) \
((ObjectClass *)(class))
#define OBJECT_CLASS_CHECK(class_type, class, name) \
((class_type *)object_class_dynamic_cast_assert(OBJECT_CLASS(class),
(name), \
__FILE__, __LINE__,
__func__))
#define INTERFACE_CLASS(klass) \
OBJECT_CLASS_CHECK(InterfaceClass, klass, TYPE_INTERFACE)
Shouldn't INTERFACE_CLASS() be named INTERFACE_CLASS_CHECK() for
consistency?
Rename would be trivial, as there are no uses.
Issue #2: INTERFACE_CHECK()
#define OBJECT_CHECK(type, obj, name) \
((type *)object_dynamic_cast_assert(OBJECT(obj), (name), \
__FILE__, __LINE__, __func__))
#define INTERFACE_CHECK(interface, obj, name) \
((interface *)object_dynamic_cast_assert(OBJECT((obj)), (name), \
__FILE__, __LINE__, __func__))
The two are identical (except the former lacks parenthesis around obj,
which is a minor bug).
Obvious question: shouldn't we de-duplicate the code?
There's a more interesting question, however. Since two two are
identical, they can be used interchangeably. And since we can, we do;
for instance
#define QAUTHZ(obj) \
INTERFACE_CHECK(QAuthZ, (obj), \
TYPE_QAUTHZ)
even though TYPE_QAUTHZ is a sub-type of TYPE_OBJECT, not
TYPE_INTERFACE. Shouldn't we prevent that somehow? Or maybe embrace
they're the same and just get rid of INTERFACE_CHECK() entirely?
Issue #3: Inconsistent naming (surprise, surprise)
The confusion between object and interface types is of course aggravated
by our usual lack of discipline in naming. I recognize no less than
three naming conventions:
INTERFACE_CONVENTIONAL_PCI_DEVICE
INTERFACE_PCIE_DEVICE
TYPE_ACPI_DEVICE_IF
TYPE_ARM_LINUX_BOOT_IF
TYPE_TEST_IF
TYPE_TPM_IF
TYPE_IDAU_INTERFACE
TYPE_IPMI_INTERFACE
TYPE_PNV_XSCOM_INTERFACE
Yet they're used for less than half of the interface names:
TYPE_FW_PATH_PROVIDER
TYPE_HOTPLUG_HANDLER
TYPE_INTERRUPT_STATS_PROVIDER
TYPE_ISADMA
TYPE_MEMORY_DEVICE
TYPE_NMI
TYPE_NVRAM
TYPE_PPC_VIRTUAL_HYPERVISOR
TYPE_STREAM_SLAVE
TYPE_USER_CREATABLE
TYPE_XICS_FABRIC
TYPE_XIVE_NOTIFIER
Can we agree on one naming convention, and enforce it?
