Manual Pages  — KOBJ

The simplest way to create a kernel object is to call kobj_create() with a suitable class, malloc type and flags (see malloc(9) for a description of the malloc type and flags). This will allocate memory for the object based on the object size specified by the class and initialise it by zeroing the memory and installing a pointer to the class' method dispatch table. Objects created in this way should be freed by calling kobj_delete().

Clients which would like to manage the allocation of memory themselves should call kobj_init() or kobj_init_static() with a pointer to the memory for the object and the class which implements it. It is also possible to use kobj_init() and kobj_init_static() to change the class for an object. This should be done with care as the classes must agree on the layout of the object. The device framework uses this feature to associate drivers with devices.

The functions kobj_class_compile(), kobj_class_compile_static() and kobj_class_free() are used to process a class description to make method dispatching efficient. A client should not normally need to call these since a class will automatically be compiled the first time it is used. If a class is to be used before malloc(9) and mutex(9) are initialised, then kobj_class_compile_static() should be called with the class and a pointer to a statically allocated kobj_ops structure before the class is used to initialise any objects. In that case, also kobj_init_static() should be used instead of kobj_init().

To define a class, first define a simple array of kobj_method_t. Each method which the class implements should be entered into the table using the macro KOBJMETHOD() which takes the name of the method (including its interface) and a pointer to a function which implements it. The table should be terminated with two zeros. The macro DEFINE_CLASS() can then be used to initialise a kobj_class_t structure. The size argument to DEFINE_CLASS() specifies how much memory should be allocated for each object.