The DRIVER_MODULE macro declares a kernel driver. DRIVER_MODULE expands to the real driver declaration, where the phrase name is used as the naming prefix for the driver and its functions. Note that it is supplied as plain text, and not a char or char *.
busname is the parent bus of the driver (PCI, ISA, PPBUS and others), e.g. pci, isa, or ppbus.
The identifier used in DRIVER_MODULE can be different from the driver name. Also, the same driver identifier can exist on different busses, which is a pretty clean way of making front ends for different cards using the same driver on the same or different busses. For example, the following is allowed:
DRIVER_MODULE foo isa foo_driver foo_devclass NULL NULL;
DRIVER_MODULE foo pci foo_driver foo_devclass NULL NULL;
driver is the driver of type driver_t, which contains the information about the driver and is therefore one of the two most important parts of the call to DRIVER_MODULE.
The devclass argument contains the kernel-internal information about the device, which will be used within the kernel driver module.
The evh argument is the event handler which is called when the driver (or module) is loaded or unloaded (see module(9)).
The arg is unused at this time and should be a NULL pointer.
MULTI_DRIVER_MODULE is a special version of DRIVER_MODULE, which takes a list of drivers instead of a single driver instance.
device(9), driver(9), module(9)