Loading and Unloading Drivers

Opening a special file associated with the device driver causes the driver to be loaded. modload(1M) can also be used to load the driver into memory, but it does not call any routines in the module. Opening the device is the preferred method.

Normally, the system automatically unloads device drivers when they are no longer in use. During development, it might be necessary to use modunload(1M) to unload the driver explicitly. In order for modunload(1M) to be successful, the device driver must be inactive; there must be no outstanding references to the device, such as through open(2) or mmap(2).

modunload takes a runtime-dependentmodule_id as an argument. The module_id can be found by using grep to search the output of modinfo for the driver name in question and looking at the first column.

# modunload -i module_id

To unload all currently unloadable modules, specify module ID zero:

# modunload -i 0

In addition to being inactive, the driver must have working detach(9E) and _fini(9E) routines for modunload(1M) to succeed.