modlinkage Structure

	int		ml_rev;
 	void		*ml_linkage[4];

The modlinkage(9S) structure is exported to the kernel when the driver is loaded. The ml_rev field indicates the revision number of the loadable module system, which should be set to MODREV_1. Drivers can only support one module, so only the first element of ml_linkage should be set to the address of a modldrv(9S) structure. ml_linkage[1] should be set to NULL.