In the ddi_regs_map_setup(9F) call, dip is the dev_info pointer passed to attach(9E). rnumber specifies which register set to map if there is more than one. For devices with only one register set, pass 0 for rnumber. The register specifications referred to by rnumber are described by the reg property (see driver.conf(4), isa(4), eisa(4), mca(4), sysbus(4), vme(4), sbus(4), and pci(4)). ddi_regs_map_setup(9F) maps a device register set (register specification) and returns a bus address base in xsp->regp. This address is offset bytes from the base of the device register set, and the mapping extends sizeof(struct device_reg) bytes beyond that. To map all of a register set, pass zero for offset and the length.