bus_generic_read_ivar(9) on FreeBSD
The text 59a0b7c47c55, as FreeBSD 4.11-RELEASE, FreeBSD 4.10-RELEASE, FreeBSD 4.9-RELEASE, FreeBSD 4.8-RELEASE, FreeBSD 4.7-RELEASE, FreeBSD 4.6.2-RELEASE, FreeBSD 4.6-RELEASE, FreeBSD 4.5-RELEASE shipped it.
generic implementation of BUS_READ_IVAR and BUS_WRITE_IVAR for busses