bus_generic_read_ivar,

#include <sys/param.h>
#include <sys/bus.h>

int
bus_generic_read_ivar(device_t dev, device_t child, int index, uintptr_t *result);

int
bus_generic_write_ivar(device_t dev, device_t child, int index, uintptr_t value);

These functions simply return ENOENT.

device(9), driver(9)

This manual page was written by Doug Rabson.