ak8975_set_mode
ak8975_set_mode(data, POWER_DOWN);
ret = ak8975_set_mode(data, POWER_DOWN);
ret = ak8975_set_mode(data, POWER_DOWN);
ret = ak8975_set_mode(data, FUSE_ROM);
ret = ak8975_set_mode(data, POWER_DOWN);
int ret = ak8975_set_mode(data, MODE_ONCE);