int pm_busy_component(dev_info_t *dip, int component);
pm_busy_component(9F) marks the component as busy.
While the component is busy, it will not be powered off. If the component is already powered off, then marking it busy doesn't change its power level. The driver needs to call ddi_dev_is_needed(9F) for this purpose. Calls to pm_busy_component(9F) are stacked and require a corresponding number of calls to pm_idle_component(9F) to idle the component.