pub fn uevent_drain_battery(fd: &Fd) -> Option<(Option<u8>, String)>Expand description
Drain all pending uevent messages; return the last power_supply event seen.
Returns (capacity, status) where capacity is None if POWER_SUPPLY_CAPACITY
was absent from the uevent (caller should fall back to sysfs).
Returns None if the queue contained no power_supply events at all.
Must be called in a loop after EPOLLET fires to drain the edge-triggered fd.