Benjamin Berg authored Jan 13, 2020 and Bastien Nocera committed Jan 14, 2020

This API was added to libfprint to allow drivers to report the match
result early before the operation has been completed. No driver makes
use of this facility yet and instead drivers try to finish the
operation early for quick result reporting. This primarily means not
waiting for finger removal.

Once drivers are updated, fprintd reactivity will regress unless the
early match callback is implemented as they would only get an operation
finished callback when the whole of the operation was finished,
including finger removal and finishing up USB communications.

See: libfprint/fprintd#35