Drivers should only read the target_ values in the timeout, update the
timeout with the new duration and then update the position.
For the position we simply need to add the previous duration to the
position and then set the new duration + rate.
Otherwise, everything else should read the duration/rate and not use
the target_ values.
Use stdalign.h instead of union.
Fix some refcounting and return values.
Fail early in add_filters.
Minor style cleanups.
Less magical spa_dbus_async_call.
As server, put node nick in GATT Characteristic User Description, so
that clients have some information which endpoint is which in case we
have multiple. This is not in BLE MIDI standard, but cannot hurt.
As client, make use of that information, if present.
Implement BLE MIDI node, providing an input and output port. MIDI data
received is normalized and produced on output port. Data from input
port is converted to BLE MIDI and sent to the device.
Event timestamps come from device clock, whose offset to wall clock we
determine by correlating packet reception times with their timestamps.
The jitter in packet reception is likely much larger than device clock
error, so we average over that.
