Add support for using other clocks.
clock.id can be used to set one of the system clocks.
clock.device can be used to open a clock device such as a PTP clock
device.
Use a dll to track the progress of non-monotonic clocks.
When reading the timerfd gives an error, we should return right away
because the timeout did not happen.
If we change the timerfd timeout before reading it, we can get -EAGAIN.
Don't log an error in that case but wait for the new timeout.
Use `spa_loop_invoke()` to invoke a callback on the data loop
to remove an embedded `spa_source` from the data loop.
Embedded `spa_source` objects cannot be safely removed
while the loop is polling without risking potential
use-after-frees.
HAVE_DATA|NEED_DATA signals that the graph can continue processing.
OK means that the node will continue asynchronously later. This
is needed to make the dummy driver work as a follower.
When we add a new listener to an object, it will emit the full state
of the object. For this it temporarily sets the change_mask to all
changes. Restore the previous state after this or else we might not
emit the right change_mask for the next listener.
Consider the case where one there are two listeners on an object.
The object emits a change and the first listener wants to enumerate the
changed params. For this is adds a new listener and then triggers the
enumeration. If we set the change_mask to 0 after adding the listener,
the second listener would get a 0 change_mask and fail to update
its state.
This replaces the manual check for "true" and some (inconsistent) return value
of atoi. All those instances now require either "true" or "1" to parse as
true, any other value (including NULL) is boolean false.
