* Properly define the callback time of a write/commit as the time when
the pipe is available again for further writing.
* Refuse commits when writes are pending; instead, enforce a strict
order of finishing writes before committing, which makes sense since
consecutive writes are ordered this way already.
* Properly support callbacks for writes and for commits.
* Define the synchronous APIs in terms of waiting until the callbacks
for equivalent asynchronous functions are invoked (plus initial
waiting for pipes to be ready).
* Add the power management functions (mostly stable even under
overclock; requires some testing, but no known issue)
* Add a dynamic configuration system where interfaces can declare
descriptors with arbitrary endpoint numbers and additional
parameters, and the driver allocates USB resources (endpoints, pipes
and FIFO memory) between interfaces at startup. This allows
implementations of different classes to be independent from each
other.
* Add responses to common SETUP requests.
* Add pipe logic that allows programs to write data synchronously or
asynchronously to pipes, in a single or several fragments, regardless
of the buffer size (still WIP with a few details to polish and the
API is not public yet).
* Add a WIP bulk IN interface that allows sending data to the host.
This will eventually support the fxlink protocol.