Add a little state machine and a related API, to simplify sending out a
frame, receiving the Ack / No-ack status and (if acked) waiting for a
response frame from the target device, one of a list of possible
frame prefixes. The nl80211 API for this makes it complicated
enough that this new API seems to be justified, on top of that there's a
quirk when using the brcmfmac driver where the nl80211 response
(containing the operation's cookie), the Tx Status event and the response
Frame event are received from nl80211 in reverse order (not seen with
other drivers so far), further complicating what should be a pretty
simple task.
This new API is independent of netdev.c and allows actually
unregistering from receiving notifications of frames, although with some
quirks. The current API only allowed the callback for a registration to
be forgotten but our process and/or the kernel would still be woken up
when matching frames were received because the kernel had no frame
unregister call. In the new API you can supply a group-id paramter when
registering frames. If it is non-zero the frame_watch_group_remove() call
can be used to remove all frame registrations that had a given group-id
by closing the netlink socket on which the notifications would be
received. This means though that it's a slightly costly operation.
The file is named frame-xchg.c because I'm thinking of also adding
utilities for sending frames and waiting for one of a number of replies
and handling the acked/un-acked information.
Andrew Zaborowski