If the second bit of COM_ARM_MIS_EXT_REQ is set the vehicle
will only arm after receive an authorization.
The authorization flow:
vehicle/external -> command: arm authorization request -> arm authorizer
vehicle <- command ack with result in progress <- arm authorizer
vehicle <- any data request <- arm authorizer
vehicle -> data response -> arm authorizer
vehicle <- command ack authorizing or denying <- arm authorizer
Right now there is 2 ways to start the arm authorization request,
that can be configured by COM_ARM_AUTH parameter.
- One arm: When pilot request the vehicle to arm, it will request
authorization blocking the arm process up to the timeout defined in
COM_ARM_AUTH parameter.
- Two arms request: The first arm request will request the
authorization and will deny the first arm request, if authorizer
approved the request, pilot can arm again within the authorized
time and arm without any block.
The arm authorizer can be running anywhere(compute board or PX4
itself) and it is responsible to request the mission list or any
other information to vehicle before send a final response, it
should send to vehicle a COMMAND_ACK with
result = MAV_RESULT_IN_PROGRESS as soon as it receive the arm
authorization request and the final result
as after it got all the data that it needs authorize or deny the
request.
If 2 or more vehicle_command are queued a call to update() will
return the oldest vehicle_command and set the _cmd_time to the
timestamp of the last vehicle_command queued losing it.
Using update_if_changed() fix this causing all item being consumed
one at each call of send().
Instead of having several bools to each requirement to arm, lets group then
in a byte and use bitmask.
This also add a new arm requirement "arm authorization" that
will be implemented in another patch.
if _ftp_on is true, message_buffer was created and read, but it was
actually never written to, so this is not needed. It can only ever be
written to if _forwarding_on is true.
And the maximum number of configured file descriptors.
Note that this is per group, not per thread, so that e.g. logger and
log_writer_file show the same number.
This allows to run a command / function once when being deactivated. This avoids having flight modes which are not active run unnecessary code all the time.
