WIP - gimbal_manager_status and mav_cmd_do_gimbal_manager_configure support

[Davidsastresas]

WIP - Adding support for gimbal_manager_status mavlink message. This is necessary to continue the work being done in QGC:

mavlink/qgroundcontrol#10667 (comment)

I talked with @julianoes about this one, it seems we could forget for the moment about secondary control, and leave primary control at 0 unless somebody ( GCS or Autopilot ) requests control, so we change sysid and compid accordingly.

My best guess is that we should create a couple new variables for this, is Mount_Backend the proper place for it? @rmackay9 let me know your thoughts on this please.

We should also add mav_cmd_do_gimbal_manager_configure to our mavlink, because that is what the GCS will send to request and release control of the gimbal.

[rmackay9]

Hi, thanks for taking the initiative on this. I looked at this a couple of weeks ago and got this far: https://github.com/rmackay9/rmackay9-ardupilot/commits/mount-gimbal-manager-status

My intention was just to get some slightly half-baked handling of these messages into AP master so that it doesn't hold up the QGC development and then circle back and do the more difficult work of restructing the mode handling.

[rmackay9]

By the way, @khanasif786 will be our GSoC student this summer helping with the gimbal and camera integration. We have lots of work to do though so I'm still looking forward to PRs from anyone and everyone interested in improving our camera and gimbal support.

[Davidsastresas]

Sorry, again I worked over something you were already working. Shall we close this one, and continue yours? This one is very "draft", lots of details to close yet, yours is by far more completed.

I started working on it in order to continue on the QGC side. What we would need, in order to not do a lot of ugly workarounds in QGC would be:

• Support getting control using gimbal_manager_configure where primary control is GCS sysid and compid ( SUPORTED in your branch )
• Updating mavlink_control_id in your AP_Mount_Backend whenever the autopilot, or the user ( rc control ) takes command again
• Sending right away gimbal_manager_status whenever a change happens in the primary control, so all the system is updated as soon as possible of the change.
• Ignoring mavlink gimbal_manager commands if the sender sysid and compid are not in control, forcing them to send a gimbal_manager_configure first.

Thank you very much, and sorry for not talking to you before working on this, I should have imagined you were already on it!

[Davidsastresas]

Closed in favor of #23737. Thanks @rmackay9 !