param_server: add error when params are provided too late #2739
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julianoes
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The mavlink parameter protocol uses an index to set/get specific parameters. When all parameters are requested, the total count is sent out, together with all the parameters. Now once this overall count has been sent out, we can't add/provide more parameters on the server side. Until now, MAVSDK didn't care, but with this commit, we are adding a new error to signal that we can no longer change the param list. This implementation has a bit of a race condition unfortunately: if a request list message is received right in the beginning when all parameters are added, we lock the list too early. The correct fix for this would be a specific method to "end param provisions" and lock them down. However, requiring such a method would be a breaking change, so I'm not adding this now but I'm considering it for the next major version of MAVSDK.
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The mavlink parameter protocol uses an index to set/get specific parameters. When all parameters are requested, the total count is sent out, together with all the parameters.
Now once this overall count has been sent out, we can't add/provide more parameters on the server side. Until now, MAVSDK didn't care, but with this commit, we are adding a new error to signal that we can no longer change the param list.
This implementation has a bit of a race condition unfortunately: if a request list message is received right in the beginning when all parameters are added, we lock the list too early. The correct fix for this would be a specific method to "end param provisions" and lock them down. However, requiring such a method would be a breaking change, so I'm not adding this now but I'm considering it for the next major version of MAVSDK.
Alternative to #2085.
Requires mavlink/MAVSDK-Proto#388 to be merged first.