[sane-standard] sane standard proposals (1) "callbacks"

[Johannes Berg]

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1. Network protocol and callbacks/buttons

The current standard asks for a frontend to always poll the backend for
changed information, e.g. button presses.
What is the point here? Why could a reasonable RPC mechanism not allow
messages that are unilaterally sent by the server, tagged with an
appropriate code to signify what they mean.

I imagine (the standard isn't too clear on this, a few datagram diagrams
could help) that each message sent from and to the server is tagged with
a code signifying what type of request/response it is, thus it should be
possible to have the server unilaterally send a message of code "RESCAN"
which would prompt the frontend to query the buttons status.

The local frontend/backend communication would of course implement this
with a trivial sane_callback_rescan() function.

johannes

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