Re: [Jack-Devel] port callbacks, jack_port_id_t

On Fri, Apr 29, 2011 at 11:04 AM, Dan Muresan <[hidden]> wrote:
> Hi, I have some questions about the jack1 port API that the
> documentation and examples don't clarify:
>
> 1) how do I translate a jack_port_id_t to a jack_port_t or a port
> name? When the app gets a JackPortConnectCallback, how does it know
> which ports it's talking about?

read the API docs:

  jack_port_by_id (jack_client_t*, jack_port_id_t);
  jack_port_by_name (jack_client_t*, const char* name);

> 2) In what thread do the port callbacks happen?

threads for callbacks are one of the only areas where Jack1 and Jack2
appear different from a client perspective. they also differ between
OS X, Windows and other systems on which JACK runs. the following is a
table that i believe is correct:

1) Process Callback: ALWAYS called from the "process thread". There
may or may not be an "Other" thread running.

2) Other Server->Client Callbacks

                 OS X    Windows    *nix
----------------------------------------------
JACK1   |   Other     n/a            Process
JACK2   |   Oher      Other        Other


Finally, you should probably never make client->server calls from the
process callback. The API is not clearly marked with indications of
which functions involve client->server roundtrips. The best rule of
thumb is that functions involving a jack_client_t* argument are not
usable from within the process callback. This issue may go away
if/when Jack1 moves to an "always use 2 threads" model, but the
programming discipline that the rule provides is a good one. There is
some documentation on this within the refmanual.

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