Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Thu, 3 Nov 2011 16:19:15 -0500

Hi Matt,

In general for complex application I would recommend that you ignore the 
ca_array_get() and ca_pend_io() functions completely — they're designed for 
simple linear programs.  Instead you should aim to get all of your completion 
notifications from CA using callbacks, calling ca_poll() or ca_pend_event() in 
your event loop (or turning on preemptive callbacks and adding locks).  Note 
that using ca_get_callback() also means that you don't have to allocate a data 
buffer for an incoming array until it arrives.  You can't use ca_array_get() 
for variable-length arrays either.

BTW, ca_pend_event() returns ECA_TIMEOUT in normal operation, because it 
doesn't normally return until that time has elapsed.  The alternative return 
code is ECA_EVDISALLOW which means you called it from inside a callback 
routine (not allowed).

HTH,

- Andrew
-- 
Optimization is the process of taking something that works and
replacing it with something that almost works, but costs less.
-- Roger Needham

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System