Re: passive record/field to process when there is a CA read

[Dirk Zimoch <dirk.zimoch@psi.ch>]

Hello Dehong,

unfortunately EPICS does not support this.

What I normally do is to write a 1 to <record>.PROC via ca_sg_put. This call 
completes when the the record has finished processing. (You can also use 
ca_put_callback instead.) Then, I read the value with a ca_get. Of course, this 
is not an atomic action as there are two channel access calls involved. That 
means, it is possible that a second client processes the record again before you 
could read and you will read his value instead of yours. But this is normally 
not a problem.

It is a pity that EPICS leaks atomic process-and-read and read-modify-write calls.

Dirk


Dehong Zhang wrote:
> Hi,
>
> Is it possible to set up a passive record/field, which will only be processed
> when some channel access client tries to read it?
>
> Thanks and best regards,
> Dehong

--
Dr. Dirk Zimoch
Paul Scherrer Institut, WBGB/006
5232 Villigen PSI, Switzerland
Phone +41 56 310 5182