Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Fri, 13 Aug 1999 15:16:00 -0500

Hi Andreas,

you hit one of my subject areas again...

Luedeke Andreas wrote:
> 
> I'm writing a driver for a serial IP module (in-house) with
> a VME_IO type of the INP and OUT field string:
> #Cn Sm @parameter
> 
> I want to allow dynamical changes of n, m and parameter.
> Do I have to make a copy of n, m & parameter and compare it
> to identify changes or is there a kind of flag that the field has changed?

With current versions of EPICS yes you have to keep track of the link
fields yourself if you want to support dynamic changes.  Very few device
support routines do this yet as the ability to change links at run-time
was only introduced in EPICS R3.13

> I think it is possible to have a special processing in record support if
> a field has changed. That would be the most elegant way to my opinion.
> But my driver will support roughly a dozen types of records and I don't
> want to rewrite them all.

I made a proposal at the last EPICS collaboration meeting to change the
code that handles links to make them much more generic, and one of my
changes will be to allow the device support to give a routine to be called
when the link is changed.  This will be implemented (hopefully in the next
major EPICS release), but I haven't had a chance to start looking at the
code yet.  When this is released you'll have to make some minor changes to
your code, but you'll also be able to define your own link formats. 
There's a document describing the proposal at
	http://www.aps.anl.gov/asd/people/anj/lnkSup.html

- Andrew
-- 
I brake for tail-gaters

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System