Experimental Physics and
Industrial Control System

Ben Franksen <[email protected]> · Mon, 15 Nov 2010 21:40:29 +0100

On Sonntag, 14. November 2010, Ben Franksen wrote:
> On Freitag, 29. Oktober 2010, Ben Franksen wrote:
> > this is a poll to determine whether anyone is actually using the
> > sequencer with backends other than Channel Access and so needs
> > support for the pv layer between the sequencer and the backend data
> > transfer protocol.
> >
> > I would rather like to get rid of the pv layer for several reasons.
>
> The people at KECK have told me they discussed it and have decided
> they no longer need the KTL support, quote: "We're all for
> simplifying it!"
>
> So, one last time:
>
> If you are using the pv layer for anything (other than as obligatory
> bridge to CA as required by previous sequencer versions), or if you
> think that there are other important reasons to keep it, this is your
> last chance to save it, otherwise it's going to pay its debt to
> nature.

Since I have received questions off-list, like

> What exactly do you mean by "the pv layer"?
> We may be using it, but I'd have to look at the code.

which indicate that I have assumed to much knowledge of the sequencer 
internals, let me add some explanations:

I am talking about the code under src/pv in the sequencer source tree. 
This code provides a C++ implementation of a CA-client-like interface, 
so that you can use the sequencer with other protocols (that provide 
similar features) beside CA (such as KECK's KTL library). It has been 
introduced in version 2.0.

The current sequencer interface (and thus most existing SNL programs) 
need only the header file pvAlarm.h in which CA status codes and EPICS 
record status/severity are unified as pvStatXXX and pvSevrXXX. This 
header file will remain available to provide compatibility for existing 
programs. What I want to abandon is the *internal* use of the pv 
library, i.e. the C++ layer over CA.

With "using the pv layer" I mean that you use the sequencer with 
protocols other than CA, or that you have programs that directly use 
the C *functions* or C++ *classes* defined in pv.h.

Cheers
Ben
-- 
"Never confuse what is natural with what is habitual."
                                   -- attributed to Mahatma Gandhi

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System