Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Tue, 10 Mar 1998 09:49:34 -0600

Benjamin Franksen wrote:
> 
> Hello Marty (and all the others),
> 
> another proposal (suggested by Goetz Pfeiffer): Currently there is a
> 'Symb' device support for ai, ao, longin, longout, stringin and
> stringout records. Their purpose is to associate the records VALue with
> some globally visible VxWorks variable through the use of VxWorks'
> symbol table. But the implementation is rather crude: Neither is there
> any protection against race conditions while copying the value, nor is
> there the possibility to supply the name of the symbol independently
> from the record's name resp. naming convention.

In the next release of base the version of Symb* is that supplied by
William Lupton. It is a major change to the old support while keeping
compatibity. William interacted with Steve Lewis while designing and
implementing the changes.

> Both can be mended easily:
> 
> (1) To protect the data transport, simply add some
> 
>         intLock()
>         ...
>         intUnlock()
> 
> pairs around the critical section, which is for example in devAiSymb the
> single line
> 
>         pai->val = *(double *)(pai->dpvt);
> 
> (2) To enable record name independent symbol names, check the hw link if
> it equals INST_IO. If yes, get the symbol name from the link, otherwise
> (ie the link is CONSTANT) use the previous algorithm as a fallback
> method.
> 
> I'd volunteer to code the proposed changes, if there is interest and
> there are no objections to them.

I will send you the latest version. 

Marty

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System