Experimental Physics and
Industrial Control System

Michael Davidsaver via Core-talk <core-talk at aps.anl.gov> · Fri, 26 Jun 2020 16:12:50 -0700

On 6/8/20 4:18 PM, Michael Davidsaver wrote:
> ...
> 1. Add alarm message and time tag to dbCommon in Base
> 
> Not directly related to DBR_VFIELD, but adds an alarm
> message string, and time tag a la. PVA.  Also, adds
> a 'utag' server side filter which can apply a bitmask
> to the time tag.
> 
> https://github.com/epics-base/epics-base/pull/71

Continuing the discussion/review of this multi-part series,
I'd like to go into detail about the first part or the first PR.
The added ability to provide a string describing alarms.

From the prospective of a device support author,
this interface can be summarized as:

> int recGblSetSevrMsg(void *precord, epicsEnum16 new_stat,
>                      epicsEnum16 new_sevr,
>                      const char *msg)

Were currently a device support might have:

> if(!connected)
>   recGblSetSevr(prec, READ_ALARM, INVALID_ALARM);

More information could be provided with:

> if(!connected)
>   recGblSetSevrMsg(prec, READ_ALARM, INVALID_ALARM, "No Conn");

Practically, this is a way to disambiguate status codes like READ_ALARM
or COMM_ALARM which tend to have multiple meanings.

From the prospective of a user, this message will appear in
a new AMSG field.  It can be accessed like any other record string field.

An additional benefit is that with QSRV it will appear as part of
the PVA alarm meta-data.  aka. the 'alarm.message' structure field.

The PR adds a couple of internal usages of recGblSetSevrMsg().
Probably the most interesting is to the link code so that
when a link operation signals an alarm, the link field name
is given as the alarm message.

So eg. it can be seen at a glance that INPE of a calcRecord
has set a LINK_ALARM.

Open questions:

* Is a printf()-like form of recGblSetSevrMsg() needed?
  (currently message length is limited to 40 characters)

* Does struct lset need changing?  (and how?)
  Needed for eg. MSS to copy message string

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System