Experimental Physics and
Industrial Control System

Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> · Wed, 18 Mar 2020 09:54:34 -0700

On 3/18/20 9:47 AM, Mark Rivers wrote:
>> by analogy waveformRecord has
>>> db_post_events(prec, &prec->val, monitor_mask);
>> note 'val' not 'bptr'.
> 
> 
> The mca record has worked with no changes in 3.14, 3.15, and 7.0.3 with these lines:
> 
> 
> mcaRecord.dbd:
> recordtype(mca) {
>         include "dbCommon.dbd"
>         field(VERS,DBF_DOUBLE) {
>                 prompt("Code Version")
>                 special(SPC_NOMOD)
>                 initial("1")
>         }
>         field(VAL,DBF_NOACCESS) {
>                 prompt("Value")
>                 special(SPC_DBADDR)
>                 pp(TRUE)
>                 size(4)
>                 extra("void *val")
>         }
>         field(BPTR,DBF_NOACCESS) {
>                 prompt("Buffer Pointer")
>                 special(SPC_NOMOD)
>                 interest(4)
>                 size(4)
>                 extra("void *bptr")
>         }
> 
> mcaRecord.c:
>     if (MARKED(M_VAL)) db_post_events(pmca,pmca->bptr,monitor_mask);
> 
> So it is posting monitors on the bptr field, not the val field, and it seems to work fine.
> 
> 
> It looks like Pete is doing what the mca record does, but it is not working.  Why?

Ah, there is a second piece to the puzzle.

db_post_events() must be called with whatever address is in DBADDR::pfield
which by default in this case is '&val' but this can be changed in the
cvt_dbaddr callback.  Indeed waveformRecord used to do this.

https://github.com/epics-base/epics-base/commit/92d52cc415599b7dffa7df1f23d5ba8227fb4d3a

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System