Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Tue, 14 Jul 2009 23:22:27 -0500

On Tuesday 14 July 2009 17:53:25 Benjamin Franksen wrote:
> On Dienstag, 14. Juli 2009, Tim Mooney wrote:
> > Benjamin Franksen wrote:
> > > I get this message on the iocsh (base is 3.14.8.2):
> > >
> > > dbCaTask ca_array_put Channel write request failed
> > > OTERMPCGP:cmdRmp has DB CA link to OTERMPCGP:colStRmp.PROC
> >
> > Ben,  I get that same error message when I use a CA link (from any
> > record) to
> > process a  record whose processing results in an error.  If your
> > situation is
> > like mine, OTERMPCGP:colStRmp should be in some kind of alarm.
>
> Interesting. I'll check this. The message is a bit misleading (if this is
> indeed what causes it), to me it suggests that I have somehow misconfigured
> the link.

I agree the message is misleading.  It occurs because any error status 
returned by device support is passed back up the call chain and is returned 
by the record type's process() routine, by dbProcess(), then by dbPutField(). 
db_put_field converts it to a 0 or -1 value and results in the channel access 
server reporting a write error to the client, which in this case is the dbCa 
link where your error message came from.

I would be interested in any thoughts on whereabouts in the above chain we 
should clear any error status from device support.  I suspect it should be 
the record type's responsibility once it has put the record into an alarm 
state (thus handling and reporting the error), but I could be persuaded 
otherwise.

- Andrew
-- 
The best FOSS code is written to be read by other humans -- Harold Welte

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System