Experimental Physics and
Industrial Control System

Ben Franksen <[email protected]> · Fri, 30 May 2008 23:43:45 +0200

On Freitag, 30. Mai 2008, Tim Mooney wrote:
> Ben Franksen wrote:
> > On Freitag, 30. Mai 2008, Mathias Steiner wrote:
> >> All would be well if it were possible to change links -- either .FLNK
> >> or .OUT -- from within a subroutine.  I've tried a couple of things
> >> without success.  Just pasting the channel name into the "value" field
> >> of the union does not, and probably should not, work.
> >>
> >> Assigning a different value to a link by copying an input link doesn't
> >> work either:
> >> psub->flnk = psub->inpb;
> >>
> >> This isn't so clear to me, since they are both of type DBLINK.  After
> >> all, I can "just" type the value into the .FLNK field of any channel
> >> using edm, and it'll work...
> >
> > It works because this operation is going via Channel Access.
> >
> > You can do the same from your subroutine: use the CA client library to
> > [...]
>
> I think I would not do this from within a sub record's subroutine, even
> though it's possible.  [...]

It's also not necessary at all. Just use plain runtime database access, see 
the same named chapter in the Developer's Guide. Specifically, dbPutField() 
calls dbPutFieldLink() which re-targets the link field being written to, 
both are defined in src/db/dbAccess.c.

So: just do a dbNameToAddr() in the init routine, save the dbAddr pointer(s) 
somewhere (DTYP comes to mind, it is reserved for device support which 
subRecord doesn't have) and do a dbPutField() in the subroutine proper. 
This is even simpler than the CA stuff and works synchronously.

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System