Re: RTYP field through the PV Gateway

["Ernest L. Williams Jr." <ernesto@slac.stanford.edu>]

Ralph Lange wrote:
> Hi Andrew,
>
> sorry for being smartass without looking at the code - I'm still on 
> vacation, at home, without a full-size computer that would be able to 
> run a reasonable editor or EPICS. The EPICS/CA code just doesn't fit 
> onto my PDA screen....
>
> Good to hear that RTYP is a database attribute and the .VAL extension 
> is implemented in the database.
> Does that mean that the CA client doesn't do anything special and 
> doing a "caget XXX.RTYP" issues a value DBR type request?
>
> Ernest: Why do you see a DBR_CLASS_NAME request at the Gateway, then?
Someone wrote that in the PV Gateway User's Guide.


Thanks,
Ernest


> Cheers,
> Ralph
>
>
> Andrew Johnson wrote:
> > Hi Ralph,
> >
> > On Thursday 08 January 2009 07:56:53 Ralph Lange wrote:
> >  
> > > RTYP is a pseudo field: When a read request for a "*.RTYP" PV comes in,
> > > the CA client library  strips the ".RTYP" and converts it to a
> > > DBR_CLASS_NAME request.
> > >     
> >
> > Wrong, RTYP is one of two standard Record Attributes, pseudo-fields 
> > supported by the database whose values are specific to the record 
> > type and can be set (and new attributes created) using 
> > dbPutAttribute().  If the .RTYP handling was an artifact of CA like 
> > you suggest I wouldn't be able to do this from the ioc shell:
> >
> > epics> dbgf mrk:stringinsyn.RTYP
> > DBR_STRING:          "stringin"
> >
> > Go read section 6.14 of the AppDevGuide.  Attributes have been part 
> > of the IOC since at least R3.13.0, just nobody uses them much...
> >
> >  
> > > The only other case of CA-EPICSdb dependency (that I know of) is adding
> > > the ".VAL" extensionsto PVs without a field name. I don't know if this
> > > is done by the client or the server right now - it should be done on 
> > > the
> > > server side for the same reasons.
> > >     
> >
> > Nothing explicitly adds .VAL to the PV name; when someone [currently 
> > RSRV, by calling db_name_to_addr()] presents a PV name to 
> > dbNameToAddr() if the name doesn't contain a field part it looks up 
> > the "VAL" field automatically.  Thus this is already done in the server.
> >
> > - Andrew
> >