Experimental Physics and
Industrial Control System

"Ernest L. Williams Jr." <[email protected]> · Fri, 09 Jan 2009 07:59:03 -0800

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

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System