RE: Accessing Record fields from asyn driver

[Mark Rivers via Tech-talk <tech-talk@aps.anl.gov>]

OK, I was too hasty in my reply to Torsten!

 

We could create a new asynMetadata interface, similar to asynOption.

 

typedef struct asynMetadata {

    asynStatus (*writeString)(void *drvPvt, asynUser *pasynUser,

                              const char *key, const char *val);

    asynStatus (*readString)(void *drvPvt, asynUser *pasynUser,

                             const char *key, char *val, int sizeval);

    asynStatus (*writeInt32)(void *drvPvt, asynUser *pasynUser,

                             const char *key, epicsInt32 val);

    asynStatus (*readInt32)(void *drvPvt, asynUser *pasynUser,

                            const char *key, epicsInt32*val);

    asynStatus (*writeFloat64)(void *drvPvt, asynUser *pasynUser,

                               const char *key, epicsFloat64 val);

    asynStatus (*readFloat64)(void *drvPvt, asynUser *pasynUser,

                              const char *key, epicsFloat64 *val);

} asynMetadata;

 

There would be well-defined, but extensible, values for “key”.  With asynOption on serial devices key can be “baud”, “parity”, etc.  For asynMetadata the keys could be “egu”, “low_alarm”, “high_alarm”, “min_value”, “max_value”, etc.

 

Mark

 

 

From: Tech-talk <tech-talk-bounces@aps.anl.gov> On Behalf Of Ralph Lange via Tech-talk
Sent: Monday, March 1, 2021 8:02 AM
To: EPICS Tech Talk <tech-talk@aps.anl.gov>
Subject: Re: Accessing Record fields from asyn driver

 

Hi Torsten,

 

In the context of the OPC UA Device Support, I have had this requirement coming up, and I think it would be worthwhile doing a design for adding this functionality.

The next important step there would be thinking about a proper definition and an easy, generic yet comprehensive way of configuring this mapping.

Polling for changes or subscribing to metadata is probably too resource expensive (at least in the OPC UA case), but reading the metadata on (re)connection should be feasible.

 

If you have input to this, I'd be happy to hear about it.

 

Cheers,
~Ralph