Experimental Physics and
Industrial Control System

Ralph,

 

Andrew has suggested naming the interface asynMetaParam.  Does this seem OK? 

 

Torsten is working on it.

 

Ø  For asynMetadata the keys could be “egu”, “low_alarm”, “high_alarm”, “min_value”, “max_value”, etc.

 

I was thinking that an issue we have never resolved is telling an asyn port driver when it should do callbacks: only when a value has changed, or every time it reads a value.  asynPortDriver currently only does callbacks when a value changes.  This is the desired behavior in most cases, but there definitely cases where we want a callback on every new reading.  For example when asynInt32Average device support is being used to average values from an ADC, etc.  For drivers to do that now requires a kluge: set the parameter to a garbage value and then to the correct value before doing the callbacks.  That forces the callback to occur.

 

This new interface could be used to communicate to the driver that callbacks should be done on all reads.  This could be done with a new info tag e.g. “asyn:CALLBACK_ALWAYS”.   It could also be done by propagating the MDEL field of the record to the driver.  But that is probably not such a good idea since it mixes the behavior of the driver with the behavior of the record.

 

Mark

 

 

 

 

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 at 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 at aps.anl.gov>
Subject: Re: Accessing Record fields from asyn driver