New asynEnumStrings interface?

[Mark Rivers <rivers@cars.uchicago.edu>]

Andrew and Eric,

One things that has been missing from asyn is the ability for a driver to provide a list of valid enum strings for a parameter.  For example, a device may support a set up choices for gain, speed, etc.  Right now the database designer needs to know those choices and hardcode them into the mbbo enum strings, for example.  It would be nice to provide an interface by which device support can query the enum strings from the driver in init_record, and support callbacks from the driver if the enum strings change (because some mode has changed, etc.).

I am thinking about supporting this in asyn.  One way would be to add a new interface, asynEnumStrings.  This is what that interface might look like:

corvette:asyn/asyn/interfaces>more asynEnumStrings.h 
/*  asynEnumStrings.h */
/***********************************************************************
* Copyright (c) 2012 The University of Chicago, as Operator of Argonne
* National Laboratory, and the Regents of the University of
* California, as Operator of Los Alamos National Laboratory, and
* Berliner Elektronenspeicherring-Gesellschaft m.b.H. (BESSY).
* asynDriver is distributed subject to a Software License Agreement
* found in file LICENSE that is included with this distribution.
***********************************************************************/

/*    30-January-2012 Mark Rivers

*/

#ifndef asynEnumStringsH
#define asynEnumStringsH

#include <asynDriver.h>
#include <epicsTypes.h>
#include <shareLib.h>

#ifdef __cplusplus
extern "C" {
#endif  /* __cplusplus */

typedef void (*interruptCallbackEnumStrings)(
              void *userPvt, asynUser *pasynUser,
              char *value[], size_t nelements);
typedef struct asynEnumStringsInterrupt {
    asynUser *pasynUser;
    int addr;
    interruptCallbackEnumStrings callback;
    void *userPvt;
} asynEnumStringsInterrupt;
#define asynEnumStringsType "asynEnumStrings"
typedef struct asynEnumStrings {
    asynStatus (*write)(void *drvPvt, asynUser *pasynUser,
                       char *value[], size_t nelements);
    asynStatus (*read)(void *drvPvt, asynUser *pasynUser,
                       char *value[], size_t nelements, size_t *nIn);
    asynStatus (*registerInterruptUser)(void *drvPvt, asynUser *pasynUser,
             interruptCallbackEnumStrings callback, void *userPvt,
             void **registrarPvt);
    asynStatus (*cancelInterruptUser)(void *drvPvt, asynUser *pasynUser,
             void *registrarPvt);
} asynEnumStrings;

#define asynEnumStringsBaseType "asynEnumStringsBase"
typedef struct asynEnumStringsBase {
    asynStatus (*initialize)(const char *portName,
                            asynInterface *pEnumStringsInterface);
} asynEnumStringsBase;
epicsShareExtern asynEnumStringsBase *pasynEnumStringsBase;

#ifdef __cplusplus
}
#endif  /* __cplusplus */

#endif /* asynEnumStringsH */



Any thoughts?  Is "char *value[]" the best way to pass the strings?

Mark