Experimental Physics and
Industrial Control System

Heinrich du Toit <[email protected]> · Thu, 23 Aug 2007 12:17:38 +0200

Ok this makes sense... sortoff.
But In my driver I call the callback from a thread I created myself as
such:
 pInt32Interrupt->callback(pInt32Interrupt->userPvt,
pInt32Interrupt->pasynUser,
				*(epicsInt32*)pPvt->ciPvt->data);

Anyways.
For some or other reason the moment I start calling this interrupt the
the int32 device starts calling my int32read function??
Why is this?

I looked in devAsynInt32.c and inside interruptCallbackInput I see a
scanIoRequest at the end. My guess is it has something to do with this?
I am unable to find where scanIoRequest comes from?

Clearly I don't really understand how interrupts are working.
It is however clear that the int32reads come through the queue and not
directly from the interruptcallback.

Thanks

On Wed, 2007-08-22 at 08:15 -0500, Mark Rivers wrote:
> Heinrich,
>  
> > As the interrupt callback is already called from inside the ASYN thread (true?)
> > then the interrupt callback wouldn't need to go throught queueRequest
> > todo anything and can therefore use the ASYN interface functions
> > directly?
> 
> No, that's not true, the interrupt callback is not done from the port thread (if one exists), it is done from another thread that the driver creates just for the callbacks.
>  
> > If callback A is called... then it should be ok if the record reads
> > directly into B and/or C
>  
> I don't think that should be done.  You should either implement 3 interrupts (if A, B, and C can change at different times or are going to different records), or implement asynInt32Array or asynFloat64Array callbacks if they all change at once and the values are all going to the same record.
>  
> Mark
>  
> 
> ________________________________
> 
> From: [email protected] on behalf of Heinrich du Toit
> Sent: Wed 8/22/2007 12:48 AM
> To: Tech-Talk EPICS
> Subject: RE: asyn - interrupts
> 
> 
> 
> Hi
> 
> Ok what you say makes sense but not completely.
> As the interrupt callback is already called from inside the ASYN thread
> (true?)
> then the interrupt callback wouldn't need to go throught queueRequest
> todo anything and can therefore use the ASYN interface functions
> directly?
> 
> The reason I'm asking this is for the case of a custom record:
> Say the record is connected to ASYN ports A,B and C. Which could be
> different interfaces or maybe just other settings.
> Anyways.
> If callback A is called... then it should be ok if the record reads
> directly into B and/or C. Because it is already in the ASYN thread and
> therefore there shouldn't be any problems or need for queueRequests and
> so forth.
> 
> Or should the record rather install 3 different interrupts?
> Wouldn't that in the end result in a lot of exstra db updates?
> 
> I guess my next question will be about what happens when a record starts
> sending db_update floods :)
> 
> -Heinrich
> 
> On Tue, 2007-08-21 at 09:09 -0500, Mark Rivers wrote:
> > Hi Heinrich,
> > 
> > You should use the data value that is passed in the callback.
> 
> >  The interrupt callback should never call the read function in the asyn interface directly (it would need
> 
> > to go through queueRequest to ensure that the read runs in the port thread in case the driver is asynchronous,
> 
> > and to ensure correct locking even for synchronous drivers).  In principle it could call queueRequest, and then
> 
> > call read() from the queueRequest callback, but there's really no need to do that.
> > 
> > Mark
> > 
> >
> > ________________________________
> >
> > From: [email protected] on behalf of Heinrich du Toit
> > Sent: Tue 8/21/2007 8:44 AM
> > To: Tech-Talk EPICS
> > Subject: asyn - interrupts
> >
> >
> >
> > Hi
> >
> > Just want to make sure about something and what is the general practice
> > that should be used.
> >
> > When an interrupt callback is called.
> > Then there is an parameter to send the "new" data in also.
> >
> > Ok so when the record support code's interrupt callback is called it
> > already receive the new data...
> > But it can obviously still call the read command for the asyn interface
> > and get the data that way.
> >
> > So do we assume that the data passed to the interrupt callback is
> > correct and that no further asyn calls is needed. Or can/should it still
> > call the read function to get data?
> >
> > I'm assuming it accepts the data in the callback and go ahead with that
> > as that would make sense to me.
> >
> > -Heinrich
> >
> >
> >
> 
> 
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System