Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Sat, 11 Mar 2006 00:22:37 +0100

On Thursday 09 March 2006 16:05, Dirk Zimoch wrote:
> StreamDevice Version 2.0 is released now.
> http://epics.web.psi.ch/software/streamdevice/
>
> It requires R3.14.6 or higher (recommended: R3.14.8.2) and asynDriver
> 4-3 or 4-4.

Hi Dirk

many thanks for this work. I will use this (together with asyn) as a 
replacement for devCommonGpib-style device supports ASAP.

I have one question: the docs say that readback from devices for output 
records (for bumpless reboot) is done synchronously, blocking iocInit 
until all such readbacks have completed. There may be situations where 
this is the right aproach. However, there are others, where one would 
wish to have the readback to proceed asynchronously, for instance if 
there are a lot of such records on an IOC.

In our MultiCAN package we do this by letting init_record 'fake' the 
first phase of asynchronous processing. That is, init_record starts 
readback, sets PACT and arranges for a special kind of process callback 
that lets processing complete with a read (instead of the normal write) 
operation.

Would it be very difficult to enable such behavior (optionally, the 
synchronous version remaining the default) for StreamDevice, too? Would 
you accept a patch that implements this?

The StreamDevice docs mention the interaction with PINI flag. I think 
the best solution is to enable readback on startup only if PINI 
is /not/ set. Reading back from teh device hardly makes sense if the 
first thing you are going to do is overwrite the value with something 
else. OTOH, if PINI is not set, then doing a readback on startup will 
at least not do any harm.

Ben
-- 
There are three kinds of programmers: those who make off by one errors, 
and those who don't.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System