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Subject: Re: Possible Access Rights improvement?
From: Ralph Lange <ralph.lange@gmx.de>
To: EPICS Core Talk <core-talk@aps.anl.gov>
Date: Thu, 24 Aug 2017 22:32:29 +0200
Hmmm....

What I remember:
When you connect a widget to an CS-Studio/BOY internal sim channel providing a sine wave, you see it as read-only with all graphical balderdash that goes with it.
When you connect the same widget to an EPICS calc record providing a sine wave, it appears writable, and while writing seems to work, it doesn't.
Shouldn't both behave the same?

And:
In a panel used for testing, that indeed routinely connects controller widgets to input records, everything works fine as long as the hardware is disconnected, i.e. you can flicker your input bits and see them on the operation panels under test.
As soon as the hardware is connected, the test panel stops working, and there's no easy way to tell. (Writing seems to work, but it doesn't.)

My recent work on the simulation mode is trying to fix the second case towards being able to use the simulation mode to simulate missing hardware (which currently doesn't work - see other thread). When that eventually works, the testing panel will connect to SVAL fields, the alarm status (SIM) can be used to signal simulation mode, and you don't have to disconnect the hardware.
The first case ... I don't know.

Cheers,
~Ralph


On Thu, Aug 24, 2017 at 5:46 PM, Kasemir, Kay <kasemirk@ornl.gov> wrote:

What is the use case?


Assume I have an AI record that reads from a PLC.

So I display that as a text update field on the UI.

Would you routinely display that record as a text entry field?


-Kay



From: core-talk-bounces@aps.anl.gov <core-talk-bounces@aps.anl.gov> on behalf of Ralph Lange <ralph.lange@gmx.de>
Sent: Thursday, August 24, 2017 3:34 AM
To: EPICS Core Talk
Subject: Possible Access Rights improvement?
 
Dear Core-talkers,

There is a possible request from our operations group to show VAL fields of input records as having no write access, if the device support would overwrite any value written at the next record processing.

Technically, these fields are writable.
Functionally, there are issues:
  • The writing client (even using put-callback) will get the new value and show the operation as having succeeded.
  • Other clients doing gets or creating new subscriptions (e.g. newly opened panels) will see the new value.
  • Existing subscriptions (e.g. archivers, gateways, already open panels) will not get an update and have no clue.
  • Depending on the situation (DTYP, SCAN) this inconsistent state may last a while.

What are your thoughts on this?

Thanks,
~Ralph



Replies:
Re: Possible Access Rights improvement? Kasemir, Kay
References:
Possible Access Rights improvement? Ralph Lange
Re: Possible Access Rights improvement? Kasemir, Kay

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