Experimental Physics and
Industrial Control System

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<== Date ==>		<== Thread ==>

Subject:	Re: CA library usage problem
From:	Andrew Johnson via Tech-talk <tech-talk at aps.anl.gov>
To:	Jörn Dreyer <j.dreyer at hzdr.de>, tech-talk at aps.anl.gov
Date:	Thu, 29 Sep 2022 12:45:07 -0500

Hi Jörn,

On 9/29/22 7:49 AM, Jörn Dreyer via Tech-talk wrote:

i guess I have a misunderstanding how to use the user callback functions 
together with a subscription to a PV variable.

In my userfunc the value of arg.status is always 1 which evaluates to a 
ca_message of "Normal successful completion". But the documentation say's to 
check against ECA_NORMAL witch is 0.

What am I doing wrong here.

Actually the macro ECA_NORMAL expands to the value 1, so arg.status == ECA_NORMAL will evaluate to true in your userfunc as described above. The status macros defined in caerr.h are somewhat confusing as they are actually a bitmask — the bottom 3 bits are a severity code, and the severity code CA_K_SUCCESS has the value 1. I suspect this may have been done to avoid using a status value of 0 which could then be used to detect the absence of a status value, although I doubt if anyone uses it like that now.

HTH,

- Andrew

-- 
Complexity comes for free, Simplicity you have to work for.

References:: CA library usage problem Jörn Dreyer via Tech-talk

Navigate by Date:: Prev: Suspicious behavior of Pmac 2-5-16 IOC. .RBV and .VAL showing wrong values. Marco A. Barra Montevechi Filho via Tech-talk; Next: Re: Suspicious behavior of Pmac 2-5-16 IOC. .RBV and .VAL showing wrong values. Torsten Bögershausen via Tech-talk; Index: 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 <2022> 2023 2024
Navigate by Thread:: Prev: CA library usage problem Jörn Dreyer via Tech-talk; Next: Suspicious behavior of Pmac 2-5-16 IOC. .RBV and .VAL showing wrong values. Marco A. Barra Montevechi Filho via Tech-talk; Index: 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 <2022> 2023 2024

ANJ, 30 Sep 2022

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System