Argonne National Laboratory

Experimental Physics and
Industrial Control System

1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019  2020  Index 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019  2020 
<== Date ==> <== Thread ==>

Subject: Setting BPTR
From: Till Straumann <strauman@slac.stanford.edu>
To: EPICS Techtalk <tech-talk@aps.anl.gov>
Date: Fri, 28 Jan 2011 15:04:10 -0600
A few records that deal with array data use a BPTR
field which holds a pointer to the array.

In some cases it is desirable for device support to
set BPTR rather than using malloced memory that
record support attached there, e.g., because
device support needs special alignment
or wants the record to read from memory-mapped
areas in a device avoiding an extra copy step.
In fact, the aai/aao records *rely* on device support
setting BPTR.

Unfortunately, this is currently broken (I'm looking
at 3.14.8.2) because device support's init_record()
function is only called during pass 1 of record
initialization when links have already been established.
After links are established BPTR must not be changed
because linked records will use a cached pointer.

I see that the problem for aao/aai was fixed in
3.14.12 but it would be nice to be able to set
BPTR for waveforms, too.

-- Till

Replies:
Re: Setting BPTR Andrew Johnson

Navigate by Date:
Prev: Re: ca_create_channel memory management pthomas
Next: ca_create_subscription element count pthomas
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019  2020 
Navigate by Thread:
Prev: Re: ca_create_channel memory management Tim Mooney
Next: Re: Setting BPTR Andrew Johnson
Index: 1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  2010  <20112012  2013  2014  2015  2016  2017  2018  2019  2020 
ANJ, 18 Nov 2013 Valid HTML 4.01! · Home · News · About · Base · Modules · Extensions · Distributions · Download ·
· Search · EPICS V4 · IRMIS · Talk · Bugs · Documents · Links · Licensing ·