Experimental Physics and
Industrial Control System

Michael Davidsaver <[email protected]> · Thu, 31 Jul 2014 10:34:31 -0400

All,

I'm working on some changes to link parsing (to facilitate some further
changes to DB locking).  In doing on this I've come across some
behaviors of the present implementation which I'd like to change (see
the numbers below).  I don't think these would have break existing code
outside Base, but would appreciate being corrected on this point.

At present handling of INP/OUT links during initialization is
complicated it is done as the .db file is parsed, so the DTYP field may
not be known yet.

I'd like to defer initial parsing of links from its present location
under dbLoadRecords() to an early stage of iocInit() before
record/driver/dset initialization and autosave pass0.

1) This would mean that the value union in DBLINK would remain
uninitialized until iocInit().

This will greatly simplify things by eliminating the seemingly circular
relationship between dbPutString() and setLinkType().

2) A pleasant side effect of these changes is that syntax errors (eg.
forgetting '#') in HW link fields will be detected and failed before the
link field is modified.  Currently this fails, but after the current
device support is detached.

3) I find that at present omitting a '@' from an INST_IO link will
succeed, but an empty string is stored.  I'd like to change this to fail.

Presently, a syntactically incorrect INP/OUT link in a .db file will
result in a partially initialized link being seen by device support.
For example, setting "#C41" for a VME_IO link will result in only the
signal member for struct vmeio being set to a non-zero value.

4) I think the device support should see only an "empty" link (correct
type with all zeros and empty parm string) if INP/OUT is omitted or
syntactically incorrect.

6) Further, I'd like to add a field to the DBLINK structure to indicate
whether it has been correctly initialized to a non-default value.
Device support can then test this.

Michael

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System