Support "link(name, lset)" syntax in DBD files

Both Perl and dbStaticLib support included.
Also added a new std/link directory for link types.
Nothing looks up the registered link support tables yet.

src/std/Makefile

@@ -20,6 +20,7 @@ dbRecStd_RCS += dbRecStd.rc
 include $(STDDIR)/rec/Makefile
 include $(STDDIR)/dev/Makefile
 include $(STDDIR)/filters/Makefile
+include $(STDDIR)/link/Makefile
 include $(STDDIR)/softIoc/Makefile
 
 include $(TOP)/configure/RULES

src/std/link/Makefile

@@ -0,0 +1,17 @@
+#*************************************************************************
+# Copyright (c) 2016 UChicago Argonne LLC, as Operator of Argonne
+#     National Laboratory.
+# EPICS BASE is distributed subject to a Software License Agreement found
+# in file LICENSE that is included with this distribution. 
+#*************************************************************************
+
+# This is a Makefile fragment, see src/std/Makefile.
+
+SRC_DIRS += $(STDDIR)/link
+
+DBD += links.dbd
+
+# dbRecStd_SRCS += ...
+
+HTMLS += links.html
+

src/std/link/links.dbd.pod

@@ -0,0 +1,92 @@
+=head1 Link Types
+
+Links are an extensible mechanism for adding new kinds of database link,
+using JSON for link addresses.
+The following link types are available in this release:
+
+=over
+
+=item * L<Constant|/"Constant Link const">
+
+=item * L<Database|/"Database Link db">
+
+=item * L<Channel Access|/"Channel Access Link ca">
+
+=back
+
+=head2 Using Links
+
+...
+must appear inside a pair of braces C< {} > expressed as a JSON
+(L<JavaScript Object Notation|http://www.json.org/>) object, which allows link
+parameters to be defined as needed.
+
+Note that due to the required presence of the double-quote characters in the
+JSON strings in a link field value string in a database file, it will usually
+be necessary to escape all double-quote characters in the JSON object by
+preceding them with a backslash C< \ > character.
+Database configuration tools that support this link mechanism must be careful
+to handle these escapes correctly on reading and writing string values from/to
+a .db file.
+
+=head2 Filter Reference
+
+=cut
+
+link(const,lsetConst)
+
+=head3 Constant Link C<"const">
+
+...
+
+=head4 Parameters
+
+...
+
+=head4 Example
+
+ ...
+
+=cut
+
+link(db,lsetDatabase)
+
+=head3 Database Link C<"db">
+
+...
+
+=head4 Parameters
+
+...
+
+=head4 Example
+
+ ...
+
+=cut
+
+link(ca,lsetChannelAccess)
+
+=head3 Channel Access Link C<"ca">
+
+...
+
+=head4 Parameters
+
+...
+
+=over
+
+=item ...
+
+...
+
+=back
+
+...
+
+=head4 Example
+
+ ...
+
+=cut

src/std/softIoc/RULES

@@ -9,8 +9,10 @@
 
 softIoc.dbd$(DEP): $(COMMON_DIR)/stdRecords.dbd
 softIoc.dbd$(DEP): $(COMMON_DIR)/filters.dbd
+softIoc.dbd$(DEP): $(COMMON_DIR)/links.dbd
 $(COMMON_DIR)/softIoc.dbd: $(COMMON_DIR)/stdRecords.dbd
 $(COMMON_DIR)/softIoc.dbd: $(COMMON_DIR)/filters.dbd
+$(COMMON_DIR)/softIoc.dbd: $(COMMON_DIR)/links.dbd
 $(COMMON_DIR)/softIoc.dbd: $(STDDIR)/softIoc/Makefile
 
 softMain$(DEP): epicsInstallDir.h

src/std/softIoc/base.dbd

@@ -16,6 +16,9 @@ include "stdRecords.dbd"
 # Channel filters & plugins
 include "filters.dbd"
 
+# Link types
+include "links.dbd"
+
 # Standard device support
 include "devSoft.dbd"