Difference between revisions of "Future Development Ideas"

From EPICSWIKI
(12-Jun am.)
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* Update the Record Reference Manual to 3.14 and beyond (generate tables automatically from DBD files?)
* Update the Record Reference Manual to 3.14 and beyond (generate tables automatically from DBD files?)
* Look at all the documentation we have and see what's missing
* Look at all the documentation we have and see what's missing
* Data Access, other new CA-related documentation...




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The ability to add aliases to existing records has already been demonstrated and is a desirable feature, although the implementation that goes into Base might be somewhat different.
The ability to add aliases to existing records has already been demonstrated and is a desirable feature, although the implementation that goes into Base might be somewhat different.
Jeff: Give CAS the ability to make use of a prefix for all PV names that get stipped before passing them to the tool.  Not efficient to implement this on RSRV.




== Unbundling ==
== Unbundling ==


Split Base into three or more independent modules.  Each module would have its own version number, and the modules can therefore each have an independent existance, although there would obviously be specific dependencies associated with particular versions. I see the modules as follows:
Split Base into three or more independent modules.  Each module would have its own version number, and the modules can therefore each have an independent existance, although there would obviously be specific dependencies associated with particular versions.


If we adopt this, we should bundle working subsets of modules together and release the complete bundle as a tarfile.
I see the unbundled modules as follows:


=== Core ===
=== Core ===
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=== IOC ===
=== IOC ===


Depends on: Core, CAC
Depends on: Core, CAC, CAS


The rest is code that runs on the IOC.
The rest is code that runs on the IOC.
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== CA Event Filtering ==
== CA Event Filtering ==


LANSCE wants Time and Flavored Data.  I think this should be implemented differently to how Jeff is currently planning, with my design involving much simpler changes to the core code but requiring a bit more applications work from the LANL software guys.  The following describes my ideas, which Jeff doesn't agree with:
LANSCE needs Time and Flavored Data to replace ancient VAXen.  Jeff's plan is to be able to attach an expression to a channel subscription, which is evaluated by the client's server thread to check each monitor event to determine whether to send it to this client or not.  This could use an enhanced CALC expression parser and evaluation routine to do the expression, we just need a better parser since the expression might include record names. Discussion about how the values for the expression get saved such that they have the value at the time the data was pushed into the event queue; they might have changed since them.  Jeff's fixed size event that contains those expression value resolves that issue, but it is very restrictive in terms of flexibility.
 
The main change would be to allow a CA client to subscribe to monitors on a channel but include another CHID in the subscription giving a channel that controls whether an individual event would be sent to that client or not.  The conditional channel would give a boolean value, which would be checked every time a monitor event is notified to the server; if true the server sends it to this client, if false it doesn't.  Initially that channel would have to be on the same IOC as the main channel, but if Jeff wants to implement a suitable CA client in the server that restriction could be removed.
 
To implement the Time and Flavored Data that they want LANSCE would have to create records (or record fields) in the IOCs that become true when their events are occurring and false otherwise. A client that wants to configure a non-standard flavor might have to ask a central facility to allocate and set up an appropriate calc record on its behalf.
 
The major advantage of this approach is that it only needs changes in the CA server and client code; there are no modifications needed to the database, record or device support layers at all.  Other sites will be able to make use of the new CA facility as well, whereas Jeff's original requirement was very LANL-specific and would be unlikely to be used much elsewhere.




== Variable Length Strings ==
== Variable Length Strings ==


I'm already adding my new BaseString C++ classes to libCom, and I intend to create a set of C wrapper routines for the base class operations.  This can form the basis of a new string type for use in the database.
I'm already adding my new BaseString C++ classes to libCom, and I intend to create a set of C wrapper routines for the base class operations (started, currently incomplete).  This can form the basis of a new string type for use in the database in addition to the DBF_STRING.




Revision as of 20:32, 12 June 2006

These are my notes for what I think we can/should add to V3 through an evolutionary process. The ordering is probably vaguely right, but not necessarily that accurate.



3.14 Changes in progress

The following modifications are currently under way in the 3.14 branch. They will probably be included in a R3.14.9 release, timescale TBD.

  • Add epicsUnitTest routines to libCom which generate output in the Test Anything Protocol (TAP) format.
  • Convert the existing test programs in libCom/test to use epicsUnitTest routines, which automates these tests.
  • Major overhaul of the calc expression parser with improved diagnostics and additional functionality.
  • Enhancements to the Access Security parser to improve diagnostics.
  • Support for 64-bit CPUs (solaris-sparc64, linux-x86_64).
  • Issues with multiple threaded CA clients


3.14 Changes needed "soon"

  • Full GDD support for alarm acknowledgements, or whatever changes the PV Gateway actually needs to properly support the alarm handler.

Jeff: Enhance CALC to allow names to be included in the CALC expression.


3.15 Cleanup

3.15 already includes the Up change to the build system; the ramifications of this change have not been followed up completely though:

  • Provide a perl script for converting 3.14 apps to 3.15
  • Bring over latest templates from 3.14
  • Implications for building extensions not worked out
  • makeBaseExt.pl is probably no longer needed
  • Install RULES files into a top level directory
    • Use this dir instead of the configure/O.arch directories so that a make clean doesn't remove them...
  • Change script installation rules (see ctlsys)
  • Version numbering - switch from alpha/beta to release candidates RC1 etc. which probably needs some change to CONFIG_BASE_VERSION

Ben's Async dbGetLinkCallback: Defer to an upgrade to the record support interface, later in the process. Or maybe include a dbGetLinkCallback() with the private callback routine, and require new record types to use this. Talk to synApps about this (Tim). 3.15

Jeff: Multiple Master problem (non-EPICS changes to output values in a PLC or similar device). This could be resolved adding a new routine to the RSET that the device support calls back when it has a new raw ouptut value to back-propagate to the VAL field. Currently done by setting PACT and calling the record's process routine to use its second-half processing only. Again, talk to Tim about this.


Documentation

Lots to do here:

  • Write a "Building EPICS" guide (chapter in AppDevGuide?)
  • Restructure the AppDevGuide to make it more accessible
  • Convert AppDevGuide into an OpenDocument Text file (keeping index markers)
  • Update the Record Reference Manual to 3.14 and beyond (generate tables automatically from DBD files?)
  • Look at all the documentation we have and see what's missing
  • Data Access, other new CA-related documentation...


Compiling DBD Files

My Perl implementation of the DBD file parser is still in process, and I'm hoping to revive this development effort to convert all DBD file information into C tables that get compiled into the IOC executable.

With this parser now being written in Perl, it will become easier to extend the new facilities that we implement, such as adding new field types (see Variable Length Strings below).


PV Aliases

The ability to add aliases to existing records has already been demonstrated and is a desirable feature, although the implementation that goes into Base might be somewhat different.

Jeff: Give CAS the ability to make use of a prefix for all PV names that get stipped before passing them to the tool. Not efficient to implement this on RSRV.


Unbundling

Split Base into three or more independent modules. Each module would have its own version number, and the modules can therefore each have an independent existance, although there would obviously be specific dependencies associated with particular versions.

If we adopt this, we should bundle working subsets of modules together and release the complete bundle as a tarfile.

I see the unbundled modules as follows:

Core

Depends on: Nothing

These are the common parts used by everything:

  • Build system
  • OSI layer
  • libCom
  • Antelope
  • Flex
  • makeApp tool


Channel Access Client

Depends on: Core

Jeff Hill's responsibility.

  • CA-specific build rules (probably none)
  • CA client library
  • CA Tools
  • CA application makeApp templates


Channel Access Server

Depends on: Core, IOC

Jeff Hill's responsibility.

  • CAS-specific build rules (probably none)
  • GDD
  • The CAS server tool
  • RSRV (the old CA server code)
  • CAS application makeApp templates


IOC

Depends on: Core, CAC, CAS

The rest is code that runs on the IOC.

  • IOC-specific build rules
  • Static and runtime database access
  • Runtime database
  • Standard record types
  • Soft device support
  • The registry
  • IOC shell
  • IOC application makeApp templates


Redundancy

DESY funded project for Bob & John to add redundant control of remote I/O, allowing hot-spare backup IOCs.


CA Event Filtering

LANSCE needs Time and Flavored Data to replace ancient VAXen. Jeff's plan is to be able to attach an expression to a channel subscription, which is evaluated by the client's server thread to check each monitor event to determine whether to send it to this client or not. This could use an enhanced CALC expression parser and evaluation routine to do the expression, we just need a better parser since the expression might include record names. Discussion about how the values for the expression get saved such that they have the value at the time the data was pushed into the event queue; they might have changed since them. Jeff's fixed size event that contains those expression value resolves that issue, but it is very restrictive in terms of flexibility.


Variable Length Strings

I'm already adding my new BaseString C++ classes to libCom, and I intend to create a set of C wrapper routines for the base class operations (started, currently incomplete). This can form the basis of a new string type for use in the database in addition to the DBF_STRING.


Alternate DB File Formats

There are calls to replace the existing DB file format with an XML-based format. Currently the DB file parser is too highly integrated into the process of record creation to be able to add a second format, but it would be feasible to separate these two and hence allow an expat-based or similar parser to be written. This would probably require a close analysis and upgrade to the locking arrangements of the database.


Online Record Creation

With good database locking, it might be feasible to look at the ability to add new record instances at runtime, and maybe delete as well. This would probably need a change to the record interface to initialize the new instances.


Dynamically Loaded Modules

After converting the DBD load process into table registration, it should become easier to allow support modules (containing record types, device support and other drivers) to be discovered and loaded dynamically. Unloading is a very different matter though.


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