Experimental Physics and
Industrial Control System

<[email protected]> · Wed, 29 Dec 2010 14:11:12 +0000

Hi Bob,

Damn, I take it that's a no then. If the last time it was done was before the device support layer was done it was probably a talk chiselled in stone or pressed into clay tablets. Not much hope for me then. I only suggested I would do it because I thought I could crib most of it.

The background behind this is that every two weeks someone in our controls group gives a talk to the group. So the audience is fairly broad, but I am aiming this unashamedly at the EPICS developers. The others will come away with a flavour, but not a great understanding. The time slot is no greater than one hour, but brevity is not discouraged.

FWIW, my notes currently look like:

1. Data Structures:
The basic static structures, of which the important ones are, I think:

 - dbBase
     |---> recordTypeList
                  |---> dbRecordType
                            |---> recordList
                            |        |---> dbRecordNode
                            |                  |---> name
                            |                  |---> precord
                            |                           |---> dset
                            |                           |---> lset etc.
                            |---> deviceList
                            |---> dbFldDes array.
                            |---> rset.

2. Libraries/modules
This might be based on the recent core-talk discussions, possibly using Michael's slide:
   https://pubweb.bnl.gov/~mdavidsaver/files/base-reorg.png

3. Processes/threads
Outline the various processes - scan*, CAS-*, CAC-*, cb*, errlog, taskwd, timerQueue, dbCaLink.

4. Processing
This is to walk through basic client operations.
   - CA address lookup
   - caput (callback)
   - caget
   - camonitor

The basic idea is to walk the typical processing flow from hardware to client or vice versa to show the processing flow. In doing this I would like to cover (or briefly visit):

  - Record locking.
  - Record processing.
  - Type conversions
  - putNotify
  - Device callbacks
  - Events
  - CA work queue's
  - array handling
  - metadata handling

I think this is already too much for the time allotted, but I would be willing to hear people's comments/suggestions on the way this is going.

Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713

From: Dalesio, Leo [mailto:[email protected]] 
Sent: 29 December 2010 12:38
To: Rees, Nick (DLSLtd,RAL,DIA)
Subject: RE: EPICS internals talks?

Hi Nick,
This is an interesting idea. The last thing I had seen on the internals for the IOC was something that we had done before Argonne made the device support layer. If you come across something please let me know. If you want to develop something - also let me know. I would be interested to participate in the development of the class.

What did you want to cover?
For instance - does everyone already understand how records actually process?
Are you starting at the thread level?
Will you go into the details of implementing device and driver support - or is that already understood?
Do they all understand the difference between a channel and a record?
Bob

-----Original Message-----
From: [email protected] on behalf of [email protected]
Sent: Wed 12/29/2010 5:00 AM
To: [email protected]
Subject: EPICS internals talks?

Hi,

I have to give a talk on EPICS internals for the Diamond group in a few
weeks. Has anyone else given or know of a similar talk and would be
willing to point me at the slides?

Cheers,

Nick Rees
Principal Software Engineer           Phone: +44 (0)1235-778430
Diamond Light Source                  Fax:   +44 (0)1235-446713

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This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail.
Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. 
Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message.
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System