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<== Date ==> <== Thread ==>

Subject: Re: Logical Naming of Hardware Addresses
From: Andrew Johnson <anj@mail.ast.cam.ac.uk>
Date: Thu, 26 May 1994 10:17:21 BST
On Wed, 25 May 94 12:42:18 -0500 mrk@phebos.aps.anl.gov wrote:

> Andrew Johnson talked about problems he had configuring reflective memory.
> I have no already existing "correct" solution. However all of us involved
> with ioc development recognize the problem and really want to come up with
> a nice solution.

...

> The solution is to replace hardware links by a reference to a new type of
> record. This record can contain fields just like existing record types. The
> difference is
> 1) The record has no database common
> 2) It is not processed.
> 
> For each device type the person providing device support provides an ascii
> record definition for the device. This record can contain all the fields
> needed to configure an instance of the device. For example a vme device record
> would have fields to define all the info in the existing vme link definition.
> The record could also contain any additional fields the developer decides
> are needed.
> 
> Database Generation Tools would allow a user to create a record instance for
> each device instance.
> 
> The existing link definitions would replace the hardware definitions by a
> definition that allows the link to reference this new type of record, i.e.
> this provides logical hardware links.

This is an interesting idea for interfacing to hardware (I can see it would 
allow more flexibility in device configuration), but I'm not sure it solves my 
problem.  I have to ensure that all IOCs have the same idea as to whereabouts in 
the Reflective Memory a particular record lives, and I'm reluctant to rely on 
the database designer calculating and inserting "Magic Numbers".

Other than by extending the database tools to add specific support code, the 
only way I can see this happening automatically is if every IOC is told about 
every RM record (even the ones which this IOC has no other interest in) so the 
driver can work the addresses out for itself.  That means adding a lot of 
redundant "hardware" records to a database, and no longer provides a single 
source of RM address information because each database has its own copy of 
these.

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