Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Wed, 25 Apr 2018 14:05:11 -0500

Hi Michael,

Since I've just started reading your page I might as well write down
some comments as I get to them. I haven't tried using this at all.

Before I get to the pvalink bit, your example for the QSRV Timestamp
option says 16 in one place and 20 elsewhere.

On 04/24/2018 12:11 PM, Michael Davidsaver wrote:
> In the past week I've added a lot of additional options for a PVA link,
> which I think brings it close to feature complete (for a first version anyway).
> 
> An example, with all of the defaults made explicit is:
> 
>> record(longin, "tgt") {}
>> record(longin, "src") {
>>     field(INP, {pva:{
>>         pv:"tgt",
>>         field:"",
>>         local:false,
>>         Q:4,
>>         pipeline:false,
>>         proc:none,
>>         sevr:false,
>>         time:false,
>>         monorder:0,
>>         retry:false,
>>         always:false,
>>         defer:false
>>     }})
>> }

Wow! Are all of these options things that may actually need to be set
separately for each link? Are there any for which an IOC-wide default
might be wanted? (maybe not, I wrote that before reading the doc...).

> I've tried to describe all of these on the documentation page, although
> it would be nice to get some comments as to how well I've succeeded.
> 
> http://mdavidsaver.github.io/pva2pva/qsrv_page.html#qsrv_link

Do you support forward links? Not covered that I can see.

In general I like your approach to option naming, just a few quibbles below.

monorder: Allowed range? This should probably be called phase, to match
the PHAS field, which is unsigned; I'm not sure that supporting -ve
numbers makes much sense. Is there any performance penalty for leaving
gaps between values, say 10,20,30 vs 1,2,3?

defer: Probably needs more explanation and an example — how does it
group puts together? Could I have 2 independent deferred groups for the
same target PV (so should the value of defer be a group name instead of
a boolean? If so, maybe defer is the wrong name?)

retry: That name doesn't make it clear that it's related to disconnected
channels, although I don't have any other naming suggestions yet.

always: Not sure I understand the description, can you try to re-word
it; an example might help.

local: Could you instead provide "host" where the user can tell you
which host should have the PV (to avoid doing broadcast searches, or
allow pointing outside the local subnet) and that would understand some
value to mean the same as local:true?

Got go to now, hope this is helpful to start with.

- Andrew

-- 
Arguing for surveillance because you have nothing to hide is no
different than making the claim, "I don't care about freedom of
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System