Experimental Physics and
Industrial Control System

Mark Davis <[email protected]> · Tue, 20 Mar 2018 07:24:28 -0400

HI Mark,

We are working on a newer version of an asynPortDriver-based driver that

creates the asyn parameters during the call to drvUserCreate() based on

the string passed to it, which means that the string must include the

asynType for the new parameter.  This avoids the need to include the

list of parameters as part of the code (requiring a unique version of

the driver for each type of device it can talk to).

This works well, but it means a bit of redundancy since the asynType is

specified both in the DTYP and the INP/OUT string for the record.

I believe the documentation for the asyn module (and emails from you on

this list ) state that the asyn module is designed so that it can be

used by clients other than the EPICS record interface, so there is the

issue of whether or not it would even be possible to provide this

information in a manner that would not depend on what the client is.

Obviously, the question as stated ("What is the DTYP" value in the

record?") assumes the call is on behalf of an EPICS record, so the

answer is NO.  On the other hand, I also assume that, whatever the

client is, it has to specify which of the asynType interfaces it is

using to communicate with the asyn layer, so the question(s) could be

restated as:  "Is the asynType known before the call to drvUserCreate(),

and if so, could it be make available to the drvUserCreate() function

(either as part of the information in the asynUser struct or a function

that drvUserCreate() can call)?"

Mark Davis
NSCL/FRIB Controls Staff Engineer
[email protected]

On 3/19/2018 6:11 PM, Mark Rivers wrote:

Hi Konrad,

I can't think of a way for the driver to know the value of DTYP.  Of course you specify both the drvUser string and the datatype when you call createParam() so your driver knows the datatype that a particular drvUser string will be using.  Why do you need to know the DTYP?

Mark

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Konrad, Martin
Sent: Monday, March 19, 2018 8:39 AM
To: EPICS Tech Talk <[email protected]>
Subject: Asyn getting DTYP field in drvUserCreate()

Hi,
I'm wondering if there is a way I can get access to the DTYP field of
the record from asynPortDriver's drvUserCreate method.

Once createParam() has been called in drvUserCreate() I can get the type
by calling getParamType() but how do I get access to this information in
drvUserCreate()?

It seems like other drivers are duplicating this information into the
INP/OUT field (see e.g. [1]). I'm wondering if there is a more elegant
way to do this.

Thanks a lot,

Martin

[1]
https://urldefense.proofpoint.com/v2/url?u=http-3A__controls.diamond.ac.uk_downloads_support_aravisGigE_0-2D3-2D&d=DwIFAg&c=nE__W8dFE-shTxStwXtp0A&r=D7ZiziuMQuq40HlGYOZPBg&m=ye8rwKce1N2smS_Qv4NJE7cxkvL2pAyhv01q1CorLNY&s=4dEd2vIEg8lp5k3Z8SyaW9RUE-YJbhcHHYpmwmR0EXg&e=
5dls5/documentation/doxygen/aravisCamera_8cpp_source.html#l00326

--
Martin Konrad
High Performance Controls Team Leader
Facility for Rare Isotope Beams
Michigan State University
640 South Shaw Lane
East Lansing, MI 48824-1321, USA
Tel. 517-908-7253
Email: [email protected]

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System