Re: enable pvAccess by default

[Han Lee via Tech-talk <tech-talk at aps.anl.gov>]

Hi Michael,

Could you explain the difference between QSRV1 and QSRV2?

Or do we have any documentation which way we have to go to develop the pvacces support IOC?

Best,

Han

On Wed, Apr 3, 2024 at 10:37 AM Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov> wrote:

On 3/31/24 13:53, William Kirstaedter via Tech-talk wrote:
> Hello Core Devs,
>
> I would like to know if you have already considered activating pvAccess for softIOCs by default.

Changing defaults seems certain to surprise someone.  I understand
the desire for change though as out of date defaults confuse new
users.

Historically, epics-base development has prioritized unsurprising
upgrades over unconfused newbies.  Still, changes are possible if
folks want to propose something concrete.  (aka. PRs welcomed)


> I would probably adapt the Makefile template and simply copy the section from the example IOC:
>
> # Link QSRV (pvAccess Server) if available
> ifdef EPICS_QSRV_MAJOR_VERSION
>      _APPNAME__LIBS += qsrv
>      _APPNAME__LIBS += $(EPICS_BASE_PVA_CORE_LIBS)
>      _APPNAME__DBD += PVAServerRegister.dbd
>      _APPNAME__DBD += qsrv.dbd
> endif

When PVXS is included in RELEASE, then PVXS_MAJOR_VERSION will be defined.
So some similar logic can be used.

> ifdef PVXS_MAJOR_VERSION
> _APPNAME__DBD += pvxsIoc.dbd
> _APPNAME__LIBS += pvxsIoc pvxs
> endif

Of course this raises the question of what to do if both are defined?

I have tried to design PVXS/QSRV2 so that both QSRV1 and QSRV2 can be linked
into the same executable.  In this happens, then on startup QSRV2 should
detect the presence of QSRV1 and disable itself.

That said, I would recommend avoiding this situation with Makefile logic like:

> ifdef PVXS_MAJOR_VERSION # prefer QSRV2 :)
> nasaAcq_DBD += pvxsIoc.dbd
> nasaAcq_LIBS += pvxsIoc pvxs
> else
> ifdef EPICS_QSRV_MAJOR_VERSION # fallback to QSRV1
> nasaAcq_LIBS += qsrv
> nasaAcq_LIBS += $(EPICS_BASE_PVA_CORE_LIBS)
> nasaAcq_DBD += PVAServerRegister.dbd
> nasaAcq_DBD += qsrv.dbd
> endif
> endif

--

Jeong Han Lee, Dr.rer.nat.

Lawrence Berkeley National Laboratory

https://orcid.org/0000-0002-1699-2660