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From: Greg Gallagher <greg@embeddedgreg.com>
Date: Mon, 14 Dec 2020 11:00:24 -0500
Message-ID: <CALLqZ8T0spXyi-iVB5bs5W+i6hdqSf7ZhK+CQiS3VxOs9_k9mQ@mail.gmail.com>
Subject: Re: [CXP][RFC] pick POSIX/cobalt for the common user API
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Philippe Gerum <rpm@xenomai.org>, "Xenomai@xenomai.org" <xenomai@xenomai.org>

On Mon, Dec 14, 2020 at 7:44 AM Jan Kiszka via Xenomai <xenomai@xenomai.org>
wrote:

> On 06.12.20 11:46, Philippe Gerum via Xenomai wrote:
> >
> > The common Xenomai platform specification is about defining the
> > commonalities among future Xenomai releases starting from 3.3, including
> > the Xenomai 4 series based on a next generation (EVL) core. A common API
> > available to applications for issuing requests to the real-time core is
> > part of this specification.
> >
> > Implementing such interface would not preclude other APIs from
> > co-existing in particular releases. However, use of this common API
> > only would guarantee portability across releases.
> >
> > Excluding the legacy RTOS emulators such as VxWorks and pSOS, Xenomai
> > 3.x provides two main APIs, a POSIX-compliant one (libcobalt) and a
> > custom RTOS API aka Alchemy (libalchemy) on top of the Copperplate
> > interface.
> >
> > PROPOSAL: Pick libcobalt as the common API defined by the CXP.
> >
> > As a consequence, Xenomai 4 would provide two direct interfaces to the
> > underlying EVL core: via the libevl API [1] which is readily
> > available, and its own implementation of libcobalt as part of a CXP
> > compliance.
> >
> >                   applications
> >       ....................................
> >       libalchemy            libevl libcobalt
> >            |                  |      |
> >            |                  |      |
> >       libcopperplate          |      |
> >            |                  |      |
> >            |                  |      |
> >        libcobalt              |      |
> >            |                  |      |
> >            v                  v      v
> >      (Cobalt core)           (EVL core)
> >       -----------            ---------
> >       Xenomai 3.x            Xenomai 4
> >
> >
> > Thanks,
> >
> > [1] https://evlproject.org/core/user-api/
> >
>
> Ack from my side.
>
> Besides using Xenomai 3.x as a stepping stone to migrate from legacy
> RTOSes like Vxworks, there may also be the option to use the mercurial
> version on top of Xenomai 4 at some point. In any case, it will first of
> all take users to actively express their long-term needs regarding such
> features - and contributions.
>
> Jan
>
> --
> Siemens AG, T RDA IOT
> Corporate Competence Center Embedded Linux
>
> ACK - looks good.  I think if someone would like to take on the
maintenance of one or all the RTOS skins then it's something to look at,
but for now it's out of scope.

-Greg