Re: Orocos and xenomai-3

On Wed, Jan 21, 2015 at 6:03 PM, Leopold Palomo-Avellaneda <
[email protected]> wrote:

> Hi,
>
> someone of you is working to migrate to Xenomai-3?
>

We are not, as there is not yet a stable release. Here are my two cents if
you or somebody else wants to give it a go.

As context, Xenomai 3 introduces a couple of big changes: It can deliver
real-time by means of a co-kernel (cobalt-core) as was done in Xenomai 2;
or it can simply rely on what Linux provides (like a PREEMPT-RT patched
kernel). Also, and very important, the default interfaces have switched to
being POSIX-based (copperplate library), so all other real-time APIs (or
skins) are implemented on top of this. In particular, the Xenomai 2 native
API (now called Alchemy) is a skin, while the POSIX API has been promoted
from a skin to the standard interface.

So, I see two alternatives for supporting Xenomai 3 in Orocos:

-  Orocos uses Xenomai 2 native API calls (Alchemy in Xenomai 3). You could
try to update the build configuration scripts to pick up Xenomai3 and use
it through the Alchemy interface. This would be the 'legacy support'
solution.

- Go for the POSIX interface and leverage the added flexibility it
provides. The OS abstraction differences between Linux and Xenomai would
become trivial, and copperplate would sit on top of glibc/ulibc or
libcobalt, depending on how real-time is delivered. I'm personally more
attracted to this approach.

I don't know which alternative would incur in a smaller porting effort, as
both POSIX (gnulinux) and Xenomai 2 native bindings already exist in Orocos.

More general info on migrating to Xenomai 3, which most likely you have
read by now:

http://xenomai.org/migrating-from-xenomai-2-x-to-3-x/

Best,

Adolfo.


> Best regards,
>
> Leopold
>
> --
> --
> Leopold Palomo-Avellaneda <[email protected]>
> Institut d'Organització i Control de Sistemes Industrials -IOC-
> Universitat Politècnica de Catalunya -UPC-
>
> Institute of Industrial and Control Engineering
> Technical University of Catalonia
> Avda. Diagonal 647, pl. 11
> 08028 BARCELONA (Spain)
>
> Tel. +34-934016655 (office)
> Tel. +34-934017163 (lab)
> Fax. +34-934016605
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