LinuxCNC RTAI kernel

[John Morris]

On 02/09/2014 06:27 AM, Sandro Mani wrote:
> 
> On 09.02.2014 09:16, John Morris wrote:
>> My goal for the forthcoming LinuxCNC release is readiness for inclusion
>> in both Fedora and Debian.
>>
> Wow exciting, thanks! How are you planning to deal with the realtime 
> kernel requirement, or is that beyond the scope of your work?

The meat of the last year-plus effort was introducing support for the
PREEMPT_RT and Xenomai RT kernels, and teaching it to build
run-time-selectable modules for all supported thread flavors in one
"./configure && make" run.

Since PREEMPT_RT has no special build requirements, those RT modules are
built and packaged by default, so I hope to 'sneak' them into Fedora,
despite lack of in-distro support.  You may then "bring your own" RT
kernel from e.g. MRG or Planet CCRMA to get hard RT behavior; otherwise,
the POSIX "simulator" threads work with no special kernel requirements
(but all bets off as far as latency requirements).

For those requiring even tighter latency than PREEMPT_RT for e.g.
software stepper motor drivers, a 3rd-party repo can supply the Xenomai
kernel, run-time libs, and matching LinuxCNC RT modules.

RTAI kernel support could be offered in the same way, but for a number
of reasons, many (but not all) of us think of RTAI support as deprecated.

For more info, here's a short paper presented at last year's OSADL Real
Time Linux Workshop:

  http://static.mah.priv.at/public/paper.pdf

Sadly, Debian has beat out the Fedora project by getting an RT kernel
into the main repo, just the latest reason I continue finding myself
alone running Red Hat-derivative distros among CAD/CAM/CNC/Maker/3D
printer circles.  I'm considering launching a campaign in the Fedora
community to raise attention these issues, but don't yet know where to
begin.  I heard previous inquiries were shut down hard, but maybe the
context has changed since the last time.

	John