On Tue, 3 Aug 1999, Roland Seuhs wrote:
> I will work for a project in September, where we will use Linux on a
> ColdFire inside a Power Quality Analyser for a small company.
> I am expirienced with C but I never wrote something like kernel-modules
> for Linux.
>
> Maybe (I don't know for sure now) it will be necessary to add
> RealTime-Support to the Analyser.
>
> So if we need it, I would volonteer to program/port RealTimeLinux to the
> ColdFire.(I'm the only guy in the company with Linux experience, so I
> will have to do the Linuxpart mostly on my own.)
>
> The ColdFire is the newest Processor from Motorola and descended from the
> 68000 - Family. There is already a Linux for this Processor, so I would
> just had to add the Real Time functionality.
Hmmm... I took a look at porting RTlinux to the primary m68k linux kernel
tree a while back, and ran into some definate complications... (more on
this bit later). I'm not sure which port the coldfire people are using
(uClinux, perhaps?) but the same issues should remain..
> So I've got some questions:
>
> Are there other people with similar projects somewhere in the world?
> (There have to be!)
I am, in a sense. :)
> Do you think that this can be done by one programmer in a reasonable time
> (1 Month)?
Porting RTlinux to a single m68k platform can probably be done in one
month by someone who was reasonbly familiar with the linux kernel or
linux/m68k in particular...
Here's a breif rundown over what kept me from getting in to deep. :)
First problem is, to answer your question below, almost everything is
going to need rewritten. Some bits can stay, but... The issue is that
the interrupt archetecture provided by the standard linux/m68k kernel is
considerably different fom the interrupt archetecture on x86. In order to
glue rtlinux into m68k, it's also going to be necessary to rewrite greater
parts of the m68k interrupt path than was needed for the original x86
port.
Second, and more daunting, is the fact that the m68k port is divided into
a great number of sub archetectures... A port of RTlinux to m68k would
more likely be, say, a port of RTlinux to the sun3, and wouldn't work for
the other m68k arch's. (basically, they all use different interrupt
controllers, and well... let the fun begin)
If your goal is simply to get a port out for a specific coldfire/m68k
based board, then, yeah, it could certainly be done. I suppose if enough
people with access to enough m68k platforms modified it eventually, you
might have something that could be considered a general purpose m68k
RTlinux.
> Do you think that implementing RealTimeLinux on the ColdFire is merely a
> simple port or has the whole thing to be rewritten? (Time estimate?)
(above). Time estimate... hard to say. I've been digging around in the
m68k kernel enough for the sun3 project that I can't guess on the initial
learning time required to do it.
> Even some comment on implementing RTLinux on the ColdFire would be very
> helpful to know if it is worth the effort.
Hope my commentary was somewhat helpful. :) And not too discouraging.
I'd like to see the RTlinux framework implemented in the m68k tree, but
it's going to be a considerable balancing act in design to make it easily
adaptable to all m68k archs.
-- Sam
"UN-altered REPRODUCTION and DISSEMINATION of this IMPORTANT
Information is ENCOURAGED, ESPECIALLY to COMPUTER BULLETIN BOARDS."
-- Robert E. McElwaine
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----
For more information on Real-Time Linux see:
http://www.rtlinux.org/~rtlinux/
