Re: [Xenomai-help] OT. A question about constraints in realtime

[Leopold Palomo Avellaneda <leo@domain.hid>]

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A Dilluns 28 Juliol 2008, Gilles Chanteperdrix va escriure:
> Leopold Palomo Avellaneda wrote:
> > The sensable people claims that their driver works with some versions of
> > Linux (till fedora 4 and some suse) but I'm not be able to run it in a
> > debian etch. I don't know if the distros provide a kernel with some kind
> > of modifications that solve it, but I don't think so.
> >
> >
> > Well, thanks in advance and I'm sorry for the noise. Really, the realtime
> > stuff is something not obvious...

First of all thanks for the answer. 

> The first thing to do is to get statistics about the scheduling latency
> of your driver. This means measuring the difference between the date
> when the driver (kernel-code) wakes up the task and the date when the
> task effectively runs. The bad news is that it will be hard with a
> binary-only driver. If the driver has some compilable glue, then you can
> hook into this glue, otherwise, you will have to resort to ugly hacks in
> the kernel code.

Well, I cannot (or it's too difficult to do it with a _only_ binary driver. 
This driver is a lib (.so) and the user use some functions of that lib. 

> If this latency is really the problem, then before resorting to xenomai,
> you have linux-only solutions, like using a real-time priority for the
> task using the driver.

Well, I guess that it's the latency. They have a loop that control each 
engine, and if the driver doesn't receive any signal in some time, it 
disconnects the engine (some rele acts) . They works well with devices with 3 
motors but the 6DOF model fails.

I have to think how to solve it ...

Regards,

Leo


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