Re: [Xenomai-help] newbie question

[Jan Kiszka <kiszka@domain.hid>]

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Gilles Chanteperdrix wrote:
> Philippe Gerum wrote:
>  > Ignacio Garc~a P~rez wrote:
>  > > Hi,
>  > > 
>  > > I'm quite new to xenomai (switching from RTAI). I noticed that the
>  > > latency_rt.ko module fails to start the timer if the posix skin module
>  > > (xeno_posix.ko) is loaded. Is this the expected behaviour?
>  > >
>  > 
>  > Yes and no. There is a change pending in my tree that makes rt_time_start() a 
>  > bit smarter, trying its best effort to check whether the requested setting fits 
>  > any current one, in which case the call returns without error. In the case you 
>  > mentioned, both timer setups at nucleus level asked for oneshot, so this should 
>  > have been ok with this patch, instead of bailing out on error rather uselessly. 
>  > The UVM skin already enforces this for instance. I have just committed it to the 
>  > SVN repo.
> 
> The problem is that you also have to make the module_exit function
> smarter and avoid to stop the system timer if another module is
> running. This means adding a sort of reference counter to the system
> timer.
> 

Another reason to look for a different way. The timer is a global
resource, let's manage it at a central place: the nucleus (module
parameter) plus maybe some sysfs variable. The days are over when skins
could decide about the whole system on their own ;). And it's also much
more comprehensible for the user when (s)he only has to look at one
place for tuning this parameter.

Jan

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