Re: [Xenomai-help] xnpod_announce_tick when migrating from 2.3 to 2.4

[Philippe Gerum <rpm@xenomai.org>]

On Thu, 2007-10-18 at 15:27 +0200, Philippe Gerum wrote:
> On Thu, 2007-10-18 at 14:11 +0200, Thomas Necker wrote:
> > Hello
> > 
> > I'm trying to migrate our software from 2.3 to 2.4 and I'm struggling
> > with the new timebase concept.
> > Here is how it works in 2.3:
> > - I have a small kernel module that calls xnpod_stop_timer and then
> > xnpod_start_timer with a handling function of my own.
> > - This handling function does some housekeeping and then calls
> > xnpod_announce_tick to trigger the nucleus (and eventually the pSOS
> > skin).
> > This is basically what Philippe suggested about a year ago.
> > Now, all these functions are gone in 2.4, how's the best way to do
> > something similar now?
> > I couldn't figure out how the new timebase concept can be used for that.
> > Thanks in advance.
> > 
> 
> It's actually much simpler with 2.4. You may install a hook into the
> periodic tick handler by calling the following helper, somewhere in your
> module init code:
> 
> 	xntbase_set_hook(psos_tbase, your_psos_hook);
> 
> The only difference compared to your current approach is that Xenomai
> will have processed the incoming tick before calling your hook, so you
> don't need to forward the tick anymore. Sidenote: this only works with
> periodic timebases so far.
> 

Actually, I now think we should rather implement to the traditional
"daisy-chain" pattern here, with the user-defined hook being called in
replacement of the genuine tick processing code, and the hook expected
to call into xntbase_tick() to signal the incoming tick when it sees
fit. This would allow the skin to implement time slowdowns etc.

Thomas, I'm going to send a patch asap to this end. Please rely on the
common behaviour (i.e. daisy-chain) you would expect from pSOS.

> You may want to have a look at the VxWorks skin (sysLib.c), which
> interposes on the global tick this way.
> 
> > Regards,
> > Thomas
> > 
> > _______________________________________________
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-- 
Philippe.