Re: [Xenomai-core] Synchronising TSC and periodic timer

[Rodrigo Rosenfeld Rosas <lbocseg@domain.hid>]

Em Segunda 20 Mar=E7o 2006 12:23, Philippe Gerum escreveu:

>...
>It's not a matter of dealing with users always doing The Right Thing,
>but preferably preventing people from doing the wrong one.

But we then have two problems and there are tradeoffs here. In one hand we=
=20
want to avoid users from making mistakes. In the other hand we want to=20
provide a way for solving the issue that generated this thread.

A solution for the last one would be to have a function that would return a=
=20
high-precision timestamp, not necessarily in sync with xenomai's timer, sin=
ce=20
it would be used for relative time calculations, but should be in sync=20
between multiple CPUs. But this solution would rise the possibility for a=20
user to do a wrong thing. Of course, the functions should be well documente=
d=20
and states the lack of sync if it is the case. So, we have to choose betwee=
n=20
turning it possible to have such design (as the example I have last message=
)=20
or avoid people from doing the wrong thing. I would choose the first case,=
=20
since I think all rt-programmers are smarter (or should be) then the averag=
e=20
programmer. They must have attention when dealing with rt-programming. So,=
=20
reading a documentation and understanding it should not be a hard task for=
=20
them... In the other hand, if the second approach was chosen, a user wantin=
g=20
to use a rt-video interface will be forced to use the aperiodic timer for=20
having reliable timestamps...

Rodrigo.

		
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