AW: AW: Dependencies of PPS API in rtems-libbsd

[Gabriel.Moyano at dlr.de]

> >> I guess you want to enable tc_poll_pps in struct timecounter as well?
> >
> > I didn't plan to do that but it can be done just removing some #ifndef, right?
> 
> Is this handler not use for the PPS support? If it is currently unused, then please let it disabled.

Ok. For now I was working with interrupts but I guess that the same can be done with polling, that's for that handler.

> 
> >
> >> For what do you need the sleep() and wakeup() support? Is this only used by the RFC 2783 PPS-API implementation?
> >
> > Yes, they are required by pps_fetch() and pps_event()
> >
> >> If you want to keep implement this in RTEMS, then you can convert
> >> this to use a condition variable from <sys/lock.h> or <rtems/thread.h>.
> >
> > Do you mean to add a condition variable, for example in struct pps_state, and to replace sleep() and wakeup() by wait and signal? It
> is good idea if we don't want to use the first functions.
> 
> Ok, it seems the pps_event() could be called by interrupt service routines. In this case, you cannot use a mutex and condition
> variables.
> You have to use a thread queue directly. Use the thread queue ISR lock for mutual exclusion. Use _Thread_queue_Enqueue() to
> emulate sleep() and
> _Thread_queue_Flush_critical() to emulate wakeup(). Check all critical sections that they can be protected by an ISR lock (no blocking
> calls and short).

Is this even so if pps_event() calls signal or broadcast? Because pps_fetch() is the only function that is waiting (and locking a mutex).

> 
> >
> >> All the uses of sleep() and wakeup() need to be clearly identified and if possible avoided.
> >
> > May I ask, what is the reason for avoiding them?
> 
> The sleep() and wakeup() synchronization is nice, but not suitable for real-time systems (use of hash tables).
> 
> >
> > What do you think about coping the functions lmax()/qmin() and the define for ENOIOCTL? For lmax()/qmin() I saw that the file
> where are defined (libkern.h) is in libnetworking. Not sure what it is the best option here, I don't like when the things are duplicated.
> 
> Since you refer to libnetworking I guess you work with RTEMS 5. Please first get it working on RTEMS 6 and then we think about a back
> port.

Yes, I'm working with RTEMS 5 but my next step is port the changes to RTEMS 6 and then submit the patches.

> 
> >
> > What about tvtohz(), which is defined in rtemsbsd/rtems/rtems-kernel-timesupport.c?

tvtohz() is used for converting timeval to hz, which is required by msleep(), msleep_spin() and tsleep but because they are not used, tvtohz() is not needed.

> 
> Maybe just copy the dependencies to kern_tc.c. Later we can try to move them to shared locations if necessary.

I did this for lmax(), qmin() and ENOIOCTL.

Thanks for your answers.