Filip Van Rillaer wrote:
> Hello, 
> 
> Our application is written with some kind of super-loop scheduling : we
> have many drivers that call rt_event_signal (when data have been written
> to the hardware or new data are available to be processed) and 1 task
> that is calling rt_event_wait. After receiving an event, the superloop
> task is then reading/writing the data from/to the appropriate
> driver. Those calls to the drivers must never block (except to some
> locking to protect the consistency of data-structures) to garantuee the
> real-time behaviour of the application.
> Now we want to communicate with the Linux-domain and thought we have to
> use the Xenomai pipe-object for that purpose.
> 
> How can the superloop task in Xenomai receive an event from
> the pipe-object when data are available to be read/written (so
> without already reading the data)?
> 
> The ideal solution would be if one can ask the pipe-driver to call a
> user-callback function when there is a change in the status (read/write)
> or an equivalent system to the EPOLL interface (from the uclinux domain).

There is a mechanism already available from the core message pipe
implementation, but it is not exported by the native API interface.

So you have two options:

- ask user-space to notify kernel space explicitly _after_ each sending; for
that you may even use rt_event_signal() from a plain Linux task to send a
specialized event to your superloop.

- try the attached patch, which exports the needed bits. It is called
rt_pipe_monitor(). Absolutely untested.

> 
> Best regards,
> Filip.
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Xenomai-help mailing list
> Xenomai-help@domain.hid
> https://mail.gna.org/listinfo/xenomai-help


-- 
Philippe.