Re: [Xenomai-help] Non-Real-Time Asynchronous Notification

[Jan Kiszka <jan.kiszka@domain.hid>]

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Robert McCullough wrote:
> Hi Jan,
> 
>   --> -----Original Message-----
>   --> From: jan.kiszka@domain.hid [mailto:jan.kiszka@domain.hid]
>   --> Sent: Tuesday, April 01, 2008 7:07 PM
>   --> To: rob@domain.hid
>   --> Cc: xenomai@xenomai.org
>   --> Subject: Re: [Xenomai-help] Non-Real-Time Asynchronous Notification
>   --> 
>   --> Robert McCullough wrote:
>   --> > Hi Jan,
>   --> >
>   --> >   --> -----Original Message-----
>   --> >   --> From: jan.kiszka@domain.hid [mailto:jan.kiszka@domain.hid]
>   --> >   --> Sent: Friday, March 21, 2008 4:10 PM
>   --> >   --> To: rob@domain.hid
>   --> >   --> Cc: xenomai@xenomai.org
>   --> >   --> Subject: Re: [Xenomai-help] Non-Real-Time Asynchronous
>   --> Notification
>   --> >   -->
>   --> >   --> Robert McCullough wrote:
>   --> >   --> > Hi Jan,
>   --> >   --> >
>   --> >   --> >   --> -----Original Message-----
>   --> >   --> >   --> From: jan.kiszka@domain.hid [mailto:jan.kiszka@domain.hid]
>   --> >   --> >   --> Sent: Thursday, March 20, 2008 3:29 PM
>   --> >   --> >   --> To: rob@domain.hid
>   --> >   --> >   --> Cc: xenomai@xenomai.org
>   --> >   --> >   --> Subject: Re: [Xenomai-help] Non-Real-Time Asynchronous
>   --> >   --> Notification
>   --> >   --> >   -->
>   --> >   --> >   --> Robert McCullough wrote:
>   --> >   --> >   --> > Hi,
>   --> >   --> >   --> >
>   --> >   --> >   --> > How do I signal an asynchronous notification from a
>   --> RTDM
>   --> >   --> real-time
>   --> >   --> >   --> task to a
>   --> >   --> >   --> > non-real-time user-space Linux thread?
>   --> >   --> >   --> > Do I use Non-Real-Time Signaling Services
>   --> >   --> (rtdm_nrtsig_init,..)?
>   --> >   --> >   --> > If so, how?
>   --> >   --> >   --> >
>   --> >   --> >   --> > Here is the current code that I am trying to port to
>   --> RTDM.
>   --> >   --> >   --> >
>   --> >   --> >   --> > Current driver code to signal non-real-time Linux
>   --> thread:
>   --> >   --> >   --> >
>   --> >   --> >   --> > 	// If event
>   --> >   --> >   --> > 	if(event){
>   --> >   --> >   --> > 		// and signal asynchronous readers
>   --> >   --> >   --> > 		if (kmdpr_device->async_queue)
>   --> >   --> >   --> >
>   --> > kill_fasync(&kmdpr_device->async_queue,
>   --> >   --> > SIGIO,
>   --> >   --> >   --> > POLL_IN);
>   --> >   --> >   --> > 	}
>   --> >   --> >   -->
>   --> >   --> >   --> Just push this code in the rtdm_nrtsig handler and
>   --> trigger the
>   --> >   --> handler
>   --> >   --> >   --> execution from RT context.
>   --> >   --> >   -->
>   --> >   --> >   --> Jan
>   --> >   --> >
>   --> >   --> > [Robert McCullough]
>   --> >   --> > Ok, I understand that but how do I specify the file
>   --> operation fasync
>   --> >   --> in my
>   --> >   --> > rtdm_device?  How do I replace or update the code marked
>   --> TODO?
>   --> >   -->
>   --> >   --> In fact, there is no fasync support available with RTDM,
>   --> specifically
>   --> >   --> as
>   --> >   --> using signals under real-time constraints is a bad idea (not
>   --> only
>   --> >   --> because Xenomai has no hard-RT signal support).
>   --> >   -->
>   --> >   --> But before suggesting any alternative pattern: What does your
>   --> >   --> application actually require to work? How does asynchronous
>   --> >   --> driver/application interaction currently look like?
>   --> >   -->
>   --> >   --> Jan
>   --> >
>   --> > [Robert McCullough]
>   --> > Here is a little background on how my driver works.
>   --> > The driver is the interface/control for an AC servo drive which
>   --> controls an
>   --> > AC motor.  The interface to the drive is done through a dual-ported
>   --> RAM.
>   --> > The I/O from the servo drive is updated and an IRQ is triggered from
>   --> the
>   --> > servo drive through the DP RAM to our MPC5200 at a 4 kHz rate.  In
>   --> my IRQ
>   --> > handler I read, process, and update the I/O in the RAM.  Some of the
>   --> data
>   --> > from the servo drive contains status bits that represent
>   --> asynchronous
>   --> > events/faults from the drive that needs to be passed up to the user
>   --> > application.  In my current non-real-time driver I used fasync to
>   --> send a
>   --> > SIGIO signal to the user application whenever one of these
>   --> events/faults
>   --> > changed and then the application would read the status bits with an
>   --> ioctl
>   --> > call and process them.
>   --> >
>   --> > I hope this clarifies the requirements a little.
>   --> > How would you suggest I solve this in my RTDM driver?
>   --> 
>   --> Well, a classic pattern is to encapsulate the async event handling in
>   --> one or more dedicated threads that block-wait on those events. Check
>   --> the
>   --> RTDM profile for serial devices for such a channel. This has the
>   --> advantage that you can cleanly specify the handling priority,
>   --> specifically compared to "normal" operations.
>   --> 
>   --> HTH,
>   --> Jan
> 
> [Robert McCullough] 
> Are you referring to the RTSER_RTIOC_WAIT_EVENT in the serial profile?
> If so, this can only be called from a real-time user-space task.
> I need to see the event in a non-real-time user-space task.
> How would I do this?

Then you can simply built the signaling on top of Linux mechanisms that 
are triggered from the RT domain via a rtdm_nrtsig. You can hook the 
non-RT API into the RTDM device by using *_nrt handlers (e.g. ioctl_nrt).

Jan


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