>On Mon, 2007-09-03 at 14:11 +0200, ROSSIER Daniel wrote:
>> I'm doing a small RT application using the I2C driver from Linux.
>> At a certain time, when the task is activated and data are written to
>> the I2C bus,
>> the driver waits for a IRQ that confirmed the data have been sent out.
>> The write function
>> actually polls a variable state until a timeout or a state change
>> occurring on reception of that IRQ (done by the handler).
>> However, since driver functions are called from the Xenomai domain,
>> the IRQ handler is not processed
>> at the reception since the hander belongs to the Linux domain. It ends
>> up with a timeout
>> during the write.
>> I implemented a local ISR within the Xenomai application, but the
>> propagation of IRQ is not performed
>> while the task is running.
>Which is expected. All the pipeline abstraction relies on the very
>fundamental assumption that domains run by priority order, which in turn
>means that a high priority domain must run until all the pending work is
>processed, and a Xenomai task in a runnable state represents some
>pending work for the Xenomai domain. Make your Xenomai task sleep on
>some synchronization object (likely a RTDM one) for synchronizing with
>the code which signals the wakeup condition, and the pending IRQ will
>flow down to Linux as expected. Busy waiting for such condition is a
>dead end here.
Ok, I totally agree. I've tried to use a rtdm_event object which I've
declared in the Linux driver side. Then, the write function is called from a RT
then it calls rtdm_event_wait() at a certain point, and the i2c ISR performs a
to wake up the RT task. However, I got a kernel crash when rtdm_event_wait() is
The i2c driver is statically linked in the kernel (zImage), but I'm not sure
if I'm right declaring a rtdm object in the kernel directly. Can you confirm?
Another point where I'm not sure: does a call to rtdm_event_signal() suspend
of the linux ISR, or will the ISR terminate properly before yielding to the RT
Because it might complicate the work between the (partially finished, without
unmasked IRQ) handler
and the RT task...
Thanks in advance for the clarification.
>> Is there a way to tell Adeos to forward the IRQ to the Linux domain
>> with no delay
>> so that the Linux handler can be called? or do I need to re-implement
>> the ISR in the Xenomai application?
>Your code cannot be on both side of the same fence. Either you want a
>real-time guarantee for interrupt delivery and task dispatching and you
>need a Xenomai ISR to process IRQs to wake-up some Xenomai task; or, you
>don't need any guarantee, but still want Linux to process the i2c IRQs
>just for the purpose of recycling some vanilla code, and in such a case,
>you need to make the Linux IRQ handler wake up the Xenomai task. In the
>latter case, the Xenomai task (in primary RT mode) must sleep at some
>point waiting for the wake up event, there is no sideways possible here.
>You may call rt_sem_v() or sem_post(), or a rtdm object signaling
>routines from a Linux context to wake up a real-time sleeper.
>> Thanks for any hints.
>> Xenomai-core mailing list
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