Bob Feretich wrote: > Gunther, > Thank you for the information. > No, the my hardware interrupt line is not being shared by other devices. > So I really don't want it to be considered "shared". However, my concern > was on how driver IRQ request calls are handled. > > If a driver invokes request_irq() without the SHARED flag, I would > expect Linux to reject subsequent request_irq() calls for the same IRQ > made by other drivers. Similarly, if the first driver invokes > request_irq() with the SHARED flag, I would expect Linux to accept > subsequent request_irq() calls for the same IRQ made by other drivers > if-and-only-if the other requests are made with the SHARED flag. > > My temporary fix for the problem I encountered required me to request > the same IRQ from Linux via request_irq() and then from Xenomai via > rtdm_irq_request(). I had expected the Xenomai request to fail. However, > that expectation assumed that there are interlocks between the > environments. I perceived problems in either case. If there are no > interlocks, then both a real-time driver and a non-real-time driver may > be loaded to service the same IRQ and be ignorant of each other. This > would probably be bad. > > If there are interlocks... > Then for a non-shared IRQ, the first driver to request the IRQ would > receive it. All other requestors, regardless of whether they are Xenomai > or Linux would be refused.
Ok. Adeos 101. Xenomai and Linux are living in different Adeos domains, each with its own interrupt handlers. The domains are organized in a pipeline. When an interrupt is received, it goes down the pipeline until a domain accepts it. The domain which accepts it may choose to propagate it or not to the next domain. So, there is nothing wrong with registering an interrupt handler for each domain. However, if the Xenomai domain interrupt handler decides not to propagate the interrupt to the Linux domain, Linux will simply never receive any interrupt. The SHARED flag applies to interrupts in the same domain, and are handled outside of the Adeos realm. The timer interrupt, on the other hand, propagates the interrupt when it sees fit, so that Linux timer handling is called. Both solutions are allowed. The reason why it is impossible to share an interrupt between two different drivers, unaware of each other, living in Xenomai and Linux domain is that it destroys the determinism. But even that can be made to work if we make a Xenomai domain driver for the Linux domain interrupt, aware of that Linux domain driver: https://mail.gna.org/public/xenomai-core/2008-07/msg00025.html > For a shared IRQ, the rules get much more complex. I believe that the > first driver to request the IRQ would receive it, but if the driver > specified the SHARED flag sharing would restricted the environment of > that first driver. Requests made from the other environment should be > rejected whether or not they specify SHARED. > Since my temporary fix (requesting and receiving a non-shared IRQ in > both the Linux and Xenomai environments) worked, if proved that there > were no interlocks. Phillippe stated that this is a flaw in the current > version of Xenomai. No, you misunderstood Philippe. What is a flaw in the current version of Xenomai is the fact that rtdm_request_irq does not configure the GPIO registers to set the GPIO interrupt to edge/level triggered, rising, falling, etc... The fact that the same interrupt can be requested in Xenomai domain and in Linux domain is perfectly normal, fits in the Adeos architecture, and is even needed for handling the timer interrupt on several architectures including arm. -- Gilles. _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
