While looking into how to implement sharing of interrupts between realtime and
non-realtime domains (and applying Wolfgang Grandegger's patch
[https://mail.gna.org/public/xenomai-core/2006-01/msg00233.html], which is
necessary to make XN_ISR_ENABLE work at all on the PowerPC platform), I'm
beginning to think that XN_ISR_CHAINED and XN_ISR_ENABLE are mutually exclusive,
since if both are set, desc->handler->end will be called twice:
1. When the realtime isr handler returns
2. When the Linux domain calls it in __do_IRQ
In the solution I have in mind at the moment, I will:
1. Add an extra iend handler argument to xnintr_init
2. If XN_ISR_ENABLE is returned from the isr handler,
replace desc->handler->end with the user supplied
iend handler.
Hereby I hope to be able to handle interrupts shared between realtime and
non-realtime domain, without having the realtime domain wait for all
non-realtime interrupts to finish. This is the scenario I'm thinking of:
1. A non-RT interrupt occurs
2. The (RT) isr handler detects the non-RT interrupt,
disables further non-RT interrupts on that irq-vector, replaces
desc->handler->end with the user supplied iend handler,
returns XN_ISR_CHAINED | XN_ISR_ENABLE.
3. RT interrupts are serviced by the (RT) isr handler,
returns XN_ISR_ENABLE
4. The Linux domain get a chance to run the chained interrupt,
and eventually calls desc->handler->end (supplied iend handler)
5. The iend handler reenables non-RT interrupts.
Comments on the above are most welcome!
--
Anders Blomdell
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