How to Use Interrupts in Applications

[Robert S. Grimes]

Robert S. Grimes wrote:
> Okay, I'm confused.  I'm not at all sure how the concepts of "old
> exception model", "new exception model", and the RTEMS "Interrupt
> Manager" are related.
>
> One guess I have is that the first two are strictly BSP constructs, and
> that the Interrupt Manager sits on top of whichever choice a BSP has
> implemented.  Is that correct?
>   
Well, I guess not, but maybe that is the intent?  See below...
> I'm using the PowerPC/Virtex BSP off the head, which uses the "new
> exception model".  I want to create a relatively simple ISR to handle a
> peripheral that is custom to one of several processor boards that all
> use the same BSP.  So it seems wise to keep it out of the BSP, and
> implement it in my application.  So do I just use the "Interrupt
> Manager", and let all the details pertaining to the interrupt controller
> be handled by the BSP?
>   
Nope!
> Is it as simple as this?
>
>     extern rtems_isr_entry myIsrFunc;
>     #define MY_INT_VECTOR  1
>
>     // Somewhere in my app init code
>     rtems_isr_entry oldIsrFunc;
>     rtems_interrupt_catch(myIsrFunc, MY_INT_VECTOR, &oldIsrFunc);
>   
Okay, no, it is not this simple.  the rtems_interrupt_catch eventually
gets to c/src/lib/libcpu/powerpc/new-exceptions/cpu.c, where it
encounters this code:

    void _CPU_ISR_install_vector(<snip>)
    {
      BSP_panic("_CPU_ISR_install_vector called\n");
    }

So it is clear to me that the "new exception" model hasn't been fully
worked out (yet), at least not at the application level.  It is safe to
say that interrupt management is broken here, or the documentation is
fully out of date.

So what am I to do now?  I'd be happy to help, but I have more unknowns
right now about what the thinking was behind the switch from old to
new.  I found a discussion in the mailing list archives from a few years
ago, but it wasn't complete enough to understand.  I need this _now_,
and will cobble something together if forced to (I'm sure the Ethernet
driver example will help me), but it doesn't seem right to just solve my
problem in an undocumented, quite possibly wrong-headed,, way, and not
fix it more generally to help future users!  I just need a bit of
direction...

Thanks,
-Bob