Re: [ECOS] HAL_INTERRUPT_ACKNOWLEDGE question

[Daniel Helgason <danielh@telus.net>]

On Wed, 2007-06-06 at 23:16 -0400, Mike Sweeney wrote:
> I am a little confused about what HAL_INTERRUPT_ACKNOWLEDGE is
> intended to do. The reference manual for eCos says that it is used if
> the interrupt controller requires you to acknowledge an interrupt. The
> reason I am confused is that an interrupt service routine for a device
> may need to clear a status flag in a peripheral status register even
> if there is no interrupt controller. Is the intent that each interrupt
> service routine handle this clearing of the flag in the peripheral
> status register on its own, in addition to calling
> HAL_INTERRUPT_ACKNOWLEDGE for handling anything that has to do with
> the interrupt controller?
> ...

I think this is because the interrupt controller is a shared resource
and there may be some 'stacking' and 'unstacking' of state required to
manage it and the priorities of interrupts that use it.

Each interrupt routine usually has exclusive access to the peripheral
that caused the interrupt and so the routine can directly handle
interrupt-related registers in the peripheral, but some, most, or all
peripheral interrupts might be channelled through the shared interrupt
controller in a target-specific way. Generally, interrupts from higher
priority sources are masked by the interrupt controller until
HAL_INTERRUPT_ACKNOWLEDGE is called. 

If you don't have an interrupt controller, then the
HAL_INTERRUPT_ACKNOWLEDGE macro/function is going to be very small if it
exists at all.

-- 
+---------------------------------------------
| Daniel Helgason <danielh@telus.net>



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