[ECOS] CYG_ISR_CALL_DSR vs CYG_ISR_HANDLED

[Gary Thomas]

On Fri, 2005-11-18 at 16:59 +0300, osv wrote:
> Hello,
> 
> In the eCos reference manual one can read:
> 
>   The return value of an ISR is normally one of CYG_ISR_CALL_DSR or
>   CYG_ISR_HANDLED. The former indicates that further processing is
>   required at DSR level, and the interrupt handlerĆæs DSR will be run as
>   soon as possible. The latter indicates that the interrupt has been
>   fully handled and no further effort is required.

This is poorly worded I think.

> 
> However, the eCos internal clock isr (Cyg_RealTimeClock::isr()) returns
> as follows:
> 
>     return Cyg_Interrupt::CALL_DSR|Cyg_Interrupt::HANDLED;
> 
> that seems to contradict with the description above. What is the truth
> about isr handler return codes?

CYG_ISR_HANDLED says that the ISR actually did something about the
interrupt.  It's used by chained interrupts to determine if another
ISR (which shares the same interrupt) should be run.

CYG_ISR_CALL_DSR indicates that the DSR which corresponds to this ISR
should be run.

These are bit values which can be successfully or'ed together to achieve
the desired result.

-- 
------------------------------------------------------------
Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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