[ECOS] Re: On ARM7 can one of FIQ/IRQ be used for non-eCos stuff?

[Grant Edwards <grante@visi.com>]

On 2008-04-02, Chris Zimman <czimman@bloomberg.com> wrote:

>> However, there quite a few spots in the arm/arch interrupt and
>> exception handling code where FIQ is being disabled.  It looks
>> like I'd have to fork the arch code and modify it to prevent
>> it from disabling FIQ.
>
> Yes, there definitely is that issue.  It's not too many places
> that have to be updated though.
>  
>> I suppose the right thing to do would be to make the arm/arch
>> stuff configurable via CDL so that it would use either FIQ or
>> IRQ or both.
>
> I would think what you'd want to do is to provide a function
> to change the FIQ vector after eCos has started.

That's easy enough, but it'd be trickier to provide a run-time
function to fix the places in vectors.S that are currently
disabling FIQ.

> If you start things without the FIQ vector assigned, and for
> whatever reason it fires, you're in trouble.

True.

> With regards to CDL, I don't know that it would make sense to
> have a CDL option to not have eCos own the FIQ vector on
> startup.

The main point of the CDL would be to avoid having to fork the
arm/arch code.  I don't really like maintaining my own separate
versions of files unless I absolutely have to.  Besides,
somebody else might actually want to use the new "feature".

-- 
Grant Edwards                   grante             Yow! I feel ... JUGULAR ...
                                  at               
                               visi.com            


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