[Open-graphics] Video interrupt enable/disable

[Timothy Normand Miller]

On 4/13/07, Patrick McNamara <wpmcnamara at yahoo.com> wrote:
> Timothy Normand Miller wrote:
[snip]
> >
> > Perhaps it would just be simpler to always set the interrupt in the
> > right instruction and have a mask bit in the global config registers.
> >
> I would certain argue for the second option.  It may take slightly more
> hardware to do, but it is certainly the simpler and more portable
> solution.  I don't know if we have discussed how video controller
> microcode is uploaded or changed, but enabling/disabling the interrupt
> should a PIO operation I think.  The reason for this is the expectation
> the system may have surrounding the toggling of interrupts.  If it is
> done as a DMA command to the card, it could be some time before the DMA
> completes, especially if there is a large transfer of some sort
> currently in progress.  If interrupts need to be disabled, they
> generally need to be disabled immediately, not some "random" time in the
> future.

I completely agree.  In fact, it's being handled entirely via PIO at
the moment anyhow, since we don't have a DMA engine.  The DMA engine
may (when the right privileges are set) have access to every register,
but at least by convention, we won't use DMA for certain things.

-- 
Timothy Normand Miller
http://www.cse.ohio-state.edu/~millerti
Open Graphics Project