Timothy Normand Miller wrote: > Something we need to be able to do is enable the interrupt for video. > Generally, we only need one interrupt per frame, so what we need to do > is set the interrupt bit in one of the instructions at the end of the > last active scanline. The thing is, it's not adequate to make that a > parameter to the programming function... we need to turn the interrupt > on and off quite a lot, so what would be nice is to have another > function to call that enables/disabled interrupts by rewriting the > right instruction with the flag changed. The problem is that we need > to somehow keep track of which instruction this is, for multiple cards > with more than one video head each. > > 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.
Patrick M _______________________________________________ Open-graphics mailing list [EMAIL PROTECTED] http://lists.duskglow.com/mailman/listinfo/open-graphics List service provided by Duskglow Consulting, LLC (www.duskglow.com)
