Re: IO and PCIy

[Tim Hockin]

> Is there a way to disable IO read/writes to a PCI device. The bit 0
> of command register in PCI configuration space can be used to 
> disable/enable memory-mapped IO but will it disable direct IO 
> (what is the proper term?) as well?
 
 There are two bits - IO enable and MMIO enable.  They are the 0x1 and 0x2
 bits in the command register, respectively.
 
> enable interrupts on vertical blanking without doing so on both 
> cards (since they both respond to the same direct IO addresses). 
 
 umm, should they be on the same IO?  I've never mucked with dual video
 cards, but that sounds odd...
 
> Of course if I knew the addresses/offsets for memory-mapped versions
> of the appropriate registers on one card I could solve this problem
> but I do not neccesarily have that info.

The pci regions are easily readable - you should dig up a copy of the PCI
spec - very good reading....