On Wed, Jan 30, 2013 at 11:48:14AM +0000, Peter Maydell wrote: > On 30 January 2013 11:39, Andreas Färber <afaerber@xxxxxxx> wrote: > > Proposal by hpoussin was to move _list_add() code to ISADevice: > > http://lists.gnu.org/archive/html/qemu-devel/2013-01/msg00508.html > > > > Concerns: > > * PCI devices (VGA, QXL) register I/O ports as well > > => above patches add dependency on ISABus to machines > > -> "<benh> no mac ever had one" > > => PCIDevice shouldn't use ISA API with NULL ISADevice > > * Lack of avi: Who decides about memory API these days? > > > > armbru and agraf concluded that moving this into ISA is wrong. > > > > => I will drop the remaining ioport patches from above series. > > > > Suggestions on how to proceed with tackling the issue are welcome. > > How does this stuff work on real hardware? I would have > expected that a PCI device registering the fact it has > IO ports would have to do so via the PCI controller it > is plugged into... All programming is done by the OS, devices do not register with controller. Each bridge has two ways to claim an IO transaction: - transaction is within the window programmed in the bridge - subtractive decoding enabled and no one else claims the transaction At the bus level, transaction happens on a bus and an appropriate device will claim it. > My naive don't-know-much-about-portio suggestion is that this > should work the same way as memory regions: each device > provides portio regions, and the controller for the bus > (ISA or PCI) exposes those to the next layer up, and > something at board level maps it all into the right places. > > -- PMM -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
