On 19/01/2015 17:17, Artyom Tarasenko wrote: > On Mon, Jan 19, 2015 at 4:31 PM, Paolo Bonzini <pbonz...@redhat.com> wrote: >> >> >> On 19/01/2015 16:22, Artyom Tarasenko wrote: >>>>>>> >>>>>>> On physical machines it's EBus, which is pretty much like 8-bit ISA. >>>>>>> So, I think modelling it as ISA is closer to to the reality. >>>>>>> But out of curiosity, would it be possible to have a sysbus device >>>>>>> somewhere in a middle of PCI space? [...] >>>>> >>>>> Why would you want to use a SysBusDevice in the first place? >>> Ask Paolo. :-) For me it's only important to have a MMIO device in the >>> proper address range. >> >> The reason I asked is simply because ISA devices never do MMIO (apart >> for the VGA window). > > You mean in the QEMU world? At least physical SCSI and Ethernet > adapters had a MMIO space for the onboard ROM.
Uh right, ROMs count as MMIO too. >>>>> I previously discussed with Mark that it should be an EBusDevice, not an >>>>> ISADevice or SysBusDevice. >>> Interesting. I can't find this discussion in the list archive. Do you >>> suggest to >>> create EBusDevices for all ISA devices (serial, parallel, keyboard, >>> floppy) used in sun4u, or only for m48t59? >>> What would be the advantage of using EBusDevice over ISADevice? >> >> Is there a description of EBus and the sun4u memory map somewhere? > > I could find only sparse pieces. "Uniprocessor System Controller > User's Manual" (805-0170.pdf) has some brief description, it's also > mentioned in the STP2223BGA and STP2200ABGA data sheets. > >> Is there an "EBus bridge" PCI device similar to the PCI-to-ISA bridge? > > As physical devices there are integrated SBus-to-EBus and PCI-to-EBus bridges. > > But actually I may have been wrong about NVRAM always sitting on the > EBus: looking at the page 28 of "UltraSPARC™-IIi User's Manual" > (805-0087.pdf), I see that NVRAM, Serial and other controllers reside > in a "PC compatible SuperIO" chip which sits on a PCI bus. That's an ISA bridge basically. I understand a little more of how this is supposed to work now, but I think it makes little sense to add this patch without the corresponding user. Paolo
