Re: [Qemu-devel] [PATCH 06/13] pci: Add INTx routing notifier

[Michael S. Tsirkin]

On Sun, Jun 10, 2012 at 01:18:15PM +0200, Jan Kiszka wrote:
> >>>>>> @@ -318,6 +322,9 @@ PCIBus *pci_register_bus(DeviceState *parent, 
> >>>>>> const char *name,
> >>>>>>                           MemoryRegion *address_space_io,
> >>>>>>                           uint8_t devfn_min, int nirq);
> >>>>>>  PCIINTxRoute pci_device_route_intx_to_irq(PCIDevice *dev, int pin);
> >>>>>> +void pci_bus_fire_intx_routing_notifier(PCIBus *bus);
> >>>>>
> >>>>> Well true it fires the notifier but what it does conceptually
> >>>>> is update intx routing.
> >>>>
> >>>> Nope, it informs about updates _after_ they happened.
> >>>
> >>> Don't we need to update the cached pin if this happens?
> >>> If yes I would this a better API would both update the cache
> >>> and then trigger a notifier.
> >>> And the notifier can then be cache change notifier,
> >>> and the "fire" function would instead be "update_cache".
> >>
> >> See above, the cached part of the route is static anyway. What changes
> >> is the host bridge configuration.
> > 
> > You are saying it is only the intx to irq routing that
> > can change?
> > So maybe "pci_bus_update_intx_to_irq_routing"?
> 
> Again, this function does not _update_ anything. It informs about a
> host-bridge-specific update, i.e. something that happened outside the
> generic code beforehand.

Yes it does what it says but it's an ugly interface all the same.
What does a host device emulation care about notifiers?
It's an implementation detail.

The *real* reason is that someone caches intx to irq routing
and you need to update that cache.

So just say so.

-- 
MST