Re: [PATCH] testdev: adjust for ISA irq changes

Markus Armbruster
2011-05-30T15:34:56Z

Jan Kiszka <jan.kiszka@web.de> writes:

> On 2011-05-29 17:26, Avi Kivity wrote:
>> On 05/29/2011 06:21 PM, Jan Kiszka wrote:
[...]
>>> We also need a better interface to discover and track legacy IRQ routes
>>> for device assignment. Markus is currently collecting requirements for
>>> qdev enhancements, and I think generic IRQ manipulation and discovery
>>> belongs there.
>>
>> Possibly. But note that attempting to shoehorn everything into
>> bus/device model may not work. Motherboard devices, especially, often
>> bypass the bus/device relationship, just because everything is available
>> to them on the motherboard, and because hardware designers didn't go to
>> software engineering schools but instead do what's necessary to get
>> things working. We have to be prepared for exceptions.
>
> Yes, the IRQ tree should probably be independent of the qdev tree. I was
> thinking of qdev as the infrastructure that allows to build and maintain
> that tree and to associate IRQ pins with qdev devices.

The bus/device model limits the connections between devices to a tree,
which can't model real world interrupt wirings. We obviously need to
generalize there.