Re: [Qemu-devel] [PATCH RFC 0/3] basic support for composing sysbus devices

[Markus Armbruster]

Jan Kiszka <address@hidden> writes:

> On 2011-06-08 13:33, Peter Maydell wrote:
>> At the moment you can't really implement one sysbus device by saying
>> that it's composed of a set of other sysbus devices. This patch adds
>> new functions sysbus_pass_mmio() and sysbus_pass_one_irq() which
>> allow a sysbus device to delegate an MMIO or IRQ to another sysbus
>> device (The approach is inspired by the existing sysbus_pass_irq()
>> which lets a sysbus device delegate all its IRQs at once).
>> 
>> This works; the most obvious deficiency is that the subcomponent
>> device will still appear as its own device on the bus.
>> 
>> So: is this a reasonable solution to the problem, or an unacceptable
>> hack? Comments welcome :-)
>
> Sounds more like a little hack. :)
>
> The relationships should be expressed via qdev, not yet another
> sysbus-specific extension. Generally, many services of sysbus should
> rather be generic qdev things.

Examples?

> Is there anything that today prevents creating a local bus and attaching
> the component devices to that? If it's multi-bus support, that should to
> be added anyway. Passing-through of MMIO and IRQs is still a worthwhile
> generic service, then probably qbus associated.

Do you mean making the container device a sysbus-sysbus-bridge, then
hanging the component devices off the inner sysbus?