Re: [Qemu-devel] [PATCH v2 07/11] versatile_pci: Implement the correct PCI IRQ mapping

[Peter Maydell]

On 26 March 2013 21:12, Michael S. Tsirkin <address@hidden> wrote:
> On Tue, Mar 26, 2013 at 11:17:55AM +0000, Peter Maydell wrote:
>> On 26 March 2013 11:08, Arnd Bergmann <address@hidden> wrote:
>> > On Tuesday 26 March 2013, Peter Maydell wrote:
>> >> On 26 March 2013 10:54, Arnd Bergmann <address@hidden> wrote:
>> >> > Yes, very good.  We will probably introduce sparse irq support on
>> >> > versatile in the near future, and then the value we write into the
>> >> > PCI_INTERRUPT_LINE field will become arbitrary from qemu's point
>> >> > of view, but I will make sure that we fix the interrupt mapping
>> >> > in the kernel at the same time so we always fall into the
>> >> > "s->broken_irq_mapping = false;" case.
>> >>
>> >> Yeah, as long as you avoid the number 27 you're ok :-)
>> >
>> > Good point. I guess we'll have to keep using a legacy domain for
>> > versatile then.
>>
>> I'm happy to provide some other way for QEMU to detect a
>> new working kernel if you want to implement one in the
>> kernel, if that's cleaner.
>
> That's why I suggested writing some number at offset 0x08
> (that's revision ID) in configuration space of device 0 on bus 0.
> It's guaranteed harmless on real hardware and QEMU could detect this
> write and say "aha new kernel, even though it uses #27".

OK, that makes sense. Would somebody like to provide a kernel
patch (preferably against 2.6.35+Arnd's patchset :-)) which
just prods that ID space, so I have something to test the
QEMU end against?

thanks
-- PMM