Re: [Qemu-devel] [PATCH 3/4] arm: Add PCIe host bridge in virt machine

[Claudio Fontana <claudio.fontana@huawei.com>]

On 08.01.2015 11:31, Peter Maydell wrote:
> On 7 January 2015 at 15:52, Claudio Fontana <claudio.fontana@huawei.com> wrote:
>> Interrupt map does not seem to work for me; incidentally this ends up being
>> the same kind of undocumented blob that Alvise posted in his series. Can
>> you add a good comment about what the ranges property contains
>> (the 0x01000000, 0x02000000 which I suspect means IO vs MMIO IIRC, but
>> there is no need to be cryptic about it).
> 
> The binding docs live in the kernel:
> https://www.kernel.org/doc/Documentation/devicetree/bindings/pci/host-generic-pci.txt
> (which reference the upstream openfirmware specs):
> http://www.firmware.org/1275/practice/imap/imap0_9d.pdf
> 
> so we can provide a brief summary comment here, but if the kernel
> binding docs are confusing (which they kind of are) we should really
> get them improved...
> 
> On the 'compatible' string:
> https://www.kernel.org/doc/Documentation/devicetree/bindings/pci/host-generic-pci.txt
> doesn't say anything about using "pci" here in either the
> text or the example binding.

Thank you for these pointers.

I think that putting a comment with this information (even just a pointer to the effect of "just look at host-generic-pci.txt in the Linux kernel documentation to understand what's going on here" would be helpful, or even go directly referring to the "Open Firmware Recommended Practice: Interrupt Mapping", since QEMU should be guest OS agnostic - to some extent.. -).

Also I think Alex' proposal to use defines for IO Space vs Memory Space instead of hardcoding 0x1000000 / 0x2000000 is a good thing.

I think the kernel binding docs could be made more helpful, but since I am in the position of trying to figure this stuff out I am not in the best position to make them better..

Thanks,

Claudio