Re: [Qemu-devel] Re: [PATCH 1/6] Make config space accessor host bus trapable

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jan 05, 2010 at 07:10:58AM +1100, Benjamin Herrenschmidt wrote:
> On Mon, 2010-01-04 at 13:07 +0200, Michael S. Tsirkin wrote:
> > BTW, I think we really should think about the right way to address the
> > swap/noswap issue without using a preprocessor. Maybe make pci host
> > bridge explicitly specify whether to swap bytes?  How about adding a
> > field in PCIHostState to make it do this? 
> 
> No, this is a non issue if you get your design right. Just abstract out
> the reference to a device in a struct like Alex is proposing and have
> the host bridge specific code fill that up appropriately. I don't see
> why there would be any need for swapping and in any case, this should go
> away once the host bridge code knows how to interpret the write to
> whatever config access registers it exposes.
> 
> Ben.

Well, the main issue if I understand correcttly is that basically the
same hardware bridge can be connected to host in different ways. Yes, we
can say "if it's connected differently it's a different device" but this
is slightly ugly, device should not have to know how it's connected. It
would be cleaner to have a "connector" device in the middle that swaps
bytes.  Even though yes, what you describe would be less ugly than using
proprocessor as we do now.

-- 
MST