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Re: [Xen-devel] USB virt port to 2.6 status

On Wed, 2005-03-09 at 15:28 +0000, Mark Williamson wrote:
> > > I created a new bus device to represent a virtual bus where each USB
> > > back-end will be represented as a device.
> >
> > [Harry, not sure I understood your scheme fully, so excuse a few
> > dumb questions]
> >
> > I'm assuming that means: real USB Device = 1 backend?
> In Linux you have to create a bus device (which is not a USB device) that 
> represents the USB bus.  Multiple USB devices are then associated with this 
> bus device.  I think this is what Harry is referring to.

So, the new hc_driver interface assumes that your USB host controllers
are bridges from another bus type to USB.

Most of the USB host controllers are PCI devices and so bridge from the
PCI bus to USB.  For those controllers there is therfore a PCI BUS and a
PCI device on the PCI bus which represents the host controller.

To make the 2.6 USB code fit in with this, I have created a new bus type
which is the equivalent of the PCI bus above. i.e. it basically
represents the inter-domain communication interface but at present only
the USB aspects of the inter-domain communication interface.

We ought to extend this bus to be a virtual bus for all the different
types of devices exported over the inter-domain communication interface.

I expect to have to rip this out and change it when the new architecture
is defined.

> Harry, how would you feel about getting any working 2.6 code checked in 
> before 
> commoning up the drivers?

Yes, I'll check in the code as soon as it is equivalent to the 2.4 code.

> > The expectation is that all the following permutations:
> >     2.4 be <-> 2.4 fe
> >     2.6 be <-> 2.4 fe
> >     2.4 be <-> 2.6 fe
> >     2.6 be <-> 2.6 fe
> >
> > will work?

This is what I'm aiming at.

The current protocol doesn't seem to support multiple back-end domains
though. I'm going to work within this limitation for the time being.


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