Re: USB virt port to 2.6 status

[Nivedita Singhvi <niv@us.ibm.com>]

Harry Butterworth 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?

Does this need to remain USB specific or could this
virtual bus be generalized to include a broader range
of devices?

> I created a new device for the above bus to represent a USB back-end.

So this is something present only on dom0/driver domains?
I'm a little confused by what the guest domains (front-end
domains) see as a device(?).

> I created a new driver to drive instances of the above devices. The
> driver creates a new virtual USB host controller for each device
> instance (i.e. one per back-end). The virtual USB host controller is
> created using the USB hc_driver interface which is new to 2.6 and
> eliminates redundancy in the host controller driver implementations.
> 
> This framework is all present in a single loadable module and currently
> loads into 2.6, installs the bus and driver and a dummy device, the

Also works compiled into the kernel?

> driver gets matched to the device and successfully creates a virtual USB
> host controller. All the objects appear in sysfs OK.
> 
> Next step is to create a test machine with a 2.4 dom0 and working USB
> devices and construct the 2.6 front end within the new 2.6 framework by
> porting forwards the remaining function from the 2.4 code.

Will 2.4 backends be compatible with your new 2.6 frontends?

> After that I'll work on the 2.6 back end which I expect to be easier.

Did you mean 2.6 backend (which you said you had) or 2.4?

> I'm expecting to have to make changes to this new code for the new
> persistent store mechanism for discovery and hotplug. Specifically, I'm
> expecting that the new bus device will probably be moved out of the usb
> front end driver and made common between all xen virtualised devices and
> that this bus will perform discovery using the persistent store.

Ah, good. Is anyone working on a new virtual bus infrastructure?

> Once I'm done with both the 2.6 back and front end code I'll look at
> commoning up code between the 2.4 and 2.6 drivers.

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?

> Any comments on approach etc welcome.

Very interesting so far, Harry.

thanks,
Nivedita



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