Re: Split Device Driver for video card?

["Daniel P. Berrange" <berrange@redhat.com>]

On Wed, Jan 09, 2008 at 10:37:12AM -0500, Teddy Song wrote:
> 
> Hi, all.
> 
> I am trying to figure out how split device drivers work in Xen. However,
> when I start a guest domain, I only see the following fields showing up in
> Xenstore:
> 
> /local/domain/1/device/console/ .....
> /local/domain/1/device/vbd/769/ .....
> 
> I didn't see other /local/domain/1/device fields. Does it mean not all device
> drivers in Xen follow the split device driver model? (in other words, not all
> device drivers in Xen have a frontend and a backend) If that's true, does video
> card device driver follow the split device driver model?

The console node you see  is actually the text mode console - this does
not follow XEn's usual mode for split device drivers. The video card does
follow the usual architecture - look for  'vfb' and 'vkbd' (keyboard/mouse)
backend nodes in /local/domain/0/backend/{vfb,vkbd} and frontend nods in
/local/domain/[guest id]/device/{vfb,vkbd}.  The only slightly unusual
thing about the video driver is that the backend is a 100% pure userspace
driver, whereas disk & network have their backends in kernel-space.

Dan.
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