RE: [Xen-devel] Re: [PATCH 2/2] Virtual frame buffer: user space backend

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> On Fri, 07 Jul 2006 17:57:52 +0100, Christian Limpach wrote:
> 
> > On 6/26/06, Markus Armbruster <armbru@xxxxxxxxxx> wrote:
> >> Straightforward conversion to Xenstore.
> >>
> >> Applies to hg repository at http://hg.codemonkey.ws/vncfb
> >
> > Ideally, we'd move qemu's vnc support into a library to make it
reusable.
> 
> I had considered this.  It's a little awkward since b/c of the
dependence
> on QEMU's async IO routines but it wouldn't be that bad.
> 
> At this point, it probably makes most sense to communicate the linear
> offsets within the framebuffer that are dirty instead of computing a
rect.
>  Since the QEMU VNC code already does rectangle finding and maintains
>  dirty tile bitmap, we don't really have to attempt to find the rect
in
> the frontend at all.

The generic interface I'd opt for would be to round up the framebuffer's
size in each direction to the next power of 2, then divide the region
into 32 tiles by 32 i.e. for a 1280x1024 the size of each tile would be
64x32. 

Just using page-level protection to find the updated area in the
frontend we'll be setting runs of bits, but for e.g. a smart Xserver the
2D nature of the bitmap should enable us to do better.

Ian




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