Rusty Russell wrote:
On Mon, 2007-06-11 at 10:16 +0200, Gerd Hoffmann wrote:
Hi,
Framebuffer is an interesting one. Virtio doesn't assume shared memory,
so naively the fb you would just send outbufs describing changed memory.
This would work, but describing rectangles is better. A helper might be
the right approach here
Rectangles work just fine for a framebuffer console. They stop working
once you plan to run any graphical stuff such as an X-Server on top of
the framebuffer. Only way to get notified about changes is page faults,
i.e. 4k granularity on the linear framebuffer memory.
Yes, I discussed this with Ben Herrenschmidt a couple of months ago. It
would be better to provide a fb ioctl which X could use to describe
changed rectangles if available. In the virtio case we could hand that
information through, and other virtualized framebuffers would be able to
use it similarly.
The X fbdev driver is going to make supporting a new fb ioctl pretty
fun. It currently doesn't even support the existing fb ioctls and has a
strange abstraction layer.
I reckon writing a new X driver from scratch (or based on something like
the vnc X driver) would be easier in the long run.
Regards,
Anthony Liguori
Cheers,
Rusty.
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