Re: Re: More virtio users

[Anthony Liguori <anthony@codemonkey.ws>]

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.