Re: [Xen-devel] Xen frame buffer related
Dushmanta Mohapatra, le Thu 03 Apr 2008 09:57:11 -0400, a écrit :
> I see two xenfb.c files in the Xen (3.2) source. One in tools/ioemu/hw/ and
> other in linux-2.6.18-xen.hg/drivers
> /xen/fbfront/. So I think the first one is the userspace-backend and the
> one is the kernel-space front-end.
> I do not understand why originally the
> back-end was not made a part of kernel like other devices?
Why should it be? In the case of PVFB, he backend is responsible for
actually showing the frame buffer. A userspace X11 application or VNC
server is thus the logical way.
> Also could you please tell me how to use this backend userspace tool.
You just need to add
vfb = [ 'type=sdl' ]
if you want to have an SDL window showing up when you start your domain,
vfb = [ 'type=vnc' ]
if you want to have a VNC server started instead.
> If I have understood it correctly then in Xen 3.1, this back end tool uses
> VNCServer for displaying the contents of Frontend frambuffer. So what has
> changed with the use of QEMU.
There is now the SDL choice.
> Finally just to give you an idea about my project: Lets suppose a domU gets
> migrated from a Physical machine having a display of X1xY1 to another physical
> machine having a display of X2xY2.
In the unstable tree, there is an OpenGL rendering which can accomodate
with this by rescaling the frame buffer.
> Also a similar example can be a domU getting migrated from a machine
> having one type of keyboard to a machine having another type of
Mmm, you may have a problem here, because PVFB uses Linux keycodes, not
keysyms. I.e. whatever the configuration of the host machine, the guest
keyboard configuration will be used.
> If I see Xen
> 3.2 code in the user space backend framebuffer code (/tools/ioemu/hw/xenfb.c)
> see functions like "static int xenfb_read_frontend_fb_config(struct xenfb
> *xenfb)" and "static int xenfb_read_frontend_kbd_config(struct xenfb *xenfb)".
That's to get the initial size, but in the unstable tree we now have a
PVFB event that permits the guest to change the size dynamically.
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