Re: [uml-devel] A shared memory framebuffer for UML

[root <vincent-perrier@club-internet.fr>]

Hello Ron Yorston,
I would like to have both audio and video on the host during a 
sip communication with linphone, ekiga or another open source
between 2 UML machines in a virtual network.
I already have the sound but the sip softwares show ugly screens
and need /dev/video... to get a display.
At http://clownix.net a virtual network with sound is availlable,
pulseaudio transfers the audio to and from the host through the
virtual network.
Now my question: would this framebuffer help in the video part
of the sip communication? Could the sip application transmit
images to the host's display? Could the sip application receive
from a real webcam?
My questions may not concern your work at all, as I do not know 
much about webcams and displays yet. 
Regards
Vincent Perrier


Le dimanche 23 novembre 2008 à 17:28 +0000, Ron Yorston a écrit :
> I've done some work on a patch to implement a shared memory framebuffer
> for UML.  (Patch to follow in a separate message, or pick it up from
> my website:  http://intgat.tigress.co.uk/rmy/shmfb/index.html)
> 
> Apply the patch and build the kernel in the usual way:
> 
>    tar xfj linux-2.6.27.7.tar.bz2
>    cd linux-2.6.27.7
>    patch -p1 <linux-2.6.27.7-shm-fb.patch
>    make defconfig ARCH=um
>    make menuconfig ARCH=um
>    make linux ARCH=um
> 
> During the menuconfig phase you should enable framebuffer devices
> (UML-specific options/Graphics support/Support for frame buffer
> devices). Then, in the UML-specific options/Graphics support/Console
> display driver support menu disable VGA text console, enable Framebuffer
> Console support, enable Select compiled-in fonts and select a suitable
> font, for example, VGA 8x16 font. Back in the UML-specific options menu
> enable Shared Memory Framebuffer driver.
> 
> To enable the shared memory framebuffer device add the option
> shmfb=widthxheightxdepth to the kernel command line. For example,
> shmfb=800x600x4. The width and height can have any reasonable values. The
> depth can currently only be 2 or 4 bytes per pixel.
> 
> When the kernel boots it will use the framebuffer device as its console,
> but you won't be able to see anything! To make the framebuffer console
> visible you need a separate client application to run on the host. Two
> clients are provided, a simple Xt-based window and a VNC server:
> 
>    http://intgat.tigress.co.uk/rmy/shmfb/uml_fb-0.1.0.tar.gz
> 
> To build the VNC server client you'll need libvncserver. If this isn't
> in your distro's package repository you can get it from the project's
> Sourceforge page: http://libvncserver.sourceforge.net/.
> 
> Once you've built the clients you can run them as:
> 
>    uml_xtfb --umid <name>
> 
> or
> 
>    uml_vncfb --umid <name>
> 
> where <name> is the name of your UML instance. If you've run the VNC
> client you still won't be able to see anything! You now need to run a
> VNC viewer:
> 
>    vncviewer localhost:0
> 
> As an alternative to starting the client programs by hand you can also use
> a kernel command line option of the form shmfb_client=<path_to_client>,
> where <path_to_client> is, as you might expect, the path to the client
> you'd like to use.
> 
> There are a few problems with the client programs:
> 
>     * the cursor in the virtual console doesn't track the mouse very well;
>     * the X server in the UML instance tends to get confused and sends
>       the mouse to the top left hand corner of the display, where it sits
>       and sulks.
>     * the mouse wheel doesn't work;
>     * the VNC client is hardcoded for a US keyboard. (Probably. I've
>       got a UK keyboard, so some of the less used characters may not be
>       quite right);
>     * if any keys are pressed when the client loses focus it never sees
>       the key release, so thinks that, for example, the control key is
>       always pressed.
> 
> (Adjusting the mouse acceleration in the console mouse server (gpmd)
> or X server (set m, or your desktop manager's GUI equivalent) helps with
> some of the mouse issues.)
> 
> The kernel patch is based on the X11 framebuffer driver by Gerd
> Knorr. Without Gerd's work I wouldn't have been able to achieve
> anything. Thanks!
> 
> Any problems with the patch are my fault.  In particular, I'd very much
> appreciate some hint as to what should be done about fb_pgprotect in fb.h.
> 
> Ron
> 
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