UML and fbdev

UML and fbdev

[Geert Uytterhoeven]

	Hi,

Are you aware of anyone working on frame buffer devices for UML?

I was thinking about creating a frame buffer device that displays as an X
window. Making it work for user space applications can be tricky, because
writes to the frame buffer must be trapped to update the screen (or use
periodic update, or a combination). But it should work fine for text consoles
(fbcon) and virtual terminals, and for debugging multi-head support.

Gr{oetje,eeting}s,

						Geert

P.S. Please CC me, as I'm not (yet) subscribed to user-mode-linux-devel.
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds



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Re: [Linux-fbdev-devel] UML and fbdev

[Jon Smirl]

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I have a patch for UML (from April so it is out of
date) that will allow you to run any device driver
from inside UML. This patch makes it very easy to
debug things like the framebuffer driver since you can
use a normal debugger on them.

It works by dedicating the piece of hardware to UML
use. You don't load any drivers for it in the host OS.
Instead I have a small driver in the host that
forwards interrupts to UML using signals. The main
driver loads in UML and completely controls the
hardware from there. It supports interrupts, mem
mapping, DMA, etc.

I was using it to debug DRM drivers.

I tired to get it merged into UML without sucess.

--- Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> 	Hi,
> 
> Are you aware of anyone working on frame buffer
> devices for UML?
> 
> I was thinking about creating a frame buffer device
> that displays as an X
> window. Making it work for user space applications
> can be tricky, because
> writes to the frame buffer must be trapped to update
> the screen (or use
> periodic update, or a combination). But it should
> work fine for text consoles
> (fbcon) and virtual terminals, and for debugging
> multi-head support.
> 
> Gr{oetje,eeting}s,
> 
> 						Geert
> 
> P.S. Please CC me, as I'm not (yet) subscribed to
> user-mode-linux-devel.
> --
> Geert Uytterhoeven -- There's lots of Linux beyond
> ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I
> call myself a hacker. But
> when I'm talking to journalists I just say
> "programmer" or something like that.
> 							    -- Linus Torvalds
> 
> 
> 
>
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=====
Jon Smirl
jonsmirl@yahoo.com

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Re: [uml-devel] Re: UML and fbdev

[Jeff Dike]

jonsmirl@yahoo.com said:
> I tired to get it merged into UML without sucess. 

I've been working on getting another stable release of UML ready.  So, I've
been saving new functionality for later.  This is compounded by the fact that
I've had a real lack of spare time recently.

> I was using it to debug DRM drivers. 

It looks like Geert was looking for a virtual frame buffer that would display
in an X window or something.  I don't know of such a beast.

				Jeff



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Re: [uml-devel] Re: UML and fbdev

[Henrik Nordstrom]

On Wed, 13 Aug 2003, Jeff Dike wrote:

> It looks like Geert was looking for a virtual frame buffer that would display
> in an X window or something.  I don't know of such a beast.

Wasn't there someone working on a VNC backend to a virtual framebuffer for 
UML? This should be quite similar in many aspects.

Regards
Henrik



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Re: [uml-devel] UML and fbdev

[Antonio Vargas]

On Wed, Aug 13, 2003 at 06:07:29PM +0200, Geert Uytterhoeven wrote:
> 	Hi,
> 
> Are you aware of anyone working on frame buffer devices for UML?
> 
> I was thinking about creating a frame buffer device that displays as an X
> window. Making it work for user space applications can be tricky, because
> writes to the frame buffer must be trapped to update the screen (or use
> periodic update, or a combination). But it should work fine for text consoles
> (fbcon) and virtual terminals, and for debugging multi-head support.

What about using the "page was changed" bit at the page level?
Changing any byte on a framebuffer page would trigger an update
on the changed bit, and then a periodic task could read these bits
and make a list of pages to be sent over.

For an example about this technique, this was used on AmigaOS
for MacOS framebuffer emulation on shapeshifter.
 
> Gr{oetje,eeting}s,
> 
> 						Geert
> 
> P.S. Please CC me, as I'm not (yet) subscribed to user-mode-linux-devel.
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> 							    -- Linus Torvalds
> 
> 
> 
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-- 
winden/network

1. Dado un programa, siempre tiene al menos un fallo.
2. Dadas varias lineas de codigo, siempre se pueden acortar a menos lineas.
3. Por induccion, todos los programas se pueden
   reducir a una linea que no funciona.


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