On 04/18/2013 09:54 PM, Jiří Zárevúcky wrote:
> Hi,
> I have encountered the following problem with framebuffer.
> If I disable compositor in the init program (to force legacy console
> even with framebuffer), then after the framebuffer driver loads,
> nothing is drawn on the screen. It's still possible to use kernel
> console, but not the userspace. See the attached screenshots. Can
> anyone reproduce or possibly tell me why it doesn't work?
> 
> PS: The reason I want to disable compositor is because it still locks
> up for me (qemu i386 with or without kvm, updated Arch Linux).

This is because the screen is still in the graphics mode. The output
server can write to the EGA text frame buffer, but cannot switch the mode.

Just for the record:

<jermar> I can reproduce your behavior
<jermar> another observation is that when you don't configure fb
support, console starts normally
<jermar> I suspect console is somehow no longer able to run on a
graphical fb
<jirkazr> yes, it seems like it
<jermar> the output server cannot do fb
<jermar> it can do ega, but since the mode is set to the graphics mode,
you don't see anything
<jermar> the fb functionality was moved to a ddfized fb driver,which is
used by the compositor
<jirkazr> I see
<jermar> kfb to be exact
<jirkazr> but it stops printing anything the instant kfb loads, why is that?
<jirkazr> I guess kfb takes charge of the screen but doesn't do anything
with it, right?
<jermar> in my case,I see some other output some time after kfb starts
<jermar> then I need to press F12 to switch from the invisible bdsh to
the visible kconsole
<jermar> besides the visibility problem, everything seems to be working
<jermar> which confirms my theory that we just don't see the ega text
buffer because of the wrong mode

Jakub

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